Publications

Tungsten oxide nanopowders: pulse alternating current electrosynthesis, structure optimization and performance in a flow photocatalytic fuel cell

Photocatalytic fuel cell (PFC) is a promising technology to produce electrical energy from transformation of both light and chemical energy of waste products/biomass. Tungsten oxide (WO3) nanopowder is synthesized via a facile and ecologically sound top-down approach using pulse alternating current as an oxidant and aqueous ammonium chloride solution as an electrolyte without any surfactants and organic solvents. The large photocurrent density enhancement for WO3 nanopowder annealed at 500 C demonstrates the importance of WO3 crystallinity in governing its photo-assisted water oxidation. The improved photoactivity of WO3-500 photoanode is due to reduction of the density of deep trap states boosting the charge transfer efficiency. The optimized WO3 photoanode was used to build up a solar light responsive PFC system with a Pt/C air-breathing cathode and the organic electron donors with different functional groups acting as fuels. The maximum power density value increases in the order of formic acid, glycerol, ethanol, and glucose. When glucose was used as the fuel, the WO3-Pt/C PFC obtained the highest power density (Pmax) and current density (Jmax) of 140.8 mW cm-2 and 704 mA cm-2, respectively. This study provides an efficient way for large-scale electrochemical preparation of WO3 nanopowders from bulk tungsten for solar light responsive waste products/biomass-fueled PFC system.

More

Fomes fomentarius as a Bio-Template for Heteroatom-Doped Carbon Fibers for Symmetrical Supercapacitors

Nowadays, commercial electric double-layer supercapacitors mainly use porous activated carbons due to their high specific surface area, electrical conductivity, and chemical stability. A feature of carbon materials is the possibility of obtaining them from renewable plant biomass. In this study, fungi (Fomes fomentarius) were used as a bio-template for the preparation of carbon fibers via a combination of thermochemical conversion approaches, including a general hydrothermal pre-carbonization step, as well as subsequent carbonization, physical, or chemical activation. The relationships between the preparation conditions and the structural and electrochemical properties of the obtained carbon materials were determined using SEM, TEM, EDAX, XPS, cyclic voltammetry, galvanostatic measurements, and EIS. It was shown that hydrothermal pretreatment in the presence of phosphoric acid ensured the complete removal of inorganic impurities of raw fungus hyphae, but at the same time, saved some heteroatoms, such as O, N, and P. Chemical activation using H₃PO₄ increased the amount of phosphorus in the carbon material and saved the natural fungus’s structure. The combination of a hierarchical pore structure with O, N, and P heteroatom doping made it possible to achieve good electrochemical properties (specific capacitance values of 220 F/g) and excellent stability after 25,000 charge/discharge cycles in a three-electrode cell. The electrochemical performance in both three- and two-electrode cells exceeded or was comparable to other biomass-derived porous carbons, making it a prospective candidate as an electrode material in symmetrical supercapacitors.

More

Tuning Sugar Biomass Waste Conversion for the Preparation of Carbon Materials for Supercapacitors and Catalysts for Oxygen Reduction

Agriculture is the most massive material circulation activity of humans, with significant annual volumes of production as well as substantial amounts of waste. Transforming agricultural wastes into high-value-added products is the key to sustainable development with efficient usage of renewable resources. The present study demonstrates the fine-tuning of the sugar beet pulp processing to access two types of materials for cutting edge applications—supercapacitors and fuel cells. Alkaline fine-tuning results in N,O-doped carbon material (CM) with an advantageous combination of surface area and morphology that allows to achieve high specific capacitance (308 F g⁻¹), and excellent stability (>10 000 charge/discharge cycles). Not limited to the CM preparation and characterization, a real device is created in the present study to demonstrate the efficient usage of the carbon electrode in the form of the assembled coin cell. Acidic fine-tuning, in contrast, yields a methodology for P,N,O-doped material and optimizes to form active sites with electrocatalytic activity in the oxygen reduction reaction that is used for electricity production in proton-exchange membrane fuel cells. The developed approach demonstrates the tuning of functional properties and morphology of CMs under experimentally simple conditions using conventional reagents (KOH and H₃PO₄) and opens up new directions in the circular biomass usage projects.

More

Fabrication of nano-In2O3 phase junction by pulse alternating current synthesis for enhanced photoelectrochemical performance: Unravelling the role of synthetic conditions

Rational design and controllable synthesis of materials with improved activity and stability remains one of the key challenges to be addressed in the field of photoelectrochemical water splitting. In this work, a series of nano-In₂O₃ (c- and c/rh-In₂O₃) with tunable cubic-to-rhombohedral phase ratios was obtained via pulse alternating current electrosynthesis followed by air annealing. The physicochemical characterization of In₂O₃ using XRD, FESEM, TEM, XPS, Raman, UV–vis DRS and BET techniques along with photoelectrochemical test indicate that synthetic conditions greatly influence on structural, morphological and optical properties. The c/rh-phase ratio was feasibly controlled by altering the nature of the electrolyte (LiCl, KCl, NaCl and Na₂SO₄) without adding any organic additives. The c/rh-In₂O₃ synthesized using NaCl aqueous electrolyte shows enhanced photoelectrochemical activity (0.35 mA/cm² at 1.23 V vs RHE) and photoconversion efficiency (0.09%) as well as excellent long-term stability (over 7 h). The improved performance of the c/rh-In₂O₃ results from the constructing the well-defined phase-junction with optimal phase ratio (72% c-/28% rh-) and the high oxygen deficiency providing a synergistic effect between rh-In₂O₃ and c-In₂O₃ for more efficient separation and transfer of photogenerated charges. These results lead to a better understanding of designing metal oxide phase-junctions for photoelectrochemical applications.

More

“Liquid-to-solid” conversion of biomass wastes enhanced by nitrogen doping for the preparation of high-value-added carbon materials for energy storage with superior characteristics

Sustainable development of mankind urgently recalls for decreasing the cost of energy storage. Continuous massive consumption of dedicated carbon electrode materials with complex internal molecular architecture calls for re-thinking both the source of materials and the process of their production. Finding an efficient sustainable solution is focused on the reuse and development of waste processing into corresponding high-value-added carbon materials. The processing of solid wastes into solid value-added carbon materials (“solid-to-solid”) is relatively well developed but can be a two-stage process involving carbon architecture rearrangement and heteroatom doping. Processing liquid wastes into high-value-added solid material (“liquid-to-solid”) is typically much more challenging with the need for different production equipment. In the present study, a new approach is developed to bypass the difficulty in the “liquid-to-solid” conversion and simultaneously built in the ability for heteroatom doping within one production stage. Polycondensation of liquid humins waste with melamine (as a nitrogen-containing cross-linking component) results in solidification with preferential C and N atomic arrangements. A complete sequence is reported in the present study, including liquid waste processing, nitrogen incorporation, carbon material production, structural study of the obtained materials, detailed electrochemical evaluation and real supercapacitor device manufacture and testing.

More

Electrochemical Synthesis-Dependent Photoelectrochemical Properties of Tungsten Oxide Powders

A rapid, facile, and environmentally benign strategy to electrochemical oxidation of metallic tungsten under pulse alternating current in an aqueous electrolyte solution was reported. Particle size, morphology, and electronic structure of the obtained WO3 nanopowders showed strong dependence on electrolyte composition (nitric, sulfuric, and oxalic acid). The use of oxalic acid as an electrolyte provides a gram-scale synthesis of WO3 nanopowders with tungsten electrochemical oxidation rate of up to 0.31 g·cm−2·h−1 that is much higher compared to the strong acids. The materials were examined as photoanodes in photoelectrochemical reforming of organic substances under solar light. WO3 synthesized in oxalic acid is shown to exhibit excellent activity towards the photoelectrochemical reforming of glucose and ethylene glycol, with photocurrents that are nearly equal to those achieved in the presence of simple alcohol such as ethanol. This work demonstrates the promise of pulse alternating current electrosynthesis in oxalic acid as an efficient and sustainable method to produce WO3 nanopowders for photoelectrochemical applications.

More

Graphene structures prepared via pulse alternating current technique

Graphene structures have been obtained by exfoliating thermally expanded graphite using a pulse alternating current technique. The electrochemical properties of these materials used in supercapacitors, lithium-ion batteries and electrocatalysts have been investigated.

More

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for NiII, CoII and CuII compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1–5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.

More

One-step synthesis of γ-Fe2O3/Fe3O4 nanocomposite for sensitive electrochemical detection of hydrogen peroxide

Maghemite/magnetite nanocomposite (γ-Fe2O3/Fe3O4) was prepared via an electrochemical method using pulse alternating current and applied for electrocatalytic reduction and sensing of hydrogen peroxide. The structural and compositional analysis of the γ-Fe2O3/Fe3O4 was characterized by XRD, SEM, TEM and XPS. Its thermal decomposition behavior was studied using TG/DSC. The mechanism for γ-Fe2O3/Fe3O4 nanocomposite formation was proposed. Furthermore, the H2O2 sensing performance of the γ-Fe2O3/Fe3O4 nanocomposite was evaluated in 0.1 M KH2PO4. The sensor exhibited a fast electron transfer process in γ-Fe2O3/Fe3O4 nanocomposite. The optimized H2O2 sensor revealed a remarkable low limit of detection of 0.05 μM, a wide linear range from 0.0002 to 8 mM, and a fast response time of 2 s. These results demonstrated that γ-Fe2O3/Fe3O4 prepared via an electrochemical method using pulse alternating current is a promising efficient material for electrochemical sensing of H2O2.

More

Photocatalytic degradation of ciprofloxacin in water at nano-ZnO prepared by pulse alternating current electrochemical synthesis

Ciprofloxacin (CIP) is a broad spectrum synthetic antibiotic of the fluoroquinolone group frequently detected in hospital wastewater, sewage treatment plant effluent, and surface water. The current study investigates the CIP photocatalytic degradation at nano-ZnO synthesized by a novel large-scale and environmentally friendly electrochemical method using pulse alternating current. This method implies the use of LiCl, KCl, NaCl and Na2SO4 as the electrolytes without adding any organic additives or post annealing. The effect of electrolytic media on the morphological, structural, optical and electronic properties of the resulting nano-ZnO was evaluated. The highest CIP removal efficiency reached 93.6 % in 30 min and the TOC removal efficiency reached 51.0 % in 60 min under optimal conditions (5 mg L−1 initial CIP concentration, pH 6.5, catalyst dosage 0.5 g L−1, UV light intensity 2.0 mW cm−2) in the presence of ZnO nanoparticles prepared in LiCl. The efficiency values are higher than those of commercial ZnO due to the increased surface area and the improved separation of charge carriers. Reactive species study confirmed the main role of h+ in the photodegradation process. The photocatalytic performance of the synthesized ZnO samples suggests that these materials can be used for water treatment in environmental applications.

More

Furan monomers and polymers from renewable plant biomass

Ciprofloxacin (CIP) is a broad spectrum synthetic antibiotic of the fluoroquinolone group frequently detected in hospital wastewater, sewage treatment plant effluent, and surface water. The current study investigates the CIP photocatalytic degradation at nano-ZnO synthesized by a novel large-scale and environmentally friendly electrochemical method using pulse alternating current. This method implies the use of LiCl, KCl, NaCl and Na2SO4 as the electrolytes without adding any organic additives or post annealing. The effect of electrolytic media on the morphological, structural, optical and electronic properties of the resulting nano-ZnO was evaluated. The highest CIP removal efficiency reached 93.6 % in 30 min and the TOC removal efficiency reached 51.0 % in 60 min under optimal conditions (5 mg L−1 initial CIP concentration, pH 6.5, catalyst dosage 0.5 g L−1, UV light intensity 2.0 mW cm−2) in the presence of ZnO nanoparticles prepared in LiCl. The efficiency values are higher than those of commercial ZnO due to the increased surface area and the improved separation of charge carriers. Reactive species study confirmed the main role of h+ in the photodegradation process. The photocatalytic performance of the synthesized ZnO samples suggests that these materials can be used for water treatment in environmental applications.

More

Synthesis of 5-hydroxymethylfurfural-acetone resins

5-hydroxymethylfurfural-acetone (5-HMFA) resins are obtained on the basis of 5-hydroxymethylfurfural (5-HMF) and acetone, that is, from monomers whose source of raw materials is renewable resources (agricultural waste). The 5-HMFA condensation reaction was carried out under various experimental conditions. The synthesis conditions for 5-HMFA were selected with a yield of the desired product of 51%. The resulting resins were pressed at various curing temperatures and tested for compressive strength and absorption of water. The optimum pressing temperature was set to 180 ° C. The resulting composites have a strength not inferior to the strength of phenol-formaldehyde resin composites, but have a 3 times higher water resistance.

More

Investigation of the Ambient Temperature Influence on the PEMFC Characteristics: Modeling from a Single Cell to a Stack

Power supply systems based on air-cooled proton exchange membrane fuel cell (PEMFC) stacks are becoming more popular as power sources for mobile applications. We try to create a PEMFC model that allows for predicting the PEMFC operation in various climatic conditions. A total of two models were developed and used: the membrane electrode assemble (MEA) model and the PEMFC stack model. The developed MEA model allows to determine the influence of external factors (temperature) on the PEMFC power density. The data obtained using the developed model correlate with experimental data at low ambient temperatures (10–30 °C). The difference between the simulation and experimental data is less than 10%. However, the accuracy of the model during PEMFC operation at high (>30 °C) and negative ambient temperatures remains in doubt and requires improvement. The obtained data were integrated into the air-cooled PEMFC stack model. Data of the temperature fields distribution will help to manage the processes in the PEMFC stack. The maximum temperature is slightly above 60 °C, which corresponds to the optimal conditions for the operation of the stack. The temperature gradient across the longitudinal section is very low (<20 °C), which is a positive factor for the chemical reaction. However, the temperature gradient observed across the cross section of the PEMFC stack is 30 °C. The data obtained will help to optimize the mass-dimensional characteristics of air-cooled proton exchange membrane fuel cell and increase their performance. The synergetic effect between the MEA model and the PEMFC stack model can be successfully used in the selection of materials and the development of a thermoregulation system in the PEMFC stack.

More

Mechanism of the platinum nanoparticles formation under conditions of nonstationary electrolysis

The cathodic polarization of platinum in both aqueous and nonaqueous alkali metal ion electrolytes includes electrochemical adsorption of solvent molecules as well as intercalation of the alkali metal ions into an adsorption layer. The intercalation into oxidized platinum surface proceeds more effective compared with pure platinum.

More

One step simultaneous electrochemical synthesis of NiO/multilayer graphene nanocomposite as an electrode material for high performance supercapacitors

A NiO/graphene nanocomposite has been prepared via one step electrochemical synthesis using simultaneous pulse alternating current dispersion of both Ni electrode and an electrode of thermally expanded graphite. Electron microscopy and Raman spectroscopy data reveals that the composite consists of graphene sheets with 2–5 layers having 0.5–2 μm size as well as NiO sheets with 200–250 nm dimensions comprising NiO nanoparticles of ∼3.6 nm diameter. The electrochemical capacitance of the nanocomposite is 825 F g−1, with retaining 89% of the initial value after 1000 operation cycles.

More

A comparison of «bottom-up» and «top-down» approaches to the synthesis of Pt/C electrocatalysts

Three 40 wt % Pt/C electrocatalysts prepared using two different approaches—the polyol process and electrochemical dispersion of platinum under pulse alternating current—and a commercial Pt/C catalyst (Johnson Matthey prod.) were examined via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The stability characteristics of the Pt/C catalysts were studied via long-term cycling, revealing that, for all cycling modes, the best stability was achieved for the Pt/C catalyst with the largest platinum nanoparticle sizes, which was synthesized via electrochemical dispersion of platinum under pulse alternating current. Our results show that the mass and specific electrocatalytic activities of Pt/C catalysts toward ethanol electrooxidation are determined by the value of the electrochemically active Pt surface area in the catalysts.

More

Electrochemical dispersion technique for the preparation of Sn-doped Pt particles and their use as electrocatalysts

The Pt nanoparticles doped with tin were prepared by an electrochemical dispersion pulse alternating current technique, and their enhanced catalytic activity in the electrochemical oxidation of ethanol was estimated.

More

Data on the thermo-fluid simulation of open-cathode fuel cell stack depending on the location of the oxidizer/cooling supply system

The content of this paper provides simulation data of the distribution of temperature fields, and oxidizer/cooling agent (air) flows in dependence with location of the oxidizer/cooling supply system in open-cathode polymer electrolyte membrane fuel cell (PEMFC) stack. The finite element method in Solid Works Simulation and Solid Works Flow Simulation software were used for bipolar plate strength calculation and thermo-fluid simulation of PEMFC stack with forced-air convection. The simulations were carried out for two variants of the oxidizer/cooling supply system location - at the entrance to the fuel cell stack (air injection) and at the outlet of the fuel cell stack (air intake).

More

Automatic Lab scale equipment for continuous HMF production in biphasic systems

An automatic lab scale equipment for continuous HMF production by the dehydration of fructose with homogeneous catalysis in biphasic systems (water solution - MIBK) was designed, manufactured and tested. The dependencies of the HMF yield on the process parameters were studied. The feed rate of fructose varied from 50 to 100 g·h−1, the extractant (MIBK) flow rate from 0.5 to 1.4 L·h−1 and the process temperature was maintained in the range from 50 to 87 °C. The maximum productivity of the automatic lab scale equipment 33.6 g·h−1 with a high HMF yield 48 % is achieved with the following process parameters - 87 °C, the fructose feed rate 100 g·h−1 and the extractant flow rate 1 L·h−1. This automatic lab scale equipment may be prospectively used for the kilogram scale HMF synthesis.

More

Bio-based conductive polymer composite materials for fuel cells bipolar plates

Conductive polymer composite materials for polymer electrolyte membrane fuel cells bipolar plates have been successfully prepared from renewable plant biomass sources. The composites are based on various conductive fillers (natural, oxidized and colloidal graphites) and the 5-hydroxymethylfurfural synthesis by-product resin that consists of complex furanic oligomers and polymers. The influences of the resin content and type of conductive filler were investigated. The conductivity of the composite are decreased with increasing resin content, but its mechanical properties are improve. A sample with a resin content of 10 wt. % and colloidal graphite filler have showed the optimal balance between electrical conductivity and mechanical properties. The interfacial contacting resistance, flexural and compressive strength of the composite were 0.035 ohm•cm2, 18.4 MPa and 21.4 MPa, respectively. Composite based on 5-hydroxymethylfurfural synthesis by-product resin and conductive filler (colloidal graphite) are showed a great potential application as bipolar plates for polymer electrolyte membrane fuel cells.

More

New plasticizers on the based on 2,5-furandicaboxylic acid and 5,5-oxy-bis(Methylene)bis-furane-2-caboxylic acid diesters

For the first time, the possibility of synthesis of 2,5-furandicarboxylic acid (FDCA) and 5,5-oxy-bis (methylene) bis-furane-2-caboxylic acid (OBFA) diesters and using them as plasticizers of various polymers have been studied. The most effective method for the synthesis of furan diesters is the direct esterification of FDCA or OBFA with the corresponding aliphatic diols С4-С10. Methods for the synthesis of these diesters with the yield of the target product from 45 to 85 % have been developed. The physical properties and plasticizing ability of the obtained 14 diesters were investigated. The plasticizing ability of the obtained diesters with respect to polyvinyl chloride (PVC), polystyrene (PS) and polymethyl methacrylate (PMMA) was studied. The plasticizing effect depends on the chain length of the aliphatic diol and the nature of the polymer. In general, the synthesized diesters have a stronger plasticizing effect on PS than on PVC and PMMA due to the higher stiffness of the PS chain. The plasticizing ability of the synthesized furan diesters that can be obtained from renewable plant materials is slightly inferior to industrial plasticizers based on phthalic and adipic acids, and are potentially able to replace standard plasticizers derived from hydrocarbons.

More

Bio-based anti-corrosion polymer coating for fuel cells bipolar plates

A highly corrosion resistant and conductive polymer coating for polymer electrolyte membrane fuel cells bipolar plates have been successfully prepared from renewable plant biomass sources. The coating is based on the 5-hydroxymethylfurfural synthesis by-product resin that consists of complex furanic oligomers and polymers. The corrosion resistance and conductivity of coated titanium plates have been studied. As-prepared coated Ti samples are shown 0.083 μA/cm2 and 0.32 μA/cm2 corrosion current in the simulated PEMFCs cathode and anode environment respectively. In addition, the polymer coating are reduced the interfacial contact resistance of bare titanium up to 40 %. The Ti plates coated with by-products of 5-HMF synthesis are shown a great potential application as bipolar plates for PEMFCs.

More

PAC synthesis and comparison of catalysts for direct ethanol fuel cells

Pt/C, PtMOn/C (M = Ni, Sn, Ti, and PtX/C (X = Rh, Ir) catalyst systems were prepared by using the pulse alternating current (PAC) technique. Physical and electrochemical parameters of samples were carried out by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), and CO stripping. The catalytic activity of the synthesized samples for the ethanol electrooxidation reaction (EOR) was investigated. The XRD patterns of the samples showed the presence of diffraction peaks characteristic for Pt, NiO, SnO2, TiO2, Rh, and Ir. The TEM images indicate that the Pt, Rh, and PtIr (alloys) particles had a uniform distribution over the carbon surface in the Pt/C, PtRh/C, PtIr/C, and PtMOn/C (M = Ni, Sn, Ti) catalysts. The electrochemically active surface area of catalysts was determined by the CO-stripping method. The addition of a second element to Pt or the use of hybrid supported catalysts can evidently improve the EOR activity. A remarkable positive affecting shift of the onset potential for the EOR was observed as follows: PtSnO2/C > PtTiO2/C ≈ PtIr/C ≈ PtNiO/C > PtRh/C ≈ Pt/C. The addition of SnO2 to Pt/C catalyst led to the decrease of the onset potential and to significantly facilitate the EOR. The long-term cyclic stability of the synthesized catalysts was investigated. Thereby, the PtSnO2/C catalyst prepared by the PAC technique can be considered as a promising anode catalyst for direct ethanol fuel cells.

More

2,5-furandicarboxylic acid dicinamil ether and new copolymers on its basis

A method for the synthesis of dicinamyl ester of 2,5-furandicarboxylic acid (DCF) a new unsaturated compound of the furan series and potential monomer for producing copolymers with various vinyl compounds and based on them a new generation of construction and ion-exchange materials has been developed. DCF does not form homopolymers as in bulk as in solution (toluene solvent). However, DCF is actively copolymerized with styrene, methyl methacrylate, methacrylic and acrylic acids to form cross-linked polymers with varying degrees of crosslinking. The copolymerization constants of DCF with all investigated vinyl compounds were determined. The DCF copolymers are enriched with comonomer units for all ratios of the components in the initial reaction mixture. They are statistical, and the comonomer units in the macromolecule are randomly arranged. Copolymers with styrene or methyl methacrylate have higher mechanical strength compared to polystyrene and polymethyl methacrylate. Copolymers containing carboxyl groups and 10-20 % wt. crosslinking agent exhibit good ion-exchange properties with respect to heavy metals. The equilibrium adsorption amount of Cu2+ onto ion-exchange сopolymers (221-234 mg/g) was almost twice as large as that onto Amberlite IRC-748 (120.0 mg/g). Materials with a crosslinking agent content of 2.5-5% wt. form polymer gels with high water absorption. Materials containing 2.5 % wt. crosslinking agent (≥ 1400 % for copolymer DCF /acrylic acid and ≥ 1700 for copolymer DCF/methacrylic acid) are showed maximum swelling. These materials can be recommended as water absorbers.

More

Selective photocatalytic oxidation of 5-HMF in water over electrochemically synthesized TiO2 nanoparticles

TiO2 nanoparticles were prepared via an electrochemical method using pulse alternating current and applied in the photocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). Its physicochemical properties were characterized by SEM, HRTEM, XRD, and BET methods. The effect of scavenger and UVA light intensity was studied. The results revealed that electrochemically synthesized TiO2 nanoparticles exhibit higher DFF selectivity in the presence of methanol (up to 33%) compared with commercial samples

More

New Electrochemical Approach for the Synthesis of Pd-PdO/C Electrocatalyst and Application to Formic Acid Electrooxidation

Electrochemical methods for producing Pd-PdO/C catalyst today are mainly represented by electrochemical reduction of Pd ions from its salt solutions. In this paper, we presented a different electrochemical pathway for obtaining Pd-PdO/C, through the electrochemical dispersion of palladium electrodes under the action of an alternating pulsed current. The resulting catalyst showed good electrocatalytic activity in the formic acid electrooxidation reaction

More

Electrocatalytic Properties of Rh/C and Pt-Rh/C Catalysts Fabricated by the Method of Electrochemical Dispersion

The Pt/C, Rh/C, and Pt-Rh/C catalytic systems with uniform distribution of metal phase over the surface of carbon support and an average size of Pt and Rh nanoparticles of 7.3 and 6.5 nm, respectively, are fabricated by the method of electrochemical dispersion of metals in the aqueous electrolytes containing Na+. It is shown that the double-layer potential E = 300 mV (RHE) is the optimal potential of CO adsorption for determining the electrochemically active surface area of Pt/C, Rh/C, and Pt-Rh/C catalysts by the method of oxidative desorption of CO. The introduction of Rh into the Pt/C catalyst enables us to increase the specific activity and reduce the potential of the onset of methanol oxidation.

More

Efficient synthesis of diallyl esters of the furan series from fructose and preparation of copolymers on their basis

New unsaturated derivatives of the furan series, diallyl esters of furan-2,5-dicarboxylic acid and 5,5′-[oxybis(methylene)]di(2-furoic acid), which can be used as monomers and cross linking agents, were synthesized by the aerobic oxidation of 5-hydroxymethylfurfural and 5,5′-oxybis(5-methylene-2-furaldehyde) obtained by catalytic dehydration of fructose. Optimum conditions for the synthesis of the above-mentioned compounds and their copolymerization with butyl methacrylate were determined. Varying the amount of the cross-linking agent, the thermal stability, adhesion, strength and optical properties of copolymers can be controlled. New cross-linking agents obtained from renewable resources can be considered as an alternative to the important cross-linking agent, diallyl phthalate, produced from petroleum.

More

Electrochemical Synthesis of TiO2 under Pulse Alternating Current: Effect of Thermal Treatment on the Photocatalytic Activity

TiO2-NPs were successfully prepared via a large-scale and environmentally friendly electrochemical method using pulse alternating current (PAC synthesis). The effect of thermal treatment on the structural, optical, and photocatalytic properties of TiO2-NPs was investigated. The results demonstrated that the adsorption/photocatalytic properties of the poorly crystalline TiO2 strongly depended on the chemical nature of the dye. The photoactivity of anatase TiO2 for MB and RhB degradation decreased with increase in annealing temperature from 400 °C to 600 °C.

More

Photocatalytic properties of SnO 2 —SnO nanocomposite prepared via pulse alternating current synthesis

A SnO2–SnO nanocomposite was electrochemically synthesized using pulse alternating current and characterized by XRD, SEM, TEM, UV-VIS DRS, and lowtemperature N2 adsorption/desorption (BET) methods. The photocatalytic activity of nanocomposite was estimated for the degradation of methylene blue dye. The pseudo-first-order reaction constant rate k was calculated to be 79.1 × 10−3 min−1.

More

Promoting effect of pyridine bases on indirect electrochemical oxidation of alcohols

The effect of pyridine on the reaction of indirect electrochemical oxidation of alcohols to carbonyl compounds by the catalytic system of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl - iodine in a two-phase aqueous-organic medium: methylene chloride - an aqueous solution of sodium bicarbonate (pH 8.6) was studed. It was shown that the process of indirect electrochemical oxidation of alcohols is accelerated by 1.5–2 times in the presence of pyridine. The corresponding aldehydes and ketones are formed with a high yield (75-95%) after passing 2-2.2 F of electricity. Additionally, the effect of other pyridine bases (2,6-lutidine, 4-acetylpyridine, 2-methyl-5-ethylpyridine, collidine) on indirect electrochemical oxidation of alcohols was studied using the example of 1-octanol. The absence of significant differences in the promoting action of pyridine bases was established and it was shown that in all cases the octanol is obtained with a high yield and coulombic efficiency (90-95 %). A mechanism for the reaction of indirect electrochemical oxidation of alcohols with the participation of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl and pyridine bases is proposed. The promoting effect of pyridine (or other pyridine bases) consists in the formation of an intermediate complex between the base, oxoammonium cation and alcohol. The formation of the complex facilitates the rapid transfer of the proton from the alcohol to the pyridine base and the hydride ion to the oxoammonium cation with the formation of the corresponding carbonyl compound from the alcohol. The preparative methods for the electrochemical synthesis of carbonyl compounds from aliphatic, cyclic, aromatic, heterocyclic alcohols including synthesis of 2,5-diformylfuran from 5-hydroxymethylfurfuralin using the two-phases catalytic system of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl - potassium iodide in the presence of pyridine bases, are proposed.

More

Investigation of structural, microstructural and electrochemicalcharacteristics of Pt/SnOx-c electrocatalysts prepared viaelectrochemical dispersion of tin and platinum

Tin oxides powders (SnOx) with different structure and composition and Pt/SnOx-C electrocatalysts for the direct ethanol fuel cells have been prepared via the electrochemical dispersion of tin and platinum electrodes under a pulse alternating current using various types of anion electrolytes (Cl- and F- anions). As-prepared tin oxides powders, SnOx-C composite supports and Pt/SnOx-C catalysts have been examined by different methods: X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. SnO2 nanoparticles with average sizes of 5 – 8 nm was prepared in a Cl- – containing solution. In turn, the F- – containing solution was found to contain SnO nanoparticles with pronounced shape anisotropy and diverse size of particles. These tin oxides were used as precursors in the synthesis of Pt/SnOx-C catalysts (20% Pt loading, D111=10.5 – 13.5 nm) by the same pulse alternating current technique. Electrochemical active surface area of the Pt/SnOx-C electrocatalysts determined via CO-stripping method was 13-15 m2g-1. Electrocatalytic activity of the electrocatalysts was study for the ethanol electrochemcail oxidation reaction by cyclic voltammetry, rotating disc electrode technique. It was found that the presence of tin oxides is found to exert the same promoting effect on the CO-stripping and ethanol electrochemical oxidation reaction independently on structural features of their particles.

More

Synthesis of furanic polyamides and composite coatings from plant biomass

We report, for the first time, the synthesis of polyamide composite coating based on renewable plant biomass sources. 2,5-furandicarboxylic acid (FDCA) was prepared by catalytic oxidation of 5-hydroxymethylfurfural (HMF) obtained by plant biomass conversion. FDCA was used in the synthesis of aliphatic and aromatic furanic polyamides. Two approaches to furanic PAs synthesis have been investigated: (i) synthesis of hexamethylenediamine furanoate salt and its subsequent polycondensation; (ii) synthesis of FDCA dichloride and its subsequent polycondensation in a two-phase aqueous-organic system. The effect of the nature of organic solvent (tetraclormetan, dichloromethane, N-methyl-2-pyrrolidone) and the nature of diamine (hexamethylenediamine and paraphenylenediamine) on the yield and molecular weight of furanic polyamide was studied. The synthesized aliphatic polyamide was used for enamel fabrication. Colloidal graphite and activated carbon obtained from the waste of biomass conversion into HMF were used as fillers. The furanic PA composite coatings on steel provide the lower coefficient of friction and lower wear compared with that of commercial polyamide (PA6) coatings and can be considered as novel promising anti-friction coating materials.

More

PtIr/C Catalysts Synthesized by Electrochemical Dispersion Method for Proton Exchange Membrane Fuel Cells

PtIr/C electrocatalyst with the metal phase uniformly distributed over the carbon support surface and the average size of PtIr nanoparticles of 5.9 nm is synthesized by electrochemical dispersion of Pt90Ir10 alloy under the action of alternating pulse current. It is shown that the presence of iridium within the composition of a Pt/C catalyst lowers down the overpotential of CO oxidation and increases catalyst’s specific activity with respect to electrochemical oxidation of ethanol.

More

Synthesis of Co3O4/CoOOH via electrochemical dispersion using a pulse alternating current method for lithium-ion batteries and supercapacitors

We report a convenient, low-cost and ecofriendly approach for the fabrication of a Co3O4/CoOOH electrode material intended for lithium ion batteries (LIBs) and supercapacitors (SCs) using the electrochemical dispersion of the cobalt foil through the pulse alternating current (PAC) method. The synthesized material is a Co3O4/CoOOH composite (with about 10–15 wt% CoOOH) in the form of nanosheets with a length of approximately 200 nm and a thickness of 10–20 nm. It is found to exhibit high reversible discharge specific capacities and good cycling behavior while tested as the anode material in LIBs. Measuring the reversible capacitance at high (2C) and low (C/20) cycling rates gives the values of 610 mAh g−1 and 1030 mAh g−1, respectively. The specimen possesses excellent performance as the electrode for SCs with the retention of capacitance up to 98% at the current density increasing from 0.5 to 10 A g−1. After 1000 cycles at a current density of 10 A g−1 the electrode maintains about 90% of its initial capacitance which evidences the long cycle life. Hence, electrochemically prepared Co3O4/CoOOH seems to be a promising candidate for high-performance LIBs and SCs applications.

More

Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Pt/C catalysts synthesized by pulse alternating current technique

The Pt/C catalysts with various Pt content (5-30 wt%) synthesized via electrochemical pulse alternating current technique have been evaluated for the base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The higher Pt content in the catalyst (30 wt%) provides the product yield up to 65% upon performing the process in concentrated (∼0.1 M) aqueous solutions of the substrate.

More

Large-scale synthesis of ZnO nanostructures by pulse electrochemical method and their photocatalytic properties

In this paper, we report a simple environment-friendly and large-scale approach to synthesis of highly crystalline zinc oxide nanostructures using pulse alternating current (PAC). The morphological results demonstrate flower-like architectures of nanoparticle-based and nanorod-based zinc oxide (ZnO-NPs and ZnO-NRs) obtained in KCl and NaCl as electrolytes. The photocatalytic activity of the obtained materials was performed in methylene blue dye degradation reaction under UV light irradiation. A high efficiency of ~ 90% within 60 min with excellent rate constant (k = 0.0386 min−1) was observed in the presence of ZnO-NPs synthesized in 2 M KCl which is attributed to the larger specific surface area (27 m2 g−1), total pore volume and more defective structure.

More

Selective Oxidation of 5-(Hydroxymethyl)furfural to Furan-2,5-dicarbaldehyde with Sodium Nitrite in Phosphoric Acid

5-(Hydroxymethyl)furfural is readily oxidized to furan-2,5-dicarbaldehyde with sodium nitrite in phosphoric acid at room temperature (25°C). The best selectivity for furan-2,5-dicarbaldehyde is achieved using 2.5 equiv of sodium nitrite with respect to the substrate. In this case, nearly quantitative yield of furan- 2,5-dicarbaldehyde is attained in 1 h, the substrate conversion being complete. Due to high selectivity in combination with low cost and toxicity of phosphoric acid, the system NaNO2–H3PO4 is more convenient than NaNO2–CF3COOH for the preparative synthesis of furan-2,5-dicarbaldehyde.

More

Influence of Carbon Support on Catalytic Layer Performance of Proton Exchange Membrane Fuel Cells

Pt-based catalysts supported onto various carbon nanotubes (CNTs) and carbon black Vulcan XC-72 have been studied in this work. The samples have been prepared via electrochemical dispersion technique. The carbon nanotubes exhibit the mesoporous morphology with the pore size of 5—30 nm, while Vulcan XC-72 support exhibits a microporous structure. The agglomeration of Pt particles (5—7 nm) is found to be more extended at the carbon nanotubes compared to the carbon black. The examination of the synthesized catalysts in a catalytic membrane electrode assembly layer reveals that CNTs favor a power density higher than in the carbon black support owing to a more suitable porous structure of the catalyst layer. Moreover, the maximum characteristics of membrane electrode assembly are obtained for few-walled carbon nanotubes with a broad carbon having size distribution.

More

Copper oxides for energy storage application: Novel pulse alternating current synthesis

Copper oxide powders (CuOx) were reported to be electrochemically obtained under pulse alternating current by a facile and inexpensive one-pot method. The effect of the synthesis conditions on the copper electrode oxidation rate and product morphology and composition was studied. The CuOx products were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Depending on the synthesis conditions, the powders reveal different morphologies and composition, such as Cu2O octahedra, Cu2O decorated with CuO or Cu2O-CuO bilayered composite. Cyclic voltammetry and charge-discharge measurements were used to study the electrochemical energy conversion properties of the materials. The results of the electrocatalytic study indicate that the powder with Cu2O-CuO bilayered polyhedra is suitable for use in methanol oxidation; and the powder with Cu2O octahedra has shown a good specific capacitance for supercapacitors.

More

On the Evaluation of the Average Crystalline Size and Surface Area of Platinum Catalyst Nanoparticles

In the present work, the effect of grain size distribution on the diffraction profile shape is inspected via analysis of the mutual ratio of Lorentz and Gauss components in pseudo-Voigt function which is used for simulating X-ray profiles of nanoparticles. As established from the plotted dependences, the error in the average Pt nanoparticles size determination reaches 56% and the discrepancy between calculated Pt nanoparticle surface areas attains 60%. Furthermore, the determination error becomes greater with increasing the Lorentz contribution to pseudo-Voigt function, or, in fact, with enlarging particle size distribution. The empirically found electrochemical surface area of Pt/C electrocatalyst is compared with that evaluated from XRD data using the Scherrer formula and particle size distribution data analysis.

More

Electrochemically synthesized Pt-based catalysts with different carbon supports for proton exchange membrane fuel cell applications

The Pt/C catalysts containing various types of carbon support were prepared via electrochemical oxidation/dispersion. Their different catalytic activity in CO-stripping and ethanol electrooxidation was revealed.

More

Sustainable Utilization of Biomass Refinery Wastes for Accessing Activated Carbons and Supercapacitor Electrode Materials

Biomass processing wastes (humins) are anticipated to become a large-tonnage solid waste in the near future, owing to the accelerated development of renewable technologies based on utilization of carbohydrates. In this work, the utility of humins as a feedstock for the production of activated carbon by various methods (pyrolysis, physical and chemical activation, or combined approaches) was evaluated. The obtained activated carbons were tested as potential electrode materials for supercapacitor applications and demonstrated combined micro- and mesoporous structures with a good capacitance of 370 F g−1 (at a current density of 0.5 A g−1) and good cycling stability with a capacitance retention of 92 % after 10 000 charge/discharge cycles (at 10 A g−1 in 6 m aqueous KOH electrolyte). The applicability of the developed activated carbon for practical usage as a supercapacitor electrode material was demonstrated by its successful utilization in symmetric two-electrode cells and by powering electric devices. These findings provide a new approach to deal with the problem of sustainable wastes utilization and to advance challenging energy storage applications.

More

Electrochemistry and functional materials

Publications

Tungsten oxide nanopowders: pulse alternating current electrosynthesis, structure optimization and performance in a flow photocatalytic fuel cell

Fomes fomentarius as a Bio-Template for Heteroatom-Doped Carbon Fibers for Symmetrical Supercapacitors

Tuning Sugar Biomass Waste Conversion for the Preparation of Carbon Materials for Supercapacitors and Catalysts for Oxygen Reduction

Fabrication of nano-In2O3 phase junction by pulse alternating current synthesis for enhanced photoelectrochemical performance: Unravelling the role of synthetic conditions

“Liquid-to-solid” conversion of biomass wastes enhanced by nitrogen doping for the preparation of high-value-added carbon materials for energy storage with superior characteristics

Electrochemical Synthesis-Dependent Photoelectrochemical Properties of Tungsten Oxide Powders

Graphene structures prepared via pulse alternating current technique

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

One-step synthesis of γ-Fe2O3/Fe3O4 nanocomposite for sensitive electrochemical detection of hydrogen peroxide

Photocatalytic degradation of ciprofloxacin in water at nano-ZnO prepared by pulse alternating current electrochemical synthesis

Furan monomers and polymers from renewable plant biomass

Synthesis of 5-hydroxymethylfurfural-acetone resins

Investigation of the Ambient Temperature Influence on the PEMFC Characteristics: Modeling from a Single Cell to a Stack

Mechanism of the platinum nanoparticles formation under conditions of nonstationary electrolysis

One step simultaneous electrochemical synthesis of NiO/multilayer graphene nanocomposite as an electrode material for high performance supercapacitors

A comparison of «bottom-up» and «top-down» approaches to the synthesis of Pt/C electrocatalysts

Electrochemical dispersion technique for the preparation of Sn-doped Pt particles and their use as electrocatalysts

Data on the thermo-fluid simulation of open-cathode fuel cell stack depending on the location of the oxidizer/cooling supply system

Automatic Lab scale equipment for continuous HMF production in biphasic systems

Bio-based conductive polymer composite materials for fuel cells bipolar plates

New plasticizers on the based on 2,5-furandicaboxylic acid and 5,5-oxy-bis(Methylene)bis-furane-2-caboxylic acid diesters

Bio-based anti-corrosion polymer coating for fuel cells bipolar plates

PAC synthesis and comparison of catalysts for direct ethanol fuel cells

2,5-furandicarboxylic acid dicinamil ether and new copolymers on its basis

Selective photocatalytic oxidation of 5-HMF in water over electrochemically synthesized TiO2 nanoparticles

New Electrochemical Approach for the Synthesis of Pd-PdO/C Electrocatalyst and Application to Formic Acid Electrooxidation

Electrocatalytic Properties of Rh/C and Pt-Rh/C Catalysts Fabricated by the Method of Electrochemical Dispersion

Efficient synthesis of diallyl esters of the furan series from fructose and preparation of copolymers on their basis

Electrochemical Synthesis of TiO2 under Pulse Alternating Current: Effect of Thermal Treatment on the Photocatalytic Activity

Photocatalytic properties of SnO 2 —SnO nanocomposite prepared via pulse alternating current synthesis

Promoting effect of pyridine bases on indirect electrochemical oxidation of alcohols

Investigation of structural, microstructural and electrochemicalcharacteristics of Pt/SnOx-c electrocatalysts prepared viaelectrochemical dispersion of tin and platinum

Synthesis of furanic polyamides and composite coatings from plant biomass

PtIr/C Catalysts Synthesized by Electrochemical Dispersion Method for Proton Exchange Membrane Fuel Cells

Synthesis of Co3O4/CoOOH via electrochemical dispersion using a pulse alternating current method for lithium-ion batteries and supercapacitors

Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Pt/C catalysts synthesized by pulse alternating current technique

Large-scale synthesis of ZnO nanostructures by pulse electrochemical method and their photocatalytic properties

Selective Oxidation of 5-(Hydroxymethyl)furfural to Furan-2,5-dicarbaldehyde with Sodium Nitrite in Phosphoric Acid

Influence of Carbon Support on Catalytic Layer Performance of Proton Exchange Membrane Fuel Cells

Copper oxides for energy storage application: Novel pulse alternating current synthesis

On the Evaluation of the Average Crystalline Size and Surface Area of Platinum Catalyst Nanoparticles

Electrochemically synthesized Pt-based catalysts with different carbon supports for proton exchange membrane fuel cell applications

Sustainable Utilization of Biomass Refinery Wastes for Accessing Activated Carbons and Supercapacitor Electrode Materials