Catalytic Activity Of Electrode Research Articles

Revealing the modification mechanism of La-doped Ti/SnO2 electrodes related to the microelectronic structure by first-principles calculations

Elemental doping can improve the performance of an electrode, and revealing the modification mechanism is highly significant to prepare high-performance electrode materials. To investigate the modification mechanism of La doping on the electronic structure of SnO2, first-principles calculations using plane-wave pseudopotential technology based on density functional theory (DFT) were performed. First, the geometric structures of La-doped SnO2 crystals were optimized. Second, the property changes of La-doped SnO2, including the lattice constants, energy band structure, density of states and formation energy, were studied. Finally, the theoretical calculation results were verified by proper experimental studies of the electrode catalytic activity. By increasing the La doping concentration, the band gap first decreased and then increased, and the density of states at the Fermi level first increased and then decreased. The calculation results showed that the optimum La concentration was 1.39%. La doping enhanced the acceptor density, increased the quantity of holes in the valence band and improved the carrier concentration. Meanwhile, the structure of SnO2 was the most stable with a La doping concentration of 1.39%. These results revealed the relationship between the lattice change caused by La doping and the catalytic activity of the electrode based on the microstructure and improved the theoretical understanding of the preparation of high-performance electrode materials.

Preparation of Nickel Carbide Nanoparticles and Their Electrode Catalytic Activity on Oxygen Reduction Reaction

Preparation of Nickel Carbide Nanoparticles and Their Electrode Catalytic Activity on Oxygen Reduction Reaction

Effect of deposition temperature on bimetallic PtCu membrane electrode catalytic activity toward hydrogen evolution reaction

Abstract The bimetallic PtCu membrane at a certain deposition temperature was prepared by Ion Bean Sputtering (IBS) using graphite fibre cloth as the supporting material. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) tests were applied to investigate the effect of deposition temperature on hydrogen evolution reaction activity before and after modification. Amperometric I-t test was applied to investigate the catalytic stability of the electrodes. The micro-morphology was observed by STEM, the composition and phase structure of the coating was analyzed by EDS and XRD. The tests showed that the catalytic activity for hydrogen evolution reaction increased firstly and then decreased with the deposition temperature ascending. And there is the highest hydrogen-evolution activity when the deposition temperature is at 250 °C. Combined with the impact of post-process modification on hydrogen-evolution activity, there is the highest activity for bimetallic PtCu membrane electrode and optimal deposition temperature for IBS when the temperature is at 250 °C–275 °C.

Electrocatalytic Oxygen Evolution on Nanoscale Crednerite (CuMnO2) Composite Electrode

Abstract In this study, nanoscale crednerite (CuMnO2) was prepared in the system xCuO–(70–x)MnO–30SiO2 , where x has values 10, 15, 20, 25 and 30, via melting quenching glass-ceramic technique. The electrocatalytic activity of the oxygen evolution reaction (OER) on CuMnO2 deposits has been studied in 1.0 M KOH (25 ℃) by means of cyclic voltammetry, linear sweep voltammetry, chronoamperometric and electrochemical impedance techniques. The study has shown that the catalytic activity had increased with the increase of Cu content in the electrode composition, where the optimum improvement in the apparent electrode catalytic activity was obtained at the M30 electrode (with x = 30). At E = 0.6 V versus Ag/AgCl, the apparent oxygen evolution current density observed at the M30 electrode is 4 times greater than that observed with M10 (x = 10). The order of the OER with respect to OH – concentration measured at low and high potentials is ∼ 1.0 and the roughness of the electrodes was decreased with the increase of the Cu content.

In Situ Tailored Nickel Nano-Catalyst Layer for Internal Reforming Hydrocarbon Fueled SOFCs

Solid oxide fuel cells (SOFCs) have been strongly attracted as the next energy technology due to their high efficiency and eco-friendly energy convertor. SOFCs do not only directly convert to electricity from hydrogen, also from various hydrocarbon fuels such as methane, propane, and so on. However, the conventional Ni cermet anode suffers carbon deposition when directly used with hydrocarbon fuels because of pyrolysis and Boudouard reactions. In this work, non-stoichiometry perovskite (La0.8Ce0.1Ni0.4Ti0.6O3) as reforming layer can lead to Ni nano particle exsolution with homogenous distribution and high population in reduction atmosphere. This catalyst layer was applied on Ni-GDC anode supported single cell to prevent carbon deposition through reforming hydrocarbon fuel at outer surface. The catalyst layer showed excellent attachment with Ni-GDC anode and resistance of carbon deposition. The performance of Ni–GDC anode-supported single cells with catalyst layer was about 1 W/cm2 in hydrogen fuel as similar as without catalyst layer. We are also analyzing of cell performance in dry methane and partial oxidation of methane to clarify the presence of nano nickel particles in the catalyst layer and its effect on the electrode-catalytic activity and polarization resistance.

A dye-sensitized solar cell based on natural photosensitizers and a PEDOT:PSS/TiO2 film as a counter electrode

Poly(3, 4-ethylendioxythiophene)-poly(styrene sulfonate) mixed with TiO 2 nanoparticles (PEDOT:PSS/TiO 2 ) was used as a catalyst for tri-iodide reduction in dye-sensitized solar cells based on natural photosensitizers. A PEDOT:PSS/TiO 2 film was coated on a conductive glass substrate by the spin coating method. The solar cells were fabricated, having the PEDOT:PSS/TiO 2 film as a counter electrode and Pomegranate juice dye-sensitized TiO 2 as an anode. The morphology of PEDOT:PSS/TiO 2 films was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. Cyclic voltammetry (CV) was employed to characterize the catalytic activity of the PEDOT:PSS/TiO 2 film. Based on the analysis of CV, the enhancements for the electrochemical and photochemical performance of the PEDOT:PSS/TiO 2 electrode are attributed to the fact that the dispersed TiO 2 nanoparticles in the PEDOT:PSS matrix provide an improved catalytic activity and a facilitated diffusion for tri-iodide ions. The energy conversion efficiency is significantly improved after TiO 2 nanoparticle incorporation. This improvement might be attributed to an increase in the counter electrode catalytic activity. The highest efficiency of 0.73% was obtained by using 100 nm TiO 2 nanoparticles in the counter electrode.

Towards improving the catalytic activity and stability of platinum-based anodes in direct formic acid fuel cells

The current investigation presents a novel catalyst for formic acid electro-oxidation (FAO); the essential anodic reaction in direct formic acid fuel cells (DFAFCs). The catalyst is developed by a sequential electrodeposition method for Pt (PtNPs), Au (AuNPs) and nickel oxide (nano-NiOx) nanoparticles onto the surface of a glassy carbon (GC) electrode. The objective of this modification was solely dedicated to the improvement of the electrode's catalytic activity by overcoming the CO poisoning, which is usually responsible for the deterioration of the catalytic performance of DFAFCs. The deposition sequence of the catalyst ingredients (PtNPs, AuNPs, and nano-NiOx) was adjusted to optimize the electrocatalytic activity and stability of the catalyst towards FAO. Interestingly, the highest catalytic activity and stability towards FAO was obtained at the NiOx/Au/Pt/GC electrode in which PtNPs were directly deposited onto the GC electrode followed by AuNPs then nano-NiOx. The discussion is oriented to adopt the role of the ternary catalyst ingredients in the catalytic enhancement.

Application of graphene-based nanostructures in dye-sensitized solar cells

The paper reviews recent advances in the application of graphene and related materials, viz. graphene nanoplatelets (GNP), functionalized graphene sheets (FGS), graphene oxide (GO), and reduced graphene oxide (rGO) as electrode building materials in dye-sensitized solar cell (DSC). Graphene promises multifaceted use in DSC: as prospective sensitizer, photoanode additive, current collector, and electrocatalyst for the redox-shuttle turnover. Of particular significance is the use of graphene as cathode catalyst in the state of art Co-mediated solar cells. Here, it can successfully replace platinum without any compromise on the electrode's catalytic activity, associated with good optical transparency.

Glycerol electro-oxidation over glassy-carbon-supported Au nanoparticles: direct influence of the carbon support on the electrode catalytic activity

Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fuel in Direct Glycerol Fuel Cells (DGFC) for cogeneration of electricity, value-added chemicals and heat. With this motivation, in the present work, we investigated at a fundamental level the oxidation of glycerol over glassy carbon (GC) supported Au nanoparticles in alkaline medium using cyclic voltammetry. By controlling the Au deposition time, we varied the GC supported Au coverage from 0.4% to 30% maintaining a regular particle size distribution with a mean particle size of about 200 nm. An influence of the carbon support on the activity of the GC-supported Au nanoparticles was evidenced. Results from studies on the oxidation of glycerol and ethylene glycol on Au and Pt nanoparticles supported on a glassy carbon, highly ordered pyrolytic graphite and dimensionally stable anode under different pH conditions indicate that the carbon support participates actively in the oxidation of glycerol and other alcohols. We propose that active oxygenated species are gradually formed on the glassy carbon by potential cycling (up to the saturation of the carbon area) and these oxygenated species are additional oxygen suppliers for the oxidation of glycerol residues adsorbed on the Au particles, following a mechanism consisting of the synergism of two active elements: gold and carbon.

Co-Electrophoretic Deposition Multiwall Carbon Nanotubes/Pt Counter Electrodes for Dye-Sensitized Solar Cell

Multiwall carbon nanotubes (MWCNTs) and platinum (Pt) were coated on fluorine doped tin oxide (FTO) coated glass by a direct current electrophoretic method, and were used as dye-sensitized solar cell counter electrodes. Scanning electron microscopy (SEM) detected the deposition of carbon nanotubes on FTO-glass. The deposition of Pt nanoparticles on carbon nanotube surfaces was confirmed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Cell efficiencies of MWCNTs, Pt and MWCNTs/Pt dye-sensitized solar cells (DSSCs) were ∼1.41, ∼8.13, and ∼8.90%, respectively. The improvement of the composited MWCNTs/Pt cell efficiency is due to the presence of both catalysts (MWCNTs and Pt) enhancing counter electrode catalytic activity as observed by cyclic voltammetry (CV) and reducing charge-transfer resistance as observed by electrochemical impedance spectroscopy (EIS).

Co-Electrophoretic Deposition Multiwall Carbon Nanotubes/Pt Counter Electrodes for Dye-Sensitized Solar Cell

Multiwall carbon nanotubes (MWCNTs) and platinum (Pt) were coated on fluorine doped tin oxide (FTO) coated glass by a direct current electrophoretic method, and were used as dye-sensitized solar cell counter electrodes. Scanning electron microscopy (SEM) detected the deposition of carbon nanotubes on FTO-glass. The deposition of Pt nanoparticles on carbon nanotube surfaces was confirmed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Cell efficiencies of MWCNTs, Pt and MWCNTs/Pt dye-sensitized solar cells (DSSCs) were ∼1.41, ∼8.13, and ∼8.90%, respectively. The improvement of the composited MWCNTs/Pt cell efficiency is due to the presence of both catalysts (MWCNTs and Pt) enhancing counter electrode catalytic activity as observed by cyclic voltammetry (CV) and reducing charge-transfer resistance as observed by electrochemical impedance spectroscopy (EIS).

Optimization of TiO2 nanoparticle mixed PEDOT–PSS counter electrodes for high efficiency dye sensitized solar cell

Poly(3,4-Ethylendioxythiophene)–Poly(Styrene Sulfonate) (PEDOT–PSS) mixed with titanium dioxide (TiO2) nanoparticles was coated on conductive glass substrate by a doctor blading method and used as dye-sensitized solar cell (DSSC) counter electrodes. The energy conversion efficiency is significantly improved after TiO2 nanoparticle incorporation. This improvement is attributed to an increase in counter electrode catalytic activity and a decrease in counter electrode charge transfer resistance. These phenomena were observed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), respectively. The efficiency of polymer-TiO2 based DSSCs varied with the ratio of small (~25nm) to large (~100nm) TiO2 nanoparticles. The highest efficiency (~8.49%) was obtained with a ratio of 30% large to 70% small (wt/wt) nanoparticles inTiO2 electrodes. This efficiency is superior to that of Pt DSSC (~7.50%).

燃料电池的挑战和新的机遇<br>Fuel Cells Challenges and New Opportunities

固体氧化物燃料电池(solid oxide fuel cells，SOFCs)是复杂的电化学能源转换设备，相比于传统的火力发电系统，具有高转换效率、低排放、零噪音的优势。纵观100多年的SOFCs发展史，一系列的挑战仍阻碍着其商业化进程，如高成本和低稳定性，上述挑战主要归咎于离子电导率和催化活性所要求的高温运行条件。传统的阴极、电解质和阳极三部件结构SOFCs主要从降低电解质厚度和提高电极催化活性入手，至今，所取得的关键技术发展和科学突破仍不够。因此，我们不得不反思SOFCs 100年来发展方向和研究焦点。2010年，单部件无电解质燃料电池在瑞典皇家工学院的发明和研制成功(Adv. Funct. Mater. 21 (2011) 2465)，意味着燃料电池的一个革命和商业化瓶颈的突破，该研究成果被Nature Nanotechnology选为2011年研究亮点，以“FUEL CELL: Three in one”编辑文章报道。 Fuel cells, or specifically on solid oxide fuel cells (SOFCs) are complex electrochemical energy conversion devices, compared to conventional thermal power system with the advantages of high conversion efficiency, low emissions and zero noise. Throughout the 100 years of history of SOFCs development, a number of challenges still hamper their commercialization, such as high cost and low durability; these challenges are mainly attributed to the high temperature operating condition required by ionic conductivity and catalytic activity. Traditional SOFC with structure of cathode, electrolyte and anode three parts today focuses mainly on reducing the electrolyte thickness and enhancing electrode catalytic activity, the development of key technologies and scientific breakthroughs are still not enough. Therefore, we have to reflect that of SOFCs 100 years, the direction and focus of research. 2010, single-component electrolyte-free fuel cell was invented in the Swedish Royal Institute of Technology (Adv. Funct Mater. (2011) 2465), it means that the bottleneck of a revolution and commercialization of fuel cell breakthrough, the results were selected as a 2011 research highlights by Nature Nanotechnology titled as: “The FUEL CELL: Three in one”.

燃料电池的挑战和新的机遇

固体氧化物燃料电池(solid oxide fuel cells，SOFCs)是复杂的电化学能源转换设备，相比于传统的火力发电系统，具有高转换效率、低排放、零噪音的优势。纵观100多年的SOFCs发展史，一系列的挑战仍阻碍着其商业化进程，如高成本和低稳定性，上述挑战主要归咎于离子电导率和催化活性所要求的高温运行条件。传统的阴极、电解质和阳极三部件结构SOFCs主要从降低电解质厚度和提高电极催化活性入手，至今，所取得的关键技术发展和科学突破仍不够。因此，我们不得不反思SOFCs 100年来发展方向和研究焦点。2010年，单部件无电解质燃料电池在瑞典皇家工学院的发明和研制成功(Adv. Funct. Mater. 21 (2011) 2465)，意味着燃料电池的一个革命和商业化瓶颈的突破，该研究成果被Nature Nanotechnology选为2011年研究亮点，以“FUEL CELL: Three in one”编辑文章报道。 Fuel cells, or specifically on solid oxide fuel cells (SOFCs) are complex electrochemical energy conversion devices, compared to conventional thermal power system with the advantages of high conversion efficiency, low emissions and zero noise. Throughout the 100 years of history of SOFCs development, a number of challenges still hamper their commercialization, such as high cost and low durability; these challenges are mainly attributed to the high temperature operating condition required by ionic conductivity and catalytic activity. Traditional SOFC with structure of cathode, electrolyte and anode three parts today focuses mainly on reducing the electrolyte thickness and enhancing electrode catalytic activity, the development of key technologies and scientific breakthroughs are still not enough. Therefore, we have to reflect that of SOFCs 100 years, the direction and focus of research. 2010, single-component electrolyte-free fuel cell was invented in the Swedish Royal Institute of Technology (Adv. Funct Mater. (2011) 2465), it means that the bottleneck of a revolution and commercialization of fuel cell breakthrough, the results were selected as a 2011 research highlights by Nature Nanotechnology titled as: “The FUEL CELL: Three in one”.

TiO 2 nanotube-supported amorphous Ni–B electrode for electrocatalytic oxidation of methanol

Amorphous Ni–B/TiO 2 electrodes were successfully prepared by electroless plating. Highly ordered TiO 2 nanotube arrays fabricated by anodic oxidation were employed as substrate and loaded with Ni–B alloy by electroless plating. The phase formation, microstructures and catalytic activity of electrodes were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and electrochemistry analyzer, respectively. The results show that Ni–B/TiO 2 electrodes with an average particle size of 200 nm present a typical amorphous structure of Ni and B, and have high catalytic activity for methanol electrooxidation in alkaline medium. The peak current density in cyclic voltammetry (CV) curves reaches 360 mA cm −2 in the solution with 0.5 mol L −1 methanol, much higher than that of Ni–B/Ti electrode. With the methanol concentration increasing to 1.5 mol L −1, the peak current density increases to 488 mA cm −2, after which it remains almost constant. The Ni–B/TiO 2 electrodes are relatively stable according to catalytic lifetime test; the peak current density remains 72.1% of the original value after 1300 times cycles. The amorphous Ni–B/TiO 2 electrode should be a promising candidate for direct methanol fuel cell.

Nitrite electro-oxidation mediated by Co(II)-[tetra(4-aminophenyl)porphyrin]-modified electrodes: behavior as an amperometric sensor

Electro-oxidation of nitrite mediated by Co(II)-[tetra(4-aminophenyl)porphyrin]-modified electrodes (4-CoTAPP) is presented in this article. Catalytic activity of electrodes modified with porphyrin polymeric films (poly-4-CoTAPP) and with multilayer of monomers (m-4-CoTAPP) for the oxidation of nitrite was compared. The number of cycles for the electrosynthesis of poly-4-CoTAPP determines the activity of the electrode toward nitrite oxidation because the system loses its catalytic activity as the number of polymerization cycles increases above 15. The effect of pH on activity is also reported. The response for the nitrite oxidation of electrodes modified with 4-CoTAPP and with metal-free ligand, that is, tetra(4-aminophenyl)porphyrin, either as multilayer of monomers or as polymer (m-4-H2TAPP and poly-4-H2TAPP, respectively), was compared. An increase of activity in the presence of the metal was found. Furthermore, when the device was tested as an amperometric sensor for different nitrite concentrations under the optimum working conditions, only poly-4-CoTAPP exhibited a linear response throughout the concentration range studied with a reasonably low limit of detection, while m-4-CoTAPP and poly-H2TAPP systems have no linear response throughout the range of concentration. Finally, the number of electrons involved and the Tafel slope for the reaction were estimated.

Alternative perovskite materials as a cathode component for intermediate temperature single-chamber solid oxide fuel cell

This paper exploits the suitability of three perovskite materials Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF), GdBaCo 2O 5+ δ (GBC) and Ba 0.5Sr 0.5Mn 0.7Fe 0.3O 3− δ (BSMF) as SOFC cathodes in the single-chamber configuration operating at the intermediate temperature range. TG analysis showed high thermal stability depending on the crystalline phases of the materials. The catalytic activity of these three materials for hydrocarbon conversion was investigated under a realistic feed, i.e. with hydrocarbon, oxygen, water and carbon dioxide. Electrochemical impedance spectroscopy of the various cathodes tested in symmetric cell configuration revealed a B-site dependence of the electrode catalytic activity for oxygen reduction. High temperature (1000 °C) powder reactivity tests over a gadolinium doped-ceria (CGO) and perovskite cathode revealed excellent chemical compatibility of BSMF and CGO. Catalytic tests associated with thermal and structural characterization attest to the suitability of these materials in the single-chamber configuration.

Energy and exergy analysis of hydrogen production by a proton exchange membrane (PEM) electrolyzer plant

Hydrogen production by a proton exchange membrane (PEM) electrolyzer provides a promising way to store and better utilize the renewable energy resources. Presently, theoretical studies on PEM electrolyzer are still limited, impeding its technological development. Detailed thermodynamic analysis is valuable to identify the key losses and to optimise the performance of PEM electrolyzer plant for hydrogen production. In this study, energy and exergy analysis has been conducted to investigate the thermodynamic-electrochemical characteristics of hydrogen production by a PEM electrolyzer plant. One important feature of this model is that detailed electrochemical characteristics of the PEM electrolyzer are fully incorporated into the thermodynamic analysis. Heat production in the PEM cell due to irreversible losses has been investigated and compared with the thermal energy demand of PEM cell. It is found that a PEM electrolyzer normally operates in an exothermic mode as the heat production due to overpotentials exceeds the thermal energy demand. As the electrical energy input dominates the overall energy input, the exergy efficiency is found about the same as the energy efficiency. Parametric analyses have been performed to investigate the effect of important design and operating parameters on the plant energy conversion efficiency. This study has quantified how much the energy efficiency can decreases by increasing the operating temperature, lowering the current density, reducing the electrolyte thickness, and increasing the electrode catalytic activity. The analysis presented in this paper also offers better understanding of the characteristics of PEM electrolyzer plant for hydrogen production. With additional energy analysis of electricity generated from solar cells or wind turbines, the model presented in this paper is ready for complete energy/exergy analysis of advanced renewable electrolytic hydrogen production plants.

Pt/C doped by MoO x as the electrocatalyst for oxygen reduction and methanol oxidation

The oxidation of methanol and reduction of oxygen were studied on MoO x –Pt/C nano-catalysts prepared by the polyole method combined by MoO x post-deposition. The catalysts were characterized by TEM and EDX. The presented composition of the electrode is very similar to the nominal ones and post-deposited MoO x species block only a small fraction of the active Pt particle surface area. MoO x deposition on the carbon support can be ruled out from the EDX results and the low mobility of these oxides at corresponding conditions. The electrode catalytic activity in the electrooxidation of methanol and the reduction of oxygen was studied by steady-state voltammetry and cyclic voltammetry. MoO x –Pt/C catalyst exhibits higher catalytic activity than Pt/C for the oxygen reduction. The catalytic effect in oxidation of methanol is achieved only under potentiodynamic conditions, when poisoning species have no enough time to develop fully.

Mesocarbon microbeads supported PtSn catalysts for electrochemical oxidation of ethanol

Mesocarbon microbeads (MCMB) supported PtSn catalysts were prepared by alcohol reduction method and characterized by XRD, FESEM and EDX. XRD results show that the addition of Sn to Pt/MCMB extends the fcc lattice parameters of platinum and the particle size of PtSn/MCMB is about 2.6 nm, smaller than that of Pt/MCMB. The electrode catalytic activity in the electro-oxidation of ethanol was studied by cyclic voltammetry, Tafel plot, electrochemistry impedance spectra (EIS) and chronoamperometry. All the results showed that PtSn/MCMB gave higher catalytic activity for ethanol electro-oxidation than Pt/C (20 wt.% E-TEK).