Electrocatalytic Activity For Ethanol Oxidation Research Articles

Direct Electrodeposition of Tetrahexahedral Pd Nanocrystals with High-Index Facets and High Catalytic Activity for Ethanol Electrooxidation

Tetrahexahedral Pd nanocrystals (THH Pd NCs) with {730} high-index facets were directly produced on a glassy carbon substrate in a dilute PdCl(2) solution by a newly developed programmed electrodeposition method. The THH Pd NCs, thanks to their high density of surface atomic steps, exhibit 4-6 times higher catalytic activity than commercial Pd black catalyst toward ethanol electrooxidation in alkaline solutions. This straightforward method provides a promising route to facile preparation of high-index-faceted metal nanocatalysts with high catalytic activity.

Palladium Nanowires Synthesized in Hexagonal Mesophases: Application in Ethanol Electrooxidation

Palladium nanowires (of length a few tens of nanometers) are synthesized in a hexagonal mesophase formed by a quaternary system (Pd-doped water, surfactant, cosurfactant, and oil) by electron beam irradiation. The mesophases can be doped by high concentrations of palladium (0.1 M) without any disturbance of the structure of the mesophases which allows the quantitative synthesis of 1D Pd nanostructures. We found an increase in the average length of the nanowires with the amount of cosurfactant (pentanol) that assists the reduction/growth processes. The electrocatalytic oxidation of ethanol was selected as a test reaction in alkaline medium where Pd is known to be among the best electrode materials. We found that the Pd nanowires exhibit both a very important electrocatalytic activity for ethanol oxidation and a very high stability.

Synthesis, characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt, Pt–Rh, Pt–SnO 2 and Pt–Rh–SnO 2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO 2 and Pt–Rh–SnO 2 were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO 2/C catalyst: solid solution of Rh in Pt and SnO 2. The activity of Pt–Rh–SnO 2/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO 2/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H 2SO 4 concentrations (0.02–0.5 M) showed that Pt–Rh–SnO 2/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.

Ethanol electrooxidation on platinum particles dispersed on poly(neutral red) film

The conductive polymer poly(neutral red) polymerized on a graphite electrode (PNR/graphite) as a support material was used for catalytic oxidation of ethanol in acidic solution and investigated by electrochemical methods. Pt particles loaded on the surface of PNR/graphite electrode exhibited higher electrocatalytic activity for ethanol oxidation in comparison with Pt particles supported directly on graphite. With the equivalent loading mass of Pt catalyst, the special activity (SA) at peak a of the Pt/PNR/graphite electrode polymerized for 10 cycles in 5 × 10−4 M NR + 0.5 M H2SO4 solution is 3,478 A C−1 and about 2.20 times higher than that of the Pt/graphite electrode (1,582 A C−1). The results show that the electrochemical performance of Pt catalyst for ethanol oxidation is improved by the addition of PNR

High performance direct ethanol fuel cell with double-layered anode catalyst layer

Double-layered anode catalyst layers with two reverse configurations, which consist of 45 wt.% Pt 3Sn/C and PtRu black catalyst layers, were fabricated to improve the performance of a direct ethanol fuel cell (DEFC). The in-house 45 wt.% Pt 3Sn/C catalyst was characterized by XRD and TEM. The cross-sectional double-layered anode catalyst layer was observed by SEM. In DEFC performance test and anode linear sweep voltammetry measurement, the anode with double-layered catalyst layer exhibited better catalytic activity for ethanol electro-oxidation than those with single-layered 45 wt.% Pt 3Sn/C and PtRu black catalyst layers. In terms of anode product distribution, the DEFC with double-layered anode catalyst layer showed a higher yield of acetic acid than that with single-layered PtRu black catalyst layer and a higher yield of CO 2 than that with single-layered 45 wt.% Pt 3Sn/C catalyst layer, respectively. These results suggest that the double-layered anode catalyst layer possessed the advantages of both Pt 3Sn/C and PtRu black catalysts for ethanol electro-oxidation, and thus showed a higher ethanol electro-oxidation efficiency and DEFC performance in the practical polarization potential region.

Electronic Effects in Pt-Sn Alloy as Anode in Direct Ethanol Fuel Cell

Carbon supported Pt-Sn alloy catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterised by X-ray diffraction, high resolution transmission electron microscopy and X-ray absorption near-edge structure analyses. The electrocatalytic activity for ethanol oxidation was compared with that of a commercial Pt3Sn/C electrocatalysts from E-TEK. The synthetized Pt3Sn catalysts presents a lower degree of alloy that increases when the catalysts is submitted to a thermal treatment. The prepared Pt3Sn catalyst, submitted to a thermal treatment, showed a better performance as anode material in a direct ethanol fuel cell (DEFC) operating at 90 oC.

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).

Perovskite-Based Catalysts for Direct Ethanol Fuel Cells

A new catalyst development strategy, featuring an energy efficient and rapid synthesis technique so-called solution combustion (SC), and an high throughput electro-catalysts screening system (NuVant), is proposed. Under this strategy, a library of conductive perovskites were synthesized and tested as anode electrodes in the Direct Ethanol Fuel Cell conditions. It was found that a variety of Ru-based perovskites showed considerable electro-catalytic activity for ethanol oxidation. Further, it was demonstrated that the composite perovskite-platinum catalysts with low noble metal loading prepared directly by SC method exhibit comparable performance with standard Pt-Ru alloy.

Ethanol Oxidation on Carbon Supported Pt-Sn Electrocatalysts Prepared by Reduction with Formic Acid

Carbon supported alloy catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterized by X-ray diffraction, high-resolution transmission electron microscopy, and X-ray absorption spectroscopy techniques. Their electrocatalytic activity for ethanol oxidation was compared with commercial and electrocatalysts and the differences discussed in terms of intrinsic properties of the materials. The activity for ethanol oxidation in linear sweep voltammetry experiments at room temperature is greatly enhanced, mainly at low potentials, on (3:1) and (2:1) catalysts prepared by the formic acid method, while only a slight improvement is observed on (9:1) prepared with formic acid and on from E-TEK. The commercial catalyst showed a higher current performance as anode material in a direct ethanol fuel cell operating at 90 and . At the low temperatures of the electrochemical experiments, the rate determining step (rds) of ethanol oxidation is the removal of -species, which is enhanced by the presence of Sn oxides. At the higher temperatures of the fuel cell, instead, the rds is the dissociative adsorption of ethanol and/or the oxidation of acetaldehyde to acetic acid: both these reactions are favored by an increase of the Sn content in the alloyed state.

Ethanol Oxidation on Pt-Sn Electrocatalysts Supported on Carbon Prepared by Reduction with Formic Acid

Carbon supported Pt-Sn alloy catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterised by X-ray diffraction, high resolution transmission electron microscopy and X-ray absorption near- edge structure analyses. Their electrocatalytic activity for ethanol oxidation was compared with commercial Pt/C and Pt3Sn/C electrocatalysts. The synthetized PtSn catalysts presented a low degree of alloy formation and high contents of Sn oxides. The electrocatalytic activity for ethanol oxidation in linear sweep voltammetry experiments at room temperature is greatly enhanced, mainly at low potentials, on Pt3Sn and Pt2Sn catalysts prepared by reduction with formic acid, while only a slight improvement is observed on Pt9Sn prepared with formic acid. On the other hand, a commercial Pt3Sn catalyst with a high degree of alloying showed the highest current performance as anode material in a direct ethanol fuel cell (DEFC) operating at 90 and 110 oC.

Enhanced activity for ethanol electrooxidation on Pt–MgO/C catalysts

MgO promoted Pt/C electrocatalysts were rapidly prepared by intermittent microwave heating method and characterized using different techniques. Electrooxidation of ethanol on MgO promoted Pt/C catalysts in alkaline media was studied. Such electrocatalysts are superior to pure Pt electrocatalysts. The influence of the amount of MgO in the catalysts on catalytic activity for ethanol oxidation was tested. The electrode with a weight ratio of Pt to MgO of 4:1 showed the highest electrocatalytic activity for ethanol oxidation. The presence of MgO in the electrocatalysts improved the kinetic processes, giving the exchange current density for ethanol oxidation of 1.8 × 10 −5 A cm −2 on Pt–MgO/C instead of 3.3 × 10 −7 A cm −2 on Pt/C.

Electrochemical oxidation of ethanol on Pt–ZrO 2/C catalyst

In this paper, Pt–ZrO 2/C catalysts were prepared and compared with Pt/C(20 wt% E-TEK)in terms of the electrochemical activity for ethanol oxidation using cyclic voltammetry (CV), Tafel plot and electrochemical impedance spectroscopy in alkaline solutions. All the results showed that Pt–ZrO 2/C gave higher catalytic activity for ethanol electro-oxidation. The effect of Pt:ZrO 2 molar ratio on the catalytic activity was also investigated by CV and the lowest peak potential for ethanol electro-oxidation appeared at the molar ratio of 1:4.

Structure and chemical composition of supported Pt–Sn electrocatalysts for ethanol oxidation

Carbon supported PtSn alloy and PtSnO x particles with nominal Pt:Sn ratios of 3:1 were prepared by a modified polyol method. High resolution transmission electron microscopy (HRTEM) and X-ray microchemical analysis were used to characterize the composition, size, distribution, and morphology of PtSn particles. The particles are predominantly single nanocrystals with diameters in the order of 2.0–3.0 nm. According to the XRD results, the lattice constant of Pt in the PtSn alloy is dilated due to Sn atoms penetrating into the Pt crystalline lattice. While for PtSnO x nanoparticles, the lattice constant of Pt only changed a little. HRTEM micrograph of PtSnO x clearly shows that the change of the spacing of Pt (1 1 1) plane is neglectable, meanwhile, SnO 2 nanoparticles, characterized with the nominal 0.264 nm spacing of SnO 2 (1 0 1) plane, were found in the vicinity of Pt particles. In contrast, the HRTEM micrograph of PtSn alloy shows that the spacing of Pt (1 1 1) plane extends to 0.234 nm from the original 0.226 nm. High resolution energy dispersive X-ray spectroscopy (HR-EDS) analyses show that all investigated particles in the two PtSn catalysts represent uniform Pt/Sn compositions very close to the nominal one. Cyclic voltammograms (CV) in sulfuric acid show that the hydrogen ad/desorption was inhibited on the surface of PtSn alloy compared to that on the surface of the PtSnO x catalyst. PtSnO x catalyst showed higher catalytic activity for ethanol electro-oxidation than PtSn alloy from the results of chronoamperometry (CA) analysis and the performance of direct ethanol fuel cells (DEFCs). It is deduced that the unchanged lattice parameter of Pt in the PtSnO x catalyst is favorable to ethanol adsorption and meanwhile, tin oxide in the vicinity of Pt nanoparticles could offer oxygen species conveniently to remove the CO-like species of ethanolic residues to free Pt active sites.

Size-Controllable Synthesis of Monodispersed SnO2 Nanoparticles and Application in Electrocatalysts

Size-controllable tin oxide nanoparticles are prepared by heating ethylene glycol solutions containing SnCl(2) at atmospheric pressure. The particles were characterized by means of transmission electron microscopic (TEM), X-ray diffraction (XRD) studies. TEM micrographs show that the obtained material are spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of pH value, reaction time, water concentration, and tin precursor concentration. The XRD pattern result shows that the obtained powder is SnO(2) with tetragonal crystalline structure. On the basis of UV/vis and FTIR characterization, the formation mechanism of SnO(2) nanoparticles is deduced. Moreover, the SnO(2) nanoparticles were employed to synthesize carbon-supported PtSnO(2) catalyst, and it exhibits surprisingly high promoting catalytic activity for ethanol electrooxidation.