Anodic Behaviour of Y(0.20)Ti(0.18) Zr(0.62)O(1.90) Towards Hydrogen Electro-Oxidation in a High Temperature Solid Oxide Fuel Cell

The electrochemical oxidation of humid hydrogen was investigated on a Y(0.20)Ti(0.18)Zr(0.62)O(1.90) (YTZ) anode in a high temperature planar solid oxide fuel cell. Cells using platinum counter and reference electrodes on a YSZ based electrolyte were fabricated and tested in H(2)/H(2)O atmospheres versus air in the temperature range (788-932)degrees C. Steady state polarisation measurements, cyclic voltammetry and impedance analysis were used to characterise the behaviour of the anode and determine kinetic parameters of the electro-oxidation reaction. The power output of the cell H(2), H(2)O/YTZ//YSZ-Al(2)O(3)//Pt/air was stable over an operation period of 500 h. For 97% H(2)/3% H(2)O at 932 degrees C it amounted to 37 mW cm(-2) and the maximum current density obtained was 203 mA cm(-2). The apparent reaction order with respect to hydrogen was calculated to be in the region of 0.5 at 932 degrees C. The impedance spectra showed three apparent processes dependent on temperature, fuel concentration and overpotential. Anode polarisation resistance decreased significantly with anodic overpotential. At open and short circuit (E(cell) = 0 V) conditions the total area specific polarisation resistance was 12.67 and 0.96 Omega cm(2) respectively.</p

Methane Electro-Oxidation on a Y(0.20)Ti(0.18)Zr(0.62)O(1.90) Anode in a High Temperature Solid Oxide Fuel Cell

A high temperature solid oxide fuel cell has been operated in low humidity (3 % H(2)O) methane using Y(0.20)Ti(0.18)Zr(0.62)O(1.90) (YTZ) as the anode. The mechanism of methane electro-oxidation was investigated using ac and dc techniques at different anodic overpotentials and methane concentrations in the temperature range 788 - 932 degrees C. It was found that YTZ did not support methane cracking and that its electrocatalytic activity was stable over a long period of operation. Anode performance was significantly enhanced under positive polarization. Although the system showed good stability under low humidity methane conditions, the electrochemical performance was inferior to that observed for conventional anodes, albeit under high humidity methane or hydrogen fuel conditions. The overall area specific polarization resistance decreased from 167.88 Omega cm(2) to 10.14 Omega cm(2) between open and short (E(cell) = 0 V) circuit. Altering the fuel to steam ratio showed that the steam reforming of methane was the main source of power generation at low methane concentrations. Direct methane oxidation was too slow to be discerned under these conditions, but could co-exist with steam reforming at higher methane concentrations.</p

The Role of SnO2 on Electrocatalytic Activity of PtSn Catalysts

In our previous paper, we described in detail studies of Sn influence on electrocatalytic activity of PtSn catalyst for CO and formic acid oxidation (StevanoviAc et al., J. Phys. Chem. C, 118 (2014) 278-289). The catalyst was composed of a Pt phase, Pt3Sn alloy and very small SnO2 particles. Different electrochemical treatment enabled studies of PtSn/C having Sn both in surface and subsurface layers and skeleton structure of this catalyst with Sn only in subsurface layers. The results obtained revealed the promotional effect of surface Sn whether alloyed or as oxide above all in preventing accumulation of CO and blocking the surface Pt atoms. As a consequence, in formic acid oxidation, the currents are not entering the plateau but increasing constantly until reaching a maximum. It was concluded that at lower potentials the effect of Sn on formic acid oxidation was predominantly electronic but with increasing the potential bi-functional mechanism prevailed due to the leading role of SnO2. This role of SnO2 is restated in the present study. Therefore, CO and formic acid oxidation were examined at PtSnO2/C catalyst. The catalyst was synthesised by the same microwave-assisted polyol procedure. According to XRD analysis, the catalyst is composed of a Pt phase and SnO2 phase. The reactions were examined on PtSnO2/C catalyst treated on the same way as PtSn/C. Comparing the results obtained, the role of SnO2 is confirmed and at the same time the significance of alloyed Sn and its electronic effect is revealed

Electrocatalytic oxidation of methanol on a platinum modified carbon nanotube electrode

10.1007/s00604-007-0882-0Microchimica Acta1621-2235-243MIAC