H sub(2) oxidation on Ni/Y-TZP cermet electrodes - polarisation behaviour

The polarisation behaviour of Ni/3 mol % Y sub(2)O sub(3)-ZrO sub(2) (Ni/Y-TZP) cermet electrodes for H sub(2) oxidation reaction has been investigated by the galvanostatic current interruption (GCI) over a wide range of H sub(2)O content and temperature in both undiluted and diluted H sub(2) fuel. The electrode performance increases with H sub(2)O content with a maximum at 14% H sub(2)O. The reaction orders with respect to partial pressure of H sub(2)O and H sub(2) are 0.5 and 0.1, respectively. The activation energy for the reaction is about 70 kJ mol super(-1) in the H sub(2)O content range between 4 to 14% in undiluted H sub(2) and in the H sub(2) content range between 14 to 96% in diluted H sub(2). The polarisation behaviour was analysed by fitting the measured data with the Nernst-type concentration equation and an empirical rate equation. The results have demonstrated that charge transfer process may play an very important role in the polarisation behaviour for H sub(2) oxidation reaction on Ni/Y-TZP cermet electrodes. The deviation of the calculated data according to the empirical rate equation from the measured polarisation data at high current densities and low H sub(2) contents indicates that the reaction is limited by at least two electrode processes.