Experimental Investigation of Carbon Deposition on a Ni/YSZ Anode of Solid Oxide Fuel Cell

Abstract

The carbon depositions on a Ni/YSZ anode of solid oxide fuel cell (SOFC) with different gas ratios of CH4+H2 and CO+CO2 gas mixtures were experimentally studied. The carbon deposition rates for methane cracking and CO disproportionation were acquired at temperatures from 873K to 1073K. The kinetic models of the methane cracking and CO disproportionation reactions were verified by the experimental data. The results show that both the reactions of methane cracking and CO disproportionation are not solely related with the temperature or the gas mixture ratios. A kinetic model based on the elementary steps suggested by Alstrup fits well to the experimental data of methane cracking at the temperature range of 873-1073K. By assuming C-O bond cleavage as the rate-limiting step, a kinetic model of carbon deposition was derived for the CO disproportionation reaction and it is well fit to the experiments at temperature 973-1073K. The experimental results also show that the carbon deposition in the SOFCs is mainly due to the methane cracking reaction. Comparatively, the carbon deposition from CO disproportionation reaction is negligible.