Methane Electro-Oxidation on a Y0.20Ti0.18Zr0.62O1.90 Anode in a High Temperature Solid Oxide Fuel Cell

Abstract

A high temperature solid oxide fuel cell has been operated in low humidity (3 % H2O) methane using Y0.20Ti0.18Zr0.62O1.90 (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 °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 Ω cm2 to 10.14 Ω cm2 between open and short (Ecell = 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.