Oxidation of methane on a Au + SrFeO3−δ//YSZ electrode characterised by mass spectroscopy and 18O2 pulses

A solid state electrochemical reactor is described in which reactants can be oxidised at high temperatures over an anode/catalyst using co-fed oxygen gas as well as electrochemically supplied oxygen. The setup permits injection of isotopic pulses in the reactant streams. The composition and isotopic distribution in the products are recorded with a quadrupole mass spectrometer. The use of the system is exemplified by oxidation of methane over a Au + SrFeO_3?δ//YSZ anode at 800–850°C. Pulses of ¹⁸O₂ in the stream of co-fed O₂ were used to study the reactivity and products of gaseous oxygen as distinguished from the electrochemically supplied oxygen. The results indicate that the anode used supports oxygen pumping, but is only moderately active for methane oxidation. The products are mainly CO and CO₂. The content of ¹⁸O in the products is low, indicating that methane oxidation takes place by ¹⁶O-rich lattice oxygen. In comparison, a reference Au//YSZ electrode was found to be a slower anode for oxygen pumping, but a better catalyst for the reaction between CH₄ and gaseous O₂, seemingly involving adsorbed oxygen.