Solid Electrolyte Aided Study of the Oxidation of Hydrogen on Copper and Copper Oxide Catalysts

Abstract

The catalytic oxidation of hydrogen on copper and copper oxide surfaces was studied in a solid electrolyte cell at 250-365°C and 1 atm. The technique of solid electrolyte potentiometry (SEP) was used to monitor the thermodynamic activity of oxygen adsorbed on the catalyst surface during reaction. The oxygen activity value resulted from a steady-state mass balance of oxygen on the catalyst surface and under specific conditions, was several orders of magnitude lower than the gas-phase oxygen partial pressure. The stable phase of the solid was usually CuO and less frequently Cu 2O or metallic Cu. The reaction on reduced (Cu metal) surface exhibited much higher rates than on either oxide, while between the latter two, CuO was the least active surface. The rate-determining step on CuO was the surface reaction between atomically adsorbed hydrogen and oxygen. A kinetic model that quantitatively explains both kinetic and potentiometric measurements in the CuO regime is presented.