The pH-dependant stabilization and interphase coupling of Pd species during alcohol oxidation

Abstract Heterogeneous catalysts consistently suffer from the leaching of active components into the fluid phase, causing loss in activity and lifetime. Here we demonstrate, exemplified with the thermocatalytic oxidation of 1,2-propanediol, a metal stabilization mechanism arising from electrochemical coupling of half reactions between physically separated carbon-supported Au and Pd catalysts. When electrochemically coupled, polarization of each metal to an operating mixed potential occurs as a function of the Au:Pd molar ratio that, at pH 9–10, significantly reduces Pd leaching. At pH 14, where this stabilization no longer holds, we clearly show that an active redox mechanism can exist between disparate catalytic species in the liquid and solid phase, and that this leads to the cycling of Pd speciation as well as considerable enhancements in the rate of oxidation.