Enhancement of Palladium HOR Activity in Alkaline Conditions through Ceria Surface Doping

Abstract

Hydrogen oxidation reaction (HOR) electrocatalysis suffers from slow kinetics at the anode of alkaline exchange membrane fuel cells (AEMFCs). A series of Pd-CeO2-x catalyst was synthesized at low temperature by the decomposition of cerium ammonium nitrate (CAN) on Pd. This simple method yields palladium with sub-stoichiometric amorphous CeO2-x islands which nucleate and grow on the surface of Pd. The vertical growth is preferred: ceria on ceria vs. ceria on palladium as evidenced by the constant values of Pd electrochemical surface areas observed for all ceria contents. The HOR activity is enhanced compared to pristine Pd. At 0.1 V vs. RHE, the specific and mass activities could be increased by a factor of 100 and 50 respectively for the highest content ceria samples. These results show that high ceria doping is requested to activate the HOR activity of palladium in alkaline medium, which can be achieved by cerium ammonium nitrate low temperature decomposition.