Palladium–Copper Bimetallic Nanoparticles Loaded on Carbon Black for Oxygen Reduction and Zinc–Air Batteries

Increasing the exposed active sites is a pursuit of great importance for electrocatalysis. Here, an oxygen reduction reaction (ORR) electrocatalyst of palladium–copper (Pd–Cu) bimetallic nanoparticles loaded on carbon black (Pd–Cu/C) is prepared by a simple reduction of silicon–hydrogen bonds at room temperature. An unusual phenomenon is observed where the half-wave potential of the Pd–Cu/C catalyst for the oxygen reduction reaction is positively shifted from 0.840 to 0.880 V and the onset potential is positively shifted from 0.980 to 1.010 V during continuous 500 cycles of cyclic voltammetry scanning. After the self-activation process, the electrochemical active surface area (ECSA) of Pd in the Pd–Cu/C catalyst increases by about 31.7% (from 21.79 to 28.69 m2·g–1). Meanwhile, the inductively coupled plasma mass spectrometry test confirms that the content of Cu decreased by 50%. The catalysts also maintain good stability. When they are assembled into a zinc–air battery as a cathode catalyst, the battery shows an open-circuit voltage of 1.43 V. The power density reaches 219 mW·cm–2, and the durability is maintained to be 40 h. Cu dissolution provides more catalytic active sites and enhances the catalytic activity and stability. Such a self-activation effect can also be adopted in other bimetal or alloy catalytic systems.