Highly active electron-affinity for ultra-low barrier for alkaline ORR in Pd₃Cu

Abstract

The call for clean and sustainable energy raises tremendous research interests in fuel cells. However, the efficiency of low-temperature fuel cell is heavily impeded by the sluggish cathode reaction, the oxygen reduction reaction (ORR), even with the state-of-the-art Pt catalyst. Advanced ORR catalysts with better activity and lower expense are of great research interest for the development of clean energy. Pd₃Cu alloy is one of the potential non-Pt based ORR catalysts owing to its excellent balance between activity, long term stability and cost. Alkaline ORR so far receives much less theoretical study interest although alkaline medium is found to be beneficial to ORR in many aspects. Aimed to gain more theoretical insight into the reactivity of Pd₃Cu and mechanistic information of alkaline ORR, mechanism study was conducted by applying DFT calculations. The electron-affinitive of Pd₃Cu has been activated by the d-d coupling between Pd and Cu. Adsorption strengths of ORR intermediates, and especially their preferences to various adsorption sites were carefully examined and discussed. The adsorption analysis prompted us a possible ORR mechanism on Pd₃Cu surface. Reaction pathway calculations based on this mechanism unveiled an energetically favorable reaction path with an ultra-low overpotential. This theoretical support supplied a new direction for the reactivity of catalyst.