Structure-Dependent Electrocatalytic Properties of Cu2O Nanocrystals for Oxygen Reduction Reaction

Cu2O nanocrystals with different morphologies are synthesized via a reductive solution route by controlling the reaction time and using different capping agents. Introducing poly(ethylene glycol) (PEG) leads to nearly monodispersed Cu2O nanocubes with 40 nm size and dominant {100} crystal planes. With prolonged reaction time, the nanocubes are truncated and transformed into sphere-like nanocrystals with more {111} planes exposed. In the presence of poly(vinyl pyrrolidone) (PVP), porous Cu2O nanocrystals with both {100} and {111} planes present are produced. The structuredependent electrocatalytic activity of Cu2O nanocrystals toward oxygen reduction reaction (ORR) has been studied in alkaline electrolyte. The electrocatalytic activity measured on Cu2O {100} is higher than that on Cu2O {111}. In addition, the Cu2O nanocubes with dominant {100} crystal planes show the highest four-electron selectivity (n = 3.7) and lowest peroxide yield (15%) during the ORR. Kinetics analysis indicates that the ORR mechanism on Cu2O nanocrystals is controlled simultaneously by charge transfer and intermediate migration. The Cu2O nanocrystals also show better methanol tolerance and durability for ORR than the commercial Pt/C materials.