Structure-Dependent Electrocatalytic Properties of
Cu<sub>2</sub>O Nanocrystals for Oxygen Reduction Reaction
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Abstract
Cu<sub>2</sub>O 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 Cu<sub>2</sub>O 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 Cu<sub>2</sub>O nanocrystals with both
{100} and {111} planes present are produced. The structure-dependent
electrocatalytic activity of Cu<sub>2</sub>O nanocrystals toward oxygen
reduction reaction (ORR) has been studied in alkaline electrolyte.
The electrocatalytic activity measured on Cu<sub>2</sub>O {100} is
higher than that on Cu<sub>2</sub>O {111}. In addition, the Cu<sub>2</sub>O nanocubes with dominant {100} crystal planes show the highest
four-electron selectivity (<i>n</i> = 3.7) and lowest peroxide
yield (15%) during the ORR. Kinetics analysis indicates that the ORR
mechanism on Cu<sub>2</sub>O nanocrystals is controlled simultaneously
by charge transfer and intermediate migration. The Cu<sub>2</sub>O
nanocrystals also show better methanol tolerance and durability for
ORR than the commercial Pt/C materials