Developing
bifunctional electrocatalysts for oxygen evolution reaction
(OER) and hydrogen evolution reaction (HER) toward overall water splitting
with high efficiency and robust durability is highly desirable but
very challenging. Herein, we report a highly efficient and robust
bifunctional electrocatalyst for overall water splitting based on
Co@Ir core–shell nanoparticles encapsulated in nitrogen-doped
porous carbon derived from metal–organic frameworks. The series
of Co@Ir/NC-x samples were prepared through a galvanic
replacement of IrCl3 with Co/NC, which was obtained by
calcination of zeolitic imidazolate framework 67 (ZIF-67). In the
electrocatalytic characterizations toward OER and HER, Co@Ir/NC-10%
exhibited the best performance among the series, with an overpotential
of 280 mV at a current density of 10 mA cm–2 for
OER, superior to the benchmark IrO2 catalyst, and an overpotential
of −121 mV at a current density of 10 mA cm–2 for HER in 1 M KOH. Moreover, Co@Ir/NC-10% also demonstrated markedly
higher long-term stability than IrO2 for OER and superior
long-term durability than Pt/C for HER. Finally, the overall water
splitting catalyzed by the series of composites was explored and visually
observed.
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