MOF Template-Derived Carbon Shell-Embedded CoP Hierarchical Nanosheet as Bifunctional Catalyst for Overall Water Splitting

The design of earth-abundant and highly efficient bifunctional electrocatalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is crucial for hydrogen production through overall water splitting. Herein, we report a novel nanostructure consisting of vertically oriented CoP hierarchical nanosheet arrays with in situ-assembled carbon skeletons on a Ti foil electrode. The novel Zeolitic Imidazolate Framework-67 (ZIF-67) template-derived hierarchical nanosheet architecture effectively improved electrical conductivity, facilitated electrolyte transport, and increased the exposure of the active sites. The obtained bifunctional hybrid exhibited a low overpotential of 72 mV at 10 mA cm−2and a small Tafel slope of 65 mV dec−1for HER, and an improved overpotential of 329 mV and a Tafel slope of 107 mV dec−1for OER. Furthermore, the assembled C@CoP||C@CoP electrolyzer showed excellent overall water splitting performance (1.63 V) at a current density of 10 mA cm−2and superior durability. This work provides a structure engineering strategy for metal–organic framework (MOF) template-derived hybrids with outstanding electrocatalytic performance.Keywords:transition metal phosphide;metal–organic framework;hierarchical nanosheet;overall water splitting