Self-supporting CoP-C nanosheet arrays derived from a metal–organic framework as synergistic catalysts for efficient water splitting

Abstract

Here, a new strategy that combines accessible active sites and multiphase synergy in a simple process is developed for constructing bifunctional electrocatalysts toward overall water splitting. By using metal–organic framework (MOF) nanosheets hydrothermally grown on pre-oxidized nickel foam (denoted by Co₂(OH)₂(BDC)/NiO/NF) as a precursor, two novel heterogeneous nanosheet arrays including a cobalt phosphide nanoparticle embedded carbon nanotube nanosheet array supported by phosphorized nickel foam (denoted by CoP-CNT/Ni₂P/NF) and a cobalt phosphide nanorod decorated carbon nanosheet array supported by oxidized nickel foam (denoted by CoP-C/NiO/NF) are prepared. Both were confirmed to be highly efficient for hydrogen and oxygen evolution reactions. In particular, CoP-C/NiO/NF exhibits higher catalytic activity toward the hydrogen evolution reaction (η₁₀₀ = −131 mV), promoted by the synergy of oxidized nickel foam. CoP-CNT/Ni₂P/NF performs better in the oxygen evolution reaction (η₅₀ = 301 mV), benefiting mainly from its improved electrochemically active surface area. The two catalysts match well in overall water splitting with satisfactory activity (η₁₀ = 1.57 V) and stability when directly applied in a two-electrode cell. This method will bring new inspiration to maximize the electrocatalytic efficiency of MOF-derived catalysts for energy conversion applications in the future.