Oxygen-coordinated MOF membrane facilitated construction of supported Co2P/CoP@C heterostructures for water electrolysis

Abstract

Integration of cobalt phosphides (Co₂P and CoP) in a carbon matrix shows great promise for developing high-performance catalysts for water electrolysis. Nevertheless, the controlled synthesis of these two phases with an effective interface, uniform dispersion, and a simplified synthesis process is still challenging. Herein, we proposed a strategy that involves pre-construction of the Co/CoO@C heterostructure followed by post-conversion by phosphorization to achieve the precise synthesis of the Co₂P/CoP@C heterostructure, which was realized by utilizing a MOF as the self-sacrificial template. The oxygen-coordinated MOF that shows advantages in building the Co/CoO heterostructure was employed in this work and grown into a high-quality membrane via cathodic electrodeposition on the graphite substrate (Gss). The obtained catalyst (Gss-Co₂P/CoP@C-800) requires 146 and 365 mV overpotentials to achieve a current density of 100 mA cm⁻² for the HER and OER, respectively, and 1.54 V to achieve a current density of 10 mA cm⁻² for water electrolysis. Beyond the significantly enhanced conductivity that originates from the robust interaction between the MOF and Gss, the establishment of an effective Co₂P/CoP interface also plays a pivotal role in contributing to the high performance of Gss-Co₂P/CoP@C-800. As revealed by density functional theory (DFT) calculations, the unique d-orbital electron distribution of Co₂P/CoP and the enhanced state density near the Fermi level facilitate its efficient electron transport and render the Co₂P/CoP heterostructure region a crucial active site for water electrolysis. This study will provide new insights into the rational design and construction of heterostructures based on MOFs for efficient and green energy conversions.