Oxygen-Coordinated MOF Membrane Facilitated Construction of Supported Co2P/CoP@C Heterostructures for Water Electrolysis

Abstract

Integration of cobalt phosphides (Co2P and CoP) in carbon matrix shows great promise for developing high-performance catalysts for water electrolysis. Nevertheless, the control synthesis of these two phases with effective interface, uniform dispersion, and simplified synthesis process are still challenging. Herein, we proposed a strategy that involves pre-construction of Co/CoO@C heterostructure followed by post-conversion by phosphorization to achieve the precise synthesis of Co2P/CoP@C heterostructure, which was realized by utilizing MOF as the self-sacrificial template. The oxygen-coordinated MOF that shows advantages in building Co/CoO heterostructure and further conversion to phosphides 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 reach a current density of 100 mA cm-2 for HER and OER respectively, and 1.54 V to reach current density of 10 mA cm-2 for water electrolysis. Beyond the significantly enhanced conductivity that originates from the robust interaction between MOF and Gss, the establishment of 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 renders the Co2P/CoP heterostructure region a crucial active site for water electrolysis. This study would provide new insights into the rational design and construction of heterostructures based on MOFs for efficient and green energy conversions.