Construction of 3D porous MXene-based multiple heterojunction catalyst for efficient water oxidation reaction at high current density

The rational construction of efficient and stable noble-metal-free oxygen evolution reaction (OER) electrocatalysts that work under a industrial-level current density in alkaline environments are urgently needed and challenging. Here we propose a Ti3C2Tx MXene-based synthetic method for constructing Co2P/Ti3C2Tx, Fe2P/ Ti3C2Tx and Co2P/Fe2P multiple heterojunctions (labeled as CoFe-P@MXene) by using strong electrostatic adsorption-electrodeposition-low temperature phosphorization. The obtained CoFe-P@MXene possesses abundant three-dimensional porous structures and inherits the high conductivity of MXene. Experiment results and density functional theory calculations indicate that the formation of multi-heterojunctions between transition metal phosphides and Ti3C2Tx MXene can modulate the electronic structure of active sites Co and Fe, alter the dband center, and thereby optimize the adsorption energy of oxygen-containing intermediates on the active sites. Additionally, the excellent nanoporous structure constructed promotes the penetration of the electrolyte and the release of the product. Thus, The CoFe-P@MXene-based electrocatalyst exhibits excellent OER catalytic performance at both low current densities and industrial-scale current densities, with remarkable low overpotentials of 215 mV at 20 mA cm-2 and 328 mV at 1000 mA cm-2 in 1 M KOH solution, respectively. Furthermore, it exhibits good stability, capable of operating stably for 100 h at a current density of 100 mA cm-2. This work