A universal approach of constructing two-dimensional transition metal phosphide heterostructures and the superior performance in (urea-rich) water electrolysis

Abstract

Transition metal phosphides have consistently shown excellent performance in electrocatalytic hydrogen production, but challenges remain in the development of efficient diverse catalysts. We designed a superhydrophilic two-dimensional (2D) TMP heterostructure with generalized approach. The phosphidation of layered double hydroxides (LDHs) with controlled exfoliation yielded multiple phosphide heterostructures (Ni2P/CoP, CoP/Fe2P and Ni2P/Fe2P) of less than 5 nm, the thinnest phosphide sheet up to date. All 2D phosphide heterojunctions are superhydrophilic (θw=10°), which is more favourable for bubble desorption. Both XPS and XANES, among other characterizations, indicated the much stronger electron-donating effect of metal sites comparing with bulk analogues, resulting in the formation of highly electron-rich P sites for facilitated proton adsorption. 2D Ni2P/CoP showed superior activity (η10=46.1 mV) for hydrogen production. Interestingly, 2D Ni2P/CoP was also highly active (η50=112.1 mV) for urea oxidation. This work demonstrates a versatile method for building superhydrophilic 2D phosphides, opening up exciting opportunities for multifunctional applications.