Surface engineering of MOFs as a route to cobalt phosphide electrocatalysts for efficient oxygen evolution reaction

Exploring efficient routes for the fabrication of promising transition metal phosphides electrocatalysts towards oxygen evolution reaction (OER) has become a top priority in the field of water-splitting technology. Herein, a cobalt phosphide (CoxP) electrocatalyst composed of high-density small Co2P/CoP nanoparticles homogeneously embedded in one-dimensional (1-D) carbon has been synthesized by using surface-engineered cobalt benzimidazole zeolitic imidazolate framework (ZIF-9) rods as a precursor. The surface engineering strategy employs melamine to modify ZIF-9 by constructing robust Co coordination sites on ZIF-9 surface through the coordination of Co with nitrogen donor sites in melamine. DFT calculations indicate that the surface engineering of ZIF-9 triggered by melamine occurs not only at coordinatively unsaturated Co sites but also at coordinatively saturated Co sites via a thermodynamically favored ligand exchange process between benzimidazole in ZIF-9 and melamine. Subsequent reaction with red phosphorus at high temperature affords a 1-D material having highdensity of CoxP reactive sites and facilitated charge/mass transport, leading to an outstanding electrocatalytic activity for OER-even comparable to commercial RuO2-and excellent electrochemical durability. This scalable strategy involving surface engineering of MOFs represents a breakthrough in the synthesis of efficient OER electrocatalysts in water electrolyzer application.

Automated summary

This paper reports a method for synthesizing surface-engineered cobalt phosphide (CoxP) electrocatalyst, which has high-density reactive sites and facilitated charge/mass transport, leading to outstanding catalytic activity and excellent electrochemical durability towards oxygen evolution reaction.