Construction of CoP/Co₂P heterojunctions on hollow carbon rods as efficient bifunctional electrocatalysts for overall water splitting

Abstract

The development of efficient and durable bifunctional electrocatalysts for overall water splitting is crucial for sustainable hydrogen production. In this work, a nitrogen-rich porous Co-MOF precursor was employed to synthesize heterostructured CoP/Co₂P catalysts supported on nitrogen-phosphorus co-doped hollow carbon nanorods (CoP/Co₂P@NC-T-xP). The interfacial coupling between CoP and Co₂P within the catalyst facilitates rapid electron transfer and optimizes the adsorption/desorption behavior of reaction intermediates, thereby enhancing the catalytic reaction kinetics for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Density functional theory (DFT) calculations reveal that the interfacial effect in the CoP/Co₂P heterojunction can modulate the catalyst’s electronic structure, thereby optimizing the Gibbs free energy for hydrogen adsorption (ΔG_H*). Furthermore, the metal-organic framework (MOF)-derived hollow carbon support promotes electrolyte infiltration, exposes abundant active sites, and shortens the mass transport pathways for reactive species. Electrochemically, the CoP/Co₂P@NC-400-10P catalyst exhibits outstanding performance in alkaline media, achieving overpotentials as low as 127.6 mV for HER and 279.4 mV for OER at a current density of 10 mA/cm². Moreover, a CoP/Co₂P@NC-400-10P||CoP/Co₂P@NC-400-10P electrolyzer requires only 1.73 V to deliver a current density of 100 mA/cm² for overall water splitting and demonstrates excellent durability over 100 h without significant voltage degradation. This work highlights the effective synergy between the MOF-derived heterojunction structure and the hollow carbon architecture in designing highly efficient electrocatalysts, and provides a valuable reference for the development of other low-cost, high-activity bifunctional electrocatalysts.

Graphical abstract

Keywords

heterojunction interface / bifunctional catalysts / water splitting / hydrogen evolution reaction (HER) / oxygen evolution reaction (OER)

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