Inlaying CoP/Ni2P/Fe2P triple heterostructure in MOF-derived carbon nanobox for robust oxygen evolution reaction

Water electrolysis is a promising strategy for hydrogen production but the major hindrance lies in the inherently sluggish kinetics of the anodic oxygen evolution reaction (OER). Here, a potential OER catalyst with hollow nanostructure is designed and fabricated, which is composed of highly dispersed mixed metal phosphide (CoP/Ni2P/Fe2P) nanoparticles encapsulated in the mesoporous carbon nanoboxes (denoted as CoNiFeP@C NBs). Beneficial from abundant CoP/Ni2P/Fe2P interfaces in these nanoparticles, the electronic structure would be optimized and thus decrease the catalytic energy barrier. Furthermore, the porous hollow carbon layer can not only promote electron and mass transport but also expose more active sites and prevent aggregation of active CoNiFeP units. Owing to the structural and compositional advantages including the suitable electronic structure, promoted charge and mass transfer capability, and massive electrochemical catalytic active sites, the optimized CoNiFeP@C NBs exhibit excellent electrocatalytic performance towards OER. Typically, an overpotential of 260 mV is achieved for CoNiFeP@C NBs at 10 mA cm−2 with a low Tafel slope of 65.5 mV dec−1, which is among the top values of the reported Co-based OER electrocatalysts and even outperform commercial RuO2. Impressive stability is also realized in alkaline electrolyte due to the protective carbon layer. This work paves the way for developing advanced OER catalyst towards high catalytic capability and remarkable stability.