Ultrafine bimetallic phosphide nanoparticles embedded in carbon nanosheets: two-dimensional metal–organic framework-derived non-noble electrocatalysts for the highly efficient oxygen evolution reaction

Abstract

The development of noble-metal-free highly efficient oxygen evolution reaction (OER) catalysts is crucial for electrochemical energy technology but still challenging. Herein, ultrafine cobalt-iron bimetallic phosphide nanoparticles embedded in carbon nanosheets are synthesized using two-dimensional (2D) metal-organic frameworks (MOFs) as the precursor. The 2D morphology of the carbon matrix and the ultrafine character of Co1-xFexP nanoparticles make contributions to OER catalysis. By optimizing the molar ratio of Co/Fe atoms in MOFs, a series of Co1-xFexP/C catalysts are prepared. Among them, Co0.7Fe0.3P/C shows the best OER performance with an overpotential of 270 mV at a current density of 10 mA cm-2 and an ultralow Tafel slope of 27 mV dec-1 in an alkaline electrolyte. Moderate iron doping preserves the catalytically active sites and improves the ability to be oxidized of the surface of Co1-xFexP nanoparticles, and thus enhances the OER activity. Our finding paves the way to the rational design of the morphology and chemical composition of OER catalysts.