Co₂P–Ni₃S₂ Heterostructured Nanocrystals as Catalysts for\nUrea Electrooxidation\nand Urea-Assisted Water Splitting

Abstract

In order to realize efficient hydrogen production with\nlow energy\nconsumption, the urea oxidation reaction (UOR) is used as a substitute\nfor the oxygen evolution reaction (OER) to reduce the thermodynamic\npotential of water electrolysis. Highly efficient and stable nonprecious\nmetal electrocatalysts are desired to resolve the slow kinetics resulted\nfrom the six-electron transfer process inherent in UOR. Here, the\nheterostructured nanocrystals of Co₂P–Ni₃S₂ were constructed through deposition of Ni salt on acetylene\nblack coated with CoP species (Co₂P–Ni₃S₂/C) and subsequent vulcanization. Compared with single\ncomponent CoP/C and Ni₃S₂/C, the Co₂P–Ni₃S₂/C with optimal ratio of Co₂P and Ni₃S₂ shows lower potential (1.338\nV) to reach 10 mA·cm^–2, which also realizes\ngood long-term stability for nearly 100 h in chronoamperometry test.\nThe X-ray photoelectron spectroscopy and UOR results together revealed\nthat Ni³⁺ is the main site to form active intermediates,\nwhich is formed by the electron transfer from Ni₃S₂ to Co₂P through a heterostructured interface.\nInspired by the excellent UOR activity of Co₂P–Ni₃S₂/C, as an anode in electrolyte for hydrogen evolution\nthrough urea-assisted water splitting, the current density of 10 mA·cm^–2 can be achieved at a potential of only 1.389 V. Therefore,\nthe construction of two component heterostructure is conducive to\nelectron transfer and active site regulation, so as to realize the\ndevelopment of effective UOR catalyst and promote the UOR application\nfor energy-saving hydrogen production.