2D ZIF-67 derived V-doped CoP/NC nanosheets as efficient electrocatalysts for water splitting

The water splitting reaction to produce hydrogen is one of the most promising and cleanest ways to resolve the energy crisis. However, the preparation of efficient and stable electrocatalysts with low-cost remains challenging. In this work, the noble-metal free N-doped carbon (NC) incorporated V-doped cobalt phosphide (CoP) nanosheets on nickel foam (NF) (denoted as V-CoP-NC/NF) are prepared by using two-dimension zeolitic imidazolate framework (ZIF-67) as precursor followed by NaVO3 etching/doping and phosphorization. The V doping is found to be essential to enhance the electrochemical performance of CoP for water splitting. In particular, V5-CoP-NC/NF (V5 represents the concentration of NaVO3 for etching/doping is 5 mM) exhibits the highest hydrogen evolution performance in alkaline electrolyte, to achieve a current density of 10 mA cm−2, an overpotential of 119 mV (vs reversible hydrogen electrode) is required. X-ray photoelectron spectroscopy results show that the V doping significantly altered the binding energies of Co 2p, P 2p and N 1 s in V5-CoP-NC/NF, which is believed to facilitate the adsorption and dissociation of intermediates and accelerate interfacial charge transfer during hydrogen evolution reaction process. This work provides a simple route to prepare heteroatom doped CoP self-standing electrocatalysts for water splitting.