In situ formation of NiCoP@phosphate nanocages as an efficient bifunctional electrocatalyst for overall water splitting

The construction of bifunctional highly active and durable electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is attractive and challenging for overall water splitting. Herein, we reported a Ni–Co phosphide @phosphate nanocages (NCPP NCs) catalyst prepared by phosphorization of Ni–Co layered double hydroxide (Ni–Co LDH) with in-situ formation of phosphate. The NCPP NCs exhibited an improved wettability with a contact angle of approximately 0° compared with those of Ni–Co LDH (52°) and nickel-cobalt phosphides (NiCoP) (99°). NCPP NCs have been used for enhancing the water-splitting efficiency, and it only required the overpotentials of 291 mV and 140 mV for OER and HER in 0.1 M KOH to achieve the current densities of 10 mA cm−2, respectively. Impressively, the overpotential of NCPP NCs decreased by 42 mV and 64 mV at 10 mA cm−2 for OER in comparison with those of RuO2 and NiCoP (without phosphate phase). Consequently, NCPP NCs, as the bifunctional catalysts, displayed an outstanding performance for the whole water-splitting process with a small potential of 1.60 V at 10 mA cm−2 and long-term stability. These performances enabled this material to be a promising catalyst for overall water electrolysis.