Nickel iron phosphide ultrathin nanosheets anchored on nitrogen-doped carbon nanoflake arrays as bifunctional catalyst for efficient overall water splitting

Development of high-efficiency and Earth-abundant bifunctional catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is desirable to realize an efficient overall water splitting process. In this work, a highly active and durable bifunctional catalyst of coral-like nickel iron phosphide ultrathin nanosheets anchored on nitrogen-doped carbon nanoflake arrays on carbon cloth (CC-NC-NiFeP) was fabricated by using metal organic framework (MOF) derived nitrogen-doped carbon nanoflake arrays as catalyst supports. Combined with the electronic structure regulation by bimetallic phosphides and using three dimensional nitrogen-doped carbon nanoflakes as supports that provide a large specific surface area as well as fast charge/mass transport, the as-prepared CC-NC-NiFeP yields excellent bifunctional electrocatalytic activity in both the HER and OER in an alkaline medium with an overpotential of 94 mV and 145 mV to reach a current density of 10 mA cm−2, respectively. Meanwhile, the CC-NC-NiFeP can behave as both a cathode and anode simultaneously for overall water splitting, achieving a low cell voltage of 1.54 V to reach a current density of 10 mA cm−2, which outperforms that of most of the non-precious metal based catalysts.