Bifunctional self-assembled Ni0.7Co0.3P nanoflowers for efficient electrochemical water splitting in alkaline media

Abstract

The development of efficient and stable non-precious metal-based bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is central for water splitting in the practical application. In this paper, the flower-like Ni0.7Co0.3P architecture consisted of self-assembled nanosheets with numerous holes was fabricated by a facile hydrothermal–phosphorization method. The nanoflowers with open architecture and rippled nanosheets with numerous holes can enlarge the efficient reaction interface area and facilitate the mass transport, boosting the efficiency for water splitting. The obtained Ni0.7Co0.3P electrocatalyst exhibits outstanding electrocatalytic performances for both OER and HER in alkaline media with low overpotentials of 230 and 105 mV at 10 mA cm−2, as well as small Tafel slopes of 78 and 58 mV dec−1, respectively. Moreover, the resultant catalyst demonstrates excellent durability, maintaining a steady overpotential at 10 mA cm−2 after testing for 25 h toward both OER and HER. The exceptional electrocatalytic properties of Ni0.7Co0.3P nanoflowers can be explained by the following two points: (i) the exposure of abundant electroactive sites in the 3D flower-like architectures assembly by nanosheets with numerous defective holes, and (ii) the promoted kinetics of OER and HER achieved by the partial Co substitution and moderate electron delocalization.