Controlled Electrodeposition Synthesis of Co–Ni–P Film as a Flexible and Inexpensive Electrode for Efficient Overall Water Splitting

Synthesis of highly efficient and robust catalysts with earth-abundant resources for overall water splitting is essential for large-scale energy conversion processes. Herein, a series of highly active and inexpensive Co-Ni-P films were fabricated by a one-step constant current density electrodeposition method. These films were demonstrated to be efficient bifunctional catalysts for both H₂ and O₂ evolution reactions (HER and OER), while deposition time was deemed to be the crucial factor governing electrochemical performance. At the optimal deposition time, the obtained Co-Ni-P-2 catalyst performed remarkably for both HER and OER in alkaline media. In particular, it requires -103 mV overpotential for HER and 340 mV for OER to achieve the current density of 10 mA cm^-2, with corresponding Tafel slopes of 33 and 67 mV dec^-1. Moreover, it outperforms the Pt/C//RuO₂ catalyst and only needs -160 mV (430 mV) overpotential for HER (OER) to achieve 200 mA cm^-2 current density. Co-Ni-P electrodes were also conducted for the proof-of-concept exercise, which were proved to be flexible, stable, and efficient, further opening a new avenue for rapid synthesis of efficient, flexible catalysts for renewable energy resources.