Controlled tuning the morphology of CoNiP catalysts with ultra-high activity for water splitting at large current densities in alkaline medium

Developing efficient, robust and low-cost bifunctional electrocatalyst with high activity and strong stability for overall water splitting has received extensive attention. Herein, a 3D porous nanoflower spherical catalyst Co6Ni4P/NF was synthesized by one-step pulse electrodeposition, and regulating morphology of nanostructure through tuning the ratio of Co2+ and Ni2+ in the planting bath. This morphology combined the superiorities of the 3D spherical and the 2D film structures, which not only retain a large specific surface area, but also ensure the high-density of active sites. The as-prepared Co6Ni4P/NF only needs overpotentials of 336 mV and 373 mV to reach the large current density 1000 mA cm-2 for HER and OER and shows long-term stability under alkaline condition. Meanwhile, to drive overall water splitting requires only the cell voltages of 1.56 V, 1.61 V and 2.19 V to reach 50, 100 and 1000 mA cm- 2. In this work, the influence of catalyst morphology is discussed specifically, and we find the nanoflower spherical Co6Ni4P/NF presents the best performance compared with nanospheres and nanosheets in overall water splitting process, which is appealing to practical application at large current condition.