Fine Tuning of Torus-Shaped Mo-Doped NiP Nanorings for Enhanced Seawater Electrolysis.

Seawater, as one of nature's most plentiful resources, provides a virtually inexhaustible source for generating hydrogen via water electrolysis. Developing an efficient bifunctional electrocatalyst for direct seawater splitting is challenging but highly desirable. Herein, a donut-shaped Mo-doped NiP nanoring electrocatalyst is developed, which is promising for direct overall seawater splitting. The optimized MoNiP catalyst shows low overpotentials and Tafel slopes in addition to high turnover frequencies, mass activities, and exchange current densities. The MoNiP||MoNiP couple-based electrolyzer requires a cell voltage of only 1.45 V in 1.0 m KOH and 1.47 V in untreated alkaline real seawater electrolysis at 10 mA cm current density. Industrially required current densities of 500 and 1000 mA cm are achieved at record low voltages of 1.81 and 1.86 V, respectively, at 25 °C and 1.77 and 1.82 V, respectively, at 75 °C for overall alkaline seawater splitting. The catalyst exhibited long-term stability at 400 mA cm during alkaline seawater electrolysis. The synergy between Mo ions with multiple oxidation states and Ni ions, and nanoring morphology play a crucial role in increasing active sites for enhanced seawater dissociation. This work highlights the potential of Mo-doped NiP nanorings as unique catalysts for seawater electrolysis.