Eutectic molten salt assisted synthesis of highly defective and flexible ruthenium oxide for efficient overall water splitting

Designing and synthesizing efficient bifunctional electrocatalysts is of great significance for the application of overall water splitting but remains a great challenge. Herein, we synthesized low-crystallinity ruthenium oxides via a facile, eutectic molten salt-assisted method at low temperatures. Specifically, the optimized low-crystallinity RuO2-250 nanosheets with a highly defective structure and better structural flexibility showed both higher acidic OER and alkaline HER activity than commercial counterparts, reaching as low as 210 mV and 52 mV overpotentials at the current density of 10 mA cm−2 respectively. In situ Raman spectroscopy was employed to reveal the structural flexibility on the RuO2 catalyst during HER, which could contribute to its high activity. Furthermore, an electrolyzer with RuO2-250 catalyst requires only 1.57 V and 1.66 V cell voltage to achieve a current density of 10 mA cm−2 for overall water splitting under alkaline and acidic conditions respectively. This work provides a facile strategy for efficient design and preparation of low-crystalline materials and offers a new insight into the kinetic process of the water-splitting on ruthenium oxide.