Controllable synthesis of a self-assembled ultralow Ru, Ni-doped Fe2O3 lily as a bifunctional electrocatalyst for large-current-density alkaline seawater electrolysis

Highly efficient and stable bifunctional electrocatalysts that can be used for large-current-density electrolysis of alkaline seawater are highly desirable for carbon-neutral economies, but their facile and controllable synthesis remains a challenge. Here, self-assembled ultralow Ru, Ni-doped Fe2O3 with a lily shaped morphology was synthesized on iron foam (RuNi-Fe2O3/IF) via a facile one-step hydrothermal process, in which the intact lily shaped RuNi-Fe2O3/IF was obtained by adjusting the ratio of Ru/Ni. Benefitting from the Ru/Ni chemical substitution, the as-synthesized RuNi-Fe2O3/IF can act as free-standing dual-function electrodes that are applied to electrocatalysis for the hydrogen evolution (HER) and oxygen evolution reactions (OER) in 1.0 mol L−1 KOH, requiring an overpotential of 75.0 mV to drive 100 mA cm−2 for HER and 329.0 mV for OER. Moreover, the overall water splitting catalyzed by RuNi-Fe2O3/IF only demands ultralow cell voltages of 1.66 and 1.73 V to drive 100 mA cm−2 in 1.0 mol L−1 KOH and 1.0 mol L−1 KOH seawater electrolytes, respectively. The electrodes show remarkable long-term durability, maintaining current densities exceeding 100 mA cm−2 for more than 100 h and thus outperforming the two-electrode system composed of noble catalysts. This work provides an efficient, economical method to synthesize self-standing bifunctional electrodes for large-current-density alkaline seawater electrolysis, which is of significant importance for ecological protection and energy exploitation.