Amorphous Iron BorateNanosheet as Durable BifunctionalElectrocatalyst to Accelerate Overall Water Splitting Activity

Low-cost and highly stable bifunctional electrocatalysts are in high demand for the development of energy conversion devices. This study presents amorphous iron borate (FeBo/NF), a bifunctional electrocatalyst that can enhance the performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), simultaneously. The small nanoplates of iron borate were self-assembled into a nanosheet on a nickel foam substrate through a facile dip coating and drop casting by a chemical reduction method, which possesses abundant active sites for rapid charge transfer. The FeBo/NF electrode showed an ultralow overpotential of 244 mV (36 mV dec^–1) and 157 mV (84 mV dec^–1) for OER and HER, respectively, to achieve 10 mA cm^–2 and its catalytic activity being maintained for 80 h, indicating significant potential for its use in water splitting. The kinetic analysis using EIS analysis reveals significantly improved OER kinetics of FeBo/NF than its counterparts. The temperature-dependent analyses inferred that FeBo/NF showed a lower activation energy of 4.56 kJ/mol to promote the kinetics. Consequently, the overall water-splitting cell with FeBo/NF as both the anode and cathode can be driven at 1.64 V with 3.4% potential loss. The enhanced adsorption of oxygen-containing Lewis base intermediates on FeBo/NF by Lewis acid–base interactions boosted the intrinsic catalytic performance. This work path newer direction toward rational engineering of metal borate with excellent intrinsic characteristics for energy applications upscaled to industrial scale H₂ production due to production simplicity.