Electrospun Ni₃(BO₃)₂–NiO Heterointerface for Boosted Overall Water Splitting and Solar-to-Hydrogen Conversion

The development of low-cost, long-lasting, and high-performance bifunctional electrocatalysts is needed for effective electrochemical water splitting. Herein, an interface-boration engineering strategy was used to synthesize heterostructured nickel borate–nickel oxide (Ni3(BO3)2–NiO) by using the electrospinning-incineration process, which exhibited an unprecedentedly high electrocatalytic activity in alkaline media. The Ni3(BO3)2–NiO electrode showed ultralow oxygen evolution reaction and hydrogen evolution reaction overpotentials of 261 and 150 mV, respectively, to achieve 10 mA cm–2. For Ni3(BO3)2–NiO/NF-assisted alkaline as well as solar-driven electrolyzers, a low cell voltage of 1.60 V was needed to drive 10 mA cm–2 and their catalytic activity was maintained for 40 h, indicating significant potential for their use in water-splitting. Ni3(BO3)2–NiO was employed to generate H2 effectively by consuming a power of 732.33 LH2 kW h–1 lower than that of cNiO (835 LH2 kW h–1). The enhanced adsorption of oxygen-containing Lewis base intermediates on Ni3(BO3)2–NiO by Lewis acid–base interactions boosted the catalytic performance. This work provides a newer direction toward the rational engineering of the metal borate–metal oxide heterostructure with excellent intrinsic characteristics for energy applications, upscaled to industrial-scale H2 production due to production simplicity.