Unleashing the Potential of Electrospun Ni@NiO/CNFs toward Overall Water Splitting at High Current Density and Solar-to-Hydrogen Conversion Efficiency

The rational design of inexpensive, proficient electrocatalysts for water splitting remains challenging in commercial water electrolyzer systems. Herein, we report an electrospinning–carbonization approach to develop an electrocatalyst containing more active sites, high conductivity, and a large surface area to ameliorate multifunctional performance, together with long durability. The synergism of 3Ni@NiO/CNFs, highly conductive NF, porous graphite carbon, and effective contact between nanofibers with coral-like morphology and NF leads to outstanding catalytic performance. 3Ni@NiO/CNFs shows HER and OER overpotentials of 125 and 151 mV with Tafel slopes of 49.5 and 36 mV dec^–1, respectively. The kinetic study through operando EIS reveals enhanced OER kinetics, less resistance, and more conductivity of 3Ni@NiO/CNFs. The improved OER activity was further sustained by Bode analysis at various potentials. The temperature-dependent analysis inferred that 3Ni@NiO/CNFs showed lower activation energy (3.29 kJ mol^–1) than 2Ni@NiO/C (5.54 kJ mol^–1), 4Ni@NiO/C (6.71 kJ mol^–1), and NiO/C (11.77 kJ mol^–1). The higher rate constant derived from the Trumpet plot revealed that 3Ni@NiO/CNFs at various pH values inferred rapid formation of O₂ bubbles. The 3Ni@NiO/CNFs-based electrolyzer produced H₂ at 1.58 V to reach 150 mA cm^–2, and the high performance was sustained over 24 h, which is promising for industrial applications. This research provides an effective strategy that can be extended to develop a wider range of electrodes for potential renewable electrochemical energy conversion.