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.