Microwave-Assisted Template-Free Synthesis of Ni₃(BO₃)₂(NOB) Hierarchical Nanoflowers for Electrocatalytic Oxygen Evolution

The construction of cost-effective, efficient, and sustainable catalytic systems for electrocatalytic hydrogen generation by water splitting is extremely important for future fuels globally. Herein, we have prepared nickel orthoborate (NOB) via simultaneous oxidation and reduction of nickel precursors and studied their role in oxygen evolution reaction (OER) for water electrolysis. In addition, the specific role of microwave irradiation and conventional stirring in the formation of NOB was also investigated with comparative assessment of their catalytic ability in electrochemical water splitting. It was found that NOB nanoflowers prepared via microwave irradiation exhibited better OER electrocatalyst than the ones prepared by conventional heating. Interestingly, the NOB nanoflowers outperformed the commercial NiO nanopowder under the identical experimental conditions in catalyzing OER. Morphological hierarchy and high Brunauer-Emmett-Teller specific surface area were attributed for their enhanced OER activity. A long run of 6 h chronopotentiometry analysis showed a negligible degradation in activity signified the high stability and endurance of NOB nanoflowers. The numbers of merits from the electrochemical characterizations revealed that NOB nanoflowers could be an alternate, efficient, and abundant OER electrocatalyst for bulk water electrolysis.