Well-defined hierarchical teddy bear sunflower-like NiCoO electrocatalyst for superior water oxidation

• Published in: Sustainable energy & fuels 2022-12, Vol.6 (24), p.5491-552
• Main Authors: Bodhankar, Pradnya M, Dhawale, Dattatray S, Giddey, Sarbjit, Kumar, Ravi, Sarawade, Pradip B
• Format: Article
• ISSN: 2398-4902
• DOI: 10.1039/d2se01111e

The development of a robust and efficient electrocatalyst for water oxidation is challenging due to the large overpotential requirement to transfer four electrons. Herein, a novel spinel-type hierarchical teddy bear sunflower-like NiCo 2 O 4 electrocatalyst was synthesized through the facile solvothermal process and evaluated for the challenging and demanding oxygen evolution reaction (OER) in the water electrolysis process. The teddy bear sunflower-like NiCo 2 O 4 supported on nickel foam (NF) delivers a current density of 50 mA cm −2 at a small water oxidation overpotential ( η 50 = 319 mV) which is significantly lower than that of the corresponding spherical NiO/NF ( η 50 = 338 mV), and sea-urchin like Co 3 O 4 /NF ( η 50 = 357 mV). A large specific and electroactive surface area, as well as a high TOF value exhibited by the hierarchical teddy bear sunflower-like NiCo 2 O 4 electrocatalyst, demonstrates the potential of NiCo 2 O 4 to catalyze the water oxidation reaction efficiently. The impact of the near-Fermi-level d-orbital states in NiCo 2 O 4 electrocatalyst for boosting OER activity was unveiled by the density functional theory calculation. The stable performance even after 16 h and high catalyst utilization of the hierarchical teddy bear sunflower-like NiCo 2 O 4 through the OER indicates that the catalyst is highly suitable for the large-scale water oxidation process. Transition metal oxides were fabricated by a facile solvothermal route. The hierarchical NiCo 2 O 4 electrocatalyst exhibited enhanced water oxidation performance due to the unique teddy bear sunflower-like morphology.