Nickel induced electronic structural regulation of cobalt hydroxide for enhanced water oxidation

Abstract

Cobalt-based hydroxides have been extensively investigated as catalysts for water oxidation. It is well known that the addition of Fe can dramatically enhance the oxygen evolution reaction (OER) performance of Co-based materials; however, the role of Ni doping in Co-based materials for the OER is not well understood, though a similar enhancement was anticipated. In the present study, hexagonal Co(OH)₂ nanosheets were synthesized with various concentrations of Ni-doping. Detailed structural and electrochemical characterization revealed that Ni_0.25Co_0.75(OH)₂ shows the best OER performance, with an enhanced overpotential of 40 mV at j = 10 mA cm⁻² compared to Co(OH)₂. Theoretical calculations, experimental characterization and electrochemical analysis together demonstrate that the introduction of Ni could reduce the band gap, and decrease the numbers of valence electrons and active O–H and Co–O–H groups of the host Co(OH)₂, thus improving the conductivity, charge transfer, and catalytic kinetics, consequently enhancing the OER performance.