Low-coordinated surface nickel oxide as electrocatalyst for efficient water oxidation

Ni-based compounds represent promising candidates as high-performance electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. Here, a new Ni oxide electrocatalyst developed via a simple electrodeposition method is reported, exhibiting enhanced catalytic activity for OER. Structural and activity analysis of the fresh and post-reaction samples reveals that the Ni2+ center has low coordination with pyramidal symmetry (NiO5). The bulk metallic Ni readily undergoes oxidation under OER conditions to generate more lowcoordinated Ni2+ and high-valence state Ni (Ni3+) species, thereby facilitating the OER reaction. This study provides new insight into the active structure of Ni-based oxide electrocatalysts and offers a simple pathway for the design and development of cost-effective and high-performance electrocatalysts for applications in OER.