Cobalt (Oxy)hydroxide Nanosheets Supported on Nickel Foam as Efficient Electrocatalysts for Oxygen Evolution

Oxygen evolution reaction (OER) plays an essential role as the anodic reaction in numerous electrochemical systems for renewable energy conversion. However, the design of efficient electrocatalysts for the OER has been impeded by the sluggish kinetics and poor stability of the catalyst materials. Fe, Co, and Ni-based oxides and (oxy)hydroxides exhibit high OER activities, while the active phases of these catalysts are yet to be elucidated. Here, we report a facile synthesis of Co (oxy)hydroxide and oxide nanosheets supported on Ni foam as OER electrocatalysts. An Ni foam support was submerged into a CoCl2 solution and heated to evenly coat the support with Co species, which was converted to Co (oxy)hydroxides or oxides by further annealing at various temperatures. The prepared electrodes showed high active surface areas and high OER activities, which depended on the annealing temperature that determined the structure and chemical state of the Co species. The electrode annealed at a lower temperature showed a higher intrinsic activity for the OER, commensurate with the presence of Co (oxy)hydroxide phases that are most active for the OER. Our work sheds new insights into the structure-activity relationships of Co-based OER electrocatalysts for efficient electrolyzers.