Recent advances in Ni (oxy) hydroxides and Ni sulfides catalysts for oxygen evolution reactions

Clean energy may solve global warming and environmental issues caused by fossil fuel consumption. Clean energies, such as solar and wind energy, strongly depend on environmental conditions. Electrochemical water splitting converts intermittent solar and wind energy into chemical fuels, which are very convenient for storage and transportation. Oxygen evolution reaction (OER) is a critical step in water splitting and electrochemical biomass generation, but it is known to be sluggish. Therefore, developing highly active, low-cost, and stable OER catalysts is crucial for the advancement of clean energy. In recent decades, Ni (oxy) hydroxides and Ni sulfides have received numerous attention due to their comparable activity to that of precious metal-based catalysts. This review provides a brief overview of the development of Ni (oxy) hydroxides and Ni sulfides as OER catalysts, focusing on key questions in the field, such as the active phases, Fe doping, and surface reconstruction.