Recent progress in self-supported two-dimensional transition metal oxides and (oxy)hydroxides as oxygen evolution reaction catalysts

The oxygen evolution reaction (OER) is a well-recognized bottleneck reaction in overall water splitting because of its multi-electron transfer steps and sluggish reaction kinetics, which creates significant difficulties in delivering appreciable current. Both active and robust OER catalysts are highly desired to boost overall water splitting. Recently, two-dimensional and self-supported transition metal oxides and (oxy)hydroxides (2D-SS-TMOs) have received particular attention due to their high intrinsic activity, large electrolyte accessible surface area, decent electrical conductivity, and great structural stability. In this review, the recent developments of 2D-SS-TMO OER catalysts are summarized. Both fabrication methods and the strategies for activity enhancement of 2D-SS-TMOs are also reviewed. In view of their great OER performances, 2D-SS-TMOs demonstrated in photoelectrochemical water splitting and lithium air batteries are also discussed.