A self-supported NiCo2O4/CuxO nanoforest with electronically modulated interfaces as an efficient electrocatalyst for overall water splitting

The electrons transfer from Cu₂O to NiCo₂O₄ with the formation of Cu–O bonds at the interface of the NiCo₂O₄/Cu_xO, making parts of the relatively inert Cu(i) into the active Cu(ii) and introducing abundant new active sites.