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

Developing non-precious metal catalysts capable of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in an alkaline medium is of great significance in the electrocatalytic water-splitting industry. Herein, a novel nanoforest-like NiCo2O4/CuxO/Cu heterojunction with excellent overall water splitting activity and long-term stability is synthesized through the facile substrate etching and hydrothermal crystallization processes. The nanotree-like NiCo2O4/CuxO supported on Cu foam achieves a current density of 10 mA cm(-2) at small overpotential (eta(10) = 92 mV for the HER; eta(10) = 213 mV for the OER), which is significantly ahead of the corresponding pristine catalyst NiCo2O4/Cu (eta(10) = 295 mV for the HER; eta(10) = 349 mV for the OER) and CuxO/Cu (eta(10) = 309 mV for the HER; eta(10) = 347 mV for the OER). In addition, NiCo2O4/CuxO/Cu can work stably for more than 125 h, and the stability is superior to the noble metal catalysts (Pt/C and RuO2) at different potentials. The electrons transfer from Cu2O to NiCo2O4 with the formation of Cu-O bonds at the interface, making parts of the relatively inert Cu(i) into the active Cu(ii), introducing abundant new active sites. The hierarchical self-supported nanoforest-like structure enlarges the electrochemically active surface area and ensures the bonding strength of NiCo2O4/CuxO with the Cu skeleton, giving rise to excellent stability. The superb electrocatalytic performance and stability of NiCo2O4/CuxO/Cu makes it a promising bifunctional catalytic material for overall water splitting. This study provides new testimony of interface effects and the mechanism may inspire the extending design of more effective catalysts.

Automated summary

The novel nanoforest-like NiCo2O4/CuxO/Cu heterojunction, synthesized through substrate etching and hydrothermal crystallization processes, shows excellent overall water splitting activity and long-term stability. With efficient electron transfer and formation of new active sites, as well as enlarged active surface area and strong bonding with the Cu skeleton, NiCo2O4/CuxO/Cu exhibits superior stability and electrocatalytic performance for overall water splitting.