Polyoxometalate-assisted formation of CoSe/MoSe2 heterostructures with enhanced oxygen evolution activity.

The oxygen evolution reaction (OER) is a half reaction of electrochemical water splitting that suffers from a kinetically sluggish four-electron process, and it is regarded as the efficiency-limiting step in water splitting. Herein, heterostructures of CoSe (cobalt selenide) nanoparticles and MoSe₂ (molybdenum selenide) nanosheets (CoSe/MoSe₂ hybrids) were fabricated through a non-metal-induced growth method. Due to the increase in the effective specific area and the electron transfer ability caused by the formation of the heterogeneous interface, the obtained CoSe/MoSe₂ hybrids show superior OER performance (η = 262 mV at 10 mA cm⁻²) and long-term stability (20 h for continuous testing) as compared to pure CoSe, MoSe₂ and physically mixed CoSe and MoSe₂. Schematic energy band diagrams derived from ultraviolet photoelectron spectroscopy results further confirmed the electronic modulation between CoSe and MoSe₂ and revealed that the d-band center of CoSe/MoSe₂ hybrids moved closer to the Fermi level, giving rise to high charge carrier density and low intermediate adsorption energy as compared to CoSe and MoSe₂. This work provides some insight into the design and synthesis of heterostructured nanomaterials from the MOF precursors. [ABSTRACT FROM AUTHOR]