Polyoxometalate-assisted formation of CoSe/MoSe ₂ 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 MoSe ₂ (molybdenum selenide) nanosheets (CoSe/MoSe ₂ 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/MoSe ₂ 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, MoSe ₂ and physically mixed CoSe and MoSe ₂ . Schematic energy band diagrams derived from ultraviolet photoelectron spectroscopy results further confirmed the electronic modulation between CoSe and MoSe ₂ and revealed that the d-band center of CoSe/MoSe ₂ hybrids moved closer to the Fermi level, giving rise to high charge carrier density and low intermediate adsorption energy as compared to CoSe and MoSe ₂ . This work provides some insight into the design and synthesis of heterostructured nanomaterials from the MOF precursors.