Modulating the Electronic Structure on Cobalt Sites by Compatible Heterojunction Fabrication for Greatly Improved Overall Water/Seawater Electrolysis

Optimizing the electronic structure on an electrocatalyst is of primary importance to enhance the electrocatalytic activity in water electrolysis. Herein, motivated by theoretical predictions of the excellent electronic properties and suitable Gibbs free energy of active intermediates (H* for the hydrogen evolution reaction and OH* for the oxygen evolution reaction) on cobalt (Co) sites at the heterointerface between CoSe and MoSe2, a new hierarchical bimetal selenide microsphere electrocatalyst (CoSe/MoSe2) with good interfacial compatibility was designed and successfully synthesized. The as-prepared CoSe/MoSe2 exhibited excellent catalytic performance. In the meantime, it only needed 1.63, 1.69, and 1.77 V in 1.0 M KOH, simulated seawater, and alkaline seawater for overall water splitting, respectively. This was attributed to the well-matched interface between CoSe and MoSe2 that effectively disperses electrons on Co atoms and adjusts the d-band center on the Co atom, thus regulating the free energy of H*/OH* on Co sites. This work provided insights into the rational design and construction of efficient electrocatalysts with interfacial compatibility for water/seawater electrolysis.