Transition metal phosphides: Electron buffer agents for selective and durable seawater oxidation

The electron buffer effect is a powerful strategy that helps catalytic active sites attain their optimal electronic state, thereby enhancing their intrinsic activity and durability. However, the development of electron buffer agents has been largely limited to carbon materials. Here, for the first time, we demonstrate the feasibility of using affordable transition metal phosphides (TMPs) as electron buffer layers. By utilizing a catalyst system that includes cerium-doped nickel‑iron layered double hydroxides (Ce@NiFe LDH) in close contact with a cobalt‑copper phosphides (CoCuP) layer, we reveal that Ce dopants donate excess electrons to Ni sites. To balance those excess electrons, Co in CoCuP is capable of withdrawing extra electrons from the Ni site via a Ni-O-Co atomic interface. Herein seawater oxidation is used as a model reaction. With the presence of a TMPs electron buffer layer, oxygen evolution reaction (OER) performance is significantly improved. Benefiting from this effect, the catalyst achieves a low overpotential (229 mV at 100 mA cm −2 ), high OER selectivity (98.1 %), and remarkable stability (200 h at 1.0 A cm −2 ). Furthermore, to broaden the scope of TMPs-based electron buffer agents, cobalt‑molybdenum phosphides (CoMoP) and cobalt‑vanadium phosphides (CoVP) are studied. This work pioneers the use of TMPs as electron buffers and offers an innovative strategy for the design of catalysts with optimal electronic structures. • Electron buffer effect was used to tune the electronic structure of active sites. • TMPs were developed as a new type of electron buffer towards LDHs. • C@NFL/CCP showed an OER overpotential of 229 mV at 100 mA cm −2 in alkaline seawater. • Competitive and corrosive ClOR was inhibited over C@NFL/CCP. • C@NFL/CCP can operate steadily at 1 A cm −2 for 200 h.