Heterostructure Interface Engineering in CoP/FeP/CeO x with a Tailored d-Band Center for Promising Overall Water Splitting Electrocatalysis

Accomplishing a green hydrogen economy in reality throughwaterspitting ultimately relies upon earth-abundant efficient electrocatalyststhat can simultaneously accelerate the oxygen and hydrogen evolutionreactions (OER and HER). The perspective of electronic structure modulationvia interface engineering is of great significance to optimize electrocatalyticoutput but remains a tremendous challenge. Herein, an efficient tactichas been explored to prepare nanosheet-assembly tumbleweed-like CoFeCe-containingprecursors with time-/energy-saving and easy-operating features. Subsequently,the final metal phosphide materials containing multiple interfaces,denoted CoP/FeP/CeO x , have been synthesizedvia the phosphorization process. Through the optimization of the Co/Feratio and the content of the rare-earth Ce element, the electrocatalyticactivity has been regulated. As a result, bifunctional Co3Fe/Ce0.025reaches the top of the volcano for both OER and HER simultaneously,with the smallest overpotentials of 285 mV (OER) and 178 mV (HER)at 10 mA cm(-2) current density in an alkaline environment.Multicomponent heterostructure interface engineering would lead tomore exposed active sites, feasible charge transport, and strong interfacialelectronic interaction. More importantly, the appropriate Co/Fe ratioand Ce content can synergistically tailor the d-band center with adownshift to enhance the per-site intrinsic activity. This work wouldprovide valuable insights to regulate the electronic structure ofsuperior electrocatalysts toward water splitting by constructing rare-earthcompounds containing multiple heterointerfaces. Simultaneously engineering a heterointerfaceand regulatingthe Co/Fe ratio and the Ce amount in CoP/FeP/CeO x modulate the position of the d-band center, thereby renderingexceptional bifunctionality toward oxygen and hydrogen evolution electrocatalysis.