Built-in electric field drives n-n heterojunction toward enhanced electrochemical freshwater and seawater oxidation

Abstract

Optimizing the electron cloud density on the catalyst surface is the key to achieving fast kinetics for oxygen evolution reaction (OER). Here, a n-n Fe2P/NiCoP core/shell with strong built-in electric field (BEF) is successfully constructed to enable efficient local charge redistribution at heterointerface and contribute to extraordinary OER performance. Remarkably, the optimized Fe2P/NiCoP catalyst only requires the overpotentials of 272 and 291 mV to achieve a current density of 10 mA·cm−2 in 1 M KOH and alkaline seawater solutions, along with superb electrochemical stability over 140 h and 120 h, respectively. Detailed experimental and theoretical studies demonstrate that the well-designed BEF at the heterointerface of Fe2P/NiCoP n-n heterojunction can accelerate the charge transfer and enhance the conductivity. In addition, the self-propelled electron transfer across the n-n interface can prompt localized charge redistribution at the interface region, leading to enhanced adsorption of OH– and thus significantly boosting the kinetics of OER. This research paves a new avenue for the fabrication of heterostructured catalysts with BEF and optimized interfacial electron cloud for the enhanced OER.