Activating Lattice Oxygen via Proton-Decoupled Electron Transfer in Iron Chromium Phosphate for Efficient (Sea)Water Oxidation

Abstract

Given the escalating freshwater scarcity crisis, seawater oxidation has emerged as a promising approach to advancing sustainable hydrogen production; however, its practical feasibility is severely hindered by pervasive chloride-induced corrosion. In this study, we develop an efficient FeCr-phosphate (FeCrPi) as an electrocatalyst by a simple solvothermal strategy, which exhibits superior oxygen evolution reaction (OER) activity in both alkaline freshwater and seawater. The rational design of FeCrPi affords a dual advantage: phosphate groups promote the lattice oxygen mechanism (LOM), while in-situ generated CrO42- species during seawater oxidation adsorb onto the electrode surface, creating a protective layer that mitigates chloride corrosion, suppresses chlorine evolution reaction (CER), and enhances OER selectivity. As a result, FeCrPi demonstrates excellent OER activity in alkaline freshwater and alkaline real seawater, achieving a high current density of 0.5 A cm-2 at 280 and 340 mV, respectively, and also maintaining an impressive stability over 100 h at a high applied potential of 2 V in alkaline real seawater. This work establishes a viable phosphate-engineering strategy for fabricating a highly efficient chloride-resistive electrocatalyst with OER selectivity, which enables LOM-assisted seawater oxidation.