Deep reconstruction of a Mo-based electrocatalyst for high-performance water/seawater oxidation at ampere-level current density†

Abstract

Anodic reconstruction has been widely used for in situ preparation of effective catalysts as it exposes highly active amorphous active sites; however, this process usually occurs only at the catalyst surface. Herein, we present our design of deeply reconstructed amorphous FeMo oxyhydroxide (FeMoOOH/NF) catalysts with high activity and corrosion resistance achieved through in situ Mo dissolution and Fe substitution during electrolysis. Our investigations demonstrate that during the dissolution of Mo, Fe³⁺ is captured by the reconstructed amorphous structure and then reacts with OH⁻ in the electrolyte to form a large number of highly reactive and stable amorphous FeMo–OOH species. Mechanistic studies revealed that the reconstructed FeMoOOH modified the pristine electronic structure, triggered lattice oxygen activation and enhanced the oxygen evolution reaction (OER) kinetics. Meanwhile, the reconstructed FeMoOOH enriched OH⁻ on the catalyst surface to repel Cl⁻ and further protected the catalyst. The as-prepared FeMoOOH/NF catalyst features high OER activity with low overpotentials (340 mV@1.0 A cm⁻²), high stability (1000 h@1.5 A cm⁻²) and high selectivity (faradaic efficiency of 100%), highlighting that in situ deep reconstruction is an effective approach for developing highly efficient and corrosion-resistant water/seawater-based catalysts.