Constructing sulfide/phosphide heterostructure boosts the activity of iron-manganese bimetallic electrocatalysts for oxygen evolution reaction at large current densities

Designing earth-abundant electrocatalysts with high activity and stability is crucial to the industrial large-scale water splitting for hydrogen production. Herein, we report an effective electrocatalyst composed of inner FeMnP layer and outer FeMnS species for oxygen evolution reaction (OER). The interfacial coupling between two layers modulates the local electronic structure, reduces the indirect contact resistance, optimizes the kinetics of OER, and ultimately boosts the intrinsic OER activity. Meanwhile, the outer FeMnS nanoflowers composed of numerous nanosheets lead to a larger electrochemical surface area (ECSA), exposing more active sites, which also plays a major role in the improvement of ability to catalyze water oxidation. More importantly, the electrode has a hydrophilic/underwater aerophobic surface to insure electrolyte diffusion efficiently and the bubbles release rapidly at a large current density of OER. Therefore, the obtained FeMnS/FeMnP/NF can output the current density of 1000 mA/cm2 with a low overpotential of 374 mV and can remain such a high current density for over 60 h. It also presents remarkable activity and stability in 30 wt% KOH solution and simulated seawater. This work presents a promising strategy for preparing high-efficiency and low-cost self-supporting electrodes for water oxidation.