Multiple interface coupling triggered built-in electric field over double-sandwiched RGO/cobalt silicate/cobalt-iron phosphide for improving the overall water-splitting performance

Abstract

The exploration of efficient and durative bifunctional electrocatalysts for overall water splitting (OWS) is critical for hydrogen production in clean energy applications. Herein, a novel double-sandwiched architecture of reduced graphene oxide (rGO), cobalt silicate (CS), and cobalt–iron phosphides, denoted as rGO/CS/(Co,Fe)_xP_y, is designed to enhance both the oxygen evolution reaction (OER) and hydrogen ER (HER) in alkaline media. The formation of Co₂P and Fe₂P on rGO/CS not only protects the silicate from alkaline corrosion, but also generates dual-active centers that synergistically improve the conductivity and catalytic activity. Multiple interface coupling between rGO, CS, and (Co,Fe)_xP_y triggers a built-in electric field, which significantly enhances charge separation, electron transport, and reaction kinetics. This built-in electric field lowers the energy barrier for HER by facilitating H–OH bond dissociation and accelerates the OER by promoting OH⁻ adsorption. The rGO/CS/(Co,Fe)_xP_y catalyst achieves overpotentials of 256 mV (OER) and 180 mV (HER) at 10 mA cm⁻², surpassing most reported catalysts and rivaling commercial Pt/C and RuO₂. Furthermore, the rGO/CS/(Co,Fe)_xP_y (+/−) demonstrates a low OWS voltage of 1.41 V. The current work provides a new approach to catalyst design through interface engineering and electric field optimization, offering a scalable solution for sustainable hydrogen production.