Amorphous Nanoflower-like FeCo-BiOCl/Bi Heterointerface Favoring Oxygen-Participation Pathways for Alkaline Overall Water Splitting

Abstract

The widespread commercialization of water electrolysis heavily relies on deploying economically viable and structurally resilient dual-function catalysts; nevertheless, progress is frequently bottlenecked by sluggish reaction kinetics and rapid architectural degradation. A primary, though frequently neglected, cause of this catastrophic activity loss is the irreversible anodic dissolution of metal cations during severe polarization. To overcome this, we designed a self-supported, amorphous, 3D nanoflower-structured FeCo-BiOCl/Bi/NF heterointerface utilizing a straightforward single-step solvothermal route. By integrating in situ attenuated total reflection infrared spectroscopy (ATR-SEIRAS) with density functional theory (DFT) simulations, we suggest that the improved catalytic efficiency is associated with a Co–Bicoupled, oxygen-participation-favorable pathway. Bridging oxygen atoms dynamically facilitate a synergistic interaction between Co and Bi cations. This interplay facilitates lattice-oxygen participation and reduces the potential-determining-step (PDS) barrier to 0.43 eV, while helping regulate the interfacial charge distribution. This electronic modulation helps stabilize the active sites and mitigates localized overoxidation associated with cation leaching, thereby contributing to the structural stability of the heterointerface. As a result, the heterostructure requires overpotentials of 127 mV for the oxygen evolution reaction (OER) and 188 mV for the hydrogen evolution reaction (HER) to reach a current density of 10 mA cm–2. Furthermore, a symmetric two-electrode electrolyzer operates stably for over 100 h at a cell voltage of 1.46 V at 10 mA cm–2. This study provides a useful strategy for designing bismuth-integrated heterointerface electrocatalysts with improved activity and reduced metal dissolution under alkaline water-electrolysis conditions.