Fe doping intensifies the built-in electric field for tailoring the reconstruction of sulfides towards efficient oxygen evolution

Abstract

The traditional view of sulfides as stable active centers has hindered the development of a clear structure–activity relationship and the rational design of high-performance oxygen evolution reaction (OER) catalysts. In this study, we focus on regulating sulfide reconstruction and have synthesized a Fe–Ni₃S₄/Cr₂O₃ pre-catalyst. Under the combined influence of the built-in electric field (BIEF) at the heterogeneous interface and Fe doping, both the sulfide reconstruction process and the electronic structure of the reconstructed product, namely Fe–NiOOH, were effectively tuned. The enhanced BIEF induced by Fe doping generated electron-rich regions on the sulfide surface, stabilizing the reconstruction process. Fe doping into the sulfide induced the incorporation of Fe into NiOOH, modulating the electronic states near the Fermi level of the metal–oxygen bond and subsequently activating the lattice oxygen mediated mechanism (LOM) of Fe–NiOOH, which serves as the true active center. Additionally, the BIEF optimized OH⁻ diffusion dynamics and the energy consumption of hydroxyl deprotonation, reducing the energy barrier of the rate-limiting step of the LOM process, further enhancing OER activity. Remarkably, Fe–Ni₃S₄/Cr₂O₃ demonstrated excellent OER activity and commercial viability. This work offers a new perspective on the regulation of reconstruction products of pre-catalyst, providing fresh insights for the design of efficient OER catalysts.