Engineering a Strong Internal Electric Field via Heteroatom Doping in S-Scheme Heterojunctions for Efficient Photocatalytic H₂O₂ Synthesis

The precise regulation of the interfacial internal electric field (IEF) is a pivotal strategy for advancing efficiency of heterojunction photocatalysts. Herein, we report a novel ZnIn₂S₄/carbon-doped BiOBr (ZIS/C-BiOBr) S-scheme heterojunction, where the carbon doping strategically modulates the Fermi level of BiOBr to establish an enhanced IEF. The resulting significant Fermi level difference (ΔE_f = 3.14 eV) provides the key driving force for directional charge transfer. As revealed by combined theoretical and experimental investigations, this strategic design endows the material with augmented light absorption, intensified redox potential, and markedly improved charge separation efficiency. Carbon doping also enhances oxygen adsorption and promotes electron shuttling to oxygen molecules through strengthening the interfacial internal electric field. These synergistic effects directly lead to substantially enhanced photocatalytic performance. Consequently, the optimized photocatalytic H₂O₂ production rate of the ZIS/C-BiOBr4 is markedly improved, achieving values 10.0, 2.6 and 2.1 times higher than C-BiOBr, ZIS and ZIS/BiOBr heterojunction, respectively, highlighting the significant boost induced by carbon doping. This work demonstrates the profound impact of carbon doping and provides fundamental insights into coupling heteroatom doping with IEF control for designing advanced photocatalysts.