Engineering a Strong Internal Electric Field via Heteroatom Doping in S‐Scheme Heterojunctions for Efficient Photocatalytic H 2 O 2 Synthesis

ABSTRACT 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 ZnIn 2 S 4 /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 H 2 O 2 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.