Optimizing Oxygen Inhibition for Low‐Barrier Oxygen Reduction via Thiol‐Induced Electron‐Deficient Sites

Abstract Enhancing the photocatalytic production of hydrogen peroxide remains a critical challenge due to the slow kinetics of water oxidation and the complex dynamics of oxygen reduction. This study introduces a novel conceptual framework that uses engineered molecular defect states to precisely modulate orbital electron behavior at neighboring atomic sites. Electron‐deficient non‐metallic active centers that significantly improve water molecule adsorption and facilitate proton release; simultaneously, defect‐engineered metallic sites efficiently trap and activate oxygen molecules, promoting spin‐orbital interactions that drive the formation of reactive oxygen species. Zn _1.68 In _2.21 S ₅ is using trimercaptopropionic acid as a sulfur source. The thiol‐mediated synthesis introduces both metallic and non‐metallic defect states, enabling efficient intramolecular electron transfer through orbital‐level coupling. These vacancies induce an electronegativity gradient that drives S 3 p ‐Zn 3 d orbital coupling, depleting antibonding electrons from S sites to Zn vacancies. This tuning elevates the S 3 p ‐band center, strengthening S─H _ads bonds for efficient water adsorption and proton release while activating O ₂ molecules, resulting in a remarkably high hydrogen peroxide production rate of 7.98 mmol g ⁻¹ h ⁻¹ achieved in O ₂ ‐saturated water without sacrificial agents. This work offers a promising direction for next‐generation photocatalysts aimed at sustainable hydrogen peroxide synthesis and broader solar‐to‐chemical energy conversion applications.