Hollow TiO 2 @TpPa S‐Scheme Photocatalyst for Efficient H 2 O 2 Production Through 1 O 2 in Deionized Water Using Phototautomerization

Abstract Hydrogen peroxide (H 2 O 2 ) production through photocatalytic O 2 reduction reaction (ORR) is a mild and cost‐efficient alternative to the anthraquinone oxidation strategy. Of note, singlet state oxygen ( 1 O 2 ) plays a crucial role in ORR. Herein, a hollow TiO 2 @TpPa (TOTP) S‐scheme heterojunction by the Schiff base reactions involving 1,3,5‐triformylphloroglucinol (Tp) and paraphenylenediamine (Pa) for efficient photocatalytic H 2 O 2 production in deionized water has been developed. Upon irradiation, rapid phototautomerization of TaPa from enol to keto form expands π‐electron delocalization, facilitating effective conversion of the triplet excited state and consequent generation of 1 O 2 . This mechanism is supported by time‐resolved electron paramagnetic resonance (EPR) spectral analysis. Additionally, density functional theory calculations, in situ irradiated X‐ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal superior separation of photogenerated carriers in the TOTP S‐scheme composites. In deionized water, the TOTP2.4 S‐scheme heterojunction exhibits exceptional H 2 O 2 production activity, yielding 891 µmol g −1 h −1 , underscoring the critical role of 1 O 2 in the process. This research offers insights into the S‐scheme heterojunctions and emphasizes the pivotal role of 1 O 2 in enhancing H 2 O 2 production efficiency.