Abstract
Hydrogen peroxide (H2O2) production through photocatalytic O2 reduction reaction (ORR) is a mild and cost-efficient alternative to the anthraquinone oxidation strategy. Of note, singlet state oxygen (1O2) plays a crucial role in ORR. Herein, a hollow TiO2@TpPa (TOTP) S-scheme heterojunction by the Schiff base reactions involving 1,3,5-triformylphloroglucinol (Tp) and paraphenylenediamine (Pa) for efficient photocatalytic H2O2 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 1O2. 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 H2O2 production activity, yielding 891 µmol g-1 h-1, underscoring the critical role of 1O2 in the process. This research offers insights into the S-scheme heterojunctions and emphasizes the pivotal role of 1O2 in enhancing H2O2 production efficiency.
Published Version
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