Surface indium vacancies promote photocatalytic H2O2 production over In2S3

Photocatalytic oxygen reduction reaction (ORR) represents a green and cost-effective means to produce the high-value industrial compound H2O2. However, the efficient H2O2 synthesis awaits in-depth knowledge of the ORR mechanisms for the design of highly active photocatalysts. In this work, surface indium vacancies (denote hereafter as VIn) have been introduced into In2S3, which significantly boosts the photocatalytic activity for H2O2 production, with an optimal H2O2 generation rate of 4.77 ± 0.05 mmol·h−1·gcat.−1 under visible light illumination (λ ≥ 420 nm) and an apparent quantum efficiency (AQE) of 7.49 ± 0.01% at 420 ± 20 nm. Mechanistic analysis reveals the multifunctionality of VIn, such as enlarging the chemisorption capacity of O2, enriching photo-generated electrons for ORR, endorsing high reducing power to photo-generated electrons, and promoting H2O2 desorption. These findings justify that surface cation vacancies open up new possibilities for H2O2 photosynthesis by leveraging their reaction dimensions in ORR. Photocatalytic oxygen reduction reaction to produce H2O2 awaits in-depth knowledge for the design of active photocatalysts. Here, the authors identify that surface indium vacancies are the key to opening the activity of In2S3 for H2O2 photosynthesis.