Photochromic Single-Unit-Cell ZnIn2S4 Nanosheets with Large Lateral Sizes for Boosting H2O2 Photosynthesis

Abstract

Semiconductor photocatalysis is an emerging technology for chemical synthesis, but its wide application is still hindered by the inefficient photogenerated carrier utilization of photocatalysts. Herein, we successfully constructed photochromic ZnIn2S4 nanosheets with an ultrathin single-unit-cell thickness of ∼2.58 nm but large lateral sizes exceeding 600 μm (ZIS-NS) by the ultrasonic exfoliation of bulky ZnIn2S4 blocks prepared via a trisodium citrate-assisted strategy. Impressively, ZIS-NS showed a high photocatalytic performance for H2O2 photosynthesis coupled with the oxidation of 4-methoxybenzyl alcohol under air mass 1.5 global, affording H2O2 and anisaldehyde production rates of 12.09 and 12.57 mmol g–1 h–1, which are 16.1 and 15.4 times those of conventional ZnIn2S4 nanoflowers (H2O2: 0.75 mmol g–1 h–1; anisaldehyde: 0.82 mmol g–1 h–1), respectively. Furthermore, by constructing a ZIS-NS-based two-phase continuous-flow reaction system, we directly obtained a ∼200 mL H2O2 solution with a high accumulated concentration of 3.97 wt %, which is also much higher than the typical concentration of commercial H2O2 (∼3 wt %) and can be directly utilized in various fields, including environmental remediation, disinfection, and wastewater treatment. We demonstrated that the abundant sulfur vacancies in ZIS-NS can promote the separation and utilization of photogenerated charges, simultaneously endowing ZIS-NS with a photochromic property to further improve its carrier utilization efficiency. This study not only enriches the family of photochromic nanoarchitectures but also sheds light on the rational construction of highly efficient photocatalysts for advanced photosynthesis.