Photocatalytic H 2 O 2 production and recalcitrant pollutant degradation are regarded as promising clean technology toward achieving sustainable solar-to-chemical energy conversion. Herein, nonstoichiometric Zn-Cu-In-S (ZCIS) quaternary alloyed quantum dots (QDs) are rationally fabricated via a reflux method toward H 2 O 2 generation and ciprofloxacin degradation under visible light irradiation. The optimum catalyst (ZCIS-2) exhibits a notable H 2 O 2 production of 1685.2 μmole h −1 g −1 (solar-tochemical conversion efficiency (SCC), 0.19%), which is 5.3 times higher than that of CuInS 2 (CIS), and a ciprofloxacin (CIP) degradation efficiency of 96% in 2 h. The observed improvement in activity corresponds to optimized exciton separation/transfer, broad photon absorption, tunable band alignment, and effective adsorption/activation. In addition, oxygen reduction goes through both direct two-electron single-step reduction and single-electron two-step superoxide radical pathways, whereas CIP degradation proceeds via direct • O 2 − and indirect • OH radical pathways, as confirmed by scavenger experiments. An appropriate amount of defects improves the adsorption/activation of O 2 toward H 2 O 2 and active oxygen species generation that facilitates CIP degradation. The effect of operational parameters, such as pH, surrounding environment, presence of ions, sacrificial agent, etc., on both H 2 O 2 formation and CIP removal is vividly studied. Hence, the current study will provide an in-depth insight into O 2 photoreduction and micropollutant removal, which encourages further advancement of potent alloyed quantum dot-oriented photocatalytic systems.
Hydrogen is becoming a promising eco-friendly energy carrier to replace traditional nonrenewable fossil fuels. In this context, photocatalytic water splitting photosystems are considered a green tactic. Alloyed quantum dots (QDs) are considered as earth abundant, low cost, and environmentally friendly photocatalysts to be utilized effectively in photocatalytic H 2 evolution. H 2 production efficiency greatly depends upon tunable optical and electronic properties associated with chemical composition as well as nanoscale particle sizes of alloyed QDs. Recent efforts toward the fabrication of various alloyed QDs by varying the surface atomic ratio and ligand exchange for photocatalytic hydrogen production has been presented and appraised here. Furthermore, in this review, we presented the microstructure and optical properties of alloyed QDs with their advantages and the construction of efficient cadmium-bound and cadmium-free alloyed QDs toward a photocatalytic hydrogen evolution reaction. At last, the challenges as well as critical issues of alloyed QDs and alloyed QDs-based photocatalysts for H 2 evolution has been proposed, with the hope that this mini-review will give a superior perceptive of different alloyed QDs.
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