A review of carbon-based quantum dots for interfacial photocatalysis
Authors: Huang Jian, Ke Baoyi, Hu Huawen
Carbon-based quantum dots (C-QDs) have attracted growing attention in photocatalysis because of their tunable surface chemistry, unique electronic structure, and ability to regulate interfacial charge transfer. In recent years, their role has moved beyond that of simple light absorbers or general performance enhancers, and they are increasingly regarded as engineered interfacial components that can control charge separation, reaction-site microenvironments, and product selectivity. However, the broad claim that C-QDs improve photocatalytic performance often lacks clear mechanistic validation, which limits the ability to compare and reproduce reported studies. Recent advances in C-QD-based photocatalysis are reviewed with particular attention to the experimental evidence supporting their proposed roles and mechanisms. Three roles are considered: (a) electron sinks or charge reservoirs, (b) interfacial bridges or charge-transfer conduits, and (c) adsorption or microenvironment modulators. The evidence needed to support these assignments is then discussed, including measurements of band energetics and carrier dynamics, characterization of interfacial coupling, identification of reaction intermediates under working conditions, isotope-labeling experiments, and carbon balance analysis. Representative applications in hydrogen evolution, CO2 photoreduction, and pollutant degradation/photo-enhanced advanced oxidation processes are also analyzed to clarify how C-QD roles should be matched with reaction-specific metrics. Finally, the review identifies several recurring problems that hinder mechanistic interpretation and comparison between studies: C-QDs are often assigned different functions without sufficient evidence; Z-scheme and S-scheme labels are sometimes used without directly verifying the proposed charge-transfer pathways; reaction intermediates and catalyst behavior are not always examined under actual reaction conditions; and photocatalytic performance is reported using inconsistent metrics and test conditions. This review aims to provide practical guidance for building reliable structure–function relationships and for designing next-generation C-QD-based photocatalysts with clearer mechanisms, stronger reproducibility, and greater application potential.
