Carbon-Dot-Mediated Highly Efficient Visible-Driven Photocatalytic Hydrogen Evolution Coupled with Organic Oxidation

Photocatalytic hydrogen evolution coupled with organic oxidation reaction is a promising alternative to water splitting, where the efficiency is limited due to the weak correlation between charge separation and surface redox reactions. Here, employing nickel phthalocyanine (NiPc) for hole extraction, NiPc-modified carbon dots (CDs) are combined with Cu-In-Zn-S quantum dots (CIZS QDs) toward a profound understanding of electron/hole extraction and surface proton generation and reduction. The optimal hydrogen evolution rate reaches 4.10 mmol g(-1) h(-1) for CIZS/NiPc-CDs with l-ascorbic acid for hole consumption, 8.10 times to that of CIZS QDs, which is further promoted to 11.12 mmol g(-1) h(-1) under electron/hole coextraction with Ni2+ introduction. For benzyl-alcohol-oxidation-coupled H-2 evolution, this strategy shows a more dramatic activity enhancement (19.54 times), which is also appliable to methanol- or furfuryl-alcohol-oxidation coupling systems with state-of-the-art activities. Transient photovoltage spectroscopy and apparent kinetics analysis indicate, for the first time, a light-induced electrocatalysis effect consistent with the Volmer-Heyrovsky process, which establishes a quasiquantitative basis for balancing charge extraction and surface reactions.

Automated summary

In this study, NiPc-modified carbon dots (CDs) are combined with Cu-In-Zn-S quantum dots (CIZS QDs) to enhance the efficiency of photocatalytic hydrogen evolution and organic oxidation reactions. The NiPc-CDs effectively extract electrons and holes and generate and reduce protons. The optimal hydrogen evolution rate is 4.10 mmol g(-1) h(-1), which is 8.10 times higher than that of CIZS QDs and further increased to 11.12 mmol g(-1) h(-1) with the introduction of Ni2+. For benzyl-alcohol-oxidation-coupled H-2 evolution, this strategy shows a dramatic activity enhancement (19.54 times) and is applicable to other oxidation coupling systems. Transient photovoltage spectroscopy and apparent kinetics analysis reveal a light-induced electrocatalysis effect consistent with the Volmer-Heyrovsky process, providing a quasi-quantitative basis for balancing charge extraction and surface reactions.