Rational design of ZnCdS/TpPa-1-COF heterostructure photocatalyst by strengthening the interface connection in solar hydrogen production reactions

ZnCdS quantum dots (QDs) are highly coveted in photocatalysis research for their exceptional visible-light responses and high light-absorption coefficients. However, their practical application is hindered by their tendency to aggregate, due to having high surface energies. To address this issue, herein, a heterostructure is synthesized by growing ZnCdS QDs with a size of approximately 5 nm onto the surface of a two-dimensional (2D) covalent organic framework (COF), TpPa-1-COF. This approach suppresses the aggregation of the QDs and improves their stability. The ZnCdS/TpPa-1-COF composite exhibited a peak hydrogen evolution rate of 6244.16 μmol·g⁻¹·h⁻¹, which was 2.89 and 4.18 times greater than that of ZnCdS and TpPa-1-COF, respectively. The zero-dimensional/two-dimensional (0D/2D) heterojunction formed by ZnCdS and TpPa-1-COF generates a strong interfacial force, which is attributed to the intimate contact between the interfaces. Tight connections accelerate charge separation, improve the utilisation of reduced electrons, and reduce the extent of agglomeration of the ZnCdS QDs, thereby resulting in high hydrogen production activity of the composites. Meanwhile, the photocatalytic mechanism is studied using Kelvin probe force microscopy and theoretical calculations. This study offers a novel approach for creating sulfide photocatalysts and is crucial for investigating the potential practical applications of the related photocatalysts.