2, Institute for Chemical Research, Kyoto University, Uji, Kyoto, , Japan
Solar energy conversion using the photocatalytic water splitting is considered to be a powerful strategy to solve the problems of energy crisis and environmental pollution.1-4 However, the establishment of design guidelines to obtain the optimized structures for maximizing the photocatalytic performance remains a great challenge for artificial photosynthesis systems. Colloidal semiconductor nanocrystals provide us with a simple route for exploring the physical and chemical properties of nanomaterials for application in optoelectronics, energy conversion, and catalysis.5 In particular, the core–shell nanorod structures with a type-II band alignment exhibit spatial charge separation which has been widely investigated for improving the performance in photocatalytic activities. Furthermore, the efficient extraction of holes in type-II band alignment is favorable for the stable photocatalysts. However, in contrast to the intense researches about band offset tuning for photocatalysts, the relationship between nanostructures and photo-induced carrier dynamics has been still poorly explored.
In this work, we synthesized CdS core–mesoporous ZnSe shell “durian-shaped” nanocrystals (d-CdS/ZnSe NCs) with a type-II band alignment. The photo-generated carrier dynamics were investigated by fs- or ns-transient absorption spectroscopy and time resolved microwave conductivity (TRMC) technique. The d-CdS/ZnSe NCs exhibited cocatalyst-free high photocatalytic activity for H2 evolution (14.8% of apparent quantum yield at 420 nm) and excellent stability (maintaining 80% activity after 72 h) under visible light illumination. The unique hierarchical mesoporous shell enables the high photo-carriers mobility, efficient spatial charge separation, and long-lived charge separation state in the d-CdS/ZnSe NCs. We demonstrated that the hierarchical structure is favorable for high photocatalytic activity and sustainability of nanomaterials for H2 evolution.
(1) Bard, A. J.; Fox, M. A. Acc. Chem. Res. 1995, 28, 141.
(2) Chen, X.; Shen, S.; Guo, L.; Mao, S. S. Chem. Rev. 2010, 110, 6503.
(3) Moniz, S. J. A.; Shevlin, S. A.; Martin, D. J.; Guo, Z.-X.; Tang, J. Energy Environ. Sci. 2015, 8, 731.
(4) Li, Z.; Luo, W.; Zhang, M.; Feng, J.; Zou, Z. Energy Environ. Sci. 2013, 6, 347.
(5) Chica, B.; Wu, C.-H.; Liu, Y.; Adams, M. W. W.; Lian, T.; Dyer, R. B., Energy Environ. Sci. 2017, 10, 2245-2255.