Material Development for Broadband Photocatalytic Water Splitting

  • The global energy demand calls for the development of new sustainable energy technologies. Among various technologies, the photocatalytic water splitting that harvests solar light to produce hydrogen and oxygen is a promising approach to the conversion from solar to hydrogen energy. To harvest and utilize broadband light, various all-solid-state artificial Z-scheme photocatalytic systems have been developed based on two semiconductors with staggered-aligned band structures and different bandgaps. Most recently, the research group led by Prof. XIONG Yujie at the University of Science and Technology of China has developed a class of noble metal-free Z-scheme photocatalysts which exhibit the enhanced performance in photocatalytic hydrogen production, based on a facile cation-exchange approach. This work has been published in Angewandte Chemie (Angew. Chem. Int. Ed. DOI: 10.1002/anie.201700150).

    An ideal Z-scheme system should possess two structural characteristics: (1) well-defined interfaces for efficient interfacial charge transfer, and (2) exposed surfaces of both semiconductors for surface reduction and oxidation half reactions. To reduce the material costs, ideally the noble metals, which are commonly used as electron mediators to facilitate the charge transfer between semiconductors in Z scheme or as cocatalysts to promote hydrogen evolution, should be excluded from their interfaces. The exclusion of noble metals from Z scheme can also eliminate the possible backward reactions over metal surface back to water.

    Illustration for the noble metal-free Z-scheme materials towards broadband photocatalytic water splitting (Courtesy of XIONG Yujie and Angewandte Chemie)

    To meet the requirements, Xiong research group has developed a facile cation-exchange approach to form Janus-like structures between γ-MnS and Cu7S4 with exposed surfaces and high-quality interfaces without the need of using noble metals. The γ-MnS and Cu7S4 can complementarily absorb light to exhibit the dramatically enhanced photocatalytic hydrogen performance in full solar spectrum. This work provides insights into the surface and interface design of hybrid photocatalysts, and offers a noble metal-free approach to broadband photocatalytic hydrogen production.

    Prof. Junfa Zhu made an important contribution to the synchrotron radiation-based photoelectron spectroscopy characterizations in this work. This work was financially supported by the 973 Program, NSFC and CAS Key Research Program of Frontier Sciences.