title: Heterojunction of Zinc Blende/Wurtzite in Zn1-xCdxS Solid Solution for Efficient Solar Hydrogen Generation: X-ray Absorption/Diffraction Approaches.
abstract: In the past decade, inorganic semiconductors have been successfully demonstrated as light absorbers in efficient solar water splitting to generate chemical fuels. Pseudobinary semiconductors Zn1-xCdxS (0≤x≤1) have exhibited a superior photocatalytic reactivity of H2 production from splitting of water by artificial solar irradiation without any metal catalysts. However, most studies had revealed that the extremely high efficiency with an optimal content of Zn1-xCdxS solid solution was determined as a result of elevating the conduction band minimum (CBM) and the width of bandgap. In addition to corresponding band structure and bandgap, the local crystal structure should be taken into account as well to determine its photocatalytic performance. Herein, we demonstrated the correlations between the photocatalytic activity and structural properties that were first studied through synchrotron X-ray diffraction and X-ray absorption spectroscopy. The crystal structure transformed from zinc blende to coexisted phases of major zinc blende and minor wurtzite phases at a critical point. The heterojunction formed by coexistence of zinc blende and wurtzite phases in the Zn1-xCdxS solid solution can significantly improve the separation and migration of photoinduced electron-hole pairs. Besides, X-ray absorption spectra and UV-vis spectra revealed that the bandgap of the Zn0.45Cd0.55S sample extended into the region of visible light because of the incorporation of Cd element in the sample. These results provided a significant progress toward the realization of the photoelectrochemical mechanism in heterojunction between zinc blende and wurtzite phases, which can effectively separate the charge-carriers and further suppress their recombination to enhance the photocatalytic reactivity.
authors.forename: Ying-Ya
authors.initials: YY
authors.lastname: Hsu
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Nian-Tzu
authors.initials: NT
authors.lastname: Suen
authors.affiliation: Institute of Physics, Academia Sinica , Taipei 115, Taiwan.
authors.forename: Chung-Chieh
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Sung-Fu
authors.initials: SF
authors.lastname: Hung
authors.affiliation: Institute of Physics, Academia Sinica , Taipei 115, Taiwan.|National Synchrotron Radiation Research Center , Hsinchu Science Park, Hsinchu 300, Taiwan.
authors.forename: Chi-Liang
authors.initials: CL
authors.lastname: Chen
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu Science Park, Hsinchu 300, Taiwan.
authors.forename: Ting-Shan
authors.initials: TS
authors.lastname: Chan
authors.affiliation: Department of Physics, Tamkang University , Tamsui 251, Taiwan.
authors.forename: Chung-Li
authors.initials: CL
authors.lastname: Dong
authors.affiliation: Department of Chemical Engineering, Feng-Chia University , Taichung 407, Taiwan.
authors.forename: Chih-Chieh
authors.initials: CC
authors.lastname: Chan
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu Science Park, Hsinchu 300, Taiwan.
authors.forename: San-Yuan
authors.initials: SY
authors.lastname: Chen
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Hao Ming
authors.initials: HM
authors.lastname: Chen
keywords: X-ray absorption; density of states (DOS) and Rietveld structural refinements; heterojunction; hydrogen evolution reaction (HER); zinc−cadmium sulfide