title: Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light.
abstract: Controlling amount of intrinsic S vacancies was achieved in ZnS spheres which were synthesized by a hydrothermal method using Zn and S powders in concentrated NaOH solution with NaBH4 added as reducing agent. These S vacancies efficiently extend absorption spectra of ZnS to visible region. Their photocatalytic activities for H2 production under visible light were evaluated by gas chromatograph, and the midgap states of ZnS introduced by S vacancies were examined by density functional calculations. Our study reveals that the concentration of S vacancies in the ZnS samples can be controlled by varying the amount of the reducing agent NaBH4 in the synthesis, and the prepared ZnS samples exhibit photocatalytic activity for H2 production under visible-light irradiation without loading noble metal. This photocatalytic activity of ZnS increases steadily with increasing the concentration of S vacancies until the latter reaches an optimum value. Our density functional calculations show that S vacancies generate midgap defect states in ZnS, which lead to visible-light absorption and responded.
authors.affiliation: State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Baibiao
authors.initials: B
authors.lastname: Huang
authors.affiliation: School of Physics, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Zhujie
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Zaizhu
authors.initials: Z
authors.lastname: Lou
authors.affiliation: State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Zeyan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Physics, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8205, USA.
authors.forename: Myung-Hwan
authors.initials: MH
authors.lastname: Whangbo