Tuning Cu dopant of Zn0.5Cd0.5S nanocrystals enables high-performance photocatalytic H2 evolution from water splitting under visible-light irradiation

• Published in: Nano energy 2016-08, Vol.26 (C), p.405-416
• Main Authors: Mei, Zongwei, Zhang, Bingkai, Zheng, Jiaxin, Yuan, Sheng, Zhuo, Zengqing, Meng, Xianguang, Chen, Zonghai, Amine, Khalil, Yang, Wanli, Wang, Lin.-Wang, Wang, Wei, Wang, Shufeng, Gong, Qihuang, Li, Jun, Liu, Fu.-Sheng, Pan, Feng
• Format: Article
• Language: English
• Subjects: Cu dopant; Mechanism; Photocatalytic H2 evolution; Visible light; Water splitting; Zn0.5Cd0.5S
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2016.05.051

Cu-doping into Zn1−xCdxS can greatly enhance the photocatalytic H2 evolution from water splitting under visible-light irradiation. However, it is still controversial for how the Cu-dopant improves this performance. Here, we report that appropriate Cu-doped Zn0.5Cd0.5S nanocrystals reach 21.4mmol/h/g of H2 evolution rate without cocatalyst in the visible-light region, which is also 2.8 times as high as that of the undoped counterpart, and the corresponding apparent quantum efficiency is 18.8% at 428nm. It is firstly confirmed that the Cu2+ changes into Cu+ after being doped by soft X-ray absorption spectroscopy (sXAS). We theoretically propose that the transformation of 2Cu2+ to 2Cu+ results in one adjacent S2− vacancy (VS) in host during the doping process, while the Cu+-dopant and VS attract the photoexcited holes and electrons, respectively. Accordingly, the photocatalytic activity is improved due to the enhanced separation of photoexcited carriers accompanied with the enhanced light absorption resulting from the Cu+-dopant and 2Cu+/VS complex as possible active site for photocatalytic H2 evolution. [Display omitted] •It was firstly found that the Cu2+ doping source turned into Cu+ after being doped into mesoporous Zn0.5Cd0.5S aggregated by nanocrystals.•It was theoretically proposed that the Cu+ dopant resulted in the spontaneous formation of S vacancies (VS) in Zn0.5Cd0.5S.•The Cu+ dopant and VS would construct trap level and attract photoexcited holes and electrons, respectively.•Appropriate Cu-doped Zn0.5Cd0.5S nanocrystals reach the highest 21.4mmol/h/g of H2 evolution rate without cocatalyst in the visible-light region, which is also 2.8 times as high as that of the undoped counterpart.