Light-Assisted Preparation of a ZnO/CdS Nanocomposite for Enhanced Photocatalytic H₂ Evolution: An Insight into Importance of in Situ Generated ZnS

Abstract

In our work, ZnO/CdS hybrid photocatalysts were prepared by a simple and reproducible photodeposition method and the content of deposited CdS can be varied by irradiation time. The ZnO/CdS photocatalysts showed good photocatalytic H 2 evolution activities in aqueous Na 2 S + Na 2 SO 3 solution. When the content of CdS loading increased to 22.91% after an irradiation time of 120 min (ZnO/ CdS-T120), the highest photocatalytic activity was obtained (1725 μmol g −1 h −1 ), which was about 9.2 and 34.5 times than that of single ZnO and CdS photocatalysts. At the same time, ZnO/CdS-T120 presented stable photocatalytic ability (no noticeable degradation of H 2 evolution in four repeated runs in 48 h). Compared with other reported H 2 evolution photocatalysts, ZnO/CdS-T120 showed higher H 2 evolution activity and stability. Additionally, ZnO/CdS-T120 has a good natural sunlight driven H 2 evolution ability (2077 μmol g −1 h −1 ). ZnS was proved to generate on ZnO/CdS-T120 surface in process of photocatalytic H 2 evolution based on structural analyses of recycle ZnO/CdS-T120. The formation of ZnS enhanced the photocatalytic H 2 evolution activity of ZnO/CdS and extended the visible light adsorption region. Meanwhile, the generation of ZnS increased the transfer interfaces for photogenerated charge carriers and consequently promoted the separation of photogenerated electrons and holes.

Rational design of CdS@ZnO core-shell structure via atomic layer deposition for drastically enhanced photocatalytic H2 evolution with excellent photostability

“…It should be noted that two types of valences in palladium, Pd II and Pd 0 , were detected on the surface of CdS@ZnO 100 /PdS by XPS analysis (Fig. S6), indicating the co-existence of PdS and metallic Pd during the photocatalytic reaction [65]. Based on the former …”

“…8b) [53,[62][63][64]. The as-formed direct CdS@ZnO Z-scheme photocatalytic system is very important for the generation of H 2 from water splitting because the electrons in the CB of CdS have more redox power to reduce H + to H 2 than that in the CB of ZnO [65]. It has been reported that PdS is an excellent hole-captured co-catalyst [58,61,66].…”

Photoinduced Charge Transfer Properties of ZnWO4/CdS Composite and its Photocatalytic Activities under visible Light

“…As an important photocatalyst, CdS has been reported for photocatalytic hydrogen production from water and mineralization of organic pollutants under visible light irradiation [4,5]. However, the stability of of CdS photocatalytic activity is still indispensable.…”

“…However, the stability of of CdS photocatalytic activity is still indispensable. Many efforts have been made on the improvement of stability, such as morphologies, crystallinity, nanocomposite and ion doping [4][5][6]. M. Luo and co-worker found that 1.2 mol % Ni-doped CdS hollow spheres showed the highly efficient for organic pollutants RhB.…”

“…This result demonstrates that CdS nanocrystals are stable and do not photocorrode during the photocatalytic process [6].Although many methods for enhanced stability of CdS have been tried, the composite photocatalyst based on ZnWO 4 has not been reported. Instead of using a single photocatalyst, coupling of photocatalyst with other semiconductors, metals, or molecules to form a junction structure has been found to be significantly beneficial for enhancing the stability [5]. H. Zhao et al investigated the stability and durability of ZnO/CdS nanocomposite.…”