Converting the Charge Transfer in ZnO/Zn_xCd_1‐xS‐DETA Nanocomposite from Type‐I to S‐scheme for Efficient Photocatalytic Hydrogen Production

Abstract

2102497 (2 of 11) www.advmatinterfaces.de Scheme 1. Schematic diagram for the synthesis of ZOZCS nanocomposites.

Efficient Visible-Light Driven Photocatalytic Hydrogen Production by Z-Scheme ZnWO4/Mn0.5Cd0.5S Nanocomposite without Precious Metal Cocatalyst

“…In the high-resolution XPS spectra of O 1s (Figure 4f), the peaks located at 530.72 and 529.48 eV represent the characteristic peaks of lattice oxygen in ZnWO4 [31,38]. [35,39]. Figure 5c shows the BET surface areas of each sample (specific values are shown in Table 1), and the specific surface area of ZWMCS nanocomposites are gradually elevated with the increase of the content of ZnWO…”

“…These results indicate that the ZWMCS-2 nanocomposite formed by Mn 0.5 Cd 0.5 S and ZnWO 4 retains the good visible light absorption ability of Mn 0.5 Cd 0.5 S. The linear conversion of absorption curves of Mn 0.5 Cd 0.5 S and ZnWO 4 (Figure 6b) shows that the band gap (E g ) of Mn 0.5 Cd 0.5 S and ZnWO 4 are 2.24 and 3.68 eV, respectively. According to (Supporting Information Equations (S2) and (S3)) [39,40], the E VB of Mn 0.5 Cd 0.5 S and ZnWO 4 are 1.63 and 3.65 eV, respectively, and the E CB of Mn 0.5 Cd 0.5 S and ZnWO 4 are −0.61 and −0.03 eV, respectively. Therefore, the conduction and valence band positions of Mn 0.5 Cd 0.5 S are interlaced with those of ZnWO 4 , the type of heterojunction formed between Mn 0.5 Cd 0.5 S and ZnWO 4 in ZWMCS-2 nanocomposite can be Type-II or Z-scheme.…”

“…It should be noted that the heterojunction herein cannot be Type-II. According to Type-II mechanism (Figure S4), the effective valence band of the ZWMCS-2 nanocomposite is only 1.63 eV, which is much lower than the potential of H2O/OH (2.27 eV) [39], so the •OH radical cannot be generated. However, the ZWMCS-2 nanocomposite is found to have a significant •OH signal by EPR test (Figure 9d).…”

“…Figure 5a,b show the N 2 adsorption-desorption isotherms of Mn 0.5 Cd 0.5 S, ZnWO 4 and ZWMCS nanocomposites. It can be seen from the figure that all samples have hysteresis loops, corresponding to Type IV isotherms[35,39]. Figure5cshows the BET surface areas of each sample (specific values are shown in Table1), and the specific surface area of ZWMCS nanocomposites are gradually elevated with the increase of the content of ZnWO 4 .…”

Improving photocatalytic hydrogen production by switching charge kinetics from type-I to Z-scheme via defective engineering

“…[13][14][15][16] According to recent literature, the energy level formed by defects or doping on one of the semiconductors can lead to the transformation of type-I heterostructures to quasi-II or Z-scheme hetero-structures. 17,18 For instance, Li et al constructed a porous Zn x Cd 1−x S/CdS heterojunction catalyst, and proposed that the photoexcited holes of CdS can be transported to the local acceptor state (mainly zinc vacancies) in Zn 0.9 Cd 0.1 S to form a quasi-type-II heterostructure. 19 Zhang et al prepared CdS/ZnS one-dimensional/ two-dimensional heterojunctions under ambient conditions and constructed the Z-scheme and type-I hybrid heterojunctions using the Zn vacancy defect levels in ZnS.…”