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Article

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

by
Tingting Ma
1,
Zhen Li
2,
Gan Wang
1,
Jinfeng Zhang
3,* and
Zhenghua Wang
1,*
1
Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, China
2
School of Food Engineering, Anhui Science and Technology University, Fengyang 233100, China
3
Anhui Province Key Laboratory of Pollutant Sensitive Materials and Environmental Remediation, School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
*
Authors to whom correspondence should be addressed.
Catalysts 2022, 12(12), 1527; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12121527
Submission received: 9 November 2022 / Revised: 22 November 2022 / Accepted: 24 November 2022 / Published: 27 November 2022
(This article belongs to the Special Issue Advances in Heterojunction Photocatalysts)
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Abstract

:
How to restrain the recombination of photogenerated electrons and holes is still very important for photocatalytic hydrogen production. Herein, Z-scheme ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites are prepared and are applied as visible-light driven precious metal cocatalyst free photocatalyst for hydrogen generation. The ZnWO4/Mn0.5Cd0.5S nanocomposites with 30 wt% ZnWO4 (ZWMCS-2) can reach a photocatalytic hydrogen evolution rate of 3.36 mmol g−1 h−1, which is much higher than that of single ZnWO4 (trace) and Mn0.5Cd0.5S (1.96 mmol g−1 h−1). Cycling test reveals that the ZMWCS-2 nanocomposite can maintain stable photocatalytic hydrogen evolution for seven cycles (21 h). The type of heterojunction in the ZWMCS-2 nanocomposite can be identified as Z-scheme heterojunction. The Z-scheme heterojunction can effectively separate the electrons and holes, so that the hydrogen generation activity and stability of the ZWMCS-2 nanocomposite can be enhanced. This work provides a highly efficient and stable Z-scheme heterojunction photocatalyst for hydrogen generation.

1. Introduction

In order to alleviate the environmental pollution and energy shortage originated from the excessive use of fossil fuels, renewable and clean energy sources are urgently needed to replace the fossil fuels [1,2]. Hydrogen, as an ideal renewable and clean fuel, has attracted extensive attentions [3,4,5]. Visible light driven photocatalytic hydrogen evolution from water splitting is an efficient and environmentally friendly method to harvest the endless solar energy and turn it into hydrogen energy [6,7,8,9]. This method is very helpful to alleviate the environmental and energy issues originated from fossil fuels.
Currently, many photocatalysts are continuously discovered and intensively studied [10,11]. Among them, CdS, as a kind of classical semiconductor material, is widely used in solar energy generation, paints, photocatalysis, as well as other fields. Since CdS has strong absorption of visible light, and its conduction band position is lower than hydrogen evolution potential, it is expected to be an excellent photocatalytic hydrogen evolution photocatalyst [12,13,14,15]. However, numerous studies have shown that the actual photocatalytic hydrogen generation performance of CdS is not high, and the main problems are its low separation efficiency of electrons and holes and serious photo-corrosion [16,17]. Fortunately, an increasing number of reports have proposed methods to improve the weakness of CdS, such as modification of nanostructures [18], non-noble metal ion doping [19], construction of heterojunctions [20,21], and introducing surface defects [22].
Recent studies have revealed that introducing other metal ions into CdS can form solid solutions such as MnxCd1–xS [23], ZnxCd1–xS [24], CdxIn1–xS [25], and (Zn0.95Cu0.05)(1–x)CdxS [26]. MnxCd1–xS solid solution can be formed by substitute part of Cd2+ in CdS by Mn2+. The substitution of Cd2+ by Mn2+ can effectively enlarge the interlayer spacing of CdS, thus promoting the ionic diffusion kinetic properties [27,28]. By changing the molar ratio of Mn2+/Cd2+, the band edge position and the band gap width of MnxCd1–xS can be tuned [29]. So the photocatalytic hydrogen evolution activity of MnxCd1–xS can be optimized. However, some of the drawbacks of CdS are still retained in MnxCd1–xS, such as low separation efficiency of carriers [30].
As a typical metal tungstate semiconductor, ZnWO4 has been widely used in the fields of photocatalytic hydrogen generation and organic pollutant degradation due to its non-toxicity, low cost, ultra-wide band gap (3.5 eV) as well as excellent physicochemical stability [31]. However, the problems of rapid recombination of photogenerated electron-hole and weak visible light absorption still hinder the practical usage of ZnWO4 in the field of photocatalysis [32]. Therefore, the study on modification of ZnWO4 is of great significance.
In recent years, more and more studies tend to construct Z-scheme heterojunction to further promote the photocatalytic hydrogen evolution rate and stability of the photocatalyst [33,34]. For instance, Zuo et al. constructed TiO2-ZnIn2S4 nanoflower with Z-scheme heterostructure, which effectively suppressed the recombination of photogenerated electrons–holes, and improved the photocatalytic H2 generation efficiency and stability [35]. Li and co-workers successfully synthesized a Z-scheme heterostructured NiTiO3/Cd0.5Zn0.5S photocatalyst with high photocatalytic hydrogen evolution activity and stability relative to constituent materials [36].
In this work, ZnWO4/Mn0.5Cd0.5S (ZMWCS) nanocomposites with varied Mn0.5Cd0.5S contents are successfully prepared through a two-step hydrothermal method. their photocatalytic hydrogen evolution performances are measured under visible light and free of any noble-metal cocatalysts. Among them, the ZMWCS-2 nanocomposite with ZnWO4 mass ratio of 30 % shows the optimal photocatalytic hydrogen evolution activity, and it still maintains stable photocatalytic hydrogen evolution activity after 21 h cycling test. Through experiments as well as theoretical calculations, the separation method of photogenerated carriers through the heterojunction in ZMWCS-2 nanocomposite is confirmed as Z-scheme. Through the Z-scheme heterojunction, the photogenerated electrons and holes can be effectively separated, thus the hydrogen evolution reaction can be accelerated, and the self-corrosion of Mn0.5Cd0.5S can be alleviated. The existence of Z-scheme heterojunction lead to the excellent photocatalytic hydrogen evolution activity and stability of the ZMWCS nanocomposites.

2. Results

2.1. Process of Materials Synthesis

As shown in Scheme 1, ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites are synthesized via two-step hydrothermal method. First, NaWO4 solution was slowly dropped into Zn(NO)3 solution, and then the mixed solution was heated at 180 °C for 8 h to obtain ZnWO4 nanoparticles. Then, ZnWO4 nanoparticles, Cd(CH3COO)2·2H2O, Mn(CH3COO)2·4H2O, and TAA were together added in water, fully dissolved, and heated at 160 °C for 24 h. Through these two steps, ZWMCS nanocomposites were obtained.

2.2. Phase and Morphology Analysis

Figure 1 shows the X-ray powder diffraction (XRD) patterns of Mn0.5Cd0.5S, ZnWO4 and ZWMCS nanocomposites. The XRD pattern of Mn0.5Cd0.5S is very similar to that of hexagonal phase CdS (JCPDS 80-0006), except a slight shift in peak positions (Figure S1). The peak shift can be attributed to the partial substitution of Cd2+ by Mn2+ [37]. The XRD pattern of ZnWO4 is in good agreement with that of monoclinic ZnWO4 (Figure S2, JCPDS No.73-0554). These results confirm the successful preparation of Mn0.5Cd0.5S and ZnWO4. The ZWMCS nanocomposites (ZWMCS-1, ZWMCS-2, ZWMCS-3, and ZWMCS-4) contain all the characteristic peaks of ZnWO4 and Mn0.5Cd0.5S, which confirms that both ZnWO4 and Mn0.5Cd0.5S are contained in ZWMCS nanocomposites. In addition, with the increase of ZnWO4 content, the diffraction peak intensity of ZnWO4 in ZWMCS nanocomposites gradually enhances.
Figure 2 shows the scanning electron microscopy (SEM) images of Mn0.5Cd0.5S, ZnWO4 and ZWMCS-2 nanocomposite. In Figure 2a, Mn0.5Cd0.5S presented nanoparticle morphology (~50 nm). In Figure 2b, ZnWO4 exhibits rod-like morphology. In Figure 2c, numerous Mn0.5Cd0.5S and ZnWO4 are attached to each other to form the ZWMCS-2 nanocomposite. Figure 2d–f shows the energy dispersive spectroscopy (EDS) spectra of Mn0.5Cd0.5S, ZnWO4 and ZWMCS-2 nanocomposite. It reveals that Mn0.5Cd0.5S, ZnWO4, and ZWMCS-2 nanocomposite only contain the respective constituent prime peaks and no impurity peaks, which indicates the purity of the synthesized samples. The EDS mapping images in Figure 2g confirm that the constituent elements of ZWMCS-2 nanocomposite are well distributed, which further indicates the composition of the ZWMCS-2 nanocomposite.
The morphology of the material can be further observed by transmission electron microscopy (TEM). As shown in Figure 3a, Mn0.5Cd0.5S presents nanoparticles with diameter of about 50 nm. In Figure 3b, ZnWO4 takes on short nanorods morphology with a diameter in the range of 5–50 nm. Figure 3c shows the morphology of ZWMCS-2 nanocomposite. It can be seen that Mn0.5Cd0.5S and ZnWO4 cluster together to form the nanocomposite. Figure 3d shows a HRTEM image of ZWMCS-2 nanocomposite, the lattice fringe spacing of ZnWO4 is 0.293 nm, corresponding to the (111) crystal plane of ZnWO4, and the lattice fringe spacing of Mn0.5Cd0.5S is 0.173 nm, corresponding to the (112) crystal plane of Mn0.5Cd0.5S. The lattice distortion appears at the junction between them, which indicates the formation of heterojunction. The presence of heterojunctions indicates the successful formation of composites between ZnWO4 and Mn0.5Cd0.5S.

2.3. X-ray Photoelectron Spectroscopy (XPS) and Elemental Analysis

The chemical state and elemental composition of ZWMCS-2 nanocomposite are analyzed by X-ray photoelectron spectroscopy (XPS). As shown in Figure S3, the characteristic peaks of Cd, Mn, S, Zn, W, and O elements can be clearly seen in the XPS survey spectrum of ZWMCS-2 nanocomposite. Figure 4a–f shows the high-resolution XPS spectra of Cd 3d, Mn 2p, S 2p, Zn 2p, W 4f, and O 1s elements, respectively. In Figure 4a, the two peaks at 411.07 and 404.33 eV belong to Cd 3d3/2 and Cd 3d5/2, respectively [23,30]. The two peaks at 651.56 and 639.96 eV (Figure 4b) correspond to Mn 2p1/2 and Mn 2p3/2, respectively [23,30]. In Figure 4c, the peaks at 161.95 and 160.69 eV correspond to S 2p3/2 and S 2p1/2, respectively [23,30]. The peaks at 1044.08 and 1021.06 eV (Figure 4d) represent Zn 2p3/2 and Zn 2p1/2, respectively [31,38]. As shown in Figure 4e, the two peaks at 36.98 and 34.84 eV belong to W f5/2 and W f7/2, respectively [31,38]. 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].

2.4. BET Surface Area Analysis

Figure 5a,b show the N2 adsorption–desorption isotherms of Mn0.5Cd0.5S, ZnWO4 and ZWMCS nanocomposites. It can be seen from the figure that all samples have hysteresis loops, corresponding to Type IV isotherms [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 ZnWO4.

2.5. UV-Vis Diffuse Reflectance Spectroscopy and Band Gap Analysis

Figure 6a shows the UV-vis diffuse reflectance spectroscopy (DRS) of Mn0.5Cd0.5S, ZnWO4 and ZWMCS-2 nanocomposite. The absorption edges of Mn0.5Cd0.5S and ZnWO4 are at 578.15 and 358.76 nm, respectively. This result indicates that ZnWO4 is a typical invisible light excitation semiconductor material, while Mn0.5Cd0.5S has good visible light absorption ability. Figure 6a shows that ZWMCS-2 nanocomposite also has good light absorption ability. These results indicate that the ZWMCS-2 nanocomposite formed by Mn0.5Cd0.5S and ZnWO4 retains the good visible light absorption ability of Mn0.5Cd0.5S. The linear conversion of absorption curves of Mn0.5Cd0.5S and ZnWO4 (Figure 6b) shows that the band gap (Eg) of Mn0.5Cd0.5S and ZnWO4 are 2.24 and 3.68 eV, respectively. According to (Supporting Information Equations (S2) and (S3)) [39,40], the EVB of Mn0.5Cd0.5S and ZnWO4 are 1.63 and 3.65 eV, respectively, and the ECB of Mn0.5Cd0.5S and ZnWO4 are −0.61 and −0.03 eV, respectively. Therefore, the conduction and valence band positions of Mn0.5Cd0.5S are interlaced with those of ZnWO4, the type of heterojunction formed between Mn0.5Cd0.5S and ZnWO4 in ZWMCS-2 nanocomposite can be Type-II or Z-scheme.

2.6. Photocatalytic H2 Evolution Performance and Electrochemical Analysis

Figure 7a shows the photocatalytic hydrogen evolution rate of each photocatalyst under visible light and without cocatalyst conditions. Among them, the photocatalytic hydrogen evolution rate of Mn0.5Cd0.5S is 1.96 mmol g−1 h−1, which is significantly higher than that of CdS (trace). This indicates that Mn2+ doping can significantly increase the photocatalytic hydrogen evolution activity of CdS. The ZWMCS nanocomposites synthesized by combining ZnWO4 and Mn0.5Cd0.5S together have improved photocatalytic hydrogen evolution activity than the single material. Among them, the ZWMCS-2 nanocomposite has the highest photocatalytic hydrogen evolution rate of 3.32 mmol g−1 h−1, which is much higher than that of Mn0.5Cd0.5S. Cycling test shows that the ZWMCS-2 nanocomposite still maintains good photocatalytic activity after seven cycles (21 h) of photocatalytic hydrogen evolution test (Figure 7b).
In order to further explore the photogenerated electron hole separation efficiency of each photocatalyst, their photocurrent responses are tested, and the results are shown in Figure 8. The curve of ZnWO4 is almost a straight line, which indicates that the photocurrent response of ZnWO4 under visible light is very weak. Unlike ZnWO4, Mn0.5Cd0.5S show obvious photocurrent response under visible light. Compared with Mn0.5Cd0.5S, the ZWMCS-2 nanocomposite has obvious higher photocurrent. This indicates that the ZWMCS-2 nanocomposite has higher photogenerated electron-hole separation efficiency. The excellent electron-hole separation efficiency of the ZWMCS-2 nanocomposite is conducive to the photocatalytic hydrogen evolution reaction.

2.7. Photocatalytic H2 Evolution Mechanism

The type of heterojunction is studied by theoretical calculation and EPR. Figure 9a and b show the electrostatic potential diagrams of Mn0.5Cd0.5S and ZnWO4, respectively. The insets in the figure show the optimization models of Mn0.5Cd0.5S (112) and ZnWO4 (111) crystal planes, respectively. The calculation results reveal that the surface work functions of Mn0.5Cd0.5S (112) and ZnWO4 (111) are 4.29 and 5.07 eV, respectively. So, the fermi level of ZnWO4 (111) is significantly lower than that of Mn0.5Cd0.5S (112). When ZnWO4 and Mn0.5Cd0.5S are combined together, a built-in electric field is formed between ZnWO4 and Mn0.5Cd0.5S, and the electron movement direction is from Mn0.5Cd0.5S to ZnWO4. The continuous movement of electrons in the built-in electric field and the continuous accumulation of holes make the bands of Mn0.5Cd0.5S and ZnWO4 gradually bend, forming Z-scheme heterojunction, as shown in Figure 9c [40]. 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). Therefore, the separation mechanism of electrons–holes through the heterojunction in ZWMCS-2 nanocomposite does not belong to Type-II. Following the Z-scheme mechanism (Figure 9e), the effective valence band of the ZWMCS-2 nanocomposite is 3.68 eV, which is much higher than the H2O/OH potential (2.27 eV), and ·OH can be generated. As revealed by Figure 9d, obvious signals of ·OH can be detected in ZWMCS-2 nanocomposite by EPR. Therefore, the type of heterojunction in ZWMCS-2 nanocomposite is determined to be Z-scheme.
The photocatalytic hydrogen evolution mechanism of the ZWMCS-2 nanocomposite can be described as following. After irradiated by visible light, ZWMCS-2 nanocomposite generates electron-hole pairs. Due to the existence of Z-scheme heterojunction, the photogenerated electrons in the conduction band of ZnWO4 are transferred to the valence band of Mn0.5Cd0.5S, and then recombines with the photogenerated holes there. Through this process, the holes in the valence band of Mn0.5Cd0.5S are consumed, avoiding the recombination with electrons, so that a large number of photogenerated electrons are collected in the conduction band of Mn0.5Cd0.5S. The effective conduction band of the ZWMCS-2 nanocomposite is −0.61 eV, which is higher than the H+/H2 potential (0 eV) [33,34]. Therefore, the photogenerated electrons in the conduction band of Mn0.5Cd0.5S can reduce hydrogen ions in water to hydrogen. At the same time, the holes in the valence band of ZnWO4 are consumed by the sacrificial agents (S2− and SO32−). The existence of Z-scheme heterojunction promotes the effective separation of photogenerated electrons and holes, and promotes the performance of photocatalytic hydrogen evolution. Therefore, the ZWMCS-2 nanocomposite has excellent photocatalytic activity and stability for hydrogen production.

3. Materials and Methods

3.1. Synthesis of ZnWO4 Nanoparticles

Solution A was obtained by dissolving 1.65 g of NaWO4·2H2O in 15 mL of distilled water. Solution B was obtained by dissolving 1.49 g of Zn(NO)3·6H2O in 15 mL distilled water. Under continuous stirring, solution A was slowly dropped into solution B. The mixed solution was stirred for 1 h, then it was transferred to a 50 mL reaction kettle, heated at 180 °C for 8 h. After cooling to room temperature, the sample was collected by centrifugation, washed repeatedly with distilled water, and freeze-dried for 18 h.

3.2. Synthesis of ZnWO4/Mn0.5Cd0.5S Nanocomposites

First, 0.0992 g of ZnWO4, 0.2451 g of Mn (CH3COO)2·4H2O, 0.2665 g of Cd (CH3COO)2·2H2O, and 0.1503 g of TAA were dissolved in 35 mL distilled water. After continuous agitation for 1 h, the mixed suspension was transferred to a 50 mL reaction kettle and heated at 160 °C for 48 h. After cooling to room temperature, the sample was collected by centrifugation, washed repeatedly by distilled water, and freeze-dried for 18 h. This sample was named as ZWMCS-2. Other ZnWO4/Mn0.5Cd0.5S nanocomposites and Mn0.5Cd0.5S nanoparticles were synthesized by similar method with different mass contents of ZnWO4. Table 2 lists the abbreviations of the as-synthesized samples.

3.3. Photocatalytic Measurements

Photocatalytic measurements were performed in a 250 mL three-necked flask sealed by rubber stopper. The visible light source is a 300 W Xenon lamp with a λ ≥ 420 nm filter. In a typical photocatalytic hydrogen production process, 0.05 g of catalyst, 8.40 g of Na2S·9H2O, and 3.15 g of Na2SO3 were dissolved in 100 mL distilled water in the flask, and then N2 gas was passed into the flask for 30 min to remove air. The flask was illuminated by the Xenon lamp. At an interval of one hour, the gases in the flask was collected by a 1 mL syringe, and was measured by gas chromatography.

3.4. Characterizations

All the characterization equipment and their working parameters are given in the supporting information.

4. Conclusions

ZnWO4/Mn0.5Cd0.5S nanocomposites are prepared through a two-step hydrothermal method. Under visible light irradiation, and without the help of any noble metal cocatalyst, the ZWMCS-2 nanocomposite exhibits a high hydrogen evolution rate of 3.36 mmol g−1 h−1, and does not show obvious deterioration after 21 h cycling test. Moreover, the photocatalytic hydrogen evolution activity of the ZWMCS-2 nanocomposite is significantly higher than that of the constituent materials. Through experimental analysis and theoretical calculation, it is confirmed that the type of the heterojunction in the ZWMCS-2 nanocomposite is Z-scheme. The Z-scheme heterojunction can effectively separate the photogenerated electrons and holes, reduce the photo-corrosion of the single material, and maximize the photocatalytic hydrogen evolution.

Supplementary Materials

The following supporting information can be downloaded at: https://0-www-mdpi-com.brum.beds.ac.uk/article/10.3390/catal12121527/s1. Figure S1: (a) XRD patterns of as-prepared CdS, MnS, and Mn0.5Cd0.5S (S1. (b) is an enlarged view of the dotted box area.). Figure S2: XRD patterns of as-prepared ZnWO4. Figure S3: XPS survey spectra of ZWMCS-2 nanocomposite. Figure S4: The schematic diagrams of charge transfer in supposed Type-II heterojunction.

Author Contributions

T.M.: conceptualization, data curation, formal analysis, investigation, methodology, writing—original draft preparation; Z.L.: investigation, formal analysis; G.W.: writing—review and editing; J.Z.: funding acquisition, resources; Z.W.: conceptualization, funding acquisition, project administration, resources, writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financial supported by the National Natural Science Foundation of China (no. 51973078) and Natural Science Foundation of Anhui Province (2108085MB48).

Data Availability Statement

The data presented in this study can be obtained from the first author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Song, H.; Luo, S.; Huang, H.; Deng, B.; Ye, J. Solar-Driven Hydrogen Production: Recent Advances, Challenges, and Future Perspectives. ACS Energy Lett. 2022, 7, 1043–1065. [Google Scholar] [CrossRef]
  2. Feng, C.; Wu, Z.P.; Huang, K.W.; Ye, J.; Zhang, H. Surface Modification of 2D Photocatalysts for Solar Energy Conversion. Adv. Mater. 2022, 34, 2200180. [Google Scholar] [CrossRef]
  3. Yang, Y.; Zhou, C.; Wang, W.; Xiong, W.; Zeng, G.; Huang, D.; Zhang, C.; Song, B.; Xue, W.; Li, X.; et al. Recent Advances in Application of Transition Metal Phosphides for Photocatalytic Hydrogen Production. Chem. Eng. J. 2021, 405, 126547. [Google Scholar] [CrossRef]
  4. Tiwari, J.N.; Singh, A.N.; Sultan, S.; Kim, K.S. Recent Advancement of P- and D-Block Elements, Single Atoms, and Graphene-Based Photoelectrochemical Electrodes for Water Splitting. Adv. Energy Mater. 2020, 10, 2000280. [Google Scholar] [CrossRef]
  5. Lakhera, S.K.; Rajan, A.; Rugma, T.P.; Bernaurdshaw, N. A Review on Particulate Photocatalytic Hydrogen Production System: Progress Made in Achieving High Energy Conversion Efficiency and Key Challenges Ahead. Renew. Sustain. Energy Rev. 2021, 152, 111694. [Google Scholar] [CrossRef]
  6. Bie, C.; Wang, L.; Yu, J. Challenges for Photocatalytic Overall Water Splitting. Chem 2022, 8, 1567–1574. [Google Scholar] [CrossRef]
  7. Abdul Nasir, J.; Munir, A.; Ahmad, N.; ul Haq, T.; Khan, Z.; Rehman, Z. Photocatalytic Z-Scheme Overall Water Splitting: Recent Advances in Theory and Experiments. Adv. Mater. 2021, 33, 2105195. [Google Scholar] [CrossRef]
  8. Yu, J.M.; Lee, J.; Kim, Y.S.; Song, J.; Oh, J.; Lee, S.M.; Jeong, M.; Kim, Y.; Kwak, J.H.; Cho, S.; et al. High-Performance and Stable Photoelectrochemical Water Splitting Cell with Organic-Photoactive-Layer-Based Photoanode. Nat. Commun. 2020, 11, 5509. [Google Scholar] [CrossRef]
  9. Sharma, C.; Pooja, D.; Thakur, A.; Negi, Y.S. Review—Combining Experimental and Engineering Aspects of Catalyst Design for Photoelectrochemical Water Splitting. ECS Adv. 2022, 1, 030501. [Google Scholar] [CrossRef]
  10. Shen, R.; Ren, D.; Ding, Y.; Guan, Y.; Ng, Y.H.; Zhang, P.; Li, X. Nanostructured CdS for Efficient Photocatalytic H2 Evolution: A Review. Sci. China Mater. 2020, 63, 2153–2188. [Google Scholar] [CrossRef]
  11. Chiarello, G.L.; Dozzi, M.V.; Selli, E. TiO2-based materials for photocatalytic hydrogen production. J. Energy Chem. 2017, 26, 250–258. [Google Scholar] [CrossRef]
  12. Nasir, J.A.; Rehman, Z.U.; Shah, S.N.A.; Khan, A.; Butler, I.S.; Catlow, C.R.A. Recent Developments and Perspectives in CdS-Based Photocatalysts for Water Splitting. J. Mater. Chem. A 2020, 8, 20752–20780. [Google Scholar] [CrossRef]
  13. Ning, X.; Lu, G. Photocorrosion Inhibition of CdS-Based Catalysts for Photocatalytic Overall Water Splitting. Nanoscale 2020, 12, 1213–1223. [Google Scholar] [CrossRef]
  14. Cheng, L.; Xiang, Q.; Liao, Y.; Zhang, H. CdS-Based Photocatalysts. Energy Environ. Sci. 2018, 11, 1362–1391. [Google Scholar] [CrossRef]
  15. Mamiyev, Z.; Balayeva, N.O. Metal Sulfide Photocatalysts for Hydrogen Generation: A Review of Recent Advances. Catalysts 2022, 12, 1316. [Google Scholar] [CrossRef]
  16. Wang, P.; Li, H.; Sheng, Y.; Chen, F. Inhibited Photocorrosion and Improved Photocatalytic H2-Evolution Activity of CdS Photocatalyst by Molybdate Ions. Appl. Surf. Sci. 2019, 463, 27–33. [Google Scholar] [CrossRef]
  17. Chen, Y.; Zhong, W.; Chen, F.; Wang, P.; Fan, J.; Yu, H. Photoinduced Self-Stability Mechanism of CdS Photocatalyst: The Dependence of Photocorrosion and H2-Evolution Performance. J. Mater. Sci. Technol. 2022, 121, 19–27. [Google Scholar] [CrossRef]
  18. Wang, B.; Chen, C.; Jiang, Y.; Ni, P.; Zhang, C.; Yang, Y.; Lu, Y.; Liu, P. Rational Designing 0D/1D Z-Scheme Heterojunction on CdS Nanorods for Efficient Visible-Light-Driven Photocatalytic H2 Evolution. Chem. Eng. J. 2021, 412, 128690. [Google Scholar] [CrossRef]
  19. She, H.; Sun, Y.; Li, S.; Huang, J.; Wang, L.; Zhu, G.; Wang, Q. Synthesis of Non-Noble Metal Nickel Doped Sulfide Solid Solution for Improved Photocatalytic Performance. Appl. Catal. B Environ. 2019, 245, 439–447. [Google Scholar] [CrossRef]
  20. Iqbal, S. Spatial Charge Separation and Transfer in L-Cysteine Capped NiCoP/CdS Nano-Heterojunction Activated with Intimate Covalent Bonding for High-Quantum-Yield Photocatalytic Hydrogen Evolution. Appl. Catal. B Environ. 2020, 274, 119097. [Google Scholar] [CrossRef]
  21. Ren, D.; Shen, R.; Jiang, Z.; Lu, X.; Li, X. Highly Efficient Visible-Light Photocatalytic H2 Evolution over 2D-2D CdS/Cu7S4 Layered Heterojunctions. Chin. J. Catal. 2020, 41, 31–40. [Google Scholar] [CrossRef]
  22. Kumar, A.; Krishnan, V. Vacancy Engineering in Semiconductor Photocatalysts: Implications in Hydrogen Evolution and Nitrogen Fixation Applications. Adv. Funct. Mater. 2021, 31, 2009807. [Google Scholar] [CrossRef]
  23. Li, L.; Liu, G.; Qi, S.; Liu, X.; Gu, L.; Lou, Y.; Chen, J.; Zhao, Y. Highly Efficient Colloidal MnxCd1–xS Nanorod Solid Solution for Photocatalytic Hydrogen Generation. J. Mater. Chem. A 2018, 6, 23683–23689. [Google Scholar] [CrossRef]
  24. Huang, D.; Wen, M.; Zhou, C.; Li, Z.; Cheng, M.; Chen, S.; Xue, W.; Lei, L.; Yang, Y.; Xiong, W.; et al. ZnxCd1–xS Based Materials for Photocatalytic Hydrogen Evolution, Pollutants Degradation and Carbon Dioxide Reduction. Appl. Catal. B Environ. 2020, 267, 118651. [Google Scholar] [CrossRef]
  25. Dan, M.; Prakash, A.; Cai, Q.; Xiang, J.; Ye, Y.; Li, Y.; Yu, S.; Lin, Y.; Zhou, Y. Energy-Band-Controlling Strategy to Construct Novel CdxIn1–xS Solid Solution for Durable Visible Light Photocatalytic Hydrogen Sulfide Splitting. Solar RRL 2019, 3, 1800237. [Google Scholar] [CrossRef] [Green Version]
  26. Liu, J.; Feng, J.; Lu, L.; Wu, B.; Ren, P.; Shi, W.; Cheng, P. A Metal-Organic-Framework-Derived (Zn0.95Cu0.05)0.6Cd0.4S Solid Solution as Efficient Photocatalyst for Hydrogen Evolution Reaction. ACS Appl. Mater. Interfaces 2020, 12, 10261–10267. [Google Scholar] [CrossRef]
  27. Huang, H.; Wang, Z.; Luo, B.; Chen, P.; Lin, T.; Xiao, M.; Wang, S.; Dai, B.; Wang, W.; Kou, J.; et al. Design of Twin Junction with Solid Solution Interface for Efficient Photocatalytic H2 Production. Nano Energy 2020, 69, 104410. [Google Scholar] [CrossRef]
  28. Deng, W.; Chen, J.; Yang, L.; Liang, X.; Yin, S.; Deng, X.; Zou, G.; Hou, H.; Ji, X. Solid Solution Metal Chalcogenides for Sodium-Ion Batteries: The Recent Advances as Anodes. Small 2021, 17, 2101058. [Google Scholar] [CrossRef]
  29. Li, H.; Wang, Z.; He, Y.; Meng, S.; Xu, Y.; Chen, S.; Fu, X. Rational Synthesis of MnxCd1–xS for Enhanced Photocatalytic H2 Evolution: Effects of S Precursors and the Feed Ratio of Mn/Cd on Its Structure and Performance. J. Colloid Interface Sci. 2019, 535, 469–480. [Google Scholar] [CrossRef]
  30. Xiong, M.; Qin, Y.; Chai, B.; Yan, J.; Fan, G.; Xu, F.; Wang, C.; Song, G. Unveiling the Role of Mn-Cd-S Solid Solution and MnS in MnxCd1–xS Photocatalysts and Decorating with CoP Nanoplates for Enhanced Photocatalytic H2 Evolution. Chem. Eng. J. 2022, 428, 131069. [Google Scholar] [CrossRef]
  31. Kumar, G.M.; Lee, D.J.; Jeon, H.C.; Ilanchezhiyan, P.; Young, K.D.; Won, K.T. One Dimensional ZnWO4 Nanorods Coupled with WO3 Nanoplates Heterojunction Composite for Efficient Photocatalytic and Photoelectrochemical Activity. Ceram. Int. 2022, 48, 4332–4340. [Google Scholar] [CrossRef]
  32. Zhang, N.; Chen, D.; Cai, B.; Wang, S.; Niu, F.; Qin, L.; Huang, Y. Facile Synthesis of CdS-ZnWO4 Composite Photocatalysts for Efficient Visible Light Driven Hydrogen Evolution. Int. J. Hydrogen Energy 2017, 42, 1962–1969. [Google Scholar] [CrossRef]
  33. Ng, B.J.; Putri, L.K.; Kong, X.Y.; Teh, Y.W.; Pasbakhsh, P.; Chai, S.P. Z-Scheme Photocatalytic Systems for Solar Water Splitting. Adv. Sci. 2020, 7, 1903171. [Google Scholar] [CrossRef] [Green Version]
  34. Liao, G.; Li, C.; Liu, S.Y.; Fang, B.; Yang, H. Emerging Frontiers of Z-Scheme Photocatalyric Systems. Trends Chem. 2022, 4, 111–127. [Google Scholar] [CrossRef]
  35. Zuo, G.; Wang, Y.; Teo, W.L.; Xian, Q.; Zhao, Y. Direct Z-Scheme TiO2-ZnIn2S4 Nanoflowers for Cocatalyst-Free Photocatalytic Water Splitting. Appl. Catal. B Environ. 2021, 291, 120126. [Google Scholar] [CrossRef]
  36. Li, B.; Wang, W.; Zhao, J.; Wang, Z.; Su, B.; Hou, Y.; Ding, Z.; Ong, W.J.; Wang, S. All-Solid-State Direct Z-Scheme NiTiO3/Cd0.5Zn0.5S Heterostructures for Photocatalytic Hydrogen Evolution with Visible Light. J. Mater. Chem. A 2021, 9, 10270–10276. [Google Scholar] [CrossRef]
  37. Jiang, X.; Gong, H.; Liu, Q.; Song, M.; Huang, C. In Situ Construction of NiSe/Mn0.5Cd0.5S Composites for Enhanced Photocatalytic Hydrogen Production under Visible Light. Appl. Catal. B Environ. 2020, 268, 118439. [Google Scholar] [CrossRef]
  38. Cui, H.; Li, B.; Zheng, X.; Zhang, Y.; Yao, C.; Li, Z.; Sun, D.; Xu, S. Efficient Activity and Stability of ZnWO4/CdS Composite Towards Visible Light Photocatalytic H2 Evolution. J. Photochem. Photobiol. A Chem. 2019, 384, 112046. [Google Scholar] [CrossRef]
  39. Li, Z.; Ma, T.; Zhang, J.; Wang, Z. Converting the Charge Transfer in ZnO/ZnxCd1–xS-DETA Nanocomposite from Type-I to S-Scheme for Efficient Photocatalytic Hydrogen Production. Adv. Mater. Interfaces 2022, 9, 2102497. [Google Scholar] [CrossRef]
  40. Shen, C.H.; Wen, X.J.; Fei, Z.H.; Liu, Z.T.; Mu, Q.M. Novel Z-Scheme W18O49/CeO2 Heterojunction for Improved Photocatalytic Hydrogen Evolution. J. Colloid Interface Sci. 2020, 579, 297–306. [Google Scholar] [CrossRef]
Catalysts 12 01527 sch001 550
Scheme 1. Schematic diagram for the synthesis of ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites.
Scheme 1. Schematic diagram for the synthesis of ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites.
Catalysts 12 01527 sch001
Catalysts 12 01527 g001 550
Figure 1. XRD patterns of ZWMCS nanocomposites.
Figure 1. XRD patterns of ZWMCS nanocomposites.
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Catalysts 12 01527 g002 550
Figure 2. SEM images of (a) Mn0.5Cd0.5S, (b) ZnWO4, and (c) ZWMCS-2 nanocomposite; EDS spectra of (d) Mn0.5Cd0.5S, (e) ZnWO4, and (f) ZWMCS-2 nanocomposite; (g) SEM image with corresponding elemental mapping images for the EDS mapping images of Cd, Mn, S, Zn, W, and O elements of ZWMCS-2 nanocomposite.
Figure 2. SEM images of (a) Mn0.5Cd0.5S, (b) ZnWO4, and (c) ZWMCS-2 nanocomposite; EDS spectra of (d) Mn0.5Cd0.5S, (e) ZnWO4, and (f) ZWMCS-2 nanocomposite; (g) SEM image with corresponding elemental mapping images for the EDS mapping images of Cd, Mn, S, Zn, W, and O elements of ZWMCS-2 nanocomposite.
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Catalysts 12 01527 g003 550
Figure 3. TEM images of (a) Mn0.5Cd0.5S, (b) ZnWO4, and (c) ZWMCS-2 nanocomposite; (d) HRTEM images of the ZWMCS-2 nanocomposite.
Figure 3. TEM images of (a) Mn0.5Cd0.5S, (b) ZnWO4, and (c) ZWMCS-2 nanocomposite; (d) HRTEM images of the ZWMCS-2 nanocomposite.
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Catalysts 12 01527 g004 550
Figure 4. XPS spectra of the as-prepared samples: (a) Cd 3d; (b) Mn 2p; (c) S 3d; (d) Zn 2p; (e) W 4f; (f) O 1s.
Figure 4. XPS spectra of the as-prepared samples: (a) Cd 3d; (b) Mn 2p; (c) S 3d; (d) Zn 2p; (e) W 4f; (f) O 1s.
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Catalysts 12 01527 g005 550
Figure 5. N2 adsorption–desorption isotherms of (a) Mn0.5Cd0.5S, ZnWO4, ZWMCS-2 nanocomposite and (b) ZWMCS nanocomposites; (c) the BET surface area for Mn0.5Cd0.5S, ZnWO4, and ZWMCS nanocomposites.
Figure 5. N2 adsorption–desorption isotherms of (a) Mn0.5Cd0.5S, ZnWO4, ZWMCS-2 nanocomposite and (b) ZWMCS nanocomposites; (c) the BET surface area for Mn0.5Cd0.5S, ZnWO4, and ZWMCS nanocomposites.
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Figure 6. (a) UV-vis DRS of Mn0.5Cd0.5S, ZnWO4 and ZWMCS-2 nanocomposite; (b) plots of (αhv)2 versus energy (hv) for Mn0.5Cd0.5S and ZnWO4.
Figure 6. (a) UV-vis DRS of Mn0.5Cd0.5S, ZnWO4 and ZWMCS-2 nanocomposite; (b) plots of (αhv)2 versus energy (hv) for Mn0.5Cd0.5S and ZnWO4.
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Figure 7. (a) Photocatalytic H2 production of Mn0.5Cd0.5S, ZnWO4 and ZWMCS nanocomposites; (b) cycling stability for Mn0.5Cd0.5S and ZWMCS-2 nanocomposite.
Figure 7. (a) Photocatalytic H2 production of Mn0.5Cd0.5S, ZnWO4 and ZWMCS nanocomposites; (b) cycling stability for Mn0.5Cd0.5S and ZWMCS-2 nanocomposite.
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Catalysts 12 01527 g008 550
Figure 8. Photocurrent density–time curves of Mn0.5Cd0.5S, ZnWO4, and ZWMCS-2 nanocomposite.
Figure 8. Photocurrent density–time curves of Mn0.5Cd0.5S, ZnWO4, and ZWMCS-2 nanocomposite.
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Catalysts 12 01527 g009 550
Figure 9. Electrostatic potentials and optimized models of (a) Mn0.5Cd0.5S (112) facet and (b) ZnWO4 (111) facet. (c) The Z-scheme formation process of Mn0.5Cd0.5S (112) and ZnWO4 (111) facet. (d) DMPO spin trapping EPR spectra of Mn0.5Cd0.5S, and ZWMCS-2 nanocomposite. (e) The photocatalysis mechanism of ZWMCS-2 nanocomposite under visible light illumination.
Figure 9. Electrostatic potentials and optimized models of (a) Mn0.5Cd0.5S (112) facet and (b) ZnWO4 (111) facet. (c) The Z-scheme formation process of Mn0.5Cd0.5S (112) and ZnWO4 (111) facet. (d) DMPO spin trapping EPR spectra of Mn0.5Cd0.5S, and ZWMCS-2 nanocomposite. (e) The photocatalysis mechanism of ZWMCS-2 nanocomposite under visible light illumination.
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Table
Table 1. The BET surface areas and H2 evolution rate of the Mn0.5Cd0.5S, ZnWO4, and ZWMCS nanocomposites.
Table 1. The BET surface areas and H2 evolution rate of the Mn0.5Cd0.5S, ZnWO4, and ZWMCS nanocomposites.
SamplesBET Surface Area (m2 g−1)H2 Evolution Rate (mmol g−1 h−1)
Mn0.5Cd0.5S6.291.96
ZWMCS-19.481.20
ZWMCS-213.343.36
ZWMCS-315.522.28
ZWMCS-416.911.89
ZnWO424.240.06
Table
Table 2. The amounts of raw materials for preparing the ZnWO4/Mn0.5Cd0.5S nanocomposites.
Table 2. The amounts of raw materials for preparing the ZnWO4/Mn0.5Cd0.5S nanocomposites.
SamplesZnWO4
(g)		Mn(CH3COO)2·4H2O
(g)		Cd(CH3COO)2·2H2O (g)TAA (g)Content of ZnWO4 (%)
Mn0.5Cd0.5S00.24510.26650.15030
ZWMCS-10.05340.24510.26650.150320
ZWMCS-20.09920.24510.26650.150330
ZWMCS-30.15420.24510.26650.150340
ZWMCS-40.23130.24510.26650.150350
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Ma, T.; Li, Z.; Wang, G.; Zhang, J.; Wang, Z. Efficient Visible-Light Driven Photocatalytic Hydrogen Production by Z-Scheme ZnWO4/Mn0.5Cd0.5S Nanocomposite without Precious Metal Cocatalyst. Catalysts 2022, 12, 1527. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12121527

AMA Style

Ma T, Li Z, Wang G, Zhang J, Wang Z. Efficient Visible-Light Driven Photocatalytic Hydrogen Production by Z-Scheme ZnWO4/Mn0.5Cd0.5S Nanocomposite without Precious Metal Cocatalyst. Catalysts. 2022; 12(12):1527. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12121527

Chicago/Turabian Style

Ma, Tingting, Zhen Li, Gan Wang, Jinfeng Zhang, and Zhenghua Wang. 2022. "Efficient Visible-Light Driven Photocatalytic Hydrogen Production by Z-Scheme ZnWO4/Mn0.5Cd0.5S Nanocomposite without Precious Metal Cocatalyst" Catalysts 12, no. 12: 1527. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12121527

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