H2 production performance of photocatalyst and mechanism of WS2/g-C3N4 heterojunction
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摘要: 通过溶剂蒸发和二次高温煅烧石墨相碳化氮(g-C3N4)纳米片和WS2纳米片混合物构建WS2/g-C3N4异质结，该异质结保留g-C3N4和WS2主体结构的同时，在界面处形成化学键，确保该异质结的化学稳定性和热稳定性。光催化分解水制氢实验表明，WS2纳米片含量为3wt%时光催化制氢速率高达68.62 μmol/h，分别是g-C3N4纳米片和WS2纳米片的2.53倍和15.29倍，表明异质结的构建可大幅提升g-C3N4的光催化性能，循环实验表明该异质结在5次循环实验后光催化性能没有明显下降，表明该异质结的稳定性较好。光电性能测试表明异质结的构建不仅提高激发电子的转移效率，同时抑制激发电子空穴的复合率，大幅提升激发电子的利用效率，致使光催化分解水制氢速率较g-C3N4纳米片和WS2纳米片大幅提升。Abstract: The WS2/graphite phase nitrogen carbide(g-C3N4) heterojunction was established through the solvent evaporation and second calcinations the mixture of g-C3N4 nanosheets and WS2 nanosheets. The main structure of g-C3N4 and WS2 in the heterojunction is not destroyed in the calcinations process and the interface is connected by chemical bond, which enhances the stability of heterojunction. The photocatalysis results indicate that the H2 production rate reaches to 68.62 μmol/h while the content of WS2 is 3wt%, which are 2.53 times and 15.29 times as that of g-C3N4 nanosheets and WS2 nanosheets, respectively. Besides, the H2 production rate is not decreased distinctly after 5 times circulation experiments, which reveals that the WS2/g-C3N4 heterojunction has a good chemical stability. Photoelectric property indicates that the establish of heterojunction structure can not only enhance the transport rate of excited electrons, but also suppress the recombination rate of charge carriers. Thus, the H2 production rate is enhanced distinctly compared with that of pure g-C3N4 nanosheets and WS2 nanosheets.
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Keywords:
- g-C3N4 /
- WS2 /
- heterojunction /
- photocatalysis /
- hydrogen
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图 1 光催化分解水制氢装置的示意图(a)和实物图(b)
Figure 1. Equipment of H2 evolution by water splitting by sketch diagram (a) and picture (b) of real products
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图 2 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的XRD图谱
Figure 2. XRD patterns of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 3 g-C3N4纳米片(a)、WS2纳米片(b)和3-WS2/g-C3N4异质结(c)的SEM图像，g-C3N4纳米片(d)、WS2纳米片(e)和3-WS2/g-C3N4异质结(f)的TEM图像，以及g-C3N4纳米片(g)、WS2纳米片(h)和3-WS2/g-C3N4异质结(i)的HRTEM图像
Figure 3. SEM images of g-C3N4 nanosheets (a), WS2 nanosheets (b), 3-WS2/g-C3N4 heterojunction (c); TEM images of g-C3N4 nanosheets (d), WS2 nanosheets (e), 3-WS2/g-C3N4 heterojunction (f); HRTEM images of g-C3N4 nanosheets (g), WS2 nanosheets (h), 3-WS2/g-C3N4 heterojunction (i)
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图 4 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的紫外-可见吸收光图谱
Figure 4. UV-vis spectra of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 5 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的红外光谱图
Figure 5. FTIR spectra of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 6 g-C3N4和3-WS2/g-C3N4异质结XPS全图谱(a)、C1s图谱(b)、N1s图谱(c)和O1s图谱(d)
Figure 6. XPS spectra of survey spectra (a), C1s spectra (b), N1s spectra (c) and O1s spectra (d) in g-C3N4 and 3-WS2/g-C3N4 heterojunction
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图 7 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的N2吸附-脱附平衡曲线
Figure 7. N2 adsorption-desorption curves of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 8 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的光解水制氢曲线(a)；不同含量WS2纳米片异质结光催化分解水制氢曲线(b)
Figure 8. H2 evolution rate of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction (a) ; H2 evolution rate of heterojunction with different amount of WS2 nanosheets (b)
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图 10 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的光致发光光图谱
Figure 10. PL spectra of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 11 g-C3N4纳米片、WS2纳米片和3-WS2/g-C3N4异质结的光电流强度
Figure 11. Photocurrent intensity of g-C3N4 nanosheets, WS2 nanosheets and 3-WS2/g-C3N4 heterojunction
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图 12 3-WS2/g-C3N4异质结活性因子捕获实验
Figure 12. Active species trapping experiments of 3-WS2/g-C3N4 heterojunction
IPA—Isopropanol; TEOA—Triethanolamine; BQ— Benzoquinone
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图 13 WS2/g-C3N4异质结光催化机制
Figure 13. Enhanced mechanism of 3-WS2/g-C3N4 heterojunction on photocatalysis
表 1 不同WS2/石墨相碳化氮(g-C3N4)g-C3N4异质结样品中g-C3N4和WS2的质量
Table 1 Mass of graphite phase nitrogen carbide(g-C3N4) and WS2 in different WS2/g-C3N4 heterojunction samples
Sample 1-WS2/g-C3N4 2-WS2/g-C3N4 3-WS2/g-C3N4 4-WS2/g-C3N4 5-WS2/g-C3N4 WS2/g 0.025 0.050 0.075 0.100 0.125 g-C3N4/g 1 1 1 1 1 
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