Coal-based graphene as a promoter of TiO2 for photocatalytic degradation of organic dyes
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摘要: 石墨烯协同TiO2光催化降解有机物是一种很有前景的解决水体污染问题的方法。本文以低成本煤炭作为石墨烯碳源，成功地制备了TiO2-石墨烯复合催化剂。利用扫描电子显微镜、原子力显微镜、X射线衍射和拉曼光谱等研究了TiO2-石墨烯复合催化剂的微观结构和形貌。煤基石墨烯的引入促进了TiO2光催化降解有机物的反应。特别是在水热还原法制备的TiO2-石墨烯催化剂中，TiO2堆积在石墨烯片层结构上形成层状结构。由于石墨烯的引入，复合催化剂表现出良好的导电性和光电响应特性，并展示出较高的光催化活性。Abstract: A reduced graphene oxide (H-rGO)/TiO2-composite (H-TiO2@rGO) as a catalyst for photocatalytic degradation of rhodamine B (Rh B) and methyl orange (MO) was prepared by hydrothermal treating a dispersant of TiO2 nanoparticles with sizes of 5-10 nm and GO obtained by the Hummers method from coal-based graphite in water. Compared with the M-TiO2@GO and M-TiO2@rGO composites by a wet mixing method, results indicated that the TiO2 nanoparticles in H-TiO2@rGO were uniformly decorated on both sides of rGO sheet, forming a stacked-sheet structure while apparent aggregation of TiO2 nanoparticles was found in both M-TiO2@GO and M-TiO2@rGO. Therefore, H-rGO@TiO2 had the highest catalytic activity towards degradation of Rh B and MO under visible light irradiation among the three, where the incorporation of rGO into TiO2 helps to narrow the band gap of TiO2, inhibit the recombination rate of electron–hole pairs and provide conductive networks for electron transfer.
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Key words:
- Coal-based graphene /
- Hydrothermal method /
- Photocatalytic degradation /
- Titanium dioxide
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Figure 1. (a) XRD patterns of TiO2, GO and composite catalysts, (b) Raman spectra of TiO2 and composite catalysts, (c) FT-IR spectra of TiO2, rGO and catalyst catalysts, and the (d) Ti 2p, (e) O 1s, and (f) C 1s XPS spectra of H-TiO2@rGO.
Figure 2. SEM images of (a) H-TiO2@rGO, (b) M-TiO2@rGO, (c) M-TiO2@GO, (d) GO; (e) AFM images and (f) H-TiO2@rGO.
Figure 4. Adsorption-equilibrium and photocatalytic-degradation curves for (a) Rh B, (b) MO solutions over various catalysts, and first-order kinetics plots of (c) Rh B, (d) MO degradation over various catalysts, and cycle degradation experiments (e) Rh B and (f) MO over the H-TiO2@rGO catalyst.
Figure 5. (a) Diffuse reflectance absorption spectra, (b) Band-gap energy plots, (c) Transient photocurrent curves, and (d) EIS changes of TiO2 and TiO2-rGO composites.
Figure 6. Suggested mechanism of decomposition of Rh-B and MO through photodegradation by TiO2@rGO composites.
Table 1. Pore parameters of the catalysts.
Samples SBET
(m2 g−1)Total pore volume
(mL g−1)Average pore diameter (nm) TiO2 29.61 0.52 69.70 H-TiO2@rGO 35.89 0.51 34.18 M-TiO2@GO 35.52 0.61 35.00 M-TiO2@rGO 34.30 0.54 35.24 
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Table 2. Reaction rate constants of the photocatalysts.
Samples k (Rh B) k (MO) TiO2 0.00267 0.00320 H-TiO2@rGO 0.01332 0.01481 M-TiO2@GO 0.00554 0.00571 M-TiO2@rGO 0.00998 0.01031
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