# Graphene Quantum Dots Doped PVDF(TBT)/PVP(TBT) Fiber Film with Enhanced Photocatalytic Performance
## 3 Results and Discussion
### Photocatalytic Activity  
An 800 W xenon lamp was used to simulate the solar radiation source. The photocatalytic performance of the prepared photocatalyst was examined by decomposition of the RhB solution. In this study, PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, and PVDF(TBT)/PVP(TBT)-GQDs films with a size of 2 cm \(\times\) 2 cm were placed in a quartz tube containing 50 mL of RhB solution. The initial concentration of RhB solution was 15 mg/L. Meanwhile, a blank control group was also set. The results of the RhB degradation experiments showed that the degradation rates of the PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, and PVDF(TBT)/PVP(TBT)-GQDs photocatalysts were 9.66%, 12.08%, 47.71%, and 97.16% after 210 min. The reaction rate of the PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, and PVDF(TBT)/PVP(TBT)-GQDs photocatalysts to the RhB solution was 0.0069 mg/L-min, 0.0086 mg/L-min, 0.0340 mg/L-min and 0.0649 mg/L-min, respectively. Among them, PVDF(TBT)/PVP(TBT)-GQDs (0.0649 mg/L-min) and PVDF(TBT)-GQDs (0.0340 mg/L-min) showed an 8 and 3.9 times higher photocatalytic efficiency than the other photocatalysts (PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O), respectively. In particular, the PVDF(TBT)/PVP(TBT)-GQDs photocatalyst only took 210 min to degrade 97.16% of the RhB solution, as shown in Figure 7.  
Figure 8 shows the UV-Visible absorption spectra of the photocatalysts PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, and PVDF(TBT)/PVP(TBT)-GQDs. The absorption edges of PVDF(TBT)-H\({}_{2}\)O and PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O were around \(\sim\)370 nm, which are the absorption of TiO\({}_{2}\). After graphene doping, the absorption edges were extended to over 800 nm, which fell into the near infrared range. The absorption results are in good agreement with the photocatalytic performance. Both the PVDF(TBT)-GQDs and PVDF(TBT)/PVP(TBT)-GQDs photocatalyst maintained a high light absorption efficiency underlying irradiation from 200 nm to 800 nm. In particular, for PVDF(TBT)/PVP(TBT)-GQDs, the lowest absorption rate of the entire process reached 60%. In contrast, the two photocatalysts, PVDF(TBT)-H\({}_{2}\)O and PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, have specific light absorption in the 200-350 nm wavelength range, but the light absorption efficiency is negligible in the 350-800 nm wavelength range. Therefore, PVDF(TBT)-GQDs and PVDF(TBT)/PVP(TBT)-GQDs photocatalysts with attached GQDs can maintain high light absorption efficiency under sunlight. This is one of the  
Figure 6: The infrared spectra of PVDF(TBT)/PVP(TBT)-GQDs. reasons why the PVDF(TBT)-GQDs and PVDF(TBT)/PVP(TBT)-GQDs photocatalyst showed higher degradation rates. The Brunauer-Emmett-Teller (BET) measurement results showed that the specific surface areas of the PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, and PVDF(TBT)/PVP(TBT)-GQDs photocatalyst were 4.346 m/g, 6.429 m/g, 12.941 m/g, and 16.037 m/g, respectively. Obviously, the PVDF(TBT)/PVP(TBT) film showed a larger specific surface area than that of the PVDF(TBT) film. In addition, the adhesion of GQDs can effectively increase the specific surface area of the photocatalyst. Increasing the specific surface area increases the interaction  
Figure 8: UV–Visible absorption spectra of the PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, and PVDF(TBT)/PVP(TBT)-GQDs photocatalyst. Figure 7: Degradation rate of RhB by the photocatalyst prepared without the photocatalyst, PVDF(TBT)-H\({}_{2}\)O, PVDF(TBT)-GQDs, PVDF(TBT)/PVP(TBT)-H\({}_{2}\)O, and PVDF(TBT)/PVP(TBT)-GQDs. between the photocatalyst and the RhB solution, improving the photocatalytic efficiency of the photocatalyst. Moreover, the introduction of GQDs can effectively extend the lifetime of photogenerated carriers, thus improving the photocatalytic efficiency of the photocatalyst [12].