Highly Efficient Metal-Free Visible Light Driven Photocatalyst: Graphene Oxide/Polythiophene Composite

Graphene oxide/polythiophene (GO/PTh) composites were synthesized by in-situ polymerization of thiophene (Th) monomers on GO surfaces. Remarkable performance of GO/PTh composites for methylene blue (MB) photo-degradation under visible light has been achieved by tuning GO/Th ratio and graphene oxidation degrees. 100% MB degradation was achieved by the composite within 30 min under visible light, its catalytic activity (0.1149 min(-1)) is 382 and 41 times higher than that of PTh (0.0003 min(-1)) and GO (0.0028 min(-1)), respectively. The results of MB adsorption experiment, ultraviolet-visible (UV-vis) and photoluminescence (PL) spectra show that combination of GO and PTh increases MB adsorption, decreases the band gap and enhances photo-electron transfer. The composite with 36% PTh (at the fed GO/Th weight ratio of 1:2) shows the highest catalytic activity where MB adsorption ability by GO and photo-electron producing ability by PTh in the composite is well matched. The catalytic activity can be further enhanced by changing graphene oxidation degree by controlling graphite/KMnO4 ratio and post-reaction time during GO preparation. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron (XPS) spectroscopy analyses have shown that increasing oxidation degree of GO leads to a stronger pi-pi interaction between GO and PTh and a more electron-rich PTh, resulting in higher catalytic activity.