Fabrication of g-C3N4/PW12/TiO2 composite with significantly enhanced photocatalytic performance under visible light

The exploration and development of supernally effective and persistent visible-light-responsive catalysts for environment remediation is regarded as one of the most challenging topics at present. Herein, a new g-C3N4/PW12/TiO2 (CN/PT-X; X = 3.2, 6 and 9) composite photocatalyst was fabricated through a convenient electrospinning/calcination technique, followed with thermal polymerization method. In the composite, the g-C3N4 was grown on PW12/TiO2 nanofibers forming 3D nanofibrous networks, in which the g-C3N4 quality was simply operated by regulating quality ratios of urea to PW12/TiO2 during preparation process. The X-ray photoelectron spectra (XPS) results confirmed the interfacial interaction between g-C3N4 and PW12/TiO2, implying the heterojunction formation between the two components. The photocatalytic tests showed that the CN/PT composites exhibited remarkable and stable photocatalytic performance for removing tetracycline (TC), bisphenol A (BPA) and reduction of Cr(VI) with visible-light (λ > 420 nm) irradiation. Furthermore, the CN/PT-6 sample displayed the optimal catalytic activity with the rate constants of 0.03443 min−1 (TC), 0.00712 min−1 (BPA) and 0.025 min−1 (Cr(VI)), respectively. The enhanced performance could be ascribed to the enhanced adsorption in visible-light region, high specific surface area, effective separation and transfer of photoinduced charge carriers. The active species capturing tests and ESR measurements verified that h+ and ·O2− were answerable for TC degradation. The mechanism accounting for the observed photocatalytic behaviour was proposed and discussed based on the band gap structure and free radicals capture tests.