Self-doped Ti3+ mediated TiO2/In2O3/SWCNTs heterojunction composite under acidic/basic heat medium for boosting visible light induced H2 evolution

Well-designed Ti3+/In3+ mediated TiO2/SWCNTs heterojunction composite for photo catalytic H-2 evolution under visible light has been investigated. The samples, fabricated through one-step sol-gel approach with controlled acidic/basic heat treatment environment, were characterized by XRD, Raman, FE-SEM, TEM, XPS, UV-Vis and PL techniques. The maximum H-2 of 1244 ppm h(-1) was evolved over In/SWCNTs/TiO2, a 4.69, 1.54 and 1.53 times higher than using TiO2, In/TiO2 and SWCNTs/TiO2 samples, respectively. This enhancement was due to faster charges separation and higher visible light absorption by synergistic effect of In/SWCNTs. Using catalyst prepared under basic (H-2) treatment, Ti3+ was successfully embedded into In+3@TiO2@SWCNTs, exhibited H-2 production of 1446 ppm h(-1) which was 12.49% and 15.02% higher compared to catalysts prepared under CO2 and N-2 atmospheres, respectively. Thus, surface defects like Ti3+ inhibits charges recombination and enables visible light responsive. The quantum yield over Ti3+/In3+ mediated TiO2/SWCNTs composite was 0.251%, a 1.13 and 1.2 folds higher compared to CO2 and N-2 atmospheres, respectively. Besides, excellent stability for H-2 generation was observed in cyclic runs. A possible mechanism is proposed to understand synergistic effects between Ti+3/In+3 in TiO2/SWCNTs composite catalyst and has great potential as a green photocatalyst in environmental and energy applications. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.