Ti3+ defect mediated g-C3N4/TiO2 Z-scheme system for enhanced photocatalytic redox performance

Artificial direct Z-scheme system is promising in solar-fuel production owing to their efficient charge separation and high redox capability. However, direct Z-scheme system suffers from how to construct reasonable interfacial charge transfer channel for selective charge recombination. Here we fabricate a direct Z-scheme system consisting of g-C3N4 crumpled sheet with Ti-3(+)-doped TiO2 nanoparticles via polycondensation of urea with TiO2 followed by hydrogenated treatment. UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) manifest that the hydrogenated treatment conferred Ti-3(+) defect states below the conduction band minimum (CBM) of TiO2 and improved visible light absorption of the g-C3N4/Ti-3(+)-doped TiO2 composite. The g-C3N4/Ti-3(+)-doped TiO2 exhibits remarkable photocatalytic performance for water splitting and degradation of pollutants than that of g-C3N4/TiO2, C3N4, and TiO2. The H-2 evolution rates of g-C3N4/Ti-3(+)-doped TiO2 reach up to 1938 and 287 mu mol.h(-1).g(-1) under solar-light and visible-light irradiation, which is 3.4 and 2.8 times higher than that of g-C3N4/TiO2. The enhanced photocatalytic activity is ascribed to the Ti-3(+) defects assistant formation of g-C3N4/Ti-3(+)-doped TiO2 Z-scheme photocatalyst, which results in efficient interfacial charge emigration and separation. Our work points out the critical role of defects in construction of Z-scheme pathways for charge transfer and provides possibilities for developing the other efficient photocatalysts. (C) 2018 Elsevier B.V. All rights reserved.