In-situ creating elastic lattice OO bonds over semicrystalline yellow TiO2 nanoparticles for significantly enhanced photocatalytic H2 production.

Atomic defects (e.g., Ti3+, oxygen vacancies) have been intenstively investigated for modifying TiO2 in order to reach visible light active photocatalytic H2 production. However, the atomic defects within TiO2 could easily act as photo-generated charge-carrier recombination centers, resulting in relatively low H2 conversion efficiency. In this paper, semicrystalline yellow TiO2 nanoparticles rich of superoxide ions are new synthesized by a simple aqueous solution method. Instead of introducing atomic defects, we show for the first time that catalytic performance can also be significantly improved via in-situ creating lattice OO bonds within metastable semicrystalline TiO2. The synthesized semicrystalline yellow TiO2 exhibits significantly enhanced photocatalytic activity for H2 production after cycle tests. The formaldehyde in aqueous solution is used as target pollutant to simulate industrial wastewater. In-situ created elastic lattice OO bonds are proposed to improve catalytic performance through facilitating the breakage of CH bonds of HCHO. A series of internally consistent reaction equations is proposed that describes the role of in-situ created lattice OO bonds for improving the catalytic performance. This is strongly supported by that the H2 production rate at the end of the fourth cycle test is significantly more than that of the beginning of the first cycle test.