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Oxygen-vacancies-engaged efficient carrier utilization for the photocatalytic coupling reaction

Yang, Xue, Tao, Huilin, Leow, Wan Ru, Li, Jingjun, Tan, Yanxi, Zhang, Yongfan, Zhang, Teng, Chen, Xiaodong, Gao, Shuiying, Cao, Rong
Journal of catalysis 2019 v.373 pp. 116-125
benzaldehyde, benzyl alcohol, catalysts, electron transfer, electrons, engineering, nitrobenzenes, oxygen, photocatalysis, photooxidation, solar radiation, titanium dioxide
Defects can greatly optimize the solar light harvesting capability and electronic structure of oxide materials. However, it remains challenging to achieve a defect engineering strategy under mild conditions. Meanwhile, the simultaneous exploitation of photogenerated holes (h+) and electrons (e−) to promote both photooxidation and photoreduction in a coupled system has rarely been reported. For the first time, we reveal an oxygen-vacancies-mediated photocatalytic strategy in which the electrons and holes are fully utilized for nitrobenzene reduction coupled with benzyl alcohol oxidation. The oxygen vacancies (OVs) generated in situ on the surface of TiO2 greatly extend light absorption into the visible region and promote the photogenerated electron transport for efficient photocatalysis. The experimental and theoretical results together indicate that chemisorption on the TiO2 surface decreases the oxidation potential of benzyl alcohol and causes an upward shift in its HOMO, which facilitates the oxidation reaction of benzyl alcohol to benzaldehyde. The in situ generated surface OVs also act as a bridge to enable the trapping and transferring of the photoinduced electrons to the nitrobenzene. This work provides a new perspective of utilizing the chemisorption between the reactant and catalyst to achieve a defect engineering strategy for synergetic photocatalysis.