Electron Donation from Boron Suboxides via Strong p–d Orbital Hybridization Boosts Molecular O<sub>2</sub> Activation on Ru/TiO<sub>2</sub> for Low-Temperature Dibromomethane Oxidation
Guanqun Gao, Wei Liu, Zhisong Liu, Zihao Li, Haomiao Xu, Wenjun Huang, Naiqiang Yan, Zan Qu
Abstract
Low-temperature catalytic oxidation is of significance to the degradation of halogenated volatile organic compounds (HVOCs) to avoid hazardous byproducts with low energy consumption. Efficient molecular oxygen (O 2 ) activation is pivotal to it but usually limited by the insufficient electron cloud density at the metal center. Herein, Ru–B catalysts with enhanced electron density around Ru were designed to achieve efficient O 2 activation, realizing dibromomethane (DBM) degradation T 90 at 182 °C on RuB 1 /TiO 2 (about 30 °C lower than pristine Ru/TiO 2 ) with a TOF Ru value of 0.055 s –1 (over 8 times that of Ru/TiO 2 ). Compared to the limited electron transfer (0.02 e) on pristine Ru/TiO 2, the Ru center gained sufficient negative charges (0.31 e) from BO x via strong p–d orbital hybridization. The Ru–B site then acted as the electron donor complexing with the 2π* antibonding orbital of O 2 to realize the O 2 dissociative activation. The reactive oxygen species formed thereby could initiate a fast conversion and oxidation of formate intermediates, thus eventually boosting the low-temperature catalytic activity. Furthermore, we found that the Ru–B sites for O 2 activation have adaptation for pollutant removal and multiple metal availability. Our study shed light on robust O 2 activation catalyst design based on electron density adjustment by boron.