Efficient thermal- and photocatalyst of Pd nanoparticles on TiO₂ achieved by an oxygen vacancies promoted synthesis strategy.

Pd nanoparticles supported on defective TiO2 with oxygen vacancies (TiO2-OV) have been prepared by an oxygen vacancies mediated reduction strategy. The resulting Pd-TiO2-OV catalyst with uniform Pd nanoparticles deposition demonstrates a remarkably thermocatalytic activity toward rapid, efficient reduction of nitroaromatics in water. The reaction proceeds efficiently using HCOONH4 as a hydrogen source under ambient conditions. The controlled experiments show that the (•)CO2(-) radicals produced by dehydrogenation of HCOONH4 are the main active species for the selective nitro reduction. Moreover, defective TiO2 nanostructures deposited with Pd nanoparticles, featuring excellent visible-light absorption via the creation of oxygen vacancies, can take advantage of the solar and thermal energy to drive catalytic reduction reactions more efficiently at room temperature. During this process, the oxygen vacancies and Pd nanoparticles play synergetic roles in the photoreduction of nitro compounds. Our work would be beneficial for implementation of a novel defect-mediated catalytic system in which solar light energy can be coupled with thermal energy to drive an energy efficient catalytic process.