Promoted effect of PANI on the preferential oxidation of CO in the presence of H2 over Au/TiO2 under visible light irradiation

A Polyaniline (PANI) assembled Au/TiO₂ catalyst (Au/TiO₂–PANI) was prepared by deposition–precipitation with the assistance of in-situ polymerization assistance, and was performed for oxidizing CO in H₂-rich stream under visible light irradiation. It is found that the as-prepared Au/TiO₂–PANI exhibited a higher activity of CO preferential oxidation (PROX) than the Au/TiO₂ without PANI decoration at room temperature under visible light irradiation. Based on the results of structure characterization, photo-absorbance, photo-electrochemical, electron paramagnetic resonance, and adsorbing CO and H₂ of Au/TiO₂–PANI, it is proposed that the photo-excited electrons of PANI could transfer to TiO₂ accompanied by suppressing the transfer of excited electrons induced by the localized surface plasmon resonance of Au nanoparticles to TiO₂, resulting in the increases in surface electron densities of both Au and TiO₂ sites. This will promote the activation of CO adsorbed at Au sites and the formation of O₂⁻ species at TiO₂ sites, and then the oxidation of CO. Meanwhile, the protonation of N atoms in PANI could cause a spillover of the dissociative H at Au sites into PANI, resulting in the suppression of H₂ oxidation.