Enhanced Visible Light Photocatalytic Hydrogenation of CO2 into Methane over a Pd/Ce-TiO2 Nanocomposition

5 years ago

Enhanced Visible Light Photocatalytic Hydrogenation of CO2 into Methane over a Pd/Ce-TiO2 Nanocomposition

Rehana Bibi, Lingfei Wei, Quanhong Ma, Quanhao Shen, Jiancheng Zhou, Chongjiu Xu, Xiaoyue Zou, Ming Liu, Naixu Li

A series of Ce-doped TiO₂ nanoparticles were prepared by a sol–gel process and characterized by XRD, SEM, TEM, EDX mapping, UV–vis DRS, Raman spectroscopy, N₂ adsorption–desorption, PL spectra, CO₂-TPD, and XPS. It is found that Ce ions can enter the lattice matrix of TiO₂ and occupy of Ti sites. This atom replacement leads to the formation of impurity energy levels in the band gap of TiO₂, extending light absorption into the visible light region. Because Ce has a more flexible valence state, both Ce³⁺ and Ce⁴⁺ could be formed in the composites. The preference facilitates the photoinduced charge separation inside of the crystals. Moreover, Pd nanoparticles were then loaded as a co-catalyst on the surface of doped composites. As the trapping center of electrons, it can efficiently adsorb and activate CO₂ molecules, promoting their transformation into CH₄. These composites were then evaluated as photocatalysts for CO₂ hydrogenation. While all of them could efficiently catalyze the reaction, 1.0% Pd/0.5% Ce-TiO₂ catalysts show the best photocatalytic performance, with CH₄ and CO yields up to 220.61 and 27.36 μmol/g, respectively, under visible light irradiation of 3 h. The improved photocatalytic behavior could be possibly induced by the synergistic effect between Ce and Pd. A probable mechanism was thus proposed based on above characterizations and experimental results.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b07298

DOI: 10.1021/acs.jpcc.7b07298