5 years ago

Detecting the Photoactivity of Anatase TiO2(001)-(1 × 4) Surface by Formaldehyde

Detecting the Photoactivity of Anatase TiO2(001)-(1 × 4) Surface by Formaldehyde
Zhengwang Cheng, Bing Wang, Haoqi Tang, Bin Luo, Xuefeng Cui, Yuanyuan Ji, Yongliang Shi
We report our investigation using temperature-programmed desorption to detect the activity and the photoactivity of the reduced anatase TiO2(001)-(1 × 4) surface by using CH2O as a probe. We obtain the adsorption energy of 0.55 eV for CH2O on the surface and find that the defect sites in the reduced surface are the only active sites for thermally driven reaction to produce C2H4. We also identify the pathways for photodecomposition of CH2O on the anatase TiO2(001)-(1 × 4) surface, where the C−H bond breaking to form the intermediates of HCOO− should be a key step in the reactions. After the ultraviolet light irradiation, the dissociation of HCOO– produces CO and H2O at elevated temperatures. Accompanied by desorption of H2O, we observe higher production of C2H4 than that in the non-irradiated sample. We interpret our experimental results by attributing the temporary change of the (1 × 4) ridge structure to water desorption, that is, the initially oxygen-rich five-fold coordinated Ti atoms change to four-fold coordinated Ti atoms. The four-fold coordinated Ti sites thus act as the highly active sites for the coupling reaction of CH2O to produce C2H4. Our findings here provide insightful understanding for the thermal and photocatalytic reactions of CH2O on the anatase TiO2(001)-(1 × 4) surface.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b04530

DOI: 10.1021/acs.jpcc.7b04530

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