Adsorption properties of pristine and Co-doped TiO2(101) toward dissolved gas analysis in transformer oil

We theoretically studied the adsorption of dissolved gases H-2, C2H2, and C2H4 in transformer oil and in pristine and Co-doped TiO2(1 0 1), respectively, on the basis of density functional theory calculations. First, the most stable structures of TiO2 and Co-TiO2 surfaces were optimized. Then, the adsorption mechanism of dissolved gases on TiO2 and CoeTiO(2) surfaces were studied by analyzing adsorption energy, density of states, and molecular orbit theory. Pristine TiO2 exhibited weak adsorption and sensing performance to dissolved components. Co atom doping enhanced the adsorption behavior of TiO2-based material. H-2, C2H2, and C2H4 molecules exhibited strong chemisorption on TiO2 surface after geometry optimization. The adsorption ability of these gas molecules on Co-TiO2 surface is in the following order: C2H4 > C2H2 > H-2. The conductivity of the Co-TiO2 system decreased greatly after H-2 and C2H4 adsorption, whereas a slight increase was observed after C2H2 adsorption. In summary, Co-TiO2 could be a potential gas-sensing material for H-2, C2H2, and C2H4 detection due to its prominent adsorption ability.