Adsorption properties of pristine and Co-doped TiO2(1 0 1) toward dissolved gas analysis in transformer oil

•Co-doped TiO2(1 0 1) is used to detect three characteristic dissolved gases in transformer oil.•The Co doping has improved the gas selectivity of TiO2(1 0 1) to H2, C2H2, and C2H4.•Results are important to prepare gas sensor based on Co-doped TiO2(1 0 1) material. We theoretically studied the adsorption of dissolved gases H2, 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 CoTiO2 surfaces were optimized. Then, the adsorption mechanism of dissolved gases on TiO2 and CoTiO2 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. H2, C2H2, and C2H4 molecules exhibited strong chemisorption on TiO2 surface after geometry optimization. The adsorption ability of these gas molecules on CoTiO2 surface is in the following order: C2H4 ＞ C2H2 ＞ H2. The conductivity of the CoTiO2 system decreased greatly after H2 and C2H4 adsorption, whereas a slight increase was observed after C2H2 adsorption. In summary, CoTiO2 could be a potential gas-sensing material for H2, C2H2, and C2H4 detection due to its prominent adsorption ability.