Adsorption properties of Ni-doped TiO₂ towards dissolved gases in transformer oil: A DFT Study

We proposed a highly sensitive gas sensor for detecting dissolved gases in transformers oil ($\mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{C}_{2} \mathrm{H}_{4}$, $\mathrm{CH}_{4}, \mathrm{H}_{2}$, and CO) based on nickel-doped titanium dioxide (Ni - TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>). Density functional theory (DFT) has been used to conduct this research. To understand the gas adsorption and sensing properties of $\mathrm{Ni}-\mathrm{TiO}_{2}$ to the targeted gas molecules we analyzed the adsorption structures, band structures, the density of states (DOS), adsorption energy, Mulliken charge, and molecular orbitals of the systems. The analysis results show that the modification of Ni atom significantly improved the conductivity of pristine TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, which plays an important role in enhancing the gas adsorption proficiency of the sensing material. The sensor exhibits strong adsorption to $\mathrm{CO}, \mathrm{C}_{2} \mathrm{H}_{2}$, and C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>, while the adsorption for H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> is relatively lower. In addition, the conductivity of $\mathrm{Ni}-\mathrm{TiO}_{2}$ changes during the adsorption of all studied gases. In short, the theoretical research assures that $\mathrm{Ni}-\mathrm{TiO}_{2}$ could be a promising gas sensor at the transformer in the power system due to its remarkable adsorption efficiency.