Pristine and Ni-doped In2O3 pyramids response to NO2 gas: a transition state theory study

The reaction of pristine and Ni-doped In2O3 surface pyramid clusters with NO2 gas is discussed and compared with experimental findings. Ni doping effects on In2O3 with molar percentages of 1, 2, and 3% are calculated and compared with the experiment. The decomposition of NO2 gas at temperatures near 200 ̊C is considered. Gibbs free energy of transition is calculated in the range of 25 to 250 ̊C for the different doping percentages using the modified Evans–Polanyi principle. The transition state theory formalism is used to evaluate the reaction rate of NO2 with Ni-doped In2O3 surface. The present method is the only one that theoretically calculates response and response time as a function of temperature. Results include the response and response time of pristine and Ni-doped In2O3 to NO2 as a temperature and NO2 concentration function. The highest response and shortest response time were obtained at 2% Ni doping, which agrees with the experiment. The 2% Ni-doped In2O3 sensor has a high response (70) and short response time (2 s).