Computational assisted tuning of Co-doped TiO2 nanoparticles for ammonia detection at room temperatures

Improved gas sensors based on pure anatase TiO2 and Co-doped TiO2 nanoparticles were evaluated. A cobalt-doped TiO2 nanoparticle with a diameter of 40 nm was first synthesized. The morphology of the nanoparticles was analyzed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The doped Co ion was confirmed to have entered the TiO2 lattice. Subsequently, gas sensors with different Co-doping concentrations were developed to investigate gas sensitivity to NH3. Compared with pure anatase TiO2 operating at 180 °C, Co-doped TiO2 samples were developed as NH3 gas sensors operating at room temperature. The 20% Co-doped sample exhibited the best performance, with a response value of 14 for 50 ppm NH3, which was 7 times higher than that of pure TiO2. The response and recovery times of the sensor were only 25 and 48 s, respectively, and exhibited both good stability and selectivity. Based on density functional theory (DFT), the calculated bandgap of Co-doped TiO2 decreased by 72% compared to pure TiO2. Structural simulation and mechanism analysis elucidated the good gas-sensing performance at room temperature and the property enhancement of the Co-doped TiO2 gas sensor.