A Theoretical Insight of Cr Dopant in Tungsten Oxide for Gas Sensor Application

Abstract This is a study on the impact of Cr dopant in (WO3)n (n = 2 to 4) on the sensitivity and selectivity of gas sensing. The theory is based on density functional theory (DFT) at the B3LYP/LanL2DZ level. The results show the chromium doped tungsten oxide clusters, (CrWn-1O3n) (n = 2 to 4), to have lower energy gaps, high reactivity, reduced stability, and demonstrates a higher ability to accept electrons from CO, H2S and H2 gases when compared to the undoped (WO3)n (n = 2 to 4) cluster. The results showed that the highest sensitivities for the three gases; CO, H2S and H2, are observed with the CrWO6 cluster and the sensitivities of CrWO6 to CO, H2S and H2 are 6.20E + 13, 2.32E + 12, and 4.11E + 05, respectively. The study also shows a decrease in gas sensing ability when the cluster size and the dopant density are increased. In the case of CO sensing, the CrWO6 cluster is shown to have exhibits the highest sensitivity. This is attributed to a dramatic change in energy gaps between pre-adsorption and postadsorption.