Potential high-performance H2 gas sensors based on monolayer 2D metal oxide α-MoO3 doped with Pt/Rh−predicted by DFT calculations

High-performance H2 gas sensors based on monolayer 2D metal oxide α-MoO3 doped with Pt/Rh has been predicted. With a binding energy of −5.262 eV/−5.877 eV, the substitutional doping of Pt/Rh for Mo is a stable doping. After adsorbing O2 in air, the band gap of Pt/Rh-α-MoO3 decreases by 0.62 eV/0.51 eV due to the appearance of the impurity levels and the band narrowing effect. Due to such large decrease, electrons in the valence band can be excited more easily into the conduction band to produce more O2(ads)−, which would oxidize more H2 to generate H2O or hydroxyl along with releasing more electrons to the sensor and increasing the sensor’s sensitivity. First losing electrons through adsorbing O2 molecules in air and then obtaining electrons through adsorbing H2 molecules in H2, the charge variation of the sensor based on monolayer Pt/Rh-α-MoO3 is 1.487 e/0.394 e for per O2/H2, which suggests that the sensor may have higher sensitivity and lower detection limit. The larger charge variation is also confirmed by the shift of the Fermi level towards the higher energy direction after adsorbing H2.