Potential high-performance H 2 gas sensors based on monolayer 2D metal oxide a-MoO 3 doped with Pt/Rh - predicted by DFT calculations

High-performance H 2 gas sensors based on monolayer 2D metal oxide a-MoO 3 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 O 2 in air, the band gap of Pt/Rh-a-MoO 3 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 O -2( ao , which would oxidize more H 2 to generate H 2 O or hydroxyl along with releasing more electrons to the sensor and increasing the sensor's sensitivity. First losing electrons through adsorbing O 2 molecules in air and then obtaining electrons through adsorbing H 2 molecules in H 2 , the charge variation of the sensor based on monolayer Pt/Rh-a-MoO 3 is 1.487 e/0.394 e for per O 2 /H 2 , 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 H 2 .