The electronic and optical properties, gas sensor and NO removal application investigations of noble metal-adsorbed MoSi2N4

In this paper, the electronic and optical properties, gas sensor behavior and photocatalytic nitric oxide (NO) removal applications of noble metal-adsorbed MoSi2N4 (NMs-MSN, NMs = Au, Ag, Cu, Pd and Pt) are investigated and screened based on first-principles calculations. The band gaps of MoSi2N4 decrease to different degrees after noble metals are adsorbed, especially when the band gap changes from intrinsic MoSi2N4 of 1.89 eV to Pd-MoSi2N4 of 1.59 eV. Based on density of states (DOS) analysis, new degenerate energy bands formed and combined with the valence band after Pd adsorbed, which resulted in a band gap decrease. The optical property calculations show that the light absorption range and coefficient of NMs-MSN significantly increase. Then, the sensor behaviors are investigated and screened based on the adsorption and recovery behaviors of gas molecules (including NO, CO, O-2, CO2, NO2, H2O, H2S and NH3) on NMs-MSN. Based on the adsorption energy, recovery time and band gap changes after gas adsorption, it can be concluded that Ag-MSN is suitable for sensing SO2 molecules, that Au-MSN is suitable for sensing SO2, CO and O-2 molecules, and that Pd-MSN is suitable for sensing N-2, NO and NO2 molecules. The most suitable noble-metal atoms for the photocatalytic removal of NO are calculated and screened, and the Pd-MSN is determined to be most suitable for NO removal. The introduction of a Pd atom inhibits desorption of the toxic product nitrogen dioxide (NO2), inducing the main product to become a nitrate ion (NO3). The mechanism indicates that the potential barrier is greatly reduced because electron-hole complexation is suppressed. In general, noble metal atom-adsorbed MoSi2N4 can effectively change the band gap, improve the light absorption coefficient, adjust the gas sensor behavior, and enhance the photocatalytic ability for NO removal.

Automated summary

In this paper, noble metal-adsorbed MoSi2N4 (NMs-MSN) was investigated for its electronic and optical properties, gas sensor behavior, and photocatalytic nitric oxide (NO) removal applications. The results show that the adsorption of noble metals decreases the band gaps of MoSi2N4, especially Pd-MoSi2N4. The optical property calculations indicate an increase in light absorption range and coefficient for NMs-MSN. Gas sensor behavior investigation suggests that different noble metal-adsorbed MoSi2N4 are suitable for sensing specific gas molecules. The photocatalytic removal of NO is most effective using Pd-MSN due to its inhibition of desorption of toxic product NO2 and enhancement of nitrate ion production.