Sulfur spillover driven by charge transfer between AuPd alloys and SnO2 allows high selectivity for dimethyl disulfide gas sensing

Monometallic-catalyst modification is a popular means for boosting sensing performances of gas sensors based on semiconductor metal oxides, but it is restricted to the single-type of catalytic activity, hardly insuring high-level regulation of sensor performances. Herein, through combining density functional theory (DFT) calculations and in-situ testing technologies, we presented the modulation of both electronic structure and reaction kinetic process of the sensing surfaces by introducing bimetal alloy catalysts. When used AuPd alloys to modify SnO2 surfaces, it appeared obviously discriminative sensing behaviors, possessing high response signal (R-air/R-gas = 36.6) and ultra-high selectivity to 10 ppm dimethyl disulfide (DMDS) gas at 135 degrees C, which is considerably different from pure SnO2, monometallic Au or Pd doped SnO2. DFT calculations confirmed the occurrence of the charge transfer that was from AuPd alloys to SnO2 and the reinforce of surface adsorption strength for DMDS, which may be a major reason for a high gas response to DMDS. In-situ diffuse scattering Fourier transform infrared spectra and quasi in-situ XPS test demonstrated that the surface reaction site for DMDS molecules was mainly located on surfaces of AuPd alloys, and the sulfur spillover that generated from alloys surfaces to SnO2 played a crucial role during DMDS-sensing process, which was further validated by kinetic reaction-pathway calculations. This work will enrich basic research of catalytic electronics in sensor field.

Automated summary

The modification of gas sensors using bimetal alloy catalysts significantly enhances sensing performances by modulating the electronic structure and reaction processes of sensing surfaces. The introduction of AuPd alloys on SnO2 surfaces enhances the gas response and selectivity to DMDS, confirming the importance of charge transfer and surface adsorption strength in sensor performance. In-situ and quasi in-situ testing techniques validate the role of sulfur spillover from alloy surfaces to SnO2 in the sensing process, enriching the fundamental research in catalytic electronics for sensors.