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

Abstract

• Ultrafine AuPd alloys modified SnO 2 materials are fabricated by a co-reduction way. • SnO 2 /AuPd materials show superior sensing signals to dimethyl disulfide at 135 °C. • SnO 2 /AuPd sensors show high response value and selectivity to dimethyl disulfide. • The sensing process is probed by combining DFT calculations and in-situ techniques. 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 SnO 2 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 °C, which is considerably different from pure SnO 2 , monometallic Au or Pd doped SnO 2 . DFT calculations confirmed the occurrence of the charge transfer that was from AuPd alloys to SnO 2 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 SnO 2 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.