The role of AuSn alloys in optimizing SnO2 nanospheres for chemoresistive hydrogen sensing

Gas sensing reactions predominantly occur on material surface, where noble metal nanoparticles usually serve as a vital catalyst to enhance sensing performance. However, the structure-activity correlations at noble metalmetal oxide interfaces, which are critical for optimizing gas sensor design, are poorly understood. This gap hinders the effective bottom-up construction of gas sensors that meet practical requirements. In this work, the field was advanced by precisely manipulating the gold (Au) loading state on tin oxide (SnO2) supports using photochemical deposition. AuSn alloys composed of various controllable phases were formed on the surface of SnO2 nanospheres with a diameter of approximately 400 nm. Particularly, the presence of Au-rich AuSn alloy phases at the interface could enhance the response of SnO2 nanospheres to 500 ppm hydrogen (H2) at 450 degrees C by a factor of two, distinct from the Sn-rich alloy phases which exhibited a weaker sensitization effect (1.15 times). Various preparation modes derived from impregnation techniques allowed for detailed control over the phase composition at Au@SnO2 interface. Guided by the theories of catalytic spillover, chemical sensitization, and electronic sensitization effects of AuSn alloy, and combining structural characterization with gas sensing tests, the mechanism by which the interfacial alloy phase composition affected H2 sensing capabilities of SnO2 nanospheres was discussed. This work on interface state of regulation of Au@SnO2 paves the way for developing gas sensors with improved response and stability at elevated operating temperatures.