SnO₂ Nanospheres Coated with Pt or Pd as Electrode Materials for Detecting Hydrogen and Methane

In semiconducting metal oxide (SMO) gas sensing materials, the operating temperature provides the activation energy requisite for normal functioning while profoundly impacting the adsorption–desorption of gas molecules and the kinetics of sensing reactions. Current research primarily concentrates on enhancing gas sensor performance, aiming to increase sensor response, reduce operating temperature, and accelerate response and recovery speeds, yet it often neglects the impact of operating temperature variations on gas selectivity. This work employed photochemical deposition techniques to synthesize a series of M/SnO2 (M = Pt, Pd) nanospheres with an approximate diameter of 400 nm, meticulously exploring their gas sensing properties for hydrogen (H2) and methane (CH4) across an operating temperature range of 250–500 °C. Microstructural examinations revealed that Pt/SnO2 nanospheres featured an adjustable Pt-rich or Sn-rich PtSn alloy layer, along with controllable oxide species, while the surface of 5.0% Pd/SnO2 nanospheres displayed nanoparticles consisting of both mixed-phase PdSn alloy and oxide phases, with size control spanning from 35.2 to 66.9 nm. Electronic and chemical sensitization, the activation energy of gas sensing reaction, as well as the chemical states and sizes of Pd and Pd species were integrated to explain the possible selective gas sensing mechanisms of SnO2 nanospheres to H2 and CH4.