Unraveling the dynamic redox behavior of Pd species in PdOx/SnO2 hybrids: A key to superior low-temperature gas sensing

Abstract

Operando characterization techniques reveal the dynamic interplay of Pd species and gas sensing activity in a PdO_x/SnO₂ hybrid material for low-temperature CO detection. We demonstrated that Pd species exhibited a dynamic redox behavior, transitioning between various oxidation states and serving as active sites for CO adsorption and subsequent spillover-mediated oxidation. The formation of a p-n junction at the PdO_x/SnO₂ interface drove oxygen anion (O₂^–, O^-) enrichment around Pd islands, enhancing CO adsorption and facilitating rapid CO₂ formation. This resulted in electron injection into the SnO₂ depletion layer, significantly enhancing the sensing response even at temperatures as low as 50 °C. Our findings provided profound insights into the dynamic behavior of Pd species and its influence on gas sensing performance, offering a valuable strategy for designing advanced low-temperature CO sensors with enhanced sensitivity, selectivity, and operational stability.