Morphology-Engineered Pd-SnO2 Porous Networks for Enhanced Hydrogen Detection.

Hydrogen (H2) is a critical clean energy carrier, yet its flammability demands sensors that are both highly sensitive and selective. SnO2-based semiconductors show promise but typically suffer from poor selectivity, high operating temperatures, and complex fabrication methods. We report a simplified and reproducible two-step integration of flame spray pyrolysis (FSP)-derived SnO2 films with capillary-force-assisted drop-casting of 1 wt % Pd. This yields porous films with well-dispersed Pd that enhance catalytic activity and gas diffusion, while toluene-induced capillary forces promote nanoparticle necking and cluster formation, refining the microstructure. The Pd-functionalized sensor (1% Pd@M-SnO2) exhibits a strong response of ∼18.5 toward 400 ppm H2 at 200 °C, representing approximately 13- and 6-fold enhancements over pristine SnO2 (P-SnO2, ∼1.4) and surface-modified SnO2 (M-SnO2, ∼3), respectively. High H2 selectivity is further evidenced by the low cross-responses to CO, CH4, and CO2 (≤1.8 at 40 ppm and 150 °C), consistent with DFT results showing stronger H2 adsorption on Pd-SnO2 (Eads = -1.12 eV; H-H = 0.89 Å) than CO (-0.69 eV), CO2 (-0.15 eV), or CH4 (-0.13 eV). This approach bridges scalable nanomaterial synthesis with precision surface functionalization, offering a versatile route for next-generation hydrogen sensors.