Morphology-Engineered Pd−SnO 2 Porous Networks for Enhanced Hydrogen Detection

Hydrogen (H 2 ) is a critical clean energy carrier, yet its flammability demands sensors that are both highly sensitive and selective. SnO 2 -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 SnO 2 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-SnO 2 ) exhibits a strong response of ∼18.5 toward 400 ppm H 2 at 200 °C, representing approximately 13- and 6-fold enhancements over pristine SnO 2 (P-SnO 2, ∼1.4) and surface-modified SnO 2 (M-SnO 2, ∼3), respectively. High H 2 selectivity is further evidenced by the low cross-responses to CO, CH 4, and CO 2 (≤1.8 at 40 ppm and 150 °C), consistent with DFT results showing stronger H 2 adsorption on Pd−SnO 2 (E ads = −1.12 eV; H−H = 0.89 Å) than CO (−0.69 eV), CO 2 (−0.15 eV), or CH 4 (−0.13 eV). This approach bridges scalable nanomaterial synthesis with precision surface functionalization, offering a versatile route for next-generation hydrogen sensors.