Synergistic H2S Sensing in Pd-Functionalized In2S3 Flakes

Hydrogen sulfide sensors are censoriously important for environmental monitoring, industrial safety, and biomedical applications due to the highly toxic and corrosive nature of H2S gas. We report indium sulfide (In2S3) flakes were grown via chemical vapor deposition (CVD) and functionalized with palladium (Pd) nanoparticles(NPs) to develop a high-performance chemiresistive H2S gas sensor. The pristine In2S3 flakes have a porous microstructure with abundance of active sites, however the addition of Pd NPs improves the gas sensing response through enhancing charge transfer interactions along with providing catalytic spillover sites. The Pd-functionalized In2S3 sensor demonstrated a increase in respone (1.4-fold) and selectivity towards H2S, attaining a sensing response of approximately 67.60% at 50 ppm concentration at 75 oC. The sensor demonstrated rapid kinetics with response and recovery times of 48 s and 260 s, respectively, and a remarkably low limit of detection (LOD) of 59 ppb. Furthermore, the sensor confirmed high humidity tolerance up to 80% RH and excellent repeatability. Density functional theory (DFT) calculations discovered an 8-fold increase in adsorption energy (-1.51 eV) and significant charge transfer (-0.086 e-) upon Pd decoration, correlating the electronic sensitization of the Schottky barrier to the observed ppb-level sensitivity. With the use of first-principles calculations that explain the underlying sensing process, this work presents a practical strategy to develop efficient H2S gas sensors through the use of CVD-grown sulfide semiconductors with decoration of noble metal nanoparticles.