Wide-concentration-range hydrogen sensing using palladium-loaded SnO2 nanoparticle films and understanding of hydrogen concentration-dependent sensing mechanism

SnO2-based nanostructures have been extensively studied as excellent hydrogen sensing materials. While Pd loading was employed to enhance sensing performance, many reported that Pd-loaded SnO2 (denoted as Pd/ SnO2) experienced signal saturation at high H2 concentration, limiting the detection range and leaving the sensing mechanism unclear. Herein, we report a Pd/SnO2 nanoparticle (NP) film-based H2 sensor fabricated using gas -phase cluster beam deposition, achieving wide-concentration-range hydrogen detection (1.5 ppm10%). It was found that there are two H2 concentration-dependent sensing mechanisms. Below 1% H2 concentration, the response correlated linearly with the square root of the H2 concentration, predominantly due to the electronic coupling effect at the interface between palladium hydride (PdHx) and SnO2, realizing a high sensitivity of 0.23 ppm-1. As concentration increased further, a linear dependence between the response and H2 concentration was observed with a sensitivity of 0.018 ppm-1, which stemmed from the redox reaction between H atoms and O alpha- on the SnO2 surface. Additionally, the device's sensing kinetics were meticulously analyzed. Pd loading drastically reduced the response time by reducing apparent activation energy. Furthermore, our sensor exhibited notable selectivity, reproducibility, and long-term stability.