Enhanced gas sensing performance of hierarchical porous In2O3 nanocubes modified with PdO and Pd for ppb-level H2S detection

The pressing need for health and environmental protection has sparked significant interest among researchers in exploring gas sensors made from metal oxide semiconductors (MOSs). Herein, a co-modification approach involving palladium (Pd) and palladium oxide (PdO) is introduced to enhance the sensing properties of indium oxide (In 2 O 3 ) to hydrogen sulfide (H 2 S). Pd and PdO co-modified In 2 O 3 hierarchical porous nanocubes (Pd/PdO-In 2 O 3 HPNCs) were synthesized using a facile hydrothermal method. With the theoretical doping amount of 2 mol%, the synergistic effect of metal Pd and PdO-In 2 O 3 heterojunction made Pd/PdO-In 2 O 3 show excellent sensing performance to H 2 S compared to In 2 O 3 . Specifically, the material features a lower operating temperature (280 vs 300 °C), higher sensitivity (95.06 vs 28.59 to 20 ppm H 2 S; 2.28 vs 1.17–100 ppb H 2 S), and better selectivity (7.41 vs 2.32 times to triethylamine), while also demonstrating satisfactory reproducibility and stability. The synergistic sensitization mechanism of noble metal catalysis and heterojunction in Pd/PdO–In 2 O 3 HPNCs, along with their underlying mechanism, was discussed. Integrating noble metal modification with heterojunctions adds complexity to the structure and composition of the material. The synergistic effects of these two sensitization strategies on the H 2 S sensitization mechanism need further in-depth investigation.