Controlling Ni Distribution in PdNi Nanoalloys Decorated onto ZnO for Rapid and Robust ppb-Level H ₂ S Sensing

Rapid and robust ppb-level H 2 S sensing is of great importance for environmental monitoring, industrial safety, food quality control, and disease screening. However, improving the H 2 S sensing properties of semiconductor oxides under low-power conditions remains a significant challenge. In this work, an acid etching method was utilized to precisely control the elemental distribution in bimetallic nanoalloys. By tailoring the Ni distribution in PdNi alloy nanoparticles anchored on ZnO nanosheets, an ultralow detection limit of 5 ppb for H 2 S was achieved at a working temperature of 140 °C. More importantly, the sensor also demonstrated fast response and recovery kinetics, with its superior antipoisoning performance attributed to the oxidation of H 2 S into SO 2 instead of sulfates or sulfites, as evidenced by in situ FTIR spectroscopy. Additionally, density functional theory calculations were performed to elucidate the synergistic effect of the PdNi alloy, revealing that Pd atoms act as electron donors while Ni atoms facilitate H 2 S adsorption. This study provides a viable strategy for optimizing noble metal-modified oxide-based gas sensors.