Role of Cu²⁺/Cu¹⁺ induced adsorbed oxygen species in SnO₂ nanocrystals for H₂S gas detection at ppb level

This article demonstrates the impact of Cu-doped SnO₂ nanocrystals (NCs) on the H₂S gas sensing performance. The role of Cu doping-induced oxygen vacancies and adsorbed ionized oxygen species were investigated and their effect on H₂S gas sensing was explored in detail. The results demonstrate that Cu doping increased the amount of oxygen vacancies and adsorbed ionized oxygen species enabling more active sites for the adsorption of H₂S gas, resulting in higher sensor response. Cu-doped SnO₂ NCs availed increased (decreased) Cu²⁺ (Cu⁺) oxidation states leading to an increase in oxygen vacancies and adsorbed oxygen species on the surfaces. The optimized 2CuSnO₂ NCs sensor demonstrated a maximum sensing response of ∼28 for a 40 ppm exposure at 200 °C with a fast response time of ∼13.4 s. The 2CuSnO₂ NCs sensor demonstrated a lower detection limit of 100 ppb (S_R = ∼0.9) toward H₂S, which was attributed to the increased level of adsorbed ionized oxygen species, and high specific surface area.