Ultrasensitive and Selective Room-Temperature H2S Sensor Based on CuO/In2O3 Heterojunction via Dual Sensitization Mechanism

Hydrogen sulfide (H 2 S) is a highly toxic, corrosive and flammable gas. Therefore, real-time and low-power monitoring under room temperature conditions is of great significance. However, room-temperature chemical resistance sensors usually have weak signal outputs and are susceptible to humidity and coexisting gases, which remain the main challenges in practical applications. To address these issues, we developed a heterojunction-assisted, phase-change-based sensing platform. Through a two-step solvothermal method, a chemical resistance sensor based on flower-like In 2 O 3 was constructed, with uniformly covered highly dispersed CuO nanoclusters on the surface. The optimized 4.5   wt% CuO/In 2 O 3 composite exhibits an exceptional response (18,108) to 10 ppm H 2 S at 25°C, along with a detection limit as low as 10 ppb and a rapid response time of 4   s. Notably, the sensor maintains a robust response of 603 even at 80% relative humidity and demonstrates outstanding selectivity against CO and NH 3 (10 ppm) as well as typical volatile organic compounds (1000 ppm). This remarkable performance arises from a dual sensitization mechanism: the p-n junction establishes a high-resistance baseline via interfacial charge redistribution, while H₂S exposure triggers an in-situ CuO→CuS phase transition that collapses the junction barrier and produces a pronounced resistance drop. Density functional theory calculations further corroborate preferential H 2 S adsorption and strong Cu-S bond formation, supporting the proposed chemical-switching pathway. These results highlight a heterojunction-assisted phase-transition strategy for reliable, low-power, and humidity-tolerant H 2 S monitoring under practical hazardous conditions.