Regulation of receptor function in NiCo2O4-SnO2 heterojunction for H2S detection at room temperature

In recent years, the World Health Organization has increasingly emphasized air quality in production environments, leading to heightened societal demands for monitoring of pollutant gases at room temperature. Traditional semiconductor gas-sensitive materials, such as tin oxide (SnO2), have their gas-sensing performance largely limited by their receptor functions, resulting in common issues like low response and poor recovery at room temperature. Spinel-type bimetallic oxides, such as nickel cobaltate (NiCo2O4), offer a unique solution due to their rich adsorption sites on the surface, which provide distinctive receptor functions for detecting toxic gases at room temperature. Herein, NiCo2O4 is synthesized via a one-step hydrothermal method, with a porous spherical cluster structure, and combined with SnO2 to form a heterojunction. The NiCo2O4-SnO2 heterojunction film gas sensor exhibits excellent gas-sensing performance for H2S at room temperature, including high response, short response time, good repeatability, and selectivity. Additionally, the unique receptor functions of the NiCo2O4 were analyzed through first-principles calculations, revealing a semiconductor p-n conversion phenomenon in the presence of H2S gas. The composite also demonstrates a conversion from p-n heterojunction to nn homojunction during the sensing process, enhancing its gas-sensing performance. This work not only addresses the receptor function limitations of traditional gas-sensitive semiconductor but also provides a feasible approach for controlling carrier types in semiconductors.