Hollow CuCo2O4 nanocages engineered by Kirkendall effect for room-temperature sensing of ammonia gas

Abstract

Recently, binary transition metal oxide (BTMO)-based gas sensors have gained significant interest in detecting harmful gases in the atmosphere. Herein, we report a p-type BTMO, hollow CuCO2O4 (CCO) nanocages, for ammonia (NH3) gas sensing at room temperature (RT). Hollow CCO nanocages were fabricated using a two-step process, including hydrothermal synthesis followed by annealing. The sensor exhibited responses of 2.8 % and 13.6 % towards 1 and 100 ppm NH3, respectively. Furthermore, it demonstrated good selectivity and repeatability for NH3 gas. Although the response decreased in the presence of humidity, it showed a high response to NH3 in a humid atmosphere. Additionally, a flexible sensor was fabricated on a PET substrate and subjected to bending (45, 90, and 190°) and twisting (30, 60, and 90°). Generally, the sensor showed a higher response after 100 cycles of bending compared to 100 cycles of twisting. Therefore, with the promising results obtained in this study, the present sensor can be used for selective RT detection of NH3 gas in flexible applications where the sensor is subjected to bending at different angles under rapid and harsh conditions.