Extract ZnO from spent catalysts for the rapid detection of NH₃ at room temperature

Zn metal-based catalysts are widely used in many fields due to their unique advantages. After a long period of large-scale use, the waste catalysts not only occupy land resources but also cause environmental pollution. Therefore, there is an urgent need for strategies that can handle spent catalysts. In this work, ZnO was extracted from the spent catalyst by acid leaching method and ZnO based sensor was prepared for NH₃ detection. The gas-sensitive characteristics of the ZnO sensor to NH₃ were studied systematically. The response to 500 ppm ammonia can reach 101 at room temperature, and the response/recovery time is only 8/3 s, thus realizing rapid detection of NH₃, in addition to excellent selectivity, and excellent long-term stability. The strategy proposed in this work effectively reduces the production cost of ZnO sensing materials, suggests a new approach for the preparation of sensing materials, and realizes a circular economy from waste to recycling, which has far-reaching implications for sustainable development.