Optimization of Cu-Doped ZnO Nanomaterials for Ultrasensitive Detection of Trace Formaldehyde under Room Temperature...

Formaldehyde (HCHO) is a common indoor volatile organic compound (VOC) gas, which seriously endangers human health. How to accurately and rapidly detect HCHO concentration has become an important and urgent issue. Among various detection technologies, semiconductor photoelectric gas sensors with metal oxide materials as the core have attracted the most extensive attention due to their excellent performance and low cost. ZnO is an ideal photoelectric sensing material, but pristine ZnO has an inherent defect of high photogenerated carrier recombination efficiency, limiting its application scope. In this study, a high-performance Cu-ZnO gas-sensitive material was successfully synthesized using metal-organic framework (MOF) materials with a large specific surface area and high porosity as templates. Gas sensing performance tests showed that the Cu1.25-ZnO material with a doping concentration of 1.25% exhibited a maximum gas sensing response of 920% for 10 ppm of HCHO and a response/recovery time of 137/69 s for 10 ppm of HCHO with a detection limit as low as 10 ppb. Additionally, it displayed excellent selectivity, stability, and humidity resistance, making it a promising material for high-performance HCHO sensors. During the research, a combination of photovoltage techniques and density functional theory (DFT) calculations was employed to thoroughly investigate the carrier dynamics and the influence of surface gas adsorption/desorption processes on photoelectric gas-sensing performance. DFT calculations demonstrate that Cu incorporation significantly enhances the adsorption energy of HCHO molecules on ZnO surfaces, with charge transfer analysis confirming this strengthened interaction as the primary mechanism for improved gas-sensing response. This study developed a low-cost HCHO gas-sensing material and provided new insights into the impact of elemental doping on gas-sensing properties.