Preparation of Co3O4/In2O3 Nanobundles and Their High Formaldehyde-Sensitive Properties

Formaldehyde is an indoor pollutant that poses a risk to human health, and prolonged exposure may lead to various diseases. Therefore, highly sensitive and selective detection technologies are needed to accurately monitor formaldehyde concentrations. In 2 O 3 is a commonly-used semiconductor material in gas sensing. However, the gas sensing performance of pure In 2 O 3 sensors falls far from expectation and the construction of heterojunctions is an effective strategy to resolve such issue. In this study, indium oxide-based composites (Co 3 O 4 /In 2 O 3 ) with a typical p-n heterojunction were synthesized via a simple template-free hydrothermal method for high-performance formaldehyde sensing. XRD, SEM, TEM, and XPS confirmed the p-n heterojunction formation and its positive impact on enhancing surface reactivity. Gas-sensing tests demonstrated that the 3 wt% Co 3 O 4 /In 2 O 3 sensor exhibited optimal performance. The 3 wt% Co 3 O 4 /In 2 O 3 sensor exhibited a response value of 11.1 to 100 ppm formaldehyde at 300°C that was threefold higher than that of pure In 2 O 3 (3.77); its recovery time was 41 seconds quicker than that of In 2 O 3 (73 s vs. 114 s). The sensor also showed excellent selectivity, reproducibility, and stability. This research presents a scalable, heterojunction-driven design concept for the next generation of gas sensors.