Synthesis of Mesoporous Ag 2 O/SnO 2 Nanospheres for Selective Sensing of Formaldehyde at a Low Working Temperature.

Formaldehyde (HCHO) is a prevalent indoor gas pollutant that has been seriously endangering human health. Developing semiconductor metal oxide (SMO) gas sensors for selective measurement of formaldehyde at low working temperatures remains a great challenge. In this work, silver/tin-polyphenol hybrid spheres are applied as a sacrificial template for the fabrication of spherical mesoporous Ag 2 O/SnO 2 sensing materials. The obtained mesoporous Ag 2 O/SnO 2 spheres have a uniform particle size (∼80 nm), large pore size (5.8 nm), and high specific surface area (71.3 m 2 g -1 ). The response is 140 toward formaldehyde (10 ppm) at a low working temperature (75 °C). The detection limit reaches a low level of 23.6 ppb. Most importantly, it has excellent selectivity toward interfering gases. When the concentration of the interfering gas (e.g., ethanol) is 5 times as high as that of formaldehyde, the response is little affected. Theoretical calculations suggest that the addition of Ag 2 O can significantly enhance the adsorption energy toward formaldehyde, thus improving formaldehyde sensing performance. This work demonstrates an efficient self-template synthesis strategy for noble metal catalyst-decorated mesoporous metal oxide spheres, which could boost gas sensing performance at a lower working temperature.