Direct confirmation of confinement effects by NiO confined in helical SnO2 nanocoils and its application in sensors

Confinement effects in space-confined catalysts are attracting attention due to their advantages, like size control, unique nanoscale chemical environments and designable nature of the active sites. There are rarely works on the direct confirmation of confinement effects because of restrictions of nanoscale confined space. Herein, we report the fabrication of a novel structure that is composed of NiO nanoparticles confined in SnO2 nanocoils (I-NiSnNCs) via atomic layer deposition (ALD). The I-NiSnNCs displayed higher sensing performance towards hydrogen than the NiO-SnO2 film, NiO outside NiSnNC and NiO both outside and inside NiSnNC sensors. The I-NiSnNC sensor shows a response to about 7 to 50 ppm H-2 with a 2.4 s response time and 4.2 s recovery time at 260 degrees C and excellent repeatability. The synergistic effect of interfacial sites is attributed to the reaction between adsorbed H on NiO and adsorbed O at interfacial active sites. The funneling effect formed because the enrichment effect of hydrogen on the NiO surface is higher than that of the gas state as the adsorbed H quickly reacts at interfacial active sites. The enrichment effects of H-2 lead to high sensing performance to H-2, and the high reactivity of H-2 at interfacial active sites leading to rapid transfer of electrons is responsible for the high response/recovery performance. The gas sensor offers a new way to directly confirm the confinement effect. And the confinement effects in return give a novel way to design sensing materials.

Automated summary

The study presents a novel structure composed of NiO nanoparticles confined in SnO2 nanocoils, which shows higher sensing performance towards hydrogen. The sensor displays a quick response to 7-50 ppm of H-2 with short response and recovery times, along with high repeatability.