Enhanced sensing performance and sensing mechanism of hydrogenated NiO particles

Hydrogenation is successfully used to enhance the sensitivity of NiO-based gas sensors for the first time. The hydrogenated NiO sensors show significantly higher response to volatile-organic-compound vapors than the samples without hydrogenation. The enhanced sensing performance is attributed to an increase in the density of the unsaturated Ni atoms with dangling bonds on the surface resulted from the hydrogenation process. A concept of the unsaturated Ni atoms with dangling bonds serving as the active sites for the sensing reaction thus is proposed, and the sensing mechanism is described in detail at atomic and molecule level for the first time. The hydrogenation strategy may be used to improve sensing properties of other metal oxide sensors and catalytic activities of photocatalysts and other catalysts. The concept of the unsaturated metal atoms with dangling bonds serving as active sites can deepen understanding of the sensing and catalytic reaction mechanisms and afford guidance to design advanced gas sensing materials, catalysts and photoelectronic devices. (C) 2017 Published by Elsevier B.V.