Pt/GO/TiO2 room–temperature hydrogen sensing Schottky diode: High resistance to humidity interference endowed by the graphene oxide interlayer

Abstract

Room–temperature hydrogen sensors usually suffer from dramatic response drop in humid air. Aiming to solve such issue of H2 sensing Schottky diodes, a platinum/graphene oxide/titanium dioxide (Pt/GO/TiO2) Schottky diode is designed. The GO interlayer between the 50–nm–thick Pt nanolayer and TiO2 substrate significantly improves resistance to humidity interference. Remarkably, the diode with a GO loading of 0.969 mg cm−2 exhibits a response retention rate (RRH95%/Rdry) of nearly 100%. To reveal the mechanism for the improved anti–humidity performance, the H2O adsorption behavior of Pt/GO/TiO2 diode was investigated by quartz crystal microbalance and near ambient pressure X–ray photoelectron spectroscopy. H2O molecules are absent on the Pt surface of Pt/GO/TiO2 in water vapor. This is a result of the H2O adsorption effect of the GO interlayer, which stems from the superior H2O adsorption ability of the GO interlayer and causes the diffusion of H2O molecules adsorbed on the Pt surface into the GO interlayer through nanochannels in the Pt nanolayer. Additionally, the GO interlayer serves as a blocking layer for the diffusion of hydroxyl species generated on the TiO2 surface to the Pt nanolayer. Such hydroxyl blocking effect prevents the consumption of adsorbed H atoms at the Pt/GO interface.