Reliability and selectivity of H2 sensors composed of Pd Film nanogaps on an elastomeric substrate

Abstract

H2 sensors composed of Pd films of 10nm thickness were prepared on a compliant poly(dimethylsiloxane) (PDMS) substrate, using a combination of an initial H2 concentration of 0.5% and mechanical elongation of the samples by 50% of their original length. The initial feed of hydrogen gas was controlled for the PDMS/Pd films, and then an on–off switching response was measured with H2 concentrations ranging from 0.01% to 0.5%. The Pd films exhibited a nanogap width of less than 50nm. The sensors exhibited slightly degraded sensing performances in humidified H2 in a N2 environment, whereas their performance, in terms of their saturation current, showed little variation in an ambient atmosphere. This may be the result of a retarding effect caused by water adsorption on the Pd film surface, which decreases the number of active sites available for H2 adsorption. The sensor was exposed to several toxic gases such as CO, NO, NO2, and NH3, after a single cycle of H2 exposure. The nanogaps in the multi-nanogap structure exhibited selective reactivity with H2 but showed no response to the other gases to which they were exposed or no resulting degradation.