Electrodeposition of nanowires for the detection of hydrogen gas

Nanowires composed of noble metals are attractive candidates for chemical sensors because they are both ductile and chemically stable in air. The single application where electrodeposited metal nanowires have had the largest impact is that of hydrogen gas (H2) sensing. The development of sensitive, selective, power-effi cient, rapid-responding, and inexpensive H2 sensors, for the purpose of detecting leaked H2 in proximity to devices such as fuel cells, is an active area of research. In this application, a change in the dc electrical resistance of the nanowire from its background value signals the presence of H2 and provides an estimate of its concentration. Two types of nanowires have been studied for use as hydrogen sensors: Electrodeposited nanowires composed of pure palladium metal (Pd) reversibly absorb hydrogen to form a hydride according to Pd + xH2 → PdH2x. Alternatively, nanowires that transduce the presence of H2 may be prepared by decorating an inert, electrically conductive support such as a carbon nanotube or a nickel nanowire with one or more eletrodeposited palladium nanoparticles. These palladium nanoparticles impart selectivity to H2 and cause the electrical conductivity of the composite particle/support to be modulated in the presence of H2. Here we summarize recent contributions of electrodeposition to the development of nanowirebased sensors for H2.