Hydrogen sensing capabilities of highly nanoporous black gold films

Hydrogen sensing is a crucial topic for many industrial and environmental applications regarding the green deal and the use of hydrogen as a next-generation energy source/energy-storage medium. Therefore, many different approaches are being used to find sensitive, reliable and inexpensive devices for hydrogen detection. One such approach is the use of chemiresistive nanostructured materials that provide a large surface area for hydrogen adsorption. In this paper, we present a detailed study of the hydrogen sensing capabilities of highly nanoporous black gold films that show fast response and recovery times (0.5 min) while operating at low temperatures (40 degrees C). To investigate the sensing properties of black gold, films with different levels of nanoporosity were prepared and tested to a hydrogen concentration in the range of 0.25-0.95 %. Film morphology was characterised by AFM, SEM and XPS. To correctly examine the nanopores and defects in prepared films, Variable Energy Positron Annihilation Spectroscopy (VEPAS) was used. We found that nanoporous black gold is suitable as an active layer of chemiresistor for hydrogen sensing and that its sensitivity is the function of the film nanoporosity. Possible mechanisms of hydrogen-gold interactions are discussed.