Porous Thin Films with Large Specific Surface Area on the Basis of Spray-Coated Metal Aerogels

The preparation of aerogels in the form of thin filmsdepositedon a substrate (e.g., as an electrode material) is an attractive butchallenging task. Such thin films are expected to combine the highlyporous gel nanostructure, good mechanical stability, and a remarkablyhigh specific surface area with efficient charge-carrier transportvia the interconnected nanoparticle chains. All together, they makethem attractive for the fabrication of (electro)catalysts or sensorsfor microfluidics, flexible electrodes for microelectronics, softelectrodes compatible with a stress-sensitive bioenvironment, etc.In this work, thin aerogel films of colloidal Pd and PtNi buildingblocks were prepared from the corresponding wet gels using a spraytechnique. The films were fabricated on substrates of around 1.5 cm(2). During the modification of the substrates, the film thicknesscan be adjusted by controlling the ink content (flow rate, gas pressure,and temperature) and the number of spray cycles. In this way, boththe electrical (down to R (s) = & SIM;0.2kOhm/sq) and optical parameters of the thin porous films can be tuned.Comparative studies of the pore and surface structures of the filmshave confirmed their integrity and the highly porous structure typicalfor aerogels. In perspective, spray-coated aerogels can be easilyadapted to industrial applications because upscaling is possible andexpensive equipment such as supercritical or freeze-dryers is notrequired. It is important to note that the spray-coating techniqueis applicable through a mask or can be converted to inkjet printing,which allows for the desired micropatterning of aerogel thin films.