and rejoin the hydrogen ions to react with oxygen and produce water. Fuel cells are expected to find strong use in the transportation industry. Superacid catalyst for fine chemical production Nafion, as a superacid, has potential as a catalyst for organic synthesis. Studies have demonstrated catalytic properties in alkylation, isomerization, oligomerization, acylation, ketalization, esterification, hydrolysis of sugars and ethers, and oxidation. New applications are constantly being discovered. These processes, however, have not yet found strong commercial use. Several examples are shown below: Alkylation with alkyl halides Nafion-H gives efficient conversion whereas the alternative method, which employs Friedel-Crafts synthesis, can promote polyalkylation: Acylation The amount of Nafion-H needed to catalyze the acylation of benzene with aroyl chloride is 10–30% less than the Friedel-Crafts catalyst: Catalysis of protection groups Nafion-H increases reaction rates of protection via dihydropyran or o-trialkylsilation of alcohols, phenol, and carboxylic acids. Isomerization Nafion can catalyze a 1,2-hydride shift. It is possible to immobilize enzymes within the Nafion by enlarging pores with lipophilic salts. Nafion maintains a structure and pH to provide a stable environment for the enzymes. Applications include catalytic oxidation of adenine dinucleotides. Sensors Nafion has found use in the production of sensors, with application in ion-selective, metallized, optical, and biosensors. What makes Nafion especially interesting is its demonstration in biocompatibility. Nafion has been shown to be stable in cell cultures as well as the human body, and there is considerable research towards the production of higher sensitivity glucose sensors. Antimicrobial surfaces Nafion surfaces show an exclusion zone against bacteria colonization. Moreover, layer-by-layer coatings comprising Nafion show excellent antimicrobial properties. Dehumidification in spacecraft The SpaceX Dragon 2 human-rated spacecraft uses Nafion membranes to dehumidify the cabin air. One side of the membrane is exposed to the cabin atmosphere, the other to the vacuum of space. This results in dehumidification since Nafion is permeable to water molecules but not air. This saves power and complexity since cooling is not required (as needed with a condensing dehumidifier), and the removed water is rejected to space with no additional mechanism needed. Modified Nafion for PEM fuel cells Normal Nafion will dehydrate (thus lose proton conductivity) when the temperature is above ~80 °C. This limitation troubles the design of fuel cells because higher temperatures are desirable for better efficiency and CO tolerance of the platinum catalyst. Silica and zirconium phosphate can be incorporated into Nafion water channels through in situ chemical