New process for generating hydrogen fuel

A sustainable, cleaner-burning alternative to gasoline could help shrink the carbon footprint of cars and trucks. One option is to use methanol by catalytically releasing hydrogen from the liquid to power a hydrogen fuel cell.

Ding Ma of Peking University, Beijing, and coworkers report a new catalyst to do so: atomically dispersed platinum over molybdenum carbide particles that drive the efficient and relatively low-temperature “reforming” of CH₃OH and water to form H₂ (Nature 2017, DOI: 10.1038/nature21672).

The process is about five times as efficient as the previous H₂-from-methanol champ, a ruthenium-catalyzed dehydrogenation developed by Matthias Beller of the University of Rostock and coworkers (Nature 2013, DOI: 10.1038/nature11891).

The new Pt/MoC catalyst works at relatively low temperatures, 150 to 190 °C—cooler than the 200 °C or more traditionally used to reform CH₃OH vapor, but considerably hotter than Beller’s process, which works at 65 to 95 °C. But the new process has advantages over the Beller technique: It avoids the use of caustic hydroxide, and the Pt/MoC catalyst is heterogeneous, which makes it cheaper and easier to recycle than the homogeneous ruthenium catalyst.

Ma calculates that a 50-L tank of CH₃OH and catalyst with 6 to 10 g of Pt—about the weight of a wedding ring—could power a Toyota Mirai, a hydrogen fuel cell concept car, for about 690 km. The CH₃OH would cost about $15 and the Pt about $320, but the catalyst is potentially recyclable.

Pt is relatively rare and expensive compared with other metal catalysts, but Ma points out that automobile catalytic converters now contain 1 to 4 g of recyclable noble metals, “so 8 g Pt is not a big number.”

Reaction engineer Dion Vlachos of the University of Delaware comments that the new process “has a technological edge in terms of reaction rate,” but improving long-term catalyst stability, developing means for catalyst regeneration, and finding alternatives to noble metals “are important future directions for widespread commercialization.”

Beller calls Ma’s catalyst “a major breakthrough,” noting that this type of catalyst might also be useful for other aqueous-phase reforming processes, such as those involving biowaste or ethanol.