). As for the fluorocarbons, some are powerful greenhouse gases, and others break up into a small-molecule PFAS that is now accumulating in water.
Liu has developed a fluorine-free binder, but it works only for a lower-voltage battery such as one based on lithium iron phosphate. These batteries do have advantages: they last longer and don’t use critical minerals such as cobalt, nickel or manganese, important factors to consider as battery production ramps up in the fight against climate change, Liu says.
But PFASs aren’t necessary for green hydrogen: an emerging alternative to PEMs involves systems that instead move negatively charged hydroxide ions across membranes in an alkaline environment, says Benjamin Britton, a chemist who co-founded the start-up Ionomr Innovations in Vancouver, Canada.
McLinden suggests that a common-sense approach is to crack down on leaks. Refrigerants operate in a closed loop — in that if they leak, the device doesn’t work. So if manufacturers could assure no leaks, any refrigerant would be fine, he argues.The simplest but most pervasive uses of PFASs in machinery — from engines to chemical reactors — are at the interfaces between parts. Fluoropolymer greases lubricate moving surfaces, and fluoroelastomer O-rings, gaskets and seals join parts together.
PFASs are used in many ways to make computer chips. In one crucial step, manufacturers coat a silicon wafer’s surface with a ‘photoresist’ material containing PFASs: when the photoresist is illuminated, those PFASs generate strong acids that eat away at portions of the material, leaving a carefully patterned gap. In a second step, the exposed parts of the wafer are etched away — and in ‘dry etching’, a mixture of gases is used, usually containing some fluorocarbons.
In December, 3M announced it would stop making all its fluorochemical products — including fluoropolymers and fluorocarbon gases and liquids — by 2025, but did not say what would take their place. This June, it reached a $10-billion settlement to pay to clean fluorosurfactants from drinking water in parts of the United States, although it faces other unresolved lawsuits.