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4 min ago 3 min read
Researchers at the National University of Singapore (NUS) have developed ultra-thin biopolymer coatings made from biological waste that dramatically improve the efficiency of turning carbon dioxide (CO2) into useful fuels and chemicals.
The coatings, just nanometres thick, are made from chitin (sourced from seafood shells), cellulose (from wood), and chitosan.
They can be painted onto copper catalysts used in electrochemical CO2 reduction. In this process, electricity drives the reaction that splits CO2 and water, then reassembles the pieces into carbon-rich products such as ethanol and ethylene.
Copper is the best-performing catalyst for making these multicarbon fuels, but it has traditionally required toxic “forever chemicals” called PFAS – or expensive fluorinated binders like nafion – to control the surface chemistry and suppress unwanted hydrogen production.
The NUS team found that their biopolymer coatings achieve the same effect naturally by concentrating CO2 molecules near the catalyst surface.
“We have shown that the forever chemicals upon which these technologies rely could potentially be replaced with cellulose, chitin and chitosan,” said Assistant Professor Andrew Wong from the National University of Singapore.
The biopolymers can also replace nafion as the binder that holds the catalyst particles together.
Cellulose-coated copper electrodes bound with chitin reached 95% selectivity for multicarbon products – matching or exceeding the performance of conventional nafion-bound systems.
High-quality chitosan costs roughly one-thousandth as much as nafion (around $50 per kilogramme).
“Prior to this work, it was believed that materials like nafion or other water-repelling substances were essential to selectively produce ethanol and ethylene from CO2,” said Wong.
When the coated copper nanoparticles were paired with silver nanoparticles in a tandem setup designed to maximise multicarbon output, 90% of the electrical current was directed towards useful products at a current density of 1.6 A/cm². This means there are 1.6 amperes of electrical current flowing through a surface area of one square centimetre.
Even when the team pushed the current higher to a rate that would normally cause selectivity to collapse as more unwanted hydrogen gas is produced, the biopolymer-coated system maintained 83% selectivity for multicarbon products.
This suggests the coatings help keep the reaction efficient and selective even under industrially relevant, high-speed conditions that would require fewer reactors for the same output.
