With rising carbon dioxide (CO2) emissions being one of the biggest drivers of climate change, researchers are working to recapture CO2 from the air in bulk. While some propose storing that carbon underground, others aim to turn it back into clean-burning fuels or other useful chemicals, such as ethanol, using green electricity to power the process.
“Converting CO₂ to ethanol is a powerful way to fight climate change and store renewable energy,” said A*STAR Institute of High Performance Computing (A*STAR IHPC) Principal Scientist, Jia Zhang. “But it can be challenging to selective produce ethanol from CO₂, as it requires fine control over reaction intermediates. Most systems produce other chemicals such as carbon monoxide (CO) and ethylene instead.”
Catalytic electrodes are a key part of such systems as they propel CO₂’s carbon atoms through reactions with many possible intermediate and final products. Tiny tweaks to an electrode’s surface—such as a ‘decorative’ coating of small molecules—can help steer those reactions to favour ethanol production. However, these additive molecules can be easily leached away by intense voltages or liquid components of the system in operation.
Aiming to boost the viability of CO₂-to-ethanol conversion, Zhang and A*STAR IHPC colleagues joined researchers from the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2) and the National University of Singapore (NUS) in testing a method to keep small molecular additives intact on catalytic electrodes.
The researchers applied a thin protective layer of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), a stable water-repelling polymer, over the surface of a copper-based electrode. The electrode itself had been treated with 4-dimethylaminopyridine (DMAP), a small molecule additive with unique electronic properties.
Using detailed kinetic analysis, in situ spectroscopies and theoretical calculations, the team observed that DMAP—with the protection of PVDF-HFP—helped prevent CO and other carbon intermediates from prematurely escaping the catalyst. This boosted the catalyst’s selectivity towards multi-carbon (C2+) products, especially ethanol. The PVDF-HFP layer also seemed to enhance DMAP’s effect by preventing its leaching from the catalyst.
“Optimising the PVDF-HFP layer was crucial: it needed to be thin enough to allow efficient ion transport, but thick enough to protect the DMAP additive,” said Zhang.
Through careful adjustments, the NUS team found that a 4 μm-thick layer of PVDF-HFP thickness was optimal for C2+ production. Compared to an uncoated copper catalyst, PVDF-HFP improved the catalyst’s reaction selectivity by two- to threefold, yielding about 47 percent of ethanol as its final product.
“This system demonstrates how tailored surface chemistry through molecular additives, combined with a smart protective design, can significantly enhance ethanol production from CO₂,” Zhang said.
The team aims to leverage CatPlat, A*STAR IHPC’s inhouse computational catalysis platform, to potentially explore and screen for other organic molecules that could enhance the efficiency of CO₂ conversion to targeted chemicals.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of High Performance Computing (A*STAR IHPC) and A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2).
