NUS CDE Scientists Create Biowaste-Based Coatings to Enhance CO2-to-Fuel Conversion Efficiency

As the world confronts one of the most critical energy crises since the 1970s, highlighted by recent geopolitical disruptions impacting the Strait of Hormuz, the limitations and vulnerabilities of global dependence on fossil fuels have become glaringly apparent. Amid this backdrop, the urgent necessity for sustainable and renewable alternatives has propelled research into innovative fuels derived not from crude oil, but from renewable electricity and captured carbon dioxide (CO2). A landmark study emerging from the National University of Singapore’s College of Design and Engineering (NUS CDE) now reveals a breakthrough in electrochemical CO2 conversion technology. This advance could radically improve the efficiency and sustainability of generating multicarbon fuels like ethylene and ethanol, which currently rely heavily on petroleum refining.

The team, led by Assistant Professor Andrew Barnabas Wong of the Department of Materials Science and Engineering, has engineered an elegant solution by harnessing biopolymers—naturally derived, biodegradable materials sourced from biological waste such as seafood shells, wood, and insect exoskeletons—to enhance copper catalyst performance in CO2 electroreduction. By applying ultrathin coatings of these materials, just two to five nanometres thick, on copper surfaces, the researchers achieved unprecedented selectivity for multicarbon products at industrially relevant current densities. Specifically, the system attained a remarkable 90% selectivity at 1.6 amperes per square centimetre and maintained an 83% selectivity rate even when pushed to 2.2 A/cm², surpassing most current copper-based catalytic benchmarks.

Electrochemical CO2 conversion operates by utilizing renewable electrical energy to split CO2 and water molecules into their constituent atoms and then reconstituting them into valuable hydrocarbon products. Copper catalysts are pivotal in this process, given their unique ability to facilitate the formation of multicarbon compounds, including ethylene and ethanol, which are fundamental to the global chemical and fuel industries. Historically, achieving high selectivity for these products necessitated coating copper electrodes with fluorinated ionomers like Nafion, renowned for their water-repellent and ionic transport properties. However, Nafion and related materials belong to the class of per- and polyfluoroalkyl substances (PFAS)—commonly known as “forever chemicals”—which are environmentally persistent, expensive, and increasingly subject to regulatory scrutiny due to health hazards.

The innovation by Wong’s group replaces these PFAS with nanolayers of biopolymers, namely cellulose, chitin, and chitosan. These biopolymers not only avoid environmental and health concerns associated with PFAS but also fundamentally alter the local reaction microenvironment at the catalyst interface. Through advanced spectroscopic techniques and computational modeling, the researchers demonstrated that biopolymer coatings increase local CO2 concentration near the catalyst surface, restrict the diffusion of water molecules, and promote efficient ion transport. These synergistic effects significantly suppress the hydrogen evolution reaction—a common undesired side reaction that consumes electrons and decreases the yield of carbon-based products—thereby steering the reaction towards higher production of multicarbon hydrocarbons.

Assistant Professor Wong commented that their findings challenge long-held assumptions in the field, where hydrophobic materials were thought essential for maintaining selectivity during CO2 reduction. In contrast, the biopolymer coatings are highly hydrophilic, interacting strongly with water molecules and reshaping the electrochemical environment to favour the catalytic pathways leading to ethanol and ethylene. This novel understanding opens an exciting new frontier in catalyst design, where the microenvironment created by the coating can be fine-tuned to optimize performance.

In addition to enhancing selectivity and efficiency, the team showcased the practical advantages of biopolymer coatings as multifunctional components in electrodes. When paired with silver nanoparticles to form a tandem system, the biopolymer-coated copper catalysts demonstrated substantial stability and activity at elevated current densities — conditions that simulate industrial operations demanding high throughput. Notably, performance metrics retained their high selectivity for multicarbon products, which would typically deteriorate at higher currents due to increased hydrogen generation.

The cost benefits are equally compelling. Chitosan, for example, is produced from abundant waste biomaterials at a price point approximately three orders of magnitude lower than Nafion per kilogram. This dramatic reduction in material cost, combined with the elimination of environmentally problematic PFAS components, promises to deliver a greener, more economically viable pathway for scalable CO2 electroreduction technologies. Such affordability and sustainability are critical for real-world deployment and transitioning away from fossil-based fuel and chemical production.

Beyond immediate performance gains, the use of biopolymers derived from waste streams embodies circular economy principles, transforming biological refuse into a value-added resource that advances climate-positive technology. This alignment of environmental benefits, economic feasibility, and technological innovation illustrates a holistic approach to sustainable energy conversion.

While the technology is still evolving, the potential impact of this research resonates throughout the chemical energy landscape. Electrochemical CO2 conversion powered by renewables offers an avenue to produce essential fuels and feedstocks while capturing and utilizing carbon emissions, a key pillar in mitigating climate change. The biopolymer-coated copper catalyst represents a crucial step in overcoming existing bottlenecks in efficiency and sustainability that have hindered commercialization.

Future research directions, as outlined by the researchers, include fine-tuning the biopolymer compositions and thicknesses to adjust the ratios of different multicarbon products like ethanol versus ethylene — a critical factor for matching varied industrial demands. Enhancing the long-term stability of the electrodes to extend operational lifetimes without substantial maintenance is also a priority. These ongoing efforts promise further advances, potentially enabling truly oil-free manufacturing of fuels and chemicals on an industrial scale.

This discovery stands out not just for its technical ingenuity but for its broader implications: a simple, scalable coating strategy capable of transforming CO2 electroreduction by eliminating reliance on harmful synthetic ionomers. As the world accelerates toward net zero emissions and decarbonization, innovations such as this from the NUS team spotlight the intersection of materials science, chemistry, and sustainability. They offer tangible hope for reshaping energy systems to be cleaner, cheaper, and more circular.

News Publication Date:
April 17, 2026

Web References:
http://dx.doi.org/10.1038/s41560-026-02040-7

Keywords

Energy, Materials Science, Chemical Engineering, Sustainability, Nanotechnology, Climate Change Mitigation