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Harnessing her expertise in materials chemistry, Lili Zhang of ISCE2 is tapping into the power of carbon-based materials to foster sustainable development across industries.

© A*STAR Research

Energising the carbon conversion movement

21 Jul 2022

Harnessing her expertise in materials chemistry, Lili Zhang of ISCE2 is tapping into the power of carbon-based materials to foster sustainable development across industries.

In December 2015, nearly 200 nations signed the 2015 Paris Agreement in a landmark move to tackle the climate crisis. The commitment sought to limit global warming from rising beyond 2°C above pre-industrial levels, and to instead strive for a maximum increase of just 1.5°C. While a half-degree difference in temperature may seem small, it could save hundreds of millions of people from dangerous heatwave exposure and water scarcity issues in 2050.

As climate action strategies unfolded around the world to meet this goal, Singapore also pledged to slash its greenhouse gas emissions. Energy efficiency and zero waste strategies have since taken centre stage in national concerns, with the latest Research, Innovation and Enterprise (RIE) 2025 plan dedicating a domain to address the city-state’s sustainability and liveability.

Just a month after the historic treaty in Paris, Lili Zhang—currently a Senior Scientist at A*STAR’s newly established Institute of Sustainability for Chemicals, Energy and Environment (ISCE2)—landed two sustainability projects. One was an international research collaboration with the National Natural Science Foundation of China to develop high-performance supercapacitors, building on years of fundamental research work on carbon-based materials and their applications in energy storage devices1-4. The other, facilitated by A*STAR’s T-Up programme, involved working with local start-up; A&T Inno Pte Ltd, to recycle waste tyres into commercial-grade carbon.

But before becoming a Clarivate Highly Cited Researcher that she is today, Zhang began her research with the most abundant element on earth—carbon. That element was the foundation for her continuous efforts to devise functional materials for sustainable applications. Zhang’s endeavours are aligned with the eventual focus areas of ISCE2 in decarbonisation, green materials and green processes.

From element to electricity
Zhang’s pursuit of science has always been rooted in a mission to solve environmental problems. She believes the broad vision to build a more sustainable world has given her the flexibility to explore a variety of areas such as clean energy and waste upcycling.

“I was looking for stable materials to use in energy conversion and storage devices, and carbon turned out to be one of the best candidates, even in harsh conditions,” she said. “Not only is carbon stable, it is also cheap, environmentally friendly and found in almost everything around us.”

Zhang added that carbon-based materials can be used to make energy storage and conversion devices such as supercapacitors and lithium-ion batteries used in electric vehicles. Compared to traditional batteries, supercapacitors provide higher power output, faster charge-discharge times and longer life cycles. However, challenges remain in stabilising them and improving their energy densities, the amount of energy they hold for their size, which must reach certain thresholds to be viable for any practical or real-world application.

An early foray into these challenges of energy storage inspired Zhang to build better energy storage devices to wean the world off environmentally damaging fossil-dependent sources. Over the years, she has worked with several research teams to probe the electrochemical properties of various materials.

Zhang’s innovations have included a novel three-dimensional MnO2 network explicitly arranged to result in a more stable energy storage device with high capacitance and ultrahigh specific power5,6. In another fruitful international collaboration, Zhang and colleagues engineered MXene films with improved energy density and mechanical strength, boosting the performance of the assembled supercapacitor7,8.

While Zhang has since worked with numerous other compounds, she still often returns to carbon, the one element that consistently stays on her research radar.

Transforming trash into treasure
Carbon is one of the three elements that make up organic chemistry’s powerful triumvirate: carbon, hydrogen and oxygen. They are the building blocks of just about everything, from biomass waste like peanut shells to plastics and end-of-life tyres.

The common presence of the carbon, hydrogen and oxygen trio across all these forms of waste presented a compelling opportunity for Zhang: “When these materials are no longer needed for human activities, science can turn them into valuable ‘new’ or ‘green’ materials,” she said.

Through such waste upcycling projects, Zhang is bridging use-inspired basic research with applied and translational research. By understanding the fundamental properties of materials and how to manipulate them, she opens the pathway to work with industries to make the most of these novel technologies.

An example of this is Zhang’s work with A&T Inno Pte Ltd to recover carbon black from tyres. With a soot-like appearance, carbon black particles are finely divided crystalline forms of carbon used in manufacturing tyres to enhance their resistance to wear and tear. Besides being a reinforcing filler, the material is also highly valued as a colouring agent for paint and a component of resistors in electronic devices.

However, extracting carbon black from crude oil typically comes at a steep price and a heavy carbon footprint. Deriving carbon black from end-of-life tyres is also challenging and inefficient, as dirt from the road leaves impurities in the resulting mixture when used tyres are decomposed at high heat.

To solve this problem, Zhang created an environmentally friendly “detergent” to remove the contaminants and retrieve pure carbon black. Without the need for extra chemicals and high temperatures, Zhang’s detergent-based novel recycling method reduces carbon black production costs by about half and saves energy.

Similarly, in 2019, Zhang and her team mixed industrial dye wastewater with glucose to produce graphene-like carbon for high-performance supercapacitors9. This green process simultaneously treated the wastewater and recovered nitrogen and sulfur, which are then attached to the carbon structure to improve its energy storage performance.

Another recent technology from Zhang’s lab directly addresses plastic pollution—a looming problem in Singapore, a country that recycles only four per cent of its plastic as of 2020. “Our patent involves an efficient and sustainable process to upcycle plastic waste into high-value materials and energy. Compared to current procedures, it has reported a high carbon recovery so far with 2.5kg CO2 avoided per kg of plastic waste,” she noted.

These progressive strides are the result of a collaborative environment, highlighted Zhang, who clocks in over 10,000 steps daily as she moves between A*STAR’s different labs and offices.

“Teamwork is key to solving problems,” Zhang added. “I am grateful to have a supportive group from research staff and colleagues at A*STAR to industry collaborators.”

Walking the talk
Perhaps unsurprisingly, Zhang often grapples with the tug-of-war between the urgent need for sustainable solutions and the time it takes to develop commercially viable technologies.

Even then, she emphasises quality over quantity, complemented by strong partnerships between industry and academia to push innovations forward. She also credits Deputy Chief Executive (Research) Andy Hor for instilling such an ideology across A*STAR’s research efforts, recalling Hor’s belief that “any breakthrough in translational research comes from basic research.”

Despite an already impressive history of research achievements, Zhang remains excited about the endless possibilities for sustainable manufacturing methods. She continues to exercise her creativity and is involved in several ongoing efforts to convert waste into valuable products such as hydrogen gas, jet fuels, carbons and even diamonds.

“Carbon nanotubes are 100 times more robust than steel on a molecular level while being six times lighter,” highlighted Zhang, who hopes to enable their large-scale production from wastes and natural rubbers.

Her lab at ISCE2 is also working to synthesise graphene quantum dots, another functional nanoscale carbon-based material with tremendous potential for energy storage, catalysis and biomedical imaging applications.

As a self-proclaimed nature and animal lover, Zhang’s vision for sustainability extends beyond the lab and to her advocacy and community work, as she has also engaged with non-profit organisations focusing on conservation. “The concept of ‘zero waste’ has long been ingrained in my mind, and my family and I practice this in our daily lives,” she said.

Through these experiences, Zhang realised that public awareness and education are important for changing mindsets to achieve the sustainability agenda. To that end, Zhang emphasises the need for community engagement, and the mentorship of young researchers as a vital part of translating scientific and technological advancements into societal impact.

“The world still faces many problems that will require future generations to keep working on,” concluded Zhang. “For our progress to continue, we must ensure succession in our local R&D environment by recognising potential and providing aspiring talents with plenty of opportunities to amass experience in science.”

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1. Zhang, L.L., Zhao, X., Stoller, Meryl D., Zhu, Y., et al. Highly conductive and porous activated reduced graphene oxide films for high power supercapacitors. Nano Letters 12, 1806–1812 (2012). | article
2. Zhang, L.L., Zhao, X., Ji, H., Stoller, M.D., Lai, L., et al. Nitrogen doping of graphene and its effect on quantum capacitance and a new insight towards the capacitance enhancement of N-doped carbon. Energy & Environmental Science 11, 9618–9625 (2012). | article
3. Ji, H., Zhao, X., Qiao, Z., Jung, J., Zhu, Y., et al. Capacitance limits of carbon-based electrical double-layer capacitors. Nature Communications 5, 3317 (2014). | article
4. Huang, M., Li, F., Dong, F., Zhang, Y., Zhang, L.L. MnO2-based nanostructures for high-performance supercapacitors. Journal of Materials Chemistry A 3, 21380–21423 (2015). | article
5. Zhu, S., Li, L., Liu, J., Wang, H., Wang, T., et al. Structural directed growth of ultrathin parallel birnessite on β-MnO2 for high-performance asymmetric supercapacitors. ACS Nano 12, 1033–1042 (2018). | article
6. Zhu, S., Wang, T., Liu, X., Zhang, Y., Li, F., et al. Low-charge-carrier-scattering three-dimensional α-MnO2/β-MnO2 networks for ultra-high-rate asymmetrical supercapacitors. ACS Applied Energy Materials 2, 1051–1059 (2019). | article
7. Zhao, X., Wang, Z., Dong, J., Huang, T., Zhang, Q., et al. Annealing modification of MXene films with mechanically strong structures and high electrochemical performance for supercapacitor applications. Journal of Power Sources 470, 228456 (2020). | article
8. Yao, M., Chen, Y., Wang, Z., Shao, C., Dong, J., et al. Boosting gravimetric and volumetric energy density via engineering macroporous MXene films for supercapacitors. Chemical Engineering Journal 395, 124057 (2020). | article
9. Lin, Y., Chen, H., Shi, Y., Wang, G., Chen, L., et al. Nitrogen and sulfur co-doped graphene-like carbon from industrial dye wastewater for use as a high-performance supercapacitor electrode. Global Challenges 3, 1900043 (2019). | article

This article was made for A*STAR Research by Wildtype Media Group