Sustainable materials key to solving global environmental problems

Researchers have mapped out how we can develop the crucial materials we need for everyday life in a more sustainable way.

From wind turbines and solar cells to packaging and textiles, materials make up the key components of some of the fundamental objects we require on a daily basis.

Our ability to produce and transform engineered materials over the past 150 years is responsible for our high standards of living today. However, the way in which we currently make and use materials detrimentally affects the planet, creating many severe environmental problems.

In a roadmap developed by key researchers in the field of sustainable materials including Professor Magda Titirici, Dr Hui Luo, Dr Heather Au and Dr Maria Crespo Ribadeneyra from Imperial’s Department of Chemical Engineering, scientists have highlighted the outstanding challenges and the pathways towards solving them.

Insights in materials science

Materials science is a highly interdisciplinary field of chemical engineering, covering the design, discovery and application of new materials and is the key to solving many sustainability challenges. This primarily involves creating more sustainable material alternatives using natural raw materials while making sure not to deplete important resources.

“I am very excited to see this sustainable materials roadmap published. It encompasses significant contributions from the scientific community working in this important research area across various themes". Professor Magda Titirici Department of Chemical Engineering

Critical materials represent a class of substances that make up central components of sustainable energy systems because they are the best performing. Examples include the permanent magnets based on rare earth metals used in wind turbines such as dysprosium, neodymium and praseodymium, lithium and cobalt in lithium-ion batteries, platinum in fuel cells and electrolysers, and silicon in solar cells.

The roadmap assesses how we can produce important substances like these critical materials for a more sustainable future. Lead author Professor Magda Titirici said: “I am very excited to see this sustainable materials roadmap published. It encompasses significant contributions from the scientific community working in this important research area across various themes from raw sustainable precursors to natural inspiration in making materials, different classes of materials, their applications, sustainability assessment and recycling.

She added: “I would like to acknowledge all the authors for their outstanding efforts contributing to this extremely important topic to alleviate our dependence on fossil fuel derived and critical materials a vital prerequisite to move towards a green economy.”

Sustainable quantum dots

Quantum dots (QDs) have tuneable and strong, robust fluorescence properties which have the potential for applications in solar cells, light emitting diodes, sensing and bio imaging. However, most of the semiconductor QDs contain metals that have a high toxicity and large environmental impact. 

“Carbon dots have the potential to serve as a sustainable alternative to the conventional quantum dots in applications such as solar cells, LEDs, sensing and bio-imaging." Dr Hui Luo Department of Chemical Engineering

The discovery of fluorescent carbon-based dots in 2004 bought people’s attention to this novel zero-dimensional carbon material as a potential sustainable alternative to existing quantum dots. These carbon dots usually have an average particle size below 10 nanometres and they can be produced by either top-down methods involving cutting large carbon materials such as graphite into smaller fragments, or bottom up approaches by growing small precursor molecules such as glucose into larger carbon polymers.

Producing carbon dots using this bottom up approach is considered to be more sustainable and environmentally friendly. However, the inhomogeneity of the carbon dots structure makes it difficult to acquire precise information about their chemical structure. Similarly, the carbon dot yields in the current synthesis approaches are too low to achieve a sustainable production stream and therefore use of them is currently limited.

According to co-author and Research Associate Dr Hui Luo: “Carbon dots have the potential to serve as a sustainable alternative to the conventional quantum dots in applications such as solar cells, LEDs, sensing and bio-imaging. However, challenges remain in precisely controlling their chemical and optical structures and increasing the production yield.”

“Advances have been made in research to tackle these challenges by studying the fundamentals and developing high-throughput systems, which will unlock the vast potential of carbon dots in the future society.”

Creating sustainable materials for batteries

To achieve the target of carbon neutrality by 2050, a shift in energy production to renewable sources is imperative. Sustainable batteries will play a prominent role in this energy shift.

“Emerging energy storage technologies have the potential to reach full-spectrum sustainability alongside technological advancements by learning from the shortcomings of current lithium-ion batteries (LIBs).” Dr Heather Au Department of Chemical Engineering

Lithium-ion batteries currently dominate the market but have significant environmental impacts due to their dependence on graphite and transition metal oxides. Naturally occurring graphite is in limited supply and while synthetic graphite offers a possible alternative, it is expensive to produce and derived from petroleum, a fossil fuel. Aside from this, transition oxides used to make the cathode contain cobalt, considered an endangered resource dependent on the heavy mining in the Democratic Republic of Congo.

Future energy systems will require greater demand for the storage of energy, presenting batteries as a critical area of research in the upcoming years. According to Research Fellow Dr Heather Au: “Emerging energy storage technologies have the potential to reach full-spectrum sustainability alongside technological advancements by learning from the shortcomings of current lithium-ion batteries (LIBs).”

Research Associate Dr Maria Crespo Ribadeneyra added: “Critical examination of the entire battery life cycle will help to achieve environmental balance and security by targeting high-performance materials based on abundant and non-geopolitically compromised elements, while also keeping a circular economy mindset.”

“While significant advances have been made in alternative battery chemistries, there is still great scope in developing innovations in greener materials synthesis, less energy-intensive cell manufacturing, improving battery lifetime and safety, and designing for end-of-life.”

The key to a sustainable future

In compiling the roadmap, the team hoped to demonstrate how a transition to using sustainable materials is possible for a greener future.

Dr Titirici concluded: “We hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability.”

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‘The Sustainable Materials Roadmap’ by Titirici et al., published on 25 January 2022 in JPhys Materials