Converting CO2 directly from air to fuel

15 July 2020

For Dr Xu Lu (Croucher Fellowship 2017), social impact is not just a buzz phrase or a government funding criterion. It lies at the heart of his research.

His long-term goal is to reduce the amount of carbon dioxide (CO2) in the atmosphere by converting it into a usable fuel. He knows that it is likely to be at least 15 years before such a fuel is in commercial production, but rather than being daunted by the timeframe he is enthusiastic at every stage of progress – particularly so because climate change means the amount of carbon dioxide in the atmosphere is increasing.

Indeed, his passion for his research is renewed on a daily basis by this sense of mission, he said. “Social impact is the first priority of research… that’s why we are doing it.”

Lu, 31, has spent the past three years as a member of associate professor Hailiang Wang’s research laboratory in the Department of Chemistry at Yale University in the United States.

Later in 2020, he is due to take up his first academic post as an assistant professor at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, where he will continue to collaborate with his global interdisciplinary research network.

Born in Longyan, in China’s Fujian province, Lu attended high school in China and undertook the national Joint Entrance Examination. Following this, he obtained a place at the University of Hong Kong, where he would remain for the next seven years.

After earning a bachelor degree in engineering with first class honours and a master’s degree with distinction in mechanical engineering, he continued on to his doctorate at the university, winning prestigious awards including a Lee Shau Kee Scholarship and University of Hong Kong postgraduate fellowship.

During his postgraduate study in Hong Kong, he collaborated with the Yale-based Wang lab and published in the Journal of Power Sources as first author, with Wang and others, in 2016.

Their article discussed the high cost and poor round-trip efficiency of regenerative fuel cells and their encouraging work to increase that efficiency. His subsequent research at Yale built on that foundation.

“There is so much carbon dioxide out there in the atmosphere, everything is getting hot,” he said. While renewables such as wind and solar are available, there is also the problem of intermittency with such energy sources. That is, they cannot always generate electricity due to time, weather, or other uncontrollable external factors. “For example, there is no sunlight at night,” Lu said.

“What we are trying to do is to use this renewable electricity to drive our reactors to convert carbon dioxide into a usable fuel – methanol, formic acid, or syngas.

“These are fuels people are using right now in the market, but the way to produce them is highly polluting. We want to make them from carbon dioxide, and that is fantastic. On the one hand, we could reduce carbon dioxide, and on the other we could produce the fuels.

While the objective is for the research to be applied, and there is an expectation of high-end social impact, development is still in the lab at the moment, Lu noted. “What I have been doing is trying to get it closer to a practical scenario,” he said. However, there is still a considerable way to go.

Lu explained that many researchers are trying to convert pure carbon dioxide into fuels, but that is impractical because of the cost of purifying. “What I am trying to do is to introduce some impurities.”

Because air contains not only carbon dioxide but many other components, working with impurities is essential if carbon dioxide taken from the air is to be turned into fuel, rather than undergoing expensive purification. Lu has been collaborating on this with Professor Neil McKeown of the University of Edinburgh. “We want to convert carbon dioxide directly from the air. That is my ultimate goal.”

He has been moving towards that by introducing impurities step by step. First, it was oxygen. Step two is nitrogen. Then, some of the many other impurities in air.

With 34 publications listed on ResearchGate, Lu has published extensively with colleagues on this research as it has progressed, including their work with an oxygen and carbon dioxide mixture in Angewandte Chemie International Edition in March 2020.

Looking ahead, he sees that the completion of three stages will be needed for his project to become a reality.

First is the necessity of selling the idea to investors. There is already considerable interest in the US, particularly because exploration of Mars, where the atmosphere is 95 per cent carbon dioxide, is such a hot topic.

The second stage is to develop a prototype and make it work – something he estimates could take around five years.

Finally, perhaps within 10 years, comes “lab to factory, the hardest part for research science”. This would involve an industry collaboration to create a huge device, with the aim of mass production.

Lu said an important next step would be to scale up the project. He plans to focus on this in his new post at KAUST in Saudi Arabia, where the university president is computational mathematician Professor Tony F Chan, previously president of Hong Kong University of Science and Technology.

“Now our unit reactor is as small as your hand. It is not practical at all,” Lu said. “I [will] have to utilise my engineering background to scale it up.”

This will mean drawing on the mechanical engineering skills he developed at the University of Hong Kong, whereas at Yale he focused on material behaviours in unit reactors. “I always work at the interface of science and engineering,” he said.

Dr Xu Lu obtained his BEng (First Class Honours and Dean's List), MSc (Distinction) in Mechanical Engineering and PhD, focused on microfluidics-based electrochemical CO2 utilisation, at the University of Hong Kong (HKU). Following postgraduate work at HKU, he moved to the laboratory of Dr Hailiang Wang in the Department of Chemistry at Yale University in the United States as a postdoctoral fellow. He will take up an assistant professorship at King Abdullah University of Science and Technology in Saudi Arabia later in 2020. Lu has received a Lee Shau Kee Scholarship, University of Hong Kong Postgraduate Fellowship, and a Marie Sklodowska-Curie Actions Seal of Excellence. He was awarded a Croucher Fellowship in 2017.

To view Dr Lu’s Croucher profile, please click here.