Motiar Rahaman

Brilliant Minds

How do we help the environment with eco-friendly approaches to recycling waste? Dr Motiar Rahaman, based at the Yusuf Hamied Department of Chemistry, University of Cambridge, has helped to create a solar-powered reactor that can convert two separate waste streams simultaneously into reusable materials.



Motiar was born in Kalna, West Bengal. He attained his bachelors and master’s in Chemistry in India before getting a Swiss Government Excellence Fellowship to do his PhD in Switzerland, which he completed in 2018 with Summa Cum Laude. The title of his PhD thesis was ‘Power to Value: Electrochemical Conversion of CO2 into Value-added Products’.

Following this he was awarded a Swiss National Science Foundation Early Postdoc Mobility (SNSF-EPM) Fellowship and moved to the UK in 2019 for postdoctoral research at the Yusuf Hamied Department of Chemistry, University of Cambridge, under the supervision of Professor Erwin Reisner.

He also received a Marie Sklodowska-Curie Individual European Fellowship and carried out his research as a Marie-Curie fellow before being appointed as a Senior Postdoctoral Scientist. His current research is focused on the conversion of CO2 into multicarbon fuels, carbon capture and utilization, and reforming of plastics and biomass-derived waste into valuable chemicals.


Using Innovation to Create a Circular Economy

Developing a circular economy where we make useful things from waste instead of throwing them into landfill is a vital part of addressing the climate crisis and protecting the natural world. Much of the plastic that we put into recycling bins is still either incinerated or dumped in landfill. The simultaneous conversion of plastic waste and CO2 have been separately studied – but transforming both into valuable materials with a solar-powered reactor has never been achieved before. The study, written by Motiar and co-first author Subhajit Bhattacharjee, was published in Nature Synthesis.

Motiar said, “We experienced many setbacks and it took a long time for us to deal with the challenges we faced. The breakthrough was creating a reactor that could do two things at once – convert CO2 into fuels like syngas and formate, as well as converting plastic into valuable chemicals like glycolic acid, which are widely used in the cosmetic industry.


 “The beauty of this reactor is that it is tuneable, versatile and robust, and all it needs to work is sunlight.”


The reactor takes power from the sun through a light absorber made from perovskite photovoltaics, a promising alternative to silicon solar cells that could be used in solar panels of the future.

The team designed different catalysts which were integrated into the light absorber to make a photocathode (a device that turns light into electrons). By changing the catalyst, the researchers could change the end product via the CO2 conversion process. Tests showed that the reactor could efficiently convert polyethylene terephthalate (PET) plastic bottles and CO2 into different carbon-based fuels, and it can produce these products at a far more efficient rate than photocatalytic processing technology had previously demonstrated.

Motiar said, “CO2 conversion requires a lot of energy, but with this system we have coupled a less energy-demanding process with CO2 reduction. Basically you just shine a light at the photocathode and it starts converting waste materials into something useful and sustainable.


“Prior to this we didn’t have anything that could make high-value products so selectively or efficiently.”



The Future

Motiar said, “We are witnessing a major energy crisis in the world. We cannot bring coal from the mines forever. Supplies are being exhausted, and burning fossil fuels produces more carbon dioxide. It is now time to use renewable sources, and of those, sunlight is the most abundant and exploitable energy source we have.

“We have a good amount of wind power in the UK and Europe, and even though the UK does not have an abundance of sunlight, we are still wasting what we have. This is the direction we need to go in. Efforts need to be made everywhere, from the grass roots to the highest administrative levels to follow this path.”

New funding has been sourced from the European Research Council for the Reisner Laboratory to further develop this technology. Over the next five years the team hopes to scale up the reactor and produce more complex end products.

The technology based on the science behind this reactor could be used in the future to develop a multi-purpose recycling plant powered exclusively by solar energy.


New research published in Nature Energy 

Motiar’s latest research demonstrates a photosynthesis inspired process to convert CO2, water and sunlight into multi-carbon fuels – ethanol and propanol – in a single step using a standalone artificial leaf. These fuels have a high energy density and can be easily stored or transported, which means that they can be added directly to a car’s engine in future. It makes for an important step in the transition away from a fossil fuel-based economy.  Read more about this latest research on the University website and Chemistry Department Website.


Working in Cambridge

Motiar values scientific collaborations with colleagues, and he appreciates the help and assistance that is available when he needs it at the University of Cambridge.


 “We are given the opportunity to design our own work in our own way. There are no restrictions to what we do and there is always a positive atmosphere at work, with a very international feel.


“We get the moral support to do our best work. Everything is there to help us to achieve results. I really can’t thank my supervisor Professor Erwin Reisner enough for his constant support and motivation.”



Living in Eddington

He said, “I remember the day I moved into my apartment. It was 8 April 2019. I told the housing adviser who welcomed me and showed me around Eddington that I was going to appreciate it until the end of my stay. Nearly four years on I have that same feeling. It’s perfect.’’


“Eddington is my second home away from home and I have never felt like an outsider.”


“During the Covid lockdown, without Eddington, I don’t know how I would have survived! My wife and I have a great social life and there is a strong sense of community. The other good thing is that whenever I have a problem, help is always at hand, even during public holidays. It’s amazing. I really appreciate Eddington and I will stay here for as long as I can.


“I always tell new postdocs who I meet to come and live in Eddington. You will not find better accommodation.”


Motiar values the peace and quiet that he has found in Eddington. “It’s good for concentrating and writing a scientific paper, and perfect for meditation.”

Motiar and his colleagues have so far given us a glimpse of a future based on clean energy and smart technology, enabling a circular economy that will help to mitigate against the worst effects of the climate crisis.


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