Periodic Reporting for period 1 - REFINE (From solar energy to fuel: A holistic artificial photosynthesis platform for the production of viable solar fuels)
Reporting period: 2023-11-01 to 2025-04-30
Emissions and lack of recycling of anthropogenic CO2 cause detrimental climate changes, with consequential natural and societal disasters. Taking example from nature and how natural systems such as photosynthesis recycle CO2 back to high energy value compounds can pave the way for human-made systems addressing these challenges. Artificial photosynthesis holds great promise for efficient CO2 recycling. The EU-funded REFINE project develops and demonstrates a system of artificial photosynthesis by combining conventional (dark) and light-driven reactions for the direct production of essential high-energy chemicals, such as alcohols. To achieve this, hydrogen produced by solar water photoelectrolysis is directly combined with captured industrial CO2 emissions in an advanced bioculture reactor, directly producing isobutanol as a high-energy solar fuel. The only energy input to drive this radical technological system is sunlight. To realise and bring this artificial photosynthesis system to the market, not only high-end technological developments are necessary, but also societal studies on acceptance and risk perception that can bridge the gap between laboratory scale and fully market integrated radical technologies. REFINE will provide also a solar fuels roadmap that can be used as a blueprint from stakeholders and policy makers in order to enable the definition of policy measures, legislations and their implementation.
In the first period of the project, we have developed a new type of alkaline water electrolyzer, powered fully by integrated photovoltaic (PV) modules into a single unit. Research and developments are being conducted on novel efficient electrocatalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), but also show high durability for water splitting under intermittent conditions. These are key challenges in the scientific community and REFINE is contributing with not only high performing catalysts, but also catalysts made of sustainable materials and processes. Materials selection and unit modelling are central aspects that guide the catalyst developments so that we optimize performance and sustainability. In parallel, bioengineered bacterial cultures are developed for the selective synthesis of isobutanol directly from the H2 and O2 produced by the electrolysis unit and the industrial CO2 emissions. It is important to notice that these are autotrophic conditions (presence of only CO2 and H2) and we have already seen bacterial growth comparable to heterotrophic conditions (sugars as carbon source instead of just CO2). Another key aspect in our bioengineering processes is the adaptation of the bacteria that survive under high amounts of isobutanol, which is otherwise toxic above certain levels. This has been achieved by high-end strain and DNA manipulations with targeted biological pathways.
In the next phase we will combine the two processes into one, effectively providing a true and robust system of artificial photosynthesis, transforming CO2 and H2 to isobutanol of high selectivity and purity.
In the next phase we will combine the two processes into one, effectively providing a true and robust system of artificial photosynthesis, transforming CO2 and H2 to isobutanol of high selectivity and purity.
The well-designed processes in REFINE bring already results beyond the state of the art. A striking example is the superior performance of our HER catalysts compared to the golden standard platinum (Pt). Although Pt is known as the best catalysts for the HER under acidic conditions, it is also among the best performing in alkaline media and often used as a benchmark. We have improved the HER activity of Pt in alkali by an alloying strategy with Ni. We have taken this material to synchrotron facilities to investigate its superior performance under operando conditions, and, together with theoretical calculations, we will unravel mechanistic insights for the improved performance of Pt. Another example where we push the current state of the art is in the bioengineered bacteria, which show high toxicity-tolerance against isobutanol (close to ten time more than the expected yields). Product toxicity in fermenting bacteria is very common and we are addressing this issue with novel bioengineered metabolic pathways. The last example is the stabilization of the surface of perovskite-based OER catalysts that amorphize during operation. This is a new, radical development towards understanding the surface restructuring during OER, a major topic in the literature and research on OER catalysts.