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Description
The PhotoRed project deals with an innovative solution for post-combustion CO2 capture and utilisation (CCU). The existing post-combustion carbon capture (PCCC) technologies are energy demanding and not enough environmentally viable. The capture of CO2 is a good idea, but there are more prospective CCU technologies, enabling to transform CO2 into useful products (fuels or other chemicals). They are still at the initial technology readiness level and their efficiency is low, but they are necessary to close the carbon cycle, to moderate climate change and to decrease the exploitation of fossil fuels.
Summary of project results
The project deals with an innovative solution for post-combustion CO2 capture and utilisation. The existing post-combustion carbon capture (PCCC) technologies (as amine solutions and geological storage) are energy demanding and not enough environmentally viable. The capture of carbon dioxide is a good idea, but there are much more prospective CCU (carbon capture and utilisation) technologies, being a real breakthrough enabling to transform carbon dioxide into useful products (fuels or other chemicals). These technologies are still at the very initial technology readness level and their efficiency is low, but an effort to develop them is necessary to close the carbon cycle, to moderate climate change and to decrease the exploitation of fossil fuels. In the precedent Polish-Norwegian “SolSorb” project (2014-2017) we determined carbon spheres as an excellent sorbent for CO2 capture, enabling to adsorb above 6 mmol of CO2/g/h at ambient conditions. In the present proposal the project consortium is proposing the same sorbent as a basic component for a hybrid composite, adding titania known for its photocatalytic properties. The goal of the project is to convert at least 10 micromol of CO2/g/h at ambient conditions under UV and to maintain the activity at the same level for at least 200 h. The processes will be carried out at first in the quartz laboratory reactors and during the project a scale-upgrade will be performed and the prototype stainless steel reactors will be designed and manufactured. A combined literature and experimental environmental impact assessment of the photocatalyst materials produced within the project will be performed. In addition to the technical aspects of the project, particular attention was dedicated to raising social awareness of carbon capture and utilisation (CCU) issues.
Many samples of photocatalysts based on the composites of carbon spheres with titania and with zinc oxide were produced and carefully characterized. The produced materials showed a very good stability and regenerability. Two setups for measuring the activity of prepared photocatalysts were built and a methodology for analyzing the composition of the gas mixture was developed. Using the setup for measurements in the circulating water phase, an alkaline solution of NaOH saturated with CO2 was used, and mainly hydrogen was produced there, while using the setup for measurements in the gas phase circulation, the main product was CO. An unintended project result was the production of important amount of ammonia in water phase at the bottom of the reactor. Another unintended project result was the implementation of a homogeneous inorganic photocatalyst based on zinc oxide.
In Norway the first upscaled photoelectrochemical reactor was built, based on a commercially available sandwich-type cell. To allow for the photocatalytic application, the design was modified in two different ways, the measurements can be performed with an external light source or with an internal light source.
The first toxicity studies using Daphnia magna have been conducted with some selected materials produced within the project. Results showed that all materials except pure ZnO exhibited low toxicity. The results suggest that the combining ZnO with carbon spheres significantly decreases the toxicity relative to pristine ZnO.
Eighteen research papers were published as results of the project and six Polish patents were declared.
The project responded to the need of carbon dioxide utilisation, as CO2 is one of the crucial green gases, responsible for climate changes. The PhotoRed project involved the implementation of a green process of CO2 photoreduction, carried out at ambient conditions under UV radiation and using new photocatalytic materials produced within the project.
Many samples of photocatalysts based on the composites of carbon spheres with titania and with zinc oxide, but also additionally doped with some metal compounds, as copper, cobalt, iron, ruthenium, and platinum were produced, carefully characterized, and tested for carbon dioxide reduction. The produced materials showed a very good stability and regenerability in CO2 adsorption.
Two setups for measuring the activity of prepared photocatalysts were built and a methodology for analyzing the composition of the gas mixture was developed. Using the setup for measurements in the circulating water phase, an alkaline solution of NaOH saturated with CO2 was used, and mainly hydrogen from water splitting was produced there, while using the setup for measurements in the gas phase circulation, the main product was CO.
Almost all photocatalysts produced within the project were more active in CO2 reduction than commercial photocatalyst P25.
Summary of bilateral results
The PhotoRed project was a multidisciplinary one, involving physical chemistry, chemical engineering, catalysis, electrochemistry, materials science end environmental science. A knowledge of electrochemical and catalytic processes (then - physical chemistry, electrochemistry and catalysis) was essential to choose the best catalysts configuration. The materials produced within the project were thoroughly characterised using material science characterisation techniques and the designing of the reactors belongs to the area of chemical engineering. The environmental science refers to the environmental assessment of the materials produced in the project.To answer the above needs, the consortium partners have brought various and complementary expertise: ZUT in materials synthesis and characterization, as well in photocatalysis, USN in mathematical modelling, materials science and electrochemistry and SINTEF in chemical engineering and environmental assessment. The transfer of knowledge between project partners occurred successfully during the project, very useful primarily for young researchers and student participating in the project implementation. Two Polish PhD students went for short (1 month) visits to USN to learn about photoelectrochemical processes.