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Light assisted solar fuel production by artificial CO2 Reduction and water Oxidation

Periodic Reporting for period 2 - LICROX (Light assisted solar fuel production by artificial CO2 Reduction and water Oxidation)

Período documentado: 2022-03-01 hasta 2023-08-31

The European Green Deal aims to build a sustainable growth strategy to reach climate neutrality in the continent by 2050. Radically new technologies based on renewable energies will need to be developed in the coming years to reach such an ambitious target, to the LICROX scientist’s artificial photosynthesis will have a key role to fight climate change.
The natural process of photosynthesis allows plants and other photosynthetic organisms to convert solar energy, water and carbon dioxide (CO2) in carbohydrates (their fuel). Artificial photosynthetic systems mimic this process aiming to outperform it by developing more efficient and simpler procedures. Among these, photoelectrochemical cells (PECs) have the potential to become an efficient and cost-effective technology for the direct conversion of solar energy. Current drawbacks in their development include poor PEC efficiency in absorbing sunlight, poor selectivity in the reduction of CO2 and utilization of non-abundant or toxic elements in the catalytic materials.
LICROX aims to implement a new PEC type incorporating light trapping mechanisms and catalysts made of only abundant elements to selectively drive water oxidation and CO2 reduction reactions to get carbon-based products like ethylene, a product largely used by the chemical industry, in high efficiencies. The conversion of ethylene to ethanol is an industrially known process that allows to directly achieve a solar fuel, offering new energy storing alternatives different from fossil fuels.
LICROX brings together a consortium of 7 European partners including universities, research institutes, companies and a foundation working in technology assessment: Technical University of Munich (TUM, Germany), École Polytechnique Fédérale de Lausanne (EPFL, Switzerland), Institute of Photonic Sciences (ICFO, Spain), Institute of Chemical Research of Catalonia (ICIQ, Spain), Avantama (Switzerland), Hysytech (Italy), Danish Board of Technology Foundation (DBT, Denmark).
The main advances of the project in its 7 Work Packages (WPs) are highlighted here:

WP1 – Ethics requirements.
The project has filled an environment and safety requirement analyzing possible environmental harm caused by its research activities and underlying measures that will be adopted to mitigate possible risks. Also, a document giving answer to the appropriate processing of personal data when organizing stakeholders and citizen workshops.

WP2 – CO2R Tandem catalysis and WOC
Copper based catalysts have been synthesized and tested for CO2 reduction in a liquid cell. For catalysts showing ethylene selectivity tests have also been run at high current densities in a gas-fed cell.
A family of Fe and Co complexes containing porphyrin type ligands have been synthesized and electrochemically characterized. Finally, the combination of the Cucub with the molecular catalysts, Fe porphyrins, has allowed to generate 20 times more ethylene at 0.75VRHE compared to the bare Cu cubes.

WP3 – Semiconductors for the photo-anode and cathode
Different techniques have been tested to synthesize a BiVO4 photoanode able to achieve a photocurrent density of >3.0 mA/cm2 at 1.23 V vs. RHE, under 1 sun. These photoanodes have been integrated with the other components of the cell.
Molecular water oxidation catalysts were prepared based on Cu and Fe complexes with the adequate modifications at the auxiliary ligands for their deposition into the surface of the BiVO4 semiconductor under a controlled manner.
A specific nanoparticles synthetic methodology has been developed and upscaled (Kg) for the synthesis of materials that can be used for production of electron selective back contacts.
Different Cu oxide based photocathodes have been studied, including a strategy on the use of protecting layers to increase stability.

WP4 – Light trapping in the PEC
A theoretical 1D light trapping model has been completely developed, to obtain the optimal structures for both the half cell and full cell configurations. The experimental results revealed an excellent agreement with the theoretical predictions, in terms of optical properties and photocurrent increase.
Additionally. a thorough exploration of the the light absorption and conversion limits of BiVO4 photoanodes for the OER has also been performed.

WP5 – PEC implementation and validation
A final coupling of the photoanode and OPV with a dark cathode has been achieved. Showing for the first time the light induced water and CO2 splitting in the absence of any external input except for 1 sun irradiation.
Additionally, a pre-industrial prototype has been designed and built, with two modules of 10 cm2 for the photoanode and dark cathode.

WP6 – Environmental impacts, social acceptance, dissemination and exploitation
Through the Project, a successful prospective study of life cycle assessment of the LICROX PEC has been realized.
Effective engagement of stakeholders in assessing societal concerns and technological feasibility has been achieved. Recommendations for developments in LICROX and the field of solar fuels to address societal concerns were gained. Additionally, the project has achieved a large-scale engagement of citizens across Europe to assess and identify societal concerns related to emerging energy technologies.
Efforts have also been devoted to develop an exploitation plan providing an overview on the market opportunities. Green methods complementary to bio-based ones are needed for the production of commodity chemicals and fossil-free fuels.
Finally, efforts on dissemination and communication have allowed to present the Project and its results in various events, including conferences and thematic workshops, publish open Access scientific articles and run communications tools (website, social media, etc.).

WP7 – Project Management
The main tools for smoothly project management have been established in the initial months of the Project and updated as needed throughout the Project's life, including a Data Management Plan.
The real deployment of photoelectrochemical cells and its application in industrial settings for the valorization of CO2 or its conversion to ethylene has not been achieved yet. This is mostly due to the lack of efficient and selective electrocatalysts that are at the same time abundant and cost efficient.
The LICROX Project has constructed a proof-of-concept prototype, uniting the different components developed during the action, although introducing some modifications from the initial plan.
The LICROX PEC configuration provides a high degree of flexibility in the combination of its light harvesting elements. The light management strategy facilitates reaching the needed requirements in terms of photocurrent and voltage for getting a final working device.
Finally, it is worth highlighting that both PhD candidates and postdoctoral young researchers have been involved in the project, gaining highly qualified training. LICROX’s overall goal has been achieved by assembling an interdisciplinary and complementary consortium composed of scientists, technologists and entrepreneurs from a number of disciplines.
Testing cell prototype
LICROX Logo
Infographic
Picture of the designed prototype during the project