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Photoelectrocatalytic device for SUN-driven CO2 conversion into green CHEMicals

Periodic Reporting for period 2 - SunCoChem (Photoelectrocatalytic device for SUN-driven CO2 conversion into green CHEMicals)

Reporting period: 2021-11-01 to 2023-04-30

The strong dependence in Europe on carbon feedstock imports for energy and chemical manufacturing purposes and the upward trend in CO2 emissions compromises the competitiveness of the EU28 chemical industries. “Solar-driven Chemistry” brings an opportunity to an efficient use of resources and preservation of the environment and will become a driver for the transition to a new economic cycle in chemistry/energy production. SunCoChem addresses the need of the EU Chemical Industry for highly competitive and integrated solutions enabling the carbon-neutral production of energy and high-value chemicals from solar energy, H2O and CO2. The direct use of renewable energy to convert CO2 into chemicals is crucial for reducing the dependence on carbon feedstock imports and contribute to the reduction of the GHG. However, the development of efficient systems for the production of high-value chemicals from CO2 is limited by the low CO2 chemical reactivity. Photo-electrocatalysts (PEcats) and photo-electroreactors with increased efficiency and stability, which can operate in synergy or integrated with existing ones, can contribute to solve this challenge by developing competitive systems to convert sunlight, H2O and CO2 into valuable products. SunCoChem aims to develop a competitive and modular self-biased tandem photo-electrocatalytic reactor (TPER) to efficiently produce oxo-products from CO2, water and sunlight integrating CO2 capture and conversion in a single unit. The TPER will couple catalytic photo-assisted processes: (i) CO2 reduction and (ii) H2O oxidation, with non-photoassisted catalytic ones (iii) C-C bond formation by CO-carbonylation, in a novel device directly fed by CO2-exhausts. The single-unit “capture and conversion” architecture of the reactor enables the design of a self-biased device. This is key for obtaining the cost reduction, improved sunlight-to-chemicals energy conversion efficiency and improved stability targeted by SunCoChem. From the industrial and user point of view, the modular concept will allow a reduced control, simplified maintenance and a more compact and small system able to be integrated in different factory environments at various size scales and productivity targets. Together with the use of renewable energy, this device will open the possibility of a distributed chemistry production by the exploitation of a
standalone system having low operative costs (driven by renewable energy) for wastes valorisation.
Photo-electro/catalyst development: intensive work towards the photo-electroanodes regarding BiVO4 powder synthesis, their functionalization using Ru-based sensitizers and water oxidation catalysts; establishment of a reproducible and scalable route to deposit the powders into photoelectrodes. Photoelectrochemical tests performed to demonstrate the target values. Different strategies of Cu2O/SnO2 catalysts synthesis and anchoring of Ru and Re molecular complexes, exploited as light sensitizers and co-catalyst, respectively. The highest total FE (%) was achieved with a Cu2O/SnO2_catalyst with RuRe complexes anchored by means of a Si-based functional group (VTES), tested in an ionic liquid (IL)-based electrolyte dissolved into acetonitrile (ACN).

Coupling of CO2 reduction and CO carbonylation to oxo-products: Carbonylation reaction to the three target products using syngas under the conditions used in the electro-CO2RR process evaluated by EUT. Many efforts focused on matching the best operative conditions and solvents to be used for performing the CO2-to-CO and CO-carbonylation reactions in the same electrolyte media.

Photoelectrodes (PE) scale-up: The x10 scale-up of BiVO4 photocatalyst for the anode was successfully optimized by LAU. A preparation route from Sulphur doped LAU BiVO4 powder – SOL paste – HZB electrode deposition was established. An automated screen-printing method was developed and optimized. A scalable deposition technique of the material onto electrodes needs to be optimized.
Concerning the photoanode, it was demonstrated the feasibility of the deposition of the prepared of Cu2O/SnO2-Ru-Re catalyst in powder on electrodes of 10 cm2 with an automized spry coating technique that can be easily scaled up to the final size of 10 x 10 cm2. A novel and scalable electrodeposition path (B) for anchoring the Ru and Re complexes into the semiconductor heterojunction was also developed and tested for different catalytic systems: Cu2O-SnO2 and CuGaO2.
The synthesis of Cu2O/SnO2 for cathode photoelectrode was successfully optimized at x10 and x25 scale–ups.

Membrane - electrode – Assembly (MEA): CNRS prepared the 1st generation TBM (TBM-1) by casting method. The optimization of the TBM revealed that a thicker TBM (TBM-3) with of 90 µm and AEL of 15 µm meets the KPIs of the SunCoChem project combined with higher mechanical and dimensional stability. As a result, TBM-3 type membranes have been selected as 2nd generation membranes for further optimization within the project. The low loss of transparency with Al(OH)3 nanoparticles brought CNRS to the selection of this catalyst for further development of the fully optimised 3rd generation membrane to be further upscaled in WP4.

Optimisation of CO2 capture and concentration: A set of different standards and custom-made ionic liquids was prepared by IOL. The best results were obtained with porous polysulfone membrane soaked with [BMIM][Acetate] in terms of CO2 solubility while the fastest diffusion rate was found using [BMIM][BF4]. For the direct CO2 capture, solubilities of 0,95% were achieved with 20% solutions of chemical IL sorbents.

TPER development: A preliminary design of a single TPER reactor was shared with the partners. It is a 4 chambers cell that consists of an anodic, cathodic, absorption and gas chambers. The full cell to be tested constituted by 4 single-cells will be designed and manufactured to the entire testing of the SunCoChem prototype.
New concepts and advanced designs of PEcats, a TPER with an innovative approach involving 4 simultaneous processes in a single unit.

Expected results: 1) Single TPER units and their enabling materials 2) The integration of TPER units and evaluation of potential impact vs. fossil-fuel based routes, 3) demonstration of technical and economic feasibility, 4) Evalutation of GHG emissions regarding commercial manufacturing by LCA, 5) Assessment of increase of industrial competitiveness of flavours, fragrances and chemicals industry and 6) Estimation of environmental and social benefits.

Main technological Impacts: (1) Increased efficiency of the system with sunlight to chemical energy conversion efficiency (to chemicals other than H2) higher than 5%, (2) Improved stability/robustness of the system under extended operational conditions, with loss of performance <5% in 1000h, (3) Cost Reduction/Effectiveness of the system, including recycling if relevant and continuous product recovery, with cost of production of chemicals comparable to actual route from fossil fuels along with an improved energy efficiency and <50% CO2 emissions. The development of SunCoChem’s TPER and derived technologies will provide benefits in terms of wider social and economic impacts, especially in the following aspects: (1) Increase industrial competitiveness of EU enterprises, (2) Improve local economy by promoting circular economy, (3) Establish long-term collaborations and integration between industrial and academic institutes.
Preliminary design of the TPER reactor
(A) Scanning electron microscopy images (B) EDX spectrum for Cu2O/SnO2 nanoparticles
Scheme of Ru-VLA and Re-CRC complexes electropolymerization onto Cu2O/SnO2-VTES
CO2 capture efficiencies of pure ILs (left), and as 20 % solutions in BMIM Otf (right)
Schematisation of the membrane electrode assembly in the SunCoChem TPER
(A) Scanning electron microscopy images captured (B) X–ray diffraction spectrum of BiVO4 particles
SEM micrograph of TBM-1 cross-section