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Selective Electrochemical Reduction of CO2 to High Value Chemicals

Periodic Reporting for period 1 - SELECTCO2 (Selective Electrochemical Reduction of CO2 to High Value Chemicals)

Reporting period: 2020-01-01 to 2021-06-30

With 195 nations signing the Paris Climate Accord, the world has acknowledged anthropogenic induced climate change and the need for action with EU’s approach to action based on the strategic energy technology plan (SET Plan). While fossil fuels accounts for contributes the vast majority of the anthropogenic effects from CO2 emissions, they are used in diverse, but essential fields, such as heating, transport, power generation, industry and even as the primary raw material for the entire chemicals industry. While many of these fields have established sustainable options, there are others, which are at early stages of development which need rapid development to form the complete backbone of the energy system by 2030 and 2050. One of the most EU essential (as noted by action 6 in the SET Plan) and challenging areas in need of development is the conversion to a sustainable chemicals industry.

SELECTCO2 aims to establish the technological groundwork to allow for an electrification of the chemicals industry entailing cheaper, more environmentally friendly products. SELECTCO2 will also benefit society through cleaner air, reduction in greenhouse gas emissions, and sustainably derived chemicals free of fossil fuel based contaminants such as mercury and heavy metals.

SELECTCO2 aims to contribute to the electrification of the chemicals industry through the development of highly selective and efficient devices for the conversion of CO2 to high value products at low temperatures and pressures. It is well known in the chemicals industry that costs due to separations can amount to 60-80% of the total costs of the chemicals. This same general cost percentage holds in bio-based chemicals as well. Electrochemical CO2 Reduction (ECO2R) allows the unique ability to start with a single reactant in CO2 and use catalysis to build up selectively to a given molecule. Direct conversion to a specific product allows for the mitigation or even elimination of separation costs and can greatly reduce the costs of producing a given chemical.

To create immediate impact and to provide the backbone for the emerging sustainable chemicals and fuel industry, we will create lab scale devices capable of electrochemically converting CO2 selectively into either carbon monoxide (>90%), ethanol/acetaldehyde, (>80 %), or ethylene (>90%) at high thermodynamic efficiencies (> 40%). To achieve this SELECTCO2 has a number of Objectives relating to this.

The first objective relates to improved catalysts for carbon monoxide, ethanol/acetaldehyde, and ethylene. All of these should be able to operate at high rates, be highly selective, and operate at high energy efficiencies. The second objective is to develop stable gas diffusion layers to support the catalysts and allow efficient mass transfer of reactants and products while maintaining sufficient electrical conductivity and optimal hydrophobicity. The third objective is to develop membranes and ionomers to allow for efficient ion transfer to and from the catalysts. The fourth objective is to develop accurate mass transfer models to maximize the rate of electrochemical CO2 reduction. The final objective is to analyze the techno-economic and socio-economic and environmental implications of this technology to know how to most efficiently implement it into society.
In this initial period we developed strong links between work packages and discovered how to operate in a Covid-19 environment. The technical consistency plan and standardized reactors helped in aligning project focus and allowing consistent and transferrable results throughout the consortium. CO Catalysis has been highly successful in developing single site catalysts based off metal incorporated nitrogen doped graphitic carbon based off computational discoveries. Different synthesis approaches were benchmarked and a new approach to produce Ni based catalysts has been developed, resulting in 90% selectivity to CO at 250 mA/cm2. For ethanol catlysis it was found that a Cu0.6Ag0.4 composite allows for increased ethanol selectivity. A high conversion (80%) reactor has been developed with a recycle loop able to operate at 200 mA/cm2 at 60 °C with a condensation vessel for ethanol. An understanding in both reaction intermediates and surface restructuring has been developed leading to enhanced ethylene selectivity. Computational discoveries have discovered the branching point between ethanol and ethylene selectivity.

Commercial gas diffusion layers (GDL) have been benchmarked for CO, ethanol, and ethylene production and new GDLs are being developed. New membranes have been synthesized, tested, and downselected to an ETFE backbone with N-methylpiperidine functional groups. The best membranes have operated for 200 hours with ~5% increase in voltage and no noticeable variation in product selectivity. Ionomers have also been synthesized and are being tested. GDL tomography has been accomplished as well as a continuum-scale device model improving mas transfer understanding. Additionally Life Cycle Assessment (LCA); Life Cycle Costing (LCC) analysis; and Social Life Cycle Assessment (S-LCA) was applied to CO2 conversion to CO, ethanol, and ethylene.
The major progress beyond state of the art that this project looks to produce is to push electrochemical CO2 reduction beyond laboratory testing into test-cell scale devices providing a path towards commercialization. The overall goal is to allow for integration of all the technologies necessary for electrochemical CO2 device production, thus catalysts, gas diffusion layers, membranes, and mass transfer modeling. In addition we want to integrate techno-economics and socio-economics analysis into this, allowing for the project to take a comprehensive approach towards selective electrochemical conversion of CO2 into either carbon monoxide, ethanol of ethylene.

Specifically, we expect to improve both the intrinsic activity and selectivity of catalysts for CO, ethanol and ethylene. For catalyst geared towards CO, the focus is on non-noble metal catalysts. With copper being a good catalyst for both ethylene and ethanol, this project's goal is to understand the mechanism of how both ethanol and ethylene form, and then develop ways to modify the selectivity via modifying the catalyst or the local environment in which it operates. Mass transfer modeling will develop comprehensive model that allow for a continuous model from bulk conditions down to the nanoscale, thus allowing for an understanding how bulk mass transfer modifications can affect the local environment of the catalyst. Another novelty of this project is the development of gas diffusion layers specifically designed for CO2 reduction taking into consideration the operating conditions and knowledge gained from mass transfer modeling. Anion exchange membranes developed in SELECTCO2 will both be more durable and conductive than their precursors and will also work to mitigate CO2 crossover through the membranes. Newly developed ionomers with unique functionality aim help improve catalysis as well. The socio-economics of electrochemical CO2 reduction is relatively under investigated and this project should help broaden our perspective on how this technology can best be used for societal gains.
Overall Description of SELECTCO2