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Disruptive photonic devices for highly efficient, sunlight-fueled chemical processes

Periodic Reporting for period 1 - SPOTLIGHT (Disruptive photonic devices for highly efficient, sunlight-fueled chemical processes)

Reporting period: 2021-01-01 to 2021-12-31

SPOTLIGHT’s key objective is to develop and validate a photonic device and chemical process concept for sunlight-powered conversion of CO2 and green H2 to chemical fuel methane (CH4, Sabatier process), and to carbon monoxide (CO, reverse water gas shift process) as starting material for production of the chemical fuel methanol (CH3OH). Both CH4 and CH3OH are compatible with current infrastructure, and suited for multiple applications e.g. car fuel, energy storage, and starting material for the production of valuable chemicals.
To be able to make conversions outlined above possible, various catalytic strategies are available. Thermal catalysis is traditionally applied a lot in industry, but these processes are usually difficult couple to renewable energy (RE) sources. Electrocatalysis could benefit directly from the generation of RE (i.e. electricity form solar and wind energy), but overall efficiency lacks behind due to process inefficiency and selectivity is often low. As an alternative, photocatalysis is of interest specifically for CO2 reduction because radicals are more easily formed at the (illuminated) surface. Though potentially more efficient, selectivity of photocatalytic processes are to be improved, as is the infrastructure (solar concentrators and reactors) to be able to scale up the substantial volumes. Therefore, SPOTLIGHT’s photonic device will comprise a transparent flow reactor, optimized for light incoupling in the catalyst bed at high solar intensity and with highly selective plasmonic catalysts. Furthermore, it will comprise secondary solar optics to concentrate natural sunlight and project it onto the reactor, and an energy efficient LED light source to ensure continuous operation. SPOTLIGHT’s catalysts will be plasmonic catalysts, capable of absorbing a large part of the solar spectrum. The space-time-yield achieved to date with these catalysts in the Sabatier and rWGS process are > 104 times higher than for conventional semiconductor catalysts. This makes the concept technically feasible for scale up without excessive land use, and makes it economically much more attractive because of strongly reduced capital expenditures. SPOTLIGHT’s photonic device and process concept are perfectly suited for CO2 sources up to 1 Mt p.a. which makes them complementary to existing large scale CCU processes. For the EU, we estimate that the annual CO2 reduction through use of SPOTLIGHT’s technology is maximized to 800 Mt, which is approximately 18% of the current annual total. This could generate an amount of CH4 produced in the EU which equals 14.5 EJ of energy, corresponding to 21% of the EU’s current annual energy use, and representing a value of € 393 bil. Ergo, SPOTLIGHT’s technology reduces the dependence of the EU on non-EU countries for its energy supply, and initiates a new multi-billion industry.
User requirements (URS) for SPOTLIGHT’s photonic device and chemical process concept for the entire integrated pilot-scale set-up are specified. Risk analyses and IP landscaping are performed. Design of the photonic device, fulfilling URS has been completed. The photonic device concept has been differentiated in a base case, oriented at simplicity and highest possible efficiency and an advanced case oriented at continuous operation. Latter is a technical challenge, since the reactor has to be illuminated by solar and artificial light simultaneously. Large progress is made on the base case, and a choice was made on the preferred type of advanced case to be implemented in the pilot-scale setup. Design and manufacturing of all components for the base case is started. Simulations of the secondary optics and first on-sun tests using the flux measurement system are conducted and compared. Pre-testing is performed to assess the interaction of a fast prototype LED light source and the test flux guide. The option of a luminescent solar concentrator (LSC) is explored as a spectrally tailored alternative to the mirror-based optics. For Sabatier catalysts, scalability and performance improvement are studied. Regarding scalability, a procedure for supported Ru nanoparticle catalysts was transferred from high-temperature solid-state process to scalable solution phase synthesis with comparable activity and selectivity. An alternative catalyst combination was tested, resulting in a 10-fold higher activity. rWGS catalysts are prepared and under investigation to evaluate performance. In addition, the process was transferred towards a more scalable support resulting in similar overall catalytic performance. To estimate the process performance, a dynamic system model has been developed, initially for the Sabatier reaction. Currently, the model focus has been shifted from thermodynamics to kinetics which will offer valuable guidelines for practical reactor design and operation. A similar steady-state model has also been developed for the rWGS process. An optical temperature sensor was developed to enable temperature mapping of illuminated plasmonic catalyst beds offering opportunities to distinguish between photothermal and non-thermal contributions. This revealed sharp temperature gradients, clarifying non-thermal contributions to the catalytic reaction. An empirical model was developed to study the photothermal effect by distinguishing thermal radiation to the top space, and thermal conduction to the body of the catalyst bed and to understand the overall process and calculate the optimal size of the support particle for maximum heat generation. A communication toolkit and brand identity was prepared (logo, templates, first press release, flyer, poster) and a website and social media platform.
The objective is the development and demonstration of a photonic device and chemical process concept for the sunlight-powered conversion of CO2 and green H2 with a minimum efficiency of 5% to CH4, and CO as starting material for the production of CH3OH. Based on its high space-time-yield and modular photonic device, the process is flexible in scale, and can be adjusted to the size of CO2 (point) sources < 1 Mt CO2/year with a potential to convert 2700 Mt CO2/year into chemical fuels. For the EU, it is estimated that the annual CO2 reduction through use of SPOTLIGHT’s technology is maximized to 300 Mt, which is approx. 7% of the total annual EU CO2 emission of 4500 Mt.
In the first reporting period, user requirements and first designs of the plate-shaped transparent flow reactor, LED light source and first design concepts of secondary solar optics are established. First design concept of integrated photonic device is established. A complete process model of rWGS and Sabatier is developed, and design and operational guidelines are provided. A process flow is developed for lab-scale LSC fabrication and characterization. Assessment of techno-economics and environmental impact for sunlight-powered plasmon-catalytic processes is planned for the upcoming period. For the plasmonic nanocatalysts for Sabatier, it has been shown that changing from Al2O3 to TiO2 as support results in a 10-fold increase of STY. Synthesis procedures are transferred from high-temperature solid-state process to scalable solution phase synthesis. For rWGS, various preparation techniques for Au/TiO2 are developed to validate the impact of the preparation technique on the catalyst’s structure, composition and performance.
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