By 2050 80% of Europe’s electricity should be produced through renewables. The vast majority of this (up to 65%) would be provided by solar photovoltaics and on- or offshore wind farms, with a production that is clearly subject to seasonal  and hourly weather variability. Existing ways to store excess electricity include the use of batteries or the production of hydrogen. Both methods are highly expensive as either large battery farms or massive adaptation of the current infrastructure (e.g. fuel cells) are required. While these technologies benefit from a high TRL, it would be more interesting to convert electricity and CO2 directly to fuels or chemicals with just one single step. Although the electrocatalyst still needs further improvement both in activity as selectivity, substantial progress is being made. However, an industrial CO2 electrolyzer yet needs to be developed. Within this STACkED project, we will build an industrial CO2 electrolyzer and we will screen its validity. It is not the aim of this project to deliver a ready to be commercialized device, but rather a technology concept via a lab-scale prototype and to indicate a number of potential economic valorization pathways. More specific, we will acquire knowhow on following topics:

Development of an innovative method to deposit the catalysts and to optimize coating techniques for the electrolyzer and fuel cell based reactor. The main research question here will be how to deposit the electrocatalyst without inducing a loss in performance.

Construction of a novel electrolyzer with optimal stack configuration and accompanying flow profile for the production of methanol from CO2. Impact of the stack configuration, electrode architecture and flow distribution on the current density, overpotential and selectivity will need to be unraveled. A lot of similarities between the hydrogen production by electrolysis and the electrochemical reduction of CO2 exist. This is a huge advantage compared to other carbon capture and utilization technologies as technology development can kick off with a jump start. Nonetheless, aspects such as catalyst deposition need alternative coating techniques. For the electrochemical CO2 reduction not platinum and iridium but copper, ruthenium and their oxides are promising candidates, which are much cheaper, yielding a larger degree of freedom. Consequently, the optimal deposition procedures are not driven by the cost of the electrocatalyst but rather by the product yield. To this end, two depositing techniques will be examined: spraying (bottom-up) and electrochemical deposition (topdown). Regarding stack construction also similarities with the hydrogen production are in place, but again subtle differences make that electrolyzers for the production of hydrogen are not suited for the electrochemical reduction of CO2. Water management, for instance, is a huge problem in hydrogen electrolyzers, influencing tremendously the design of the flow distribution. However, as flow distribution will be altered, hot spots can arise when using the same flow distributors. Likewise for the gas diffusion layers that maximize the mass transfer towards the electrocatalyst – which is critical as CO2 solubility is typically low – different morphologies regarding porosity and pore size will be needed. In this project innovative solutions for the individual parts of the stack have to be developed. Luckily, knowledge about aspects like machining and characterization are present, facilitating the work load. The expertise gained by this project will raise commercial interest, stating following-up projects and bringing this technology to higher TRL levels.