Objectives
SUN2CHEM’s main objective is to develop solutions to achieve efficient solar-driven CO2 reduction to energy-rich and high value chemicals. For that purpose, SUN2CHEM partners conjointly develop all the components to be integrated into tandem photoelectrochemical cells and advanced photocatalytic reactors, targeting ethylene as the final product.
This main objective is achieved through the completion of 6 clear, measurable, realistic and achievable specific objectives that are listed and detailed hereunder
Fabricate tandem photoelectrochemical devices for unbiased solar-driven CO2 reduction to ethylene
Recently, pure electrocatalytic conversion of CO2 to ethylene using CuAu and CuAg bimetallic catalysts developed by EFPL has been achieved. These catalysts exhibit ~50% faradaic efficiency of ethylene, with most of the remaining conversion into fuel (hydrogen). However, there is little research on the integration between photoabsorber and catalysts for direct photoelectrochemical (PEC) conversion of CO2 to ethylene. SUN2CHEM aims at developing an efficient, stable and sustainable photoelectrochemical (PEC) device based on earth abundant metal oxides (BiVO4 photoanode and Cu2O photocathode), with novel junction design, catalysts and protection layers for water or organic molecules oxidation at the anode and Cu-X bimetallic or single-atom modified Cu catalysts at the cathode, to investigate the PEC reduction of CO2 to ethylene. The thickness, composition and morphology of the catalysts and protection layers will be optimised onto both photoelectrodes to achieve the direct conversion of CO2 to ethylene with high selectivity, efficiency and durability. The developed photoelectrodes will then be combined in a tandem photoelectrochemical cell to achieve the unbiased reduction of CO2 to ethylene.
1.2V photovoltage
12 mA.cm-2 current density
Validate the tandem photoelectrochemical device under operating conditions
The integration of the upscaled photoelectrodes from SO1 into an efficient and stable photoelectrochemical tandem device requires proper validation in working conditions. In this context, in operando assessment tools will be developed to identify device limitations, losses and optimisation strategies. Benchmarking protocols under simulated sun irradiation, including accelerated stress tests will be established to validate performance. The results will be used to define optimisation strategies for device components, architecture and flow dynamics. This specific objective is aimed at maximising the device efficiency, ethylene production rates, stability and robustness, along establishing future perspectives for further upscaling and industrial scope.
Accelerated stress tests, including intermittent irradiation and variable temperature, will be established to validate and estimate the durability of the tandem device in simulated working conditions. With these data, long term performance will be modelled, and then transferred to LCA and LCC studies.
> 3%
solar-to-ethylene efficiency
Investigate photocatalytic systems and their mechanisms to improve light-harvesting and charge carrier separation, and validate the photocatalytic reactor under operating conditions
Another strategy for unbiased CO2 reduction consists of direct combination of the two light absorbers (i.e. anode and cathode) into heterostructured multi-phase photocatalysts, facilitating charge separation and light harvesting by exploiting intimate and suitable electronic and chemical interface contacts. Based on the above, in parallel to PEC ethylene production, SUN2CHEM also targets on the production of ethylene through the convenient photocatalytic approach using powder photocatalysts. Although both approaches (PEC and PC) share a common catalytic mechanism, photocatalysis using suspensions or layers of powder photocatalysts present the advantage of simple process engineering without the need of sophisticated processes for electrode development and the possibility of using a large variety of synthesis methodologies for controlling materials properties, which is the core for improving the overall efficiency. In addition, the direct photocatalytic approach offers the advantage of a wireless configuration with the benefit of a straightforward and compact device design.
In this approach, several dual-phase semiconductor systems will be synthesised and optimised in terms of mass proportion and protocol applied, in order to extend the charge carrier lifetime by means of Z-scheme dynamics. Moreover, the inclusion of plasmonic metal nanoparticles will be carried out for improving the light absorption and also retard hole-electron recombination. The involved catalytic mechanisms will be investigated through modeling and advanced spectroscopic characterization techniques, including in-situ and in-operando studies, relying on state-of-the art instruments and (photo)electrochemical cells, as well as on synchrotron radiation. The aim comprehends the understanding on how to improve light harvesting and charge separation by the rational design of three types of nanocomposites (heterojunctions, plasmonics and multi-phase) and then transfer this knowledge to a single photocatalytic reactor for engineering of this solution.
Increase social acceptance and energy security of end-users
Emerging renewable technologies come with integration difficulty. Since their application requires high economic efficiency to reduce cost, and urban regions are having the highest economic efficiencies, implementation on a meaningful scale inevitably involves human acceptance. To achieve agency, “willingness to act” with the public to engage in the manufacturing of renewables without enforcing it, similar to what is actually happening with PV, is a key parameter to be included in the evaluation when trying to develop such a ground-breaking way of decentralised production of energy-rich chemicals with potential market uptake. Guidelines to be implemented along the life of the SUN2CHEM project will be defined, increasing the agency towards decentralised manufacturing of solar chemical feedstock and recycling of CO2.
Perform an LCA and LCC of the final devices
The integration of the upscaled photoelectrodes from SO1 into an efficient and stable photoelectrochemical tandem device requires proper validation in working conditions. In this context, in operando assessment tools will be developed to identify device limitations, losses and optimisation strategies. Benchmarking protocols under simulated sun irradiation, including accelerated stress tests will be established to validate performance. The results will be used to define optimisation strategies for device components, architecture and flow dynamics. This specific objective is aimed at maximising the device efficiency, ethylene production rates, stability and robustness, along establishing future perspectives for further upscaling and industrial scope.
Accelerated stress tests, including intermittent irradiation and variable temperature, will be established to validate and estimate the durability of the tandem device in simulated working conditions. With these data, long term performance will be modelled, and then transferred to LCA and LCC studies.
50% reduction of GHG emissions compared to current production of ethylene from fossil resources
Establish a roadmap towards up-scaling of the SUN2CHEM technology
Establish the most relevant and promising potential markets and niches where SUN2CHEM key exploitable results can be scaled and used as successful commercial applications beyond the scope of the project in order to maximize impacts and business value. The project’s developments will provide a highly added value product at low cost in decentralized fashion.
Feasibility study and assessment of scenarios with roadmaps for the potential scaling of the developed results and technologies to terawatt scale by 2050 with an EROI superior to ten as a targeted threshold unit and KPI for assessing the viability of this scaling.
The roadmap will have to provide insights on the technical and operational necessities, challenges and milestones over the relevant time period (2050) as well as economic viability assessments of scaling with definition of necessary present and future capital needs as well as threshold return levels determined by comparative studies with other solutions and approaches.
Lead the pathway to reach the TW-scale by 2050