Multi-actor collaboration has been engaged from the onset of the project to define the specifications on simple and complex photocatalytic composites, metal oxide photoelectrodes and solar-driven catalytic systems for ethylene production, deciding parameters for evaluation of project goal. This step was crucial to ensure the development of each individual component.
Different synthesis approaches have been investigated for developing the most efficient concept for light harvesting and charge carriers separation (e.g. colloidal protective methods, photodeposition, Impregnation/chemical reduction, aiming at controlling the shape, the morphology, the content and the composition). The influence of total M content, of M1/M2 ratio, of M nanoparticle size distribution and dispersion onto SCs are investigated as well. In task 2.4 gas-phase photocatalytic CO2 reduction has been performed under continuous CO2 flow in the set-up, allowing to follow kinetics of CO2 reduction and products formation.
In parallel, BiVO4 photoanodes and Cu2O photocathodes have been synthesised and thoroughly characterised for the tandem device to be further developed. Nanoparticulated and nanostructured BiVO4 photoelectrodes have been grown and studied for both, oxygen evolution reaction (OER) and hole scavenger oxidation. BiVO4 nanoparticles have been prepared by both batch and continuous-flow processes at low temperatures, in an aqueous medium, using inexpensive precursors. Additionally, the continuous flow synthesis is suitable to scale-up the synthesis and the photoelectrodes. Nanostructured BiVO4 photoanodes have been produced and optimised by two different electrodeposition (ED) methods targeting photocurrent of 7 mA·cm-2. In line with the electrodeposited photoelectrodes, different photoanodes were prepared where nanorods of TiO2 and WO3 were previously grown, in order to obtain different heterostructures with BiVO4. On the other hand, efficient Cu2O photocathodes + CO2 RR catalyst have been prepared through the optimisation of a Cu2O buried junction. To sum up, stable photoelectrodes for the tandem PEC device have been synthesised through different optimise processes and the progress in the performance of the photocathode and the photoanode are in the range of the targeted ones ( ̴4.5 mA·cm-2 at 1.23 V vs RHE for BiVO4 and ̴6 mA·cm-2 at 0 V vs RHE for Cu2O) and mechanistic studies have been performed to understand the limiting factors of such photoelectrodes.
On this basis, the PC systems and the PEC systems have been gathered to design a solar driven catalytic system. For CO2 RR catalyst, we have used Cu metal modified with Chloride salt electrolyte, achieving electrochemical ethylene production Faradaic efficiency of > 70%. Using this catalyst, we realised photocathode – CO2 RR catalyst device. Initially, Cu2O based device were chosen as light absorber, later we changed it to Lead halide perovskite-based device, which achieved both sufficient current density and voltage (20 mA/cm2 and 1.0 V). Later, PSC-Cu photocathode achieved ethylene production Faradaic efficiency around 15% with partial photocurrent density around 1.5 mA/cm2 at -0.4 VRHE.
Each single components have firther been integrated into a single fuctional devices for performing stability assessment. The stability of the electrodes was extensively investigated using spectroelectrochemical techniques, providing deeper insights into their degradation mechanisms. Additionally, thorough analyses and simulations were conducted on how the components were assembled.
To support and anticipate futur market uptake of SUN2CHEM solution, an extensive work has been carried out regarding the environmental Life Cycle Analysis, Life Cycle Costs and Social Acceptance. In addition, a detailed market analysis and roadmap for upscaling project results has also been developed.
