The development of routes to produce sustainable fuels and chemicals by the integration of renewable energy sources is one of the major challenges for our society, and it is vital to propose disruptive strategies allowing to reach the updated Horizon Europe targets. Artificial Photosynthesis is one of the most promising strategies to decrease the fossil fuels dependence and greenhouse emissions by the transformation of CO₂ and other natural resources (H₂O, N₂, biomass…) into sustainable fuels and chemicals using renewable energy sources. Compared to other CO₂ recycling technologies like electrochemical reduction or thermo-catalytic hydrogenation, photoelectrochemical route offers a promising potential in the medium term for direct solar energy conversion/storage. For this technology to become reality and be transferred into the energy industry chain, a significant enhancement of the process in terms of efficiency and selectivity control is still needed. This enhancement must come by the hand not only of materials science for the development of highly photoactive catalysts/electrodes, but also of device engineering where efficient and scalable solar reactors are needed that maximises the overall efficiency.

This work aims to report the successful validation in the industrial setting (TRL 5) of a new concept of low-cost flow photo-reactor prototype for CO2 reduction and N2 fixation to produce fuels and chemicals (CH4, C2H4, C3H6 and NH3) coupled to the oxidation of microplastics and organic pollutants from wastewater treatment plants. This reactor can be also used in other portable or stationary locations such as chemicals, fertilizers, cement or refinery industries, homes, cements or power plants, among others. It consists of a versatile system with dual configuration: Photocathode vs Dark Anode and PV+EC Cathode vs Dark Anode configuration, overall dimensions of 300x300 mm made of PVDF and  with 20 lighting windows (20x30 mm).  The overall system for industrial validation includes in addition to the reactor, the rest of the equipment such as power source, electrolyte tanks or pumps.  Regarding the instrumentation, different flowmeters, pressure transmitters, COD transmitter, conductivimeter and pHmeter have been included to register all the main operational variables

Advanced computational fluid dynamics techniques have been also performed to optimize the prototype operation, minimizing mass transport limitations in the system. CFD results have shown very good contact properties of the fluid with the electrode surfaces if they use flow rates above 30 l/h (Inlet Re = 700). Finally, the sustainability performance of the proposed system is being assessed through a Life Cycle and Social Analysis (LCSA) perspective.