Gathering 15 partners from 9 European and associated countries and 3 from Asian countries, SUN2CHEM’s main objective is to develop solutions to achieve efficient solar-driven CO2 reduction, targeting ethylene as the final product. Ethylene, an energy-rich chemical produced from fossil fuels in industry, has both high commercial value and a giant global market. SUNCHEM’s ambitions will simultaneously reduce our dependence on fossil fuels and mitigate carbon emission by CO2 conversion. For that purpose, SUN2CHEM partners will conjointly develop all the components to be integrated into tandem photoelectrochemical (PEC) cells and advanced photocatalytic (PC) reactors. The technical part of this project includes applied and fundamental research on photocatalysis to improve light-harvesting and charge separation in heterojunctions and plasmonic bimetallic nanoparticles united in a PC reactor (WP2). Next WPs focus on the development of up-scalable efficient and stable photoelectrodes (WP3) and the design of earth-abundant catalysts (WP4), which will then be integrated into the tandem PEC (WP5). Both PC reactor and PEC device will be tested and characterised in operating conditions (WP6). In addition to this highly technical core, this project has for ambition to perform related environmental and social studies in order to integrate the developed technology within a context of circular economy, assess the energy security impacts on end-users and increase the social acceptance of chemicals produced from sunlight conversion (WP7). A prospective market analysis and roadmap towards the upscaling of the technology will then evaluate its medium-term potential and establish pathways towards its future industrial development (WP8). Achieving these ambitious developments by tackling photo-electrochemical cells, catalysts for CO2 reduction, light-harvesting and charge separation, SUN2CHEM will contribute answering Mission Innovation’s Converting Sunlight Innovation Challenge.