The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable, and efficient systems for the conversion and storage of renewable energy sources such as solar energy. The sunlight-driven production of hydrogen or other carbon-based fuels through reduction of water or CO2, with oxygen evolution as a by-product, appears to be a promising and appealing solution, which could be answered by the design of light-driven devices able to achieve light-to-chemical energy conversion. The design of such efficient photo-electrochemical systems remains to be achieved. In order to reach this ambitious goal, PhotoCAT will be undertaken by a consortium gathering teams with complementary expertise in the fields of molecular H2-evolving catalysts and surface chemistry (France CEA/LCBM), molecular CO2-reducing catalysts and homogeneous CO2-reducing photocatalysts (Tokyo Tech) and solid-state material chemistry (Kyoto Univ.). As a first step towards this end, PhotoCAT aims at designing new biomimetic materials for the engineering of photoelectrodes that will be finally implemented within a Photo-Electrochemical Cell (PEC) consisting of a photoanode for water oxidation (O2 evolution), feeding a photocathode with electrons for H2 evolution or CO2 reduction. This process reproduces the Z-scheme found in the photosynthetic machinery of plants and micro-algae. Novel H2-evolving or CO2-reducing photocathodes will be developed through the cografting of bio-inspired H2-evolving catalysts and CO2-reduction catalysts together with metal-organic and fully organic dyes onto transparent p-type semi-conductive substrates such as NiO. These photocathodes will be developed in collaboration between all three partners of PhotoCAT (Kyoto Univ for the fabrication of NiO-based materials, TokyoTech for metal-organic dyes and CO2-reducing catalysts and CEA/LCBM for H2-evolution catalysts, organic dyes and grafting methodologies. Two types of photoanode materials will be used for the construction of the final PEC devices: inorganic metal-oxide-based photoanode materials developed at Kyoto Univ. and molecular photoanode materials obtained from collaboration with a group from Arizona State University (Devens Gust, Ana and Tom Moore).