A monolithic catalyst system for the cleavage of water into hydrogen and oxygen comprises a first photoactive material capable by itself or together with an auxiliary material and/or an auxiliary catalyst when irradiated with light having a wavelength ≧420 nm of generating oxygen and protons from water, and a second photoactive material capable by itself or together with an auxiliary material and/or an auxiliary catalyst when irradiated with light having a wavelength ≧420 nm of reducing protons in water to hydrogen. The first and second photoactive materials are in electrical contact via an electron-conducting material.