NOVELTY - The system (01) comprises a substrate (02) including multiple folded thin films made of a semiconductor material (03), where the thin films have dimensions such that the electrostatic near fields are formed under incident light of nanoparticles (10) and a band bending is produced between the nanoparticles and the semiconductor material. The distribution and the size of the metal nanoparticles and the thickness of the thin films are selected such that the thin films completely or almost completely are interspersed with the metal nanoparticles by the near-fields.    USE - The photoelectrochemical system is useful for producing hydrogen (claimed) for chemical water splitting on composite plasmonic metal/semiconductor photoelectrodes.    ADVANTAGE - The system has increased conversion efficiency for conversion of incident photons into excess minority charge carriers so as to achieve increase in sales of chemical water splitting.    DETAILED DESCRIPTION - The system (01) comprises a substrate (02) including multiple folded thin films made of a semiconductor material (03), where the thin films have dimensions such that the electrostatic near fields are formed under incident light of nanoparticles (10) and a band bending is produced between the nanoparticles and the semiconductor material. The distribution and the size of the metal nanoparticles and the thickness of the thin films are selected such that the thin films completely or almost completely are interspersed with the metal nanoparticles by the near-fields. An interface of nanoparticles to the semiconductor material is greater than the boundary surface to the aqueous electrolyte. The nanoparticles have a non-spherical and non-cubic shape. The nanoparticles have a triangular, tetrahedral, or cylindrical shape, and are designed in the manner of a fishing pattern. The thin films are made of a conductive, and the light-absorbing semiconductor material is formed with a small diffusion length for the excess charge carriers. The thin films are made of porous or amorphous silicon. The thin films have a porous surface layer into which the nanoparticles are embedded. The nanoparticles have a diameter of 1-50 nm and a pitch of 100-200 nm. The near-fields have a thickness of 10-20 nm. The thin films have a thickness of 20-100 nm. A contact surface is electrically connected with the thin films. The system further comprises conductors that are arranged from an electrically conductive light-absorbing material through which the majority charge carriers are to the contact surface. The conductors are made of metal or semiconductor material. The conductors are constructed as three-dimensional network. The contact surface and the aqueous electrolyte (04) are electrically and conductively connected to a potentiostat.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of three-dimensional network thin film segments.    Photoelectrochemical system (01)    Substrate (02)    Semiconductor material (03)    Aqueous electrolyte (04)    Nanoparticles. (10)