NOVELTY - The device comprises a substrate (210) including an electrically conductive surface (205), and a nanostructure (212) in electrical contact with the electrically conductive surface, where the nanostructure includes an impurity (216) proximate a surface of the nanostructure, and the impurity allows the nanostructure to absorb light. The substrate comprises a transparent material. The electrically conductive surface includes a layer arranged on the transparent material. The layer has a thickness of 100-800 nm. The nanostructure comprises a wide-band gap semiconductor.    USE - The device is useful for solar water oxidation, where the device is a photoelectrode.    ADVANTAGE - The device is low-cost, energy efficient, optically absorptive and electrochemically stable, and possesses a required electronic band alignment with an electrochemical scale for charge carriers to have sufficient potential to drive the hydrogen and oxygen evolution reactions.    DETAILED DESCRIPTION - The device comprises a substrate (210) including an electrically conductive surface (205), and a nanostructure (212) present in electrical contact with the electrically conductive surface, where the nanostructure includes an impurity (216) proximate to a surface of the nanostructure and the impurity allows the nanostructure to absorb light. The substrate comprises a transparent material. The electrically conductive surface includes a layer arranged on the transparent material. The layer has a thickness of 100-800 nm. The nanostructure comprises a wide-band gap semiconductor. The nanostructure comprises a structure consisting of a nanorod, a nanoparticle and a nanosheet. The impurity creates energy levels that are within a band gap of the nanostructure. The impurity is located about 2-200 nm beneath the surface of the nanostructure. An internal region (218) of the nanostructure is electrically conductive internal region. The nanostructure includes a second impurity, where an electronic state of the second impurity is configured to modify the electronic band structure of the nanostructure, and the second impurity is located in an internal region of the nanostructure. The nanostructure includes defects located in the internal region of the nanostructure. The defects include oxygen vacancies. An INDEPENDENT CLAIM is included for a method for fabricating a photoelectrode.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of photoelectrodes.    Electrically conductive surface (205)    Substrate (210)    Nanostructure (212)    Impurity (216)    Internal region. (218)