NOVELTY - Reducing carbon dioxide using a device, comprises: (a) preparing the device comprising a cathode chamber, an anode chamber, and a solid electrolyte membrane, where the anode chamber comprises an anode electrode including a nitride semiconductor region on surface, a part of the surface of the nitride semiconductor region is covered with a nickel or titanium region, a first electrolyte solution is held in cathode chamber; and (b) irradiating the nitride semiconductor region on which the nickel/titanium region are formed with a light to reduce carbon dioxide in the first electrolyte solution.    USE - The method is useful for reducing carbon dioxide.    DETAILED DESCRIPTION - Reducing carbon dioxide using a device, comprises: (a) preparing the device for reducing carbon dioxide, where the device comprises a cathode chamber (102), an anode chamber (105), and a solid electrolyte membrane (106), the cathode chamber comprises a cathode electrode including a metal or a metal compound, the anode chamber comprises an anode electrode including a nitride semiconductor region on the surface, a part of the surface of the nitride semiconductor region is covered with a nickel or titanium region, the nickel or titanium region is in contact with the nitride semiconductor region, a first electrolyte solution (107) is held in the cathode chamber, a second electrolyte solution is held in the anode chamber, the cathode electrode is in contact with the first electrolyte solution, the anode electrode is in contact with the second electrolyte solution, the solid electrolyte membrane is interposed between the cathode chamber and the anode chamber, the first electrolyte solution contains the carbon dioxide, the cathode electrode is electrically connected to the anode electrode, the anode electrode comprises an anode electrode terminal for collecting electrons generated in the anode electrode, and the nickel or titanium region is apart from the anode electrode terminal; and (b) irradiating at least part of the nitride semiconductor region on which the nickel or titanium region are formed with a light having a wavelength of 250-400 nm to reduce the carbon dioxide contained in the first electrolyte solution.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a device for reducing carbon dioxide.    Cathode electrode (101)    Cathode chamber (102)    Anode electrode (104)    Anode chamber (105)    Solid electrolyte membrane. (106)