▎ 摘　　要

NOVELTY - A photoelectrode comprises a photocatalyst layer and a nano-carbon layer formed on the photo-catalyst layer. The nano-carbon layer comprises a complex of metal ions and N-doped graphene quantum dots. The N-doped graphene quantum dots include a functional group including aromatic, pyrrole, and pyridinic having at least one nitrogen atoms in the ring, and the functional group is hydroxy or carboxy group; or a hydrocarbon ring or aromatic substituted with hydroxy or carboxy group. The N-doped graphene quantum dots are N-doped graphene quantum dots derived from a polyphenol-based compound, namely tannic acid, phenylpropanoid, gallic acid and/or ellagic acid. The metal is cobalt, platinum, iridium, ruthenium, titanium, tin, zinc, manganese, magnesium, nickel, tungsten, iron, barium, indium, zirconium, copper, aluminum, bismuth, lead, silver, cadmium, yttrium, molybdenum, rhodium, palladium, antimony, caesium, lanthanum, vanadium, silicon, aluminum and/or strontium or its oxides. USE - The photoelectrode is useful for solar water splitting system (claimed), and photovoltaic water decomposition system. ADVANTAGE - The photoelectrode has excellent charge separation and charge transfer properties, and improves photo-electrochemical water decomposition efficiency and water oxidation performance. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for manufacturing photoelectrode.