▎ 摘　　要

NOVELTY - Photocatalyst comprises titanium dioxide particle comprising titanium dioxide, carbon material located on all or portion of surface of titanium dioxide particle and comprising graphene, reduced graphene oxide and carbon nanotubes (CNTs), and bimetallic nanoparticle supported on carbon material and comprising first metal nanoparticle and second metal nanoparticle. USE - Photocatalyst for use as denitrification catalyst for removing nitrate ion, and processing water (all claimed). ADVANTAGE - The photocatalyst has increased reduction efficiency of hydrogen-mediated reduction reaction, and exhibits high reaction efficiency and high selectivity. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: 1. a method for process water, which involves: performing denitrification reaction for reducing a nitrate ion (NO3-) into nitrogen gas (N2) by decomposing water using the photocatalyst as a catalyst under light irradiation; and 2. a method of preparing a photocatalyst, which involves: (a) preparing a first mixed solution comprising titanium dioxide (TiO2) particle and carbon material selected from graphene, reduced graphene oxide (rGO), and carbon nanotubes (CNTs); (b) preparing a composite comprising the titanium dioxide particle and carbon material located on all or portion of a surface of the titanium dioxide particle by stirring and drying the first mixed solution; (c) preparing a second mixed solution comprising the composite, a first metal nanoparticle precursor and a second metal nanoparticle precursor; and (d) preparing a photocatalyst comprising first metal nanoparticle and second metal nanoparticle supported on the carbon material of the composite by irradiating the second mixed solution with light.