NOVELTY - Method for producing a photocatalyst material comprising N-doped titanium dioxide nanofibers decorated with nanoparticles of high work function material or with p-type semiconductor, comprises: synthesizing titanate nanofibers by hydrothermal methods from titanium dioxide particles; cation exchanging of titanates to form hydrogen titanate nanofibers; annealing hydrogen-titanates in e.g. ammonia to obtain N-doped titanium dioxide nanofibers; and impregnating N-doped titanium dioxide nanofibers.    USE - The method is useful for producing a photocatalyst material in the form of dispersion, membrane, film or coating, where the photocatalyst is useful for: removing organic contaminant from surfaces (e.g. grease, oil, toxic moieties), air (e.g. volatile organic compounds) or water (e.g. alcohols, phenolic compounds, hydrocarbons, fatty-acids, esters); disinfecting surfaces, air or water by kill microorganisms present on them; and generating hydrogen fuel gas (all claimed).    ADVANTAGE - The photocatalyst materials: exhibit superior characteristics and catalytic activities; have enhanced visible-light activity; and are easy to produce even in industrial quantities also are prepared by utilizing low ammonium concentrations.    DETAILED DESCRIPTION - Method for producing a photocatalyst material comprising N-doped titanium dioxide nanofibers decorated with nanoparticles of high work function material or with p-type semiconductor, comprises: synthesizing the titanate nanofibers by hydrothermal methods from titanium dioxide particles; cation exchanging of titanates by soaking/washing in acids to form hydrogen titanate nanofibers; annealing hydrogen-titanates in ammonia or other nitrogen-containing base to obtain N-doped titanium dioxide nanofibers; and impregnating the N-doped titanium dioxide nanofibers with inorganic or organic precursor of high work function material or p-type semiconductor followed by decomposition of the metal/semiconductor-compounds to metal/semiconductor to obtain N-doped titanium dioxide nanofibers decorated with nanoparticles of high work function material or with p-type semiconductor. INDEPENDENT CLAIMS are also included for:    (1) photocatalyst material comprising N-doped titanium dioxide nanofibers decorated with nanoparticles of high work function material or p-type semiconductor;    (2) removing organic contaminant from surfaces (e.g. grease, oil, toxic moieties), air (e.g. volatile organic compounds) or water (e.g. alcohols, phenolic compounds, hydrocarbons, fatty-acids, esters) comprising contacting the surface, air or water with the photocatalyst material to degrade the contaminant;    (3) disinfecting surfaces, air or water comprising contacting the surface, air or the water with the photocatalyst material to kill microorganisms present on the surface; and    (4) generating hydrogen fuel gas from starting material comprising contacting the starting material with the photocatalyst material to degrade the starting material to release hydrogen gas.