Method for producing a photocatalyst support, at least micrometric in size and photocatalytically active at least in the visible region, containing nanocrystals each made up of 80 to 100 mol% of TiO 2 and 0 to 20 mol% of at least one other metal or semi-metal oxide, comprising the following steps, without using a surfactant: a1) preparing and heating an acidic aqueous solution at a given pH, between 0 and 6, and at a temperature between 20°C and 60°C, without surfactant, by adding hydrochloric acid, a2) adding a titanium oxide precursor, or a mixture of a titanium oxide precursor and at least one other precursor of another metal or semi-metal oxide, to the acidic aqueous solution, a precipitate forming in the acidic aqueous reaction medium made up of 80 to 100 mol% of TiO 2 and 0 to 20 mol% of another oxide, from the titanium oxide precursor which is a titanium alkoxide, or a mixture of this titanium oxide precursor with at least one other precursor of another metal or semi-metal oxide, a3) stirring the acidic aqueous reaction medium, so as to dissolve therein the precipitate formed in step a2), a4) reaction between the precursors obtained in step a3) and the support, to condense the precursors that attach by covalent bonds to the surface of the support, by: • spraying onto the support or • immersing of the support in the aqueous reaction medium, for a determined duration, a5) heating the heating temperature being between 40°C and 95°C, the support that is at least micrometric in terms of size allowing crystallisation of the titanium oxide precursors, or of a mixture of a titanium oxide precursor and of at least one other precursor of another metal or semi-metal oxide into nanocrystals, on its surface, without use of surfactant, in the acidic aqueous reaction medium the precursors crystallising, once bonded to the surface of the support, a6) rinsing with water and recovering: on the one hand, of support on which the crystallisation took place, the nanocrystals obtained being composed from 80 to 100 mol% of TiO 2 and from 0 to 20 mol% of at least one other metal or semi-metal oxide, these nanocrystals being bonded to the support by covalent bonds, and on the other hand a residual solution. a1) preparing and heating an acidic aqueous solution at a given pH, between 0 and 6, and at a temperature between 20°C and 60°C, without surfactant, by adding hydrochloric acid, a2) adding a titanium oxide precursor, or a mixture of a titanium oxide precursor and at least one other precursor of another metal or semi-metal oxide, to the acidic aqueous solution, a precipitate forming in the acidic aqueous reaction medium made up of 80 to 100 mol% of TiO 2 and 0 to 20 mol% of another oxide, from the titanium oxide precursor which is a titanium alkoxide, or a mixture of this titanium oxide precursor with at least one other precursor of another metal or semi-metal oxide, a3) stirring the acidic aqueous reaction medium, so as to dissolve therein the precipitate formed in step a2), a4) reaction between the precursors obtained in step a3) and the support, to condense the precursors that attach by covalent bonds to the surface of the support, by: • spraying onto the support or • immersing of the support in the aqueous reaction medium, for a determined duration, • spraying onto the support or • immersing of the support in the aqueous reaction medium, for a determined duration, a5) heating the heating temperature being between 40°C and 95°C, the support that is at least micrometric in terms of size allowing crystallisation of the titanium oxide precursors, or of a mixture of a titanium oxide precursor and of at least one other precursor of another metal or semi-metal oxide into nanocrystals, on its surface, without use of surfactant, in the acidic aqueous reaction medium the precursors crystallising, once bonded to the surface of the support, a6) rinsing with water and recovering: on the one hand, of support on which the crystallisation took place, the nanocrystals obtained being composed from 80 to 100 mol% of TiO 2 and from 0 to 20 mol% of at least one other metal or semi-metal oxide, these nanocrystals being bonded to the support by covalent bonds, and on the other hand a residual solution. on the one hand, of support on which the crystallisation took place, the nanocrystals obtained being composed from 80 to 100 mol% of TiO 2 and from 0 to 20 mol% of at least one other metal or semi-metal oxide, these nanocrystals being bonded to the support by covalent bonds, and on the other hand a residual solution.