Reivindicaciones

1. Method for obtaining a sheet of titanium having a layer of titanium dioxide in the anatase phase on the surface thereof and exhibiting photocatalytic activity, comprising-: a) Electrolytic oxidation of a sheet of titanium with purity higher than 99% with a titanium, carbon or platinum cathode at a voltage between 60 V and 200 V and a current between 10mA/m<2> -15mA/m<2> ; b) An optional heat treatment at a temperature between 500°C and 950°C for a minimum time of 120 min. 2. Method according to claim 1, wherein the electrolytic oxidation comprises the use as electrolyte of an acid selected from the groups of acids consisting of: sulfuric, nitric, hydrochloric, perchloric and phosphoric acid or its acid salts such as sodium and/or potassium bisulfates, acid phosphates of sodium and/or potassium or mixtures thereof. 3. Method according to claim 2, wherein the electrolytic oxidation comprises the use of sulfuric acid as electrolyte. 4. Method according to the preceding claims, which comprises an additional step of cleaning the surface of the sheet with an organic solvent before the heat treatment. 5. Method wherein the cleaning of the sheet is carried out with acetone. 6. Method according to claim 1, wherein the electrolytic oxidation is carried out with a cathode of titanium, carbon or platinum for a period between 1 and 2 minutes from the moment that the maximum voltage is reached, and the subsequent heat treatment. 7. Method according to claim 1, wherein the electrolytic oxidation is carried out with a titanium cathode for a period between 80 and 100 minutes from the moment that the maximum voltage is reached, without the subsequent heat treatment. 8. A sheet of titanium comprising a layer of titanium dioxide in the anatase phase on the surface thereof and exhibiting photocatalytic activity and which is obtainable according to the method of any of claims 1-7. 9. A sheet of titanium according to claim 8, wherein the titanium dioxide layer provides an aesthetic coloured effect on it. 10. A sheet of titanium according to any of claims 8 or 9 wherein it has a wavy form. 11. A building material comprising a sheet of titanium according to any of claims 8 to 10. 12. Use of a sheet of titanium according to any of claims 8 to 10 or of a building material according to claim 11 for the decontamination of gaseous media or environments containing hydrogen sulphide, sulphurous anhydrides, nitrogen oxides or volatile organic compounds (VOCs). 13. Use of a sheet of titanium according to any of claims 8 to 10 or of a building material according to claim 11 for the decontamination of liquid media or environments and as neutralizer of liquid currents. 14. Use of a sheet of titanium according to any of claims 8 to 10 or of a building material according to claim 11 for decorative purpose of facades and claddings.