In this paper, the combined addition of copper or iron and sulphate ions onto TiO₂ prepared by a simple sol-gel method is studied for formic acid photocatalytic conversion. A wide structural and morphological characterization of the different photocatalysts was performed by X-ray diffraction (XRD), N₂-physisorption for BET surface area measurements, scanning and transmission electronic microscopies (SEM and TEM), UV-Vis diffuse spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS), in order to correlate the physico-chemical properties of the materials to their photocatalytic efficiencies for formic acid oxidation. Results have shown important differences among the catalysts depending on the metal added. Sulphated TiO₂/Cu (1%Cu) was the best photocatalyst obtaining about 100% formic acid conversion in only 5 min. The appropriate physico-chemical features of this photocatalyst, given by the addition of combined copper and sulphate ions, explain its excellence in photocatalytic reaction.