Nitrogen doped TiO2 for hydrogen production under visible light irradiation

► Hydrogen generation and organic removal are obtained by using N-doped TiO2/Pt and visible light. ► Low quantum and energy efficiencies are obtained. ► Nitrogen doping and activity under visible light are lost after repeated catalyst use. Heterogeneous photocatalytic production of H2 from water by visible light activation of N-doped TiO2 samples has been studied. Two different TiO2 samples (Degussa P25 and a sol–gel prepared powder) and two nitrogen sources (urea and NH4NO3) have been selected to produce several catalyst combinations. In all cases, the platinization of the TiO2 surface dramatically improved the H2 generation efficiency. Photonic and energy efficiencies associated to the production of hydrogen are reported. They turned out to be clearly low (below 1% under visible light irradiation). The performance of the same samples improved if UVA light irradiation was used. The N-doping had no a noticeable detrimental effect on the catalyst performance under UVA irradiation. Reutilization experiments showed a clear deactivation of the catalytic activity, especially between the 1st and 2nd experiments, and parallel to this deactivation there was always a nitrogen leakage to the solution in the form of NH4+, a fact that hinders the practical application of the N-doped catalysts.