Nitrogen doped TiO_2 for hydrogen production under visible light irradiation

摘要

Heterogeneous photocatalytic production of H_2 from water by visible light activation of N-doped TiO_2 samples has been studied. Two different TiO_2 samples (Degussa P25 and a sol-gel prepared powder) and two nitrogen sources (urea and NH_4NO_3) have been selected to produce several catalyst combinations. In all cases, the platinization of the TiO_2 surface dramatically improved the H_2 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 1 st and 2nd experiments, and parallel to this deactivation there was always a nitrogen leakage to the solution in the form of NH_4~+, a fact that hinders the practical application of the N-doped catalysts.