Hydrogen Via Heterogeneous Photocatalysis with Binary Promoted TiO2

The need for renewable energy focuses attention on hydrogen obtained by the sustainable and green methods. The new family of the binary promoted photocatalysts N-M-TiO₂ (N = nitrogen, M = none, Cr, Co, Ni, Cu) have been synthesized via sol-gel method followed by drying and calcination. The binary promoted photocatalysts have been characterized by Raman spectroscopy, BET, UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS), and photoluminescence spectroscopy. The synthesis of the N-M-TiO₂ photocatalysts via hydrolysis of Ti isopropoxide at pH>11 in the presence of nitrogen precursor yields the non-crystalline solids that do not produce any hydrogen, while hydrolysis at the neutral pH yields the photocatalytically active materials containing nanocrystalline anatase. The N-M-TiO₂ photocatalysts show absorption bands at 370-450 nm (due to N promoter) and 500-800 nm (due to M promoter). The photocatalysts have been tested for the photocatalytic production of hydrogen from water with and without sustainable sacrificial donor glycerol, under ambient conditions, and near-UV/visible light. The N-Ni-TiO₂ is 5-fold more effective than the benchmark P25 TiO₂, while N-Cu-TiO₂ is 44-fold more active. The photocatalytic activity of the N-M-TiO2 increases from Cr to Co to Ni and Cu, while the photoluminescence decreases; the change in activity is due to the modulation of charge recombination. Certain N-M-TiO2 can be prepared in-situ by photochemical reduction of the precursors, and the activity of the in-situ synthesized N-M-TiO2 was determined as the function of experimental conditions and the amount of the deposited promoter element. Acknowledgments: A.S. thanks Research Corporation for Science Advancement (RCSA) for his Cottrell College Science grant, and Rutgers University for his Research Council Award.