Production of Hydrogen by Glycerol Photoreforming Using Binary Nitrogen–Metal‐Promoted N‐M‐TiO₂ Photocatalysts

Abstract

The need for renewable energy focuses attention on hydrogen obtained by using sustainable and green methods. The sustainable compound glycerol can be used for hydrogen production by heterogeneous photocatalysis. A novel approach involves the promotion of the TiO2 photocatalyst with a binary combination of nitrogen and transition metal. We report the synthesis and spectroscopic characterization of the new N-M-TiO2 photocatalysts (M=none, Cr, Co, Ni, Cu), and the photocatalytic reforming of glycerol to hydrogen under ambient conditions and near-UV or visible light versus benchmark P25 TiO2 . In units of activity μmol m(-2) h(-1) , N-Ni-TiO2 is five-fold more active than P25, and N-Cu-TiO2 is 44-fold more active. The photocatalytic activity of N-M-TiO2 increases from Cr to Co and Ni, whereas the photoluminescence decreases; the change in activity is due to the modulation of charge recombination.

Exploring the effect of boron and tantalum codoping on the enhanced photocatalytic activity of TiO2

“…However, monodoping has inadvertently increased recombination losses, and thus did not always lead to significant improvement of photocatalytic activities companying the extension of photo-response region [10,24,25]. Several factors might contribute to the observed limited photocatalytic activity of mondoped TiO 2 .…”

“…This is mostly attributed to the fast recombination of electron-hole pairs and a relatively large energy gap of TiO 2 (E g = 3.2 eV for anatase phase and E g = 3.0 eV for rutile phase), limiting its light absorption to the ultraviolet fraction of the solar energy spectrum [1,2,5]. Numerous efforts have been devoted to extending the optical response regime of TiO 2 toward visible region, and/or suppress the charge carrier recombination [1,2,[6][7][8][9][10][11][12][13][14][15].…”

Unraveling the Cooperative Mechanism of Visible-Light Absorption in Bulk N,Nb Codoped TiO2 Powders of Nanomaterials

“…Rather, even detrimental effects were observed in some cases. 16 The doping effects are somehow different in the case of TiO2 doped with high valence Sb(V) (d …”

Conventional and cryo-synchronous luminescence spectra of orthorhombic calcium titanate

“…Further, we reported using the in-situ PL emission and excitation spectroscopy in the studies of transfer of photoexcited charge in titania-based photocatalytic colloids [36]. We also reported radiative transitions in the nanocrystalline binary nitrogen and transition metal promoted TiO 2 , as found by the PL emission spectroscopy [37]. Herein, we report, for the first time, characterization of nanocrystalline CaTiO 3 by synchronous PL spectroscopy at 77 K termed "cryo-synchronous PL spectroscopy" versus "conventional" PL emission spectroscopy.…”