Visible Light Driven Photoelectrochemical Water Oxidation on Nitrogen-Modified TiO₂ Nanowires

Abstract

We report hydrothermal synthesis of single crystalline TiO(2) nanowire arrays with unprecedented small feature sizes of ~5 nm and lengths up to 4.4 μm on fluorine-doped tin oxide substrates. A substantial amount of nitrogen (up to 1.08 atomic %) can be incorporated into the TiO(2) lattice via nitridation in NH(3) flow at a relatively low temperature (500 °C) because of the small cross-section of the nanowires. The low-energy threshold of the incident photon to current efficiency (IPCE) spectra of N-modified TiO(2) samples is at ~520 nm, corresponding to 2.4 eV. We also report a simple cobalt treatment for improving the photoelectrochemical (PEC) performance of our N-modified TiO(2) nanowire arrays. With the cobalt treatment, the IPCE of N-modified TiO(2) samples in the ultraviolet region is restored to equal or higher values than those of the unmodified TiO(2) samples, and it remains as high as ~18% at 450 nm. We propose that the cobalt treatment enhances PEC performance via two mechanisms: passivating surface states on the N-modified TiO(2) surface and acting as a water oxidation cocatalyst.

Sequential Processes to Produce N-TiO2Films Through Rf Plasmas

“…Considering the proposed by Fang Tian et al [34], the ratio of the Raman vibrational modes intensities between E 1g and A 1g for TiO 2 and N-TiO 2 films, the percentage are approximately of 11%, i.e., the symmetric and antisymmetric vibrations remain without perceptible change. Figure 5 shows the thickness measurement of the film doped with nitrogen carried out with the profilometer y correspond to ~1370 nm, similar results has been obtained by Hoang et al [36]. Finally, AFM was used to show the morphology and roughness surface of TiO 2 ( Fig.…”

Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production

“…Doping with metal or non-metal elements is known as a feasible means to tune the electronic structure of TiO 2 and to introduce new states into the TiO 2 band gap for visible light response [7][8][9][10][11][12][13][14][15][16][17] . In general, doping with non-metal elements, for example, C, N and S, can build acceptor states above the valence band from the p states of non-metal ions 16 , and doping with metal elements, for example, Fe and Cr, can build donor states below the conduction band 2 .…”

Fabrication of Photocatalyst Composite Coatings of Cr-TiO2 by Mechanical Coating Technique and Oxidation Process

“…With adding Cr, the color of the samples obviously changes at each oxidation condition. The color change of photocatalyst composite coatings hints that the Cr had effected on the oxygen vacancies, which produces the color centers of Ti 3+ in the TiO2 [17,18]. No characteristic peak of chromium oxide has been found, which hints either doped Cr was incorporated in the crystalline structure of the TiO2, or the chromium oxide was highly dispersed and its size was too small to be detected.…”