Photocatalytic decomposition of methanol over La/TiO2 materials

Abstract

Lanthanum-modified TiO photocatalysts (0.2-1.5 wt% La) were investigated in the methanol decomposition in an aqueous solution. The photocatalysts were prepared by the common sol-gel method followed by calcination. The structural (X-ray diffraction, Raman, X-ray photoelectron spectroscopy), textural (N physisorption), and optical properties (diffuse reflectance spectroscopy, photoelectrochemical measurements) of all synthetized nanomaterials were correlated with photocatalytic activity. Both pure TiO and La-doped TiO photocatalysts proved higher yields of hydrogen in comparison to photolysis. The photocatalyst with optimal amount of lanthanum (0.2 wt% La) showed almost two times higher amount of hydrogen produced at the same time as in the presence of pure TiO. The photocatalytic activity increased with both increasing photocurrent response and decreasing amount of lattice and surface O species. It has been shown that both direct and indirect mechanisms of methanol photocatalytic oxidation participate in the production of hydrogen. Both direct and indirect mechanisms take part in the formation of hydrogen.

Successful Immobilization of Lanthanides Doped TiO2 on Inert Foam for Repeatable Hydrogen Generation from Aqueous Ammonia

“…The addition of lanthanides did not significantly change the band gap energy value of the prepared photocatalysts compared to the pure TiO2. This is in agreement with our previous results observed for La/TiO2 and Nd/TiO2 materials containing 0.2-1.5 wt.% of lanthanide [18]. In principle, another reason for changing the value of the band gap energy could be the presence of different phases of titanium dioxide.…”

“…Only unmeasurable traces of lanthanides were identified in the case of the La-and Nd-doped TiO 2 samples. In all photocatalysts, two photoelectron peaks at 458.4 eV and 464.1 ± 0.1 eV, corresponding to Ti 2p 3/2 and Ti 2p 1/2 levels, confirmed the existence of Ti 4+ exclusively [18,19]. On the other hand, surface oxygen was distributed in the form of lattice O 2− (529.7 eV) as well as OH − species (530.8 ± 0.1 eV).…”

“…The pure TiO 2 micellar solution was prepared following the procedure described in [17], mixing 40.6 mL of cyclohexane, 18 mL of non-ionic surfactant Triton X-114, 0.610 mL of distilled water, and 10 mL of titanium (IV) isopropoxide as a Ti source. The micellar solutions for the preparation of TiO 2 photocatalysts containing 0.1 wt.% of lanthanum or neodymium where prepared, according to [18,19] with using lanthanum(III) nitrate hexahydrate (La(NO 3 ) 3 •6H 2 O, Aldrich) and neodymium (III) nitrate hexahydrate (Nd(NO 3 ) 3 •6H 2 O, Aldrich) as metal cation sources. First, the proper amount of lanthanum (0.00718 g) or neodymium (0.00704 g) precursor was dissolved in 3 mL of absolute ethanol.…”

“…In principle, another reason for changing the value of the band gap energy could be the presence of different phases of titanium dioxide. However, the preparation of these materials always led to the presence of the pure anatase form in TiO 2 , La/TiO 2 , and Nd/TiO 2 (Figure 3) [18,20].…”

Nd/TiO2 Anatase-Brookite Photocatalysts for Photocatalytic Decomposition of Methanol

“…The flow arrangement of the pressurized hot fluid processing/crystallization offers following advantages: (i) faster heating, (ii) change of the chemical composition of the fluid/medium (e.g., to water, to water/methanol mixture, water/ethanol mixture) during the processing can affect the solubility of used organic precursors for-sol gel synthesis and, thus the purity and further crystallization of sol-gel derived nanomaterials. This processing results in nanocrystalline TiO 2 of anatase-brookite crystal structure showing higher surface area then calcined analog of anatase crystal structure (Kocí et al, 2017 ). The aim of this study is to investigate the influence of the Nd dopant in TiO 2 anatase-brookite on the H 2 yields in photocatalytic decomposition of methanol.…”