In this study, we successfully prepared Bi-based single perovskites of the A3Bi2I9 type (A = Cs, Rb, MA, FA), and, for the first time, attempted to experimentally obtain double perovskites Cs2B'BiI6 ...type (B′ = Ag, Au, In, Cu). Despite the premises available in theoretical studies, our research has proven the impossibility of the existence of double perovskites of this type. Nevertheless, both types of obtained materials were subjected to detailed analysis of their physicochemical features and photocatalytic abilities in the hydrogen evolution reaction. This study proved the stability of the Cs3Bi2I9 in HI electrolyte compared to the methanolic solution, with this phenomenon resulting in almost 36 times higher photoactivity.
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•Rb3Bi2I9 and FA3Bi2I9 perovskites were photocatalytic studies for the first time.•Perovskites of the type Cs2B'BiI6 (B′ = Ag, Au, In, Cu) were attempted to be obtained.•H2 evolution over Cs3Bi2I9 reaches 2304 μmol/gcat. under UV–Vis light in HI/H3PO2.•HI/H3PO2 electrolyte causes stabilization of Cs3Bi2I9 structure in photoreactions.•Aqueous methanolic solution decomposes of Cs3Bi2I9 perovskite structure to BiOI.
•RE doping enhanced the photocatalytic activity under visible irradiation.•Acetic acid oxidation over RE-TiO2 under Vis light leads to formation of CO2.•All rare earth metals are present in the form ...of oxides (RE2O3) at the TiO2 surface.•RE-TiO2 could be excited under visible light in the range from 420 to 450nm.
Preparation of new rare earth metal-containing TiO2 nanocomposites (Nd3+/Er3+, Nd3+/Eu3+, Eu3+/Ho3+-TiO2) using sol–gel route and their photoactivity under visible and ultraviolet light is reported. The obtained photocatalysts were subsequently characterized by Brunauer–Emmett–Teller (BET) method, UV–vis diffuse-reflectance spectroscopy (DRS), luminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis (XRD). Photodegradation efficiency of phenol and acetic acid was estimated for visible light (λ>420nm) and UV irradiation. It was found that introduced rare earth (RE) metals are presented in the form of metal oxides (RE2O3) at TiO2 surface. Our study demonstrated that Eu3+/Ho3+co-doped titania exhibited higher photocatalytic activity than P25 in phenol degradation under visible light, whereas Nd3+/Eu3+ co-doped TiO2 showed one of the highest activities in both phenol and acetic acid degradation reaction either under UV and visible light among all the rare earth doped samples. Action spectra analysis of the selected samples clearly showed that RE-doped TiO2 could be excited under visible light in the range from 420 to 450nm.
We present a facile and green approach to produce crystalline TiO2 nanoparticles on a surface of different carbonaceous materials derived from lignocellulosic biomass such as STARBON‐800® obtained by ...carbonization at 800 °C and biochar‐SWP700 (Soft Wood Pellets (SWP) obtained by pyrolysis at 700 °C) via novel low‐temperature ultrasound‐promoted green methodology coupled with citric acid as a cross‐linking agent. In comparison to other methods, the developed method has several significant benefits such as simplicity, great ability to get crystalline TiO2 particles (elimination of high‐temperature treatment (material calcination at >300 °C) needed in the conventional sol‐gel method, which is extremely important in transforming amorphous TiO2 into a photoactive crystalline phase) elimination of risky chemicals and oxidizing agent, and also ability to change some parameters (e. g. ultrasound intensity). Prepared materials were characterized by XRD, DR UV−vis, N2 physisorption, HR‐XPS, XRF, HR‐TEM, FT‐IR and subsequently tested for their photocatalytic activities both in photocatalytic phenol degradation (in water) and oxidation of methanol (in air) under UV and visible light irradiation.
The sweet sound of progress: Immobilization of TiO2 on lignocellulose‐based carbons via low‐temperature ultrasound‐promoted sol‐gel methodology and elimination of the high‐temperature treatment step required in the conventional sol‐gel method. The plausible mechanism for the formation of TiO2 on lignocellulosic carbon materials was deeply explored.
Hybrid materials based on graphitic carbon nitride (g-C3N4) and NTU-9 metal–organic frameworks (MOF) were designed and prepared via solvothermal synthesis and calcination in air. The as-prepared ...photocatalysts were subsequently characterized using Brunauer–Emmett–Teller (BET) analysis, UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) emission spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The obtained NTU-9/C3N4 composites showed a greatly improved photocatalytic performance for the degradation of toluene in the gas phase under LED visible-light irradiation (λmax = 415 nm). The physicochemical properties and photocatalytic activities of the obtained NTU-9/C3N4 materials were tuned by varying the NTU-9 content (5–15 wt%) and preparation method of the composite materials. For composites prepared by calcination, the photocatalytic activity increased with decreasing NTU-9 content as a result of the formation of TiO2 from the MOFs. The best photocatalytic performance (65% of toluene was photodegraded after 60 min) was achieved by the NTU-9/C3N4 sample prepared via the solvothermal method and containing 15 wt% MOF, which can be attributed to the appropriate amount and stable combination of composite components, efficient charge separation, and enhanced visible-light absorption ability. The photocatalytic mechanisms of the prepared hybrid materials depending on the preparation method are also discussed.
The nitrogen doping of titanium dioxide nanotubes (TiO2 NTs) was investigated as a result of well-controlled plasma nitriding of TiO2 NTs at a low temperature. This way of nitrogen doping is proposed ...as an alternative to chemical/electrochemical methods. The plasma nitriding process was performed in a preparation chamber connected to an X-ray photoelectron spectroscopy (XPS) spectrometer, and the nitrogen-doped TiO2 NTs were next investigated in situ by XPS in the same ultrahigh vacuum (UHV) system. The collected high-resolution (HR) XPS spectra of N 1s, Ti 2p, O 1s, C 1s, and valence band (VB) revealed the formation of chemical bonds between titanium, nitrogen, and oxygen atoms as substitutional or interstitial species. Moreover, the results provided a characterization of the electronic states of N–TiO2 NTs generated by various plasma nitriding and annealing treatments. The VB XPS spectrum showed a reduction in the TiO2 band gap of about 0.6 eV for optimal nitriding and heat-treated conditions. The TiO2 NTs annealed at 450 or 650 °C in air (ex situ) and nitrided under UHV conditions were used as reference materials to check the formation of Ti–N bonds in the TiO2 lattice with a well-defined structure (anatase or a mixture of anatase and rutile). Scanning electron microscopy microscopic observations of the received materials were used to evaluate the morphology of the TiO2 NTs after each step of the nitriding and annealing treatments.
Nd-modified TiO2 photocatalysts have been obtained via hydrothermal (HT) and sol–hydrothermal (SHT) methods. The as-prepared samples were characterized by X-ray diffraction (XRD), BET surface area ...measurements, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), luminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the synthesized samples was evaluated by the degradation of phenol in aqueous solution under irradiation with UV–vis (λ > 350 nm) and vis (λ > 420 nm) light, as well as by the degradation of gaseous toluene under irradiation with vis (λmax = 415 nm) light. It was found that Nd-modified TiO2 is an efficient photocatalyst for the degradation of phenol and toluene under visible light. XPS analysis revealed that the photocatalyst prepared via HT method contains a three-times higher amount of hydroxy groups at the surface layer and a two-times higher amount of surface defects than that obtained by the SHT method. The photocatalytic efficiency of phenol and toluene degradation under vis irradiation in the presence of 0.25% Nd-TiO2(HT) reached 0.62 and 3.36 μmol·dm−1·min−1, respectively. Photocatalytic activity tests in the presence of Nd-TiO2 and scavenger confirm that superoxide radicals were responsible for the visible light-induced degradation of the model pollutant in aqueous solution.
Photocatalytic water splitting has great potential in solar-hydrogen production as a low-cost and environmentally friendly method. Different unique techniques used to obtain photocatalysts with ...various modifications to improve H2 generation have been introduced. In the present work, SrTiO3 was successfully synthesized via the solvothermal method in the presence of ionic liquid (IL) - 1-butyl-3-methylimidazolium bromide (BMIMBr) followed by surface decoration with Pt particles using the photodeposition method. The effect of the noble metal content and presence of IL on the morphology, optical and surface properties of SrTiO3, thereby the effectiveness of hydrogen generation, has been thoroughly examined and presented. Unexpectedly, the presence of BMIMBr at the SrTiO3 surface affected the interaction between the semiconductor surface and platinum particles formed throughout photodeposition. Platinum particles at the surface of SrTiO3_IL were found to be in the form of 2D clusters with a size of 1 nm. In comparison, Pt deposited on SrTiO3 photocatalyst without application of IL created larger, three-dimensional structures with a diameter exceeding 5 nm. This is the reason why the total amount of platinum deposited on the SrTiO3_IL sample is smaller than that on SrTiO3 and justifies a higher efficiency of hydrogen generation of Pt modified SrTiO3 photocatalyst in comparison to SrTiO3 prepared in the presence of IL. The mechanism of H2 generation in the water-splitting reaction in the presence of SrTiO3_Pt photocatalyst was discussed.
•Pt decorated SrTiO3 was obtained in the presence of ILs for photocatalytic H2 evolution.•The photocatalytic hydrogen evolution rate of SrTiO3_IL_Pt is 677.84 μmol/min.•Samples prepared with ILs is covered with Pt clusters with diameter ~1 nm.
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•Ti90RE20 alloys were applied as a working electrode to formed RE2O3-modified TiO2 NTs.•Influence of rare earth metals (RE = Ho, Er, Nd, Y, Ce, Tm) on the photocatalytic activity of ...TiO2.•Photocurrent for Ti90Ho10_40V was over 10 times higher compared to the reference.
Application of Ti90RE10 alloys (RE = Ho, Er, Nd, Y, Ce, Tm) as a working electrode, instead of Ti pure foil in anodic oxidation in a fluoride-based electrolyte, resulted in formation of well-ordered nanotubes made of TiO2 and RE2O3 mixture, which could be efficiently used for pollutant removal from water and air phase upon UV and visible irradiation and easily separable from the reaction mixture to recycle. The as-prepared NTs were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), diffuse reflectance spectroscopy (DRS), luminescence spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the synthesized samples was investigated used phenol and toluene as a model compounds to follow degradation kinetics. The influence of the RE metals on the photoelectrochemical performance of modified TiO2 NTs was investigated. Surface morphology analysis showed formation of uniform and vertically oriented NTs structures with an open tube top and smooth walls. The results of EDX, XRD and XPS analysis proved that RE ions exist as surface compounds (RE3+ oxides). Visible light induced photoactivity (both photocatalytic and photoelectrochemical) is mostly pronounced in the presence of nanotubes obtained by anodic oxidation of Ti90Ho10 alloy. These nanotubes are able to degrade toluene in the gas phase even by irradiation of low-powered light source, such as light emitting diodes (λmax = 465 nm). Photocatalytic test of phenol degradation in the presence of scavenger indicates that photogenerated electrons and superoxide radicals play a meaningful role in the photocatalytic degradation of pollutants under visible irradiation. In addition, the photoelectrochemical tests performed under the influence of visible light irradiation confirmed that the RE-modification of TiO2 NTs caused a significant increase of photocurrent (up to 10 times higher). The new and original results on the preparation of RE2O3/TiO2 nanotubes obtained in one step anodic oxidation and photocatalytic activity in aqueous and gas phases represent an important contribution then will benefit photocatalytic surfaces preparation technologies.
We propose a simple and effective scheme for the modification of the walls of microfluidic channels fabricated in polycarbonate (PC) after the device has been bonded. The method prevents both static ...and dynamic wetting of PC by aqueous solutions including viscous, non-Newtonian solutions of polymers as e.g. alginate. The procedure uses dodecylamine, which readily reacts with the carbonate groups of PC to produce a hydrophobic surface. We characterize the dependence of the contact angles and homogeneity of the modified surfaces on the time, temperature, and concentration-all important parameters-of the reaction and provide optimal conditions for the process.
The article presents a systematic study of Sb-doped Zn1−xMgxO layers, with various concentrations of Mg, that were successfully grown by plasma-assisted MBE on polar a- and c-oriented and non-polar ...r-oriented sapphire substrates. X-ray diffraction confirmed the polar c-orientation of alloys grown on c-and a-oriented sapphire and non-polar structures grown on r-oriented substrates. A uniform depth distribution of the Sb dopant at level of 2 × 1020 cm−3 was determined by SIMS measurements. Raman spectroscopy revealed the presence of Sb-related modes in all samples. It also showed that Mg alloying reduces the compressive strain associated with Sb doping in ZnO. XPS analysis indicates that the chemical state of Sb atoms in ZnMgO is 3+, suggesting a substitutional position of SbZn, probably associated with two VZn vacancies. Luminescence and transmission spectra were measured to determine the band gaps of the Zn1−xMgxO layers. The band gap energies extracted from the transmittance measurements differ slightly for the a, c, and r substrate orientations, and the differences increase with increasing Mg content, despite identical growth conditions. The differences between the energy gaps, determined from transmission and PL peaks, are closely correlated with the Stokes shift and increase with the Mg content in the analyzed series of ZnMgO layers.
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