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In this work, a conversion of carbon dioxide (CO2) into methane, carbon monoxide, as well as hydrogen was investigated. The TiO2/rGO photocatalysts were prepared by two steps: solvothermal method and calcination at 500, 800, and 1000 °C in an argon atmosphere. The obtained samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflection spectroscopy (UV–vis/DRS), N2 adsorption-desorption and analysis of carbon content. The activity of photocatalysts was evaluated in the photocatalytic reduction of CO2. The TiO2/rGO-10 without calcination showed the highest activity toward CO2 conversion. It was found that all samples after rGO modification exhibited good activity toward H2 generation with high selectivity. The enhanced photocatalytic performance was attributed mainly to the presence of graphene due to its excellent electron transport/collection ability.

DC magnetization of a series of titania nanocomposites modified with reduced graphene oxide (rGO) has been investigated. Hysteresis loops observed at room temperature disappeared at low temperatures. At a temperature of about 100 K, a phase transition to the superferromagnetic order state was observed, probably due to the linear expansion and self-reorientation of the magnetic moments. Processes associated with magnetic moment reorientation can cause a hysteresis loop to disappear at low temperatures as well as superferromagnetic ordering. It was suggested that the isolated nanoparticle in the nanopore could be used to create a “compass” at a nanometer-sized level that would be many times more sensitive than the conventional one. Measurements of the zero-field cooling and field cooling modes do not exclude the possibility of the coexistence of a superparamagnetic state.

In this work, a series of TiO2/rGO photocatalysts were obtained by hydrothermal method and calcination at 500 °C. These nanomaterials were prepared with different content of rGO (1–8 wt. %). The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-VIS/DRS) and surface-enhanced FRaman spectroscopy. The BET specific surface area was also measured. The photocatalytic activity of the photocatalysts was investigated on the basis of methylene blue decomposition under UV-VIS light with high UV intensity. The TiO2/rGO hybrids show enhanced adsorption properties and photocatalytic activity in comparison to references samples. It was found that adsorption plays an important role in methylene blue decomposition due to interactions between methylene blue molecules and aromatic regions from rGO.

Photocatalysis can offer solutions for the transformation of greenhouse gases, such as methane and carbon dioxide. In the paper, a candidate for such a photocatalyst is presented, based on a composite of titania with carbon spheres. The material was obtained using microwave assisted solvothermal synthesis, enabling good dispersion of titania. The studies of carbon dioxide and methane adsorption were performed under ambient pressure and temperatures of 40, 60, and 80 °C. The effect of temperature increase was less favorable for carbon dioxide than for methane. Satisfying values of carbon dioxide and methane uptake were obtained—3.94 mmol CO2/g and 2.77 mmol CH4/g at 40 °C.

This brief review presents the principal results of studies on the photocatalytic and antimicrobial activity of TiO2/graphene nanohybrid materials with an application for water and wastewater treatment. The impact of different kind of graphene materials on the photoactivity of new hybrid photocatalysts was discussed in detail. It was generally concluded that graphene matrix acts as an acceptor and transporter of electrons photogenerated during TiO2 excitation. Mentioned charge carriers can be freely transferred through the graphene sheets reducing the fast e−−h+ recombination, thus enhancing the photocatalytic performance of TiO2-graphene systems. Additionally, theoretically negatively charged and high surface area of graphene flakes benefits the enhancement of an adsorption rate of pollutants contained in water (especially cationic dyes like methylene blue). Formation of chemical interactions between d orbital in TiO2 and π orbital in graphene impacts on the narrowing of the bang-gap of new hybrid nanocomposites, hence the significant enhancement of photocatalytic activity in the visible region. The occurrence of chemical bonds strongly depends on the type of fabrication method, conditions of preparation, as well as the presence of different functional groups on graphene matrix that greatly facilitates the formation of d−π interactions. The higher amount of reactive oxygen species, especially hydroxyl radicals mainly responsible for the effective oxidation of organic compounds, increases the photocatalytic decomposition rate of degraded pollutants. The effectiveness of OH formation in TiO2/graphene systems could be also attributed to the use of titania nanoparticles with exposed {001} active facets.

TiO2 is the most promising oxide semiconductor extensively used as photocatalyst in solar energy conversion into hydrogen and electric energy as well as in degradation of contaminants in water. To increase its efficiency, carbon dopants are applied. A series of TiO2/graphitic carbon nanocomposites with enhanced photocatalytic performance was synthesized at different temperatures in the 300 – 850°C range in the presence of benzene vapours. To investigate the magnetic properties of these nanocomposites, the dc magnetic susceptibility and electron paramagnetic resonance (EPR) measurementswere carried out. Magnetometry revealed the presence of three very different components: a temperature independent and easily recognized in the high-temperature range, another one in 20 – 100 K range displaying a slow increase with temperature decrease and saturation at low temperatures, and the third one observed at T < 20 K showing a sharp increase with decreasing temperature. Five types of EPR spectra were detected in the investigated samples and attributed to various paramagnetic centres. The role of TiO2 phase composition, nanocrystalline sizes, carbon content in its different forms in establishing static and dynamic magnetic response of our samples will be discussed.

Sol-gel method was used for preparation of TiO2 having different structure and phase composition. Prepared titania samples were applied for acetaldehyde decomposition under UV light irradiation. The obtained results showed, that TiO2 consisted from mixed phases of anatase and brookite, which was prepared at neutral pH and calcined at 450 °C was the most active. Charge separation of free carriers was investigated by measurements of electron traps density. It was proved, that density of electron traps can be enhanced by nitrogen doping or by coexisting of two phases such as anatase and brookite. However nitrogen doping to TiO2 did not increase of its photocatalytic activity towards acetaldehyde decomposition. Therefore preparation of TiO2 having mixed phases of anatase and brookite appeared to be the most favourable towards elimination of acetaldehyde under UV at ambient conditions. Moreover, temperature of calcination such as 450 °C was the most optimal, because at that temperature total crystallisation of amorphous titnia occurrs and then interparticle contact increases, which facilitates the interfacial charge transfer between titania particles.

Hybrid carbon-TiO2 spheres (TiO2/C spheres) were prepared via the CVD method in the atmosphere of benzene vapours at 800–1000 °C. Structure and morphology of prepared hybrid composites were examined by means of SEM, TEM, XPS, TG, Raman spectroscopy, XRD and UV–Vis/DRS methods. The SEM and TEM analysis confirmed the presence of uncovered rutile crystallites as well as the different forms of carbon-modified TiO2 forms: rutile TiO2/C spheres and thin flakes of graphite and thin graphene sheets. The average thickness of the typical spheres varied between 30 and 40 nm for samples prepared at lower temperatures (800–900 °C), but the carbon core-shell thickness could be even up to 100 nm for samples obtained at 950–1000 °C. The XPS, TG, Raman spectroscopy and XRD measurements allowed to characterize in detail the carbonaceous nature of carbon layers of the fabricated spheres, indicating the graphitic character of TiO2/C hybrids.

Co-modified TiO2 photocatalysts (TiO2-N,C) were added to commercial gypsum to obtain self-cleaning building material. The gypsum/TiO2 composite were also studied towards their mechanical properties. The highest photocatalytic activity was obtained for gypsum samples containing TiO2/N,C photocatalyst treated at 100–300 °C, attributed to high anatase phase participation, relatively high nitrogen and carbon content and high BET surface area (ca. 170–270 m2/g). In this case (300 °C) the model pollutant (azo dye) degradation rate was 85% and 70% after 15 h of UV and vis irradiation, respectively. Higher compressive strength values was observed for gypsum sample loaded with photocatalysts treated at higher temperatures (600–800 °C), attributed to rutile phase presence and large crystallite size. The grinding operation during gypsum/TiO2 composite preparation can contribute towards the increase of compressive strength (even 40%) by reduction of gypsum particle size whereas photocatalyst particles act as the effective fillers of void spaces in gypsum material.

The gypsum building material was enriched with photocatalytic properties for indoor air purification. The photocatalytic additive to gypsum was TiO2 modified with carbon from various sources. The photocatalytic activity of gypsum plates was performed towards NO x removal. Carbon doping into TiO2 improved not only total degradation of NO x on corresponding gypsum plates but also NO2 selectivity was changed, limiting the production of toxic NO2. The exhibition of photocatalysts on the visible and ultraviolet irradiation has been also carried out to examine their durability. First, the stability of modifying element – carbon in TiO2 structure was analysed, indicating on the gradual reduction of carbon content with irradiation time, especially when the carbon source was cyclic hydrocarbon. Second, the photocatalytic activity of the gypsum plates was performed at each stage of the ageing process. Based on this insight, the correlation between carbon content in modified photocatalysts loaded to gypsum plates and photocatalytic activity of them was described in detail.

In this paper titanium dioxide carbon modification with benzene as a carbon source is presented. A TiO2/graphitic carbon nanocomposites were synthesized by thermal modification in the presence of benzene vapours at different temperature (300–700 °C). The new materials were characterized by a various techniques, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-vis/DR), surface-enhanced Raman spectroscopy. BET specific surface area was also measured. The photocatalytic activity of obtained nanocomposites was measured by the decomposition of acetic acid and methylene blue under UV–vis irradiation. The results show that photocatalytic activity increasing with increase in carbon concentration and temperature of modification. It can be noted that adsorption degree has a very high impact on methylene blue decomposition. The highest photocatalytic activity was found for the photocatalyst modified at 600 °C contains 1.13 wt% of carbon. It should be noted that, the influence of crystallite size, crystal structure changes and specific surface area for photocatalytic activity are presented.

Carbon spheres were prepared by carbonisation of phenolic resin spheres obtained using a modified Stober method in a microwave assisted solvothermal reactor. Preparation process involved water–ethanol, ammonia water, resorcinol, potassium oxalate and formaldehyde. The mixture was stirred for 24 h at room temperature and then subjected to a pressure treatment, in which the solution was treated in a microwave assisted solvothermal reactor for 15 min at a pressure of 1–3 MPa. The proposed synthesis resulted in a material containing microporous carbon spheres having high surface area (from 1178 to 1648 m2/g), with diameters from 200 to 350 nm, total pore volume from 0.49 to 0.78 cm3/g, and high CO2 adsorption capacity from 3.86 to 5.03 mmol/g measured at 0.1 MPa and 25 °C. Taking into account the properties of the obtained material, it can be applied as a sorbent for CO2 capture.

In this paper, the antibacterial activity of titanium dioxide modified with reduced graphene oxide (rGO) was presented. TiO2/rGO photocatalysts were prepared by the hydrothermal method under elevated pressure at 180°C and heated at 100°C in Ar flow. The obtained photocatalysts were characterized by means of XRD, FTIR/DRS, UV-vis/DR, Raman spectroscopy and scanning electron microscopy (SEM). The carbon content was also examined. FTIR/DRS and Raman analysis confirmed the presence of rGO in the TiO2 structure, suggesting a successful modification. The antimicrobial photoactivity of photocatalysts was conducted against E. coli under an artificial solar light. The results show that all TiO2/rGO photocatalysts exhibited an antibacterial activity higher than unmodified TiO2. The best result was found for sample with 1.5wt% additive of reduced graphene oxide. In this case, total inactivation of E. coli was noticed after 75min of irradiation. It was found that the presence of rGO in sample improves the antimicrobial activity.

In this study, a series of TiO2/rGO photocatalysts were obtained with a two-step procedure: a solvothermal method and calcination at 300–900 °C in an argon atmosphere. It was noted that the presence of rGO in photocatalysts had an important role in the changes in crystallite size and specific surface area. In TiO2/rGO samples, different surface functional groups, such as C−Cgraph, C−Caliph, C−OH, C=O, and CO(O), were found. It was observed that rGO modification suppressed the anatase-to-rutile phase transformation. The photocatalytic activity of the obtained nanomaterials was investigated through the decomposition of methylene blue under UV and artificial solar light irradiation. It was found that the adsorption degree played an important role in methylene blue decomposition. The experimental results revealed that TiO2/rGO samples exhibited superior removal efficiency after calcination for methylene blue compared toTiO2 without rGO, as well as a commercial photocatalyst KRONOClean 7000. It was noted that photocatalytic activity increased with the increase in the calcination temperature. The highest activity was observed for the sample calcined at 700 °C, which consisted of 76% anatase and 24% rutile. This study clearly demonstrated that TiO2/rGO samples calcined in argon can be used as efficient photocatalysts for the application of methylene blue decomposition.

A hybrid nanocomposites containing nanocrystalline TiO2 and graphene related materials (graphene oxide and reduced graphene oxide) were successfully prepared elevated pressure using hydrothermal method. The structural and textural properties as well as the presence of different carbonaceous structures on the surface of obtained nanocomposites have been characterized by means of XRD, FTIR/DRS and Raman spectroscopy. FTIR/DRS analysis allowed to find characteristic peaks of graphene oxide: epoxy stretching at 1229 cm−1 and alkoxy stretching vibration at 1059 cm−1. In the spectrum of nanocomposites containing rGO, all the bands decreased or even disappear. It can be indicated that GO was successfully reduced to rGO. SEM studies showed difference between graphene oxide (aggregated, crumpled, non-transparent) and reduced graphene oxide (thin and transparent) flakes. The Time Resolved Microwave Conductivity analysis have been utilized to investigate the excess of charge-carrier lifetimes in TiO2-graphene oxide and TiO2-reduced graphene oxide hybrid nanocomposites. It was generally concluded that modification of starting TiO2 with carbonaceous precursors leads to the slight increase of intensity of the TRMC signals, indicating that more electrons are induced in the conduction band of hybrid nanocomposites. It is also worth mentioning that the decay of studied signals of modified powders depends on added carbon precursor, indicating that the type of deposited species may affect the slight or significant suppression of recombination or charge-carriers trapping.

Semiconducting polymers are promising materials for photocatalysis, batteries, fuel applications, etc. One of the most useful photocatalysts is polymeric carbon nitride (PCN), which is usually produced during melamine condensation. In this work, a novel method of obtaining a PCN nanocomposite, in which PCN forms an amorphous layer coating on oxide nanoparticles, is presented. Microwave hydrothermal synthesis (MHS) was used to synthesize a homogeneous mixture of nanoparticles consisting of 80 wt.% AlOOH and 20 wt.% of ZrO2. The nanopowders were mechanically milled with melamine, and the mixture was annealed in the temperature range of 400&ndash, 600 &deg, C with rapid heating and cooling. The above procedure lowers PCN formation to 400 &deg, C. The following nanocomposite properties were investigated: band gap, specific surface area, particle size, morphology, phase composition, chemical composition, and photocatalytic activity. The specific surface of the PCN nanocomposite was as high as 70 m2/g, and the optical band gap was 3 eV. High photocatalytic activity in phenol degradation was observed. The proposed simple method, as well as the low-cost preparation procedure, permits the exploitation of PCN as a polymer semiconductor photocatalytic material.

The effect of the ZnO nanoparticles (NPs) size on the photocatalytic degradation of phenol in a water solution under the influence of UV and Vis radiation was discussed. For the first time, research on photocatalytic degradation has used ZnO NPs produced by only one method (microwave solvothermal synthesis without heat treatment or other processes of reduction/oxidisation of the surface of NPs samples). ZnO NPs average size was determined using the Scherrer's formula, Nanopowder XRD Processor Demo web application, by converting the results of the specific surface area-density, and TEM tests. The ZnO NPs (average size between 23 nm and 71 nm) characterise by uniform morphology and narrow size distribution. The photocatalytic performance of ZnO NPs increases with the increase of the particle size and the decrease of the specific surface area. For both UV and Vis radiation, the highest reaction rate for phenol degradation was found for ZnO sample with the average particle size of 71 nm. Low concentrations of resorcine and hydroquinone (co-products of phenol degradation) were found for UV light photocatalytic test. However, high concentrations of hydro- and p-benzoquinone were observed for visible light photoactivity due to the slower decomposition of the main contamination associated with the utilized of other type of radiation. The photocatalytic activity was found to be attributable to the decrease in the charge carrier recombination rate.

Visible light-active TiO 2 –reduced graphene oxide photocatalysts were prepared using simple mechanical mixing of titanium dioxide with different amounts of rGO (0.1, 0.5, 1.0 and 2.0 wt.%) in the presence of 1-butyl alcohol. Structures and morphologies of the samples were examined by means of FTIR/DRS, UV–vis/DR, XRD, SEM, TEM and Raman spectroscopy. The photocatalytic properties were checked on the basis of acetic acid photooxidation (the steady rate of linear increase of the CO 2 yield was used for the estimation of photocatalytic activity). The maximum photodegradation rate was observed for TiO 2 decorated with 0.5 wt.% of rGO. The enhancement of photodegradation efficiency should be related to π-conjugation system, two-dimensional planar structure and efficient charge separation of reduced graphene oxide nanosheets.

Antibacterial properties of 15 titania photocatalysts, mono- and dual-modified with nitrogen and carbon were examined. Amorphous TiO2, supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO2, C-TiO2, N-TiO2 and N,C-TiO2 calcined at 300°C, 400°C, 500°C, 600°C, 700°C). The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artificial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artificial sunlight irradiation. The efficiency of disinfection process conducted under artificial sunlight irradiation with carbon (C-TiO2) and carbon/nitrogen (N,C-TiO2) photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.

In this paper the antibacterial properties of the group of titanium dioxide photocatalysts modified with glucose are presented. TiO2/glucose samples were calcined at 200–800 °C. It was found that the antibacterial activity under artificial solar light depends mainly on the carbon content in studied materials. It should be noted that presence of carbon in tested samples caused the enhancement of the antibacterial activity in comparison with non-carbon containing samples. Thus, using carbon for TiO2 modification is highly desirable. The best results were found for TiO2-G-400 and TiO2-G-600 samples with total reduction of bacteria number after 15 min of irradiation with artificial solar light.

Clay bricks containing different kinds of titanium dioxide (TiO2) photocatalysts were obtained. The samples have shown high photocatalytic activity during thin layers of oleic acid deposited on their surface decomposition. The self-cleaning effectiveness of the bricks was evaluated on the basis of the water contact angle measurements, or more precisely, wettability rate (WR) changes on the greasy surface layers. It appeared that despite the high-temperature clay firing process (950°C), the presence of quartz and aluminosilicates in clay have caused the inhibition of anatase–rutile transformation. The highest photocatalytic efficiency, determined on the basis of the WR measurements, was observed for TiO2/nitrogen (N) and TiO2/N, carbon (C)-loaded bricks. It should be noted that in the case of the bricks loaded with the TiO2/N,C photocatalyst, the carbon dopant present in the material was burnt out during the high-temperature kiln firing. The N content in latter samples show closely the same results (∼0.03 and ∼0.04 wt% of N for brick loaded with TiO2/N and TiO2/N,C, respectively). In the context of the photocatalytic activity of studied materials, the N presence was found to be one of the most important feature.

The (nCo,N)-TiO2(n = 1, 5 and 10 wt.% of Co) nanocomposites were investigated by magnetic resonance spectroscopy in 4 K to 290 K range. Analyses of ferromagnetic/electron paramagnetic resonance (FMR/EPR) spectra in terms of four Callen lineshape components revealed the existence of two types of magnetic centers, one derived from metallic cobalt nanoparticles in superparamagnetic (SPM) phase and the other from cobalt clusters in the TiO2lattice. Additionally, at low temperature the EPR spectrum arising from Ti3+ ions was also registered. Both relaxations of the Landau-Lifshitz type and the Bloch-Bloembergen type played an important role at high temperature in determining the linewidths and the latter relaxation was prevailing at low temperature. Analysis of the integrated intensity showed that the SPM signal is due to small size FM cobalt nanoparticles while the paramagnetic signal from Co clusters originates from those nanoparticles in which the concentration of magnetic polarons is below the percolation threshold.

A simple method of preparation of artificial solar light-active TiO2 photocatalysts is presented. The new TiO2/C samples were obtained by thermal treatment (150, 250, 350 and 450 °C) of industrial titanium dioxide (TiO2-starting) in the presence of naphthalene vapours. The obtained nanomaterials were investigated by means of UV-vis/DR, Fourier transform infrared spectroscopy/diffuse reflectance infrared and X-ray powder diffraction methods. Brunauer–Emmett–Teller (BET) specific surface area and carbon content were also measured. The photocatalytic activity of the photocatalysts was investigated on the basis of phenol degradation under artificial solar light. TiO2/C photocatalysts show higher photocatalytic activity in comparison with TiO2-starting and commercial KRONOClean 7000 photocatalysts. It was noted that the highest decomposition and mineralisation degree of phenol and its degradation co-products were found for sample obtained at 450 °C and contained 0.19 wt.% of carbon. The carbon content, BET surface area and anatase crystallite size are the mean features, which strongly contribute the photocatalytic activity of new carbon-modified TiO2 photocatalysts under artificial solar light. Modification of TiO2 with naphthalene vapours is a promising method, especially taking the mineralisation of phenol and the co-products of its degradation into account.

The aim of the investigations was a modification of DTO, a commercial activated carbon (AC), to improve CO2 adsorption capacity. The adsorption of CO2 up to 40 bar at 40 ◦C temperature was investigated. The volumetric method was applied for CO2 adsorption isotherm measurements. The starting material — DTO — was modified using chemical activation (KOH, ZnCl2, K2CO3). The textural parameters of all the ACs were determined by nitrogen adsorption at the liquid nitrogen temperature of –196 ◦C on Quadrasorb SI. Results showed that the AC modified with KOH had the highest SBET, Vtot, Vmic values of 2063 m/g, 1.13 cm/g, and 0.67 cm/g, respectively. ACs with a wider pore size distribution (from micropores to mesopores) were obtained. The maximum CO2 adsorption was equal to 14.44 mmol/g for DTO/KOH — modified carbon whereas 8.07 mmol/g of CO2 was adsorbed at DTO. The CO2 adsorption capacities of the ACs were found to be closely correlated with the BET surface areas of the materials tested. The experimental data was fitted to the Freundlich, Langmuir, Sips and Toth equations to determine the model isotherm. The Sips model was found to be the best for fitting the adsorption of CO2.

In this article, the influence of calcination temperature on the photocatalytic properties and stability of titanium dioxide modified with 3-aminopropyltriethoxysilane (APTES) was presented. The new APTES-functionalized TiO2 nanomaterials were obtained by solvothermal process and thermal modification in the argon atmosphere. The obtained photocatalysts were characterized via various techniques including diffuse reflectance spectroscopy (UV–vis/DRS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR/DRS), SEM, BET surface area measurement and zeta potential analyses. Modification with APTES suppressed phase transformation and the growth of crystallite size of anatase and rutile during heating. The crystallites size of anatase was in the range of 14−52 nm for heat-treated starting-TiO2 and 14−31 nm for APTES-modified TiO2. Calcination process influenced the surface characteristics i.e. zeta potential of APTES-modified TiO2 nanomaterials. The photocatalytic activity of obtained samples was investigated during the decomposition of methylene blue using as a model water contaminant under UV light irradiation. Thermal modification in the argon atmosphere significantly enhanced adsorption properties and photocatalytic activity of obtained nanomaterials. Furthermore, calcination up to 700 °C improved photocatalytic stability of the examined photocatalysts. It is also worth mentioning that APTES modification significantly improved photocatalytic performance of nanomaterials calcined at 900 °C. In this case the decomposition degree of TiO2-4h-180 °C-2000 mM-Ar-900 °C in comparison to TiO2-Ar-900 °C increased by 50 %.

In this paper, titanium dioxide modification with 3-aminopropyltriethoxysilane as a silicon source is presented. The TiO2/APTES photocatalysts were obtained utilizing a solvothermal method. Different concentrations of APTES dissolved in ethanol were used for materials preparation (10−3000 mM). The samples were characterized by different analytical methods such as FT-IR/DRS, UV–vis/DRS, XRD, SEM. The carbon and nitrogen content to confirm, as well as the BET specific surface area, were also measured. The analysis confirmed the presence of silicon, carbon and nitrogen in the TiO2 structure, suggesting that modification was carried out successfully. The carbon and nitrogen were also indications in the sample after the reusability test in water. The photocatalytic activity of the nanomaterials was investigated on the basis of methylene blue decomposition under UV light irradiation. Photocatalytic activity increases with the increase of APTES concentration used for modification. The novelty of research was to check the possibility of photocatalysts reuse. In this case, the sample with the highest decomposition degree was subjected to the reusability test. It it was found that the samples after this type of modification are not stable due to destruction of the APTES alkyl chains and detachment the amine groups during UV irradiation.

Oxygen evolution reaction (OER) is a key process in electrochemical conversion technologies. The rational design of efficient catalyst and understanding of structure-property relationship in catalysis still remain grand challenge. Herein, nitrogen-coordinated CoS2 ultrafine nanoparticles (NPs) self-encapsulated in graphene (N-CoS2@graphene) are obtained through employing zeolitic imidazolate frameworks (ZIFs) as precursors. An in-situ N-coordinated and graphene self-encapsulated strategy is developed to improve the catalytic activity and stability. As expected, the N-CoS2@graphene achieved an extremely low overpotentials of only 205 and 292 mV at the current density of 10 and 100 mA cm−2 for OER, respectively, showing superior activities as compared with state-of-the-art transition-metal-based catalysts. Mechanism explorations reveal that the N-CoS2@graphene offers unique graphene self-encapsulated structure and modulated electron structure of the catalytic sites, which synergistically promotes intrinsic activity and stablility of catalyst. It is expected that the strategy presented here provides prospects for the design of other highly active electrocatalysts for energy conversion.

In the study the self-cleaning properties of photoactive gypsum plasters are presented. The modified gypsum plasters were obtained by addition of 1 and 3 wt.% of nitrogen-modified titanium dioxide (TiO2/N) and 0.1, 0.3, and 0.5 wt.% of glass fiber. The self-cleaning ability of the obtained materials was tested during two dyes decomposition: Methylene Blue (MB) and Reactive Orange (RO). It was found that presence of glass fiber increased photocatalytic activity of modified gypsum plasters, which may be due to the fact glass fiber may act as ducts for light and transport it to sites screened by TiO2 or glass fiber can retard charge recombination. Moreover, unexpectedly the addition of glass fiber did not increase the mechanical properties of modified gypsum plasters, which may be because gypsum does not strongly adhere to the surface of glass fibers.

A hybrid nanocomposites containing nanocrystalline TiO2 and graphene-related materials (graphene oxide or reduced graphene oxide) were successfully prepared by mechanical mixing and the hydrothermal method in the high-pressure atmosphere. The presented X-ray photoelectron spectroscopy (XPS) study and quantitative elemental analysis confirm similar content of carbon in graphene oxide GO (52 wt% and 46 wt%, respectively) and reduced graphene oxide rGO (92 wt% and 98 wt%, respectively). No chemical interactions between TiO2 and GO/rGO was found. TiO2 nanoparticles were loaded on GO or rGO flakes. However, Fourier transform infrared-diffuse reflection spectroscopy (FTIR/DRS) allowed finding peaks characteristic of GO and rGO. XPS study shows that since the concentration of TiO2 in the samples was no less than 95 wt%, it was assumed that the interactions between TiO2 and graphene should not influence the lower layers of titanium atoms in the TiO2 and they occurred as Ti4+ ions. Hydrothermal treatment at 200 &deg, C did not cause the reduction of GO to rGO in TiO2-GO nanocomposites. In general, the one-step hydrothermal method must be considered to be inefficient for preparation of chemically-bonded composites synthesized from commercially available TiO2 and unfunctionalized graphene sheets obtained from graphite powder.

In presented studies the photocatalytic decomposition of NOx on gypsum plates modified by TiO2-N,Cphotocatalysts were presented. The gypsum plates were obtained by addition of 10 or 20 wt.% of different types of titanium dioxide, such as: pure TiO2 and carbon and nitrogen co-modified TiO2 (TiO2-N,C) to gypsum. TiO2-N,C photocatalysts were obtained by heating up the starting TiO2 (Grupa Azoty Zakłady Chemiczne Police S.A) in the atmosphere of ammonia and carbon at the temperature: 100, 300 i 600ºC. Photocatalyst were characterized by FTIR/DRS, UVVis/DR, BET and XRD methods. Moreover the compressive strength tests of modified gypsum were also done. Photocatalytic activity of gypsum plates was done during NOx decomposition. The highest photocatalytic activity has gypsum with 20 wt.% addition of TiO2-N,C obtained at 300ºC.

The photocatalytic activity of cement pastes containing nitrogen and carbon co-modified TiO2 photocatalysts (TiO2-N,C) were evaluated trough the degradation of model organic water contaminate (Reactive Red 198) under UV–vis light source. It was found that cement plates containing TiO2-N,C photocatalysts exhibited higher photocatalytic efficiency than those containing unmodified TiO2.

The investigations on the influence of TiO 2 photocatalyst (Aeroxide® TiO 2 P25) loading, feed cross-flow velocity ( v F ) and transmembrane pressure (TMP) on the fouling and stability of ceramic membranes in a photocatalytic membrane reactor are presented. Two ultrafiltration membranes with molecular weight cut-off of 5 kDa (Filtanium 5) and 100 kDa (Filtanium 100), and one microfiltration membrane (Filtanium 0.2) with maximum pore size of 0.2 μm were used. Regardless of the applied v F (3–6 m/s), TMP (1–3 bar) and TiO 2 P25 loading (0.5–1.5 g/dm 3 ) no permeate flux decline was observed when the UF membranes were used. On the opposite, an increase of the flux for 5–10% compared to pure water flux due to abrasion of the membranes separation layer by TiO 2 P25 particles was found. In case of MF membrane a significant influence of v F and TMP on permeate flux was observed. Application of v F = 3 m/s led to a significant membrane fouling while at v F = 6 m/s the permeate flux exceeded pure water flux in the whole range of TMP. The fine UF Filtanium 5 membrane lost its separation properties due to abrasion by TiO 2 P25 particles, whereas the performance of the ordinary UF Filtanium 100 membrane did not change during 100 h of operation in the PMR. Additionally, the influence of a commercial TiO 2 ST01 (Ishihara Sangyo, Japan) and laboratory made A700 (anatase) and A800 (rutile) on the permeate flux through Filtanium 100 membrane were assessed. The difference between the lowest and the highest values of the permeate fluxes measured for various TiO 2 materials did not exceed 12%.

The electronic structure of N-TiO2 samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti3+ were detected. Sample prepared at 300 degrees C revealed the highest intensity line of the nitrogen paramagnetic centers, whereas that prepared at 400 degrees C showed a paramagnetic line for Ti3+. Measurements of the electron trap distribution showed higher density of electron traps for sample prepared at 400 degrees C than that at 300 degrees C. Sample prepared at 300 degrees C, which revealed the highest amount of nitrogen built in the titania in the interstitial position was the most active under visible light. It was evidenced that photocatalytic decomposition of acetaldehyde was dependent strongly on the BET surface area and electrokinetic potential of the photocatalyst surface. The UV content in the fluorescent lamp affected the yield of acetaldehyde decomposition.

a b s t r a c t A comparison study of metal (Fe, Co, or Ni) - modification, nitrogen - doping of rutile titanium dioxide via impregnation followed by calcination method is presented. The aim of this study was to obtain a highly photoactive rutile titanium dioxide and to establish the origin of its photoactivity with reference to the influence of the physicochemical properties of the modified materials and the type of the applied metal. Moreover, the properties of the co-modified photocatalysts were compared to those of the single (metal or nitrogen) modified materials. For this purpose highly advanced analytical methods such as SEM with EDS, XPS, EPR-AFMR, XRD, ICP-OES, UV-vis/DR, N2 adsorption/desorption at 77 K and elemental analysis were employed. We have proved that a proper modification of rutile may lead to obtaining highly visible and/or UV light active materials. It has been revealed that the metal applied for rutile titanium dioxide modification plays a crucial role in its photocatalytic performance. In case of visible light the Fe > Ni > Co order and in case of UV light activity the Ni > Fe > Co order, for both single-modified and co-modified materials, is followed. Moreover, it was proven that the co-modified samples exhibited significantly higher activity than the single-modified rutile. An effort has been made in order to shed light on this new, unexplored area of titanium dioxide modification and application.

In this paper, the antibacterial properties of TiO2 photocatalysts modified by 3-aminopropyltriethoxysilane (APTES) are presented. It has been observed that the APTES modification enhancement of antibacterial efficiency (against Escherichia coli ATCC 29425) under artificial solar light (ASL). The results showed that all modified titania had higher disinfection efficiencies than starting TiO2. For TiO2-4h-120 °C-300 a total sample elimination of the E. coli was achieved after 180 min of ASL irradiation. Improvement of antibacterial properties was attributed to the changes in the surface properties, i.e. zeta potential.

A simple way of preparation of Ni-modified and Ni,N-co-modified rutile TiO 2 from an industrial grade amorphous titanium dioxide via impregnation followed by calcination at 1073 K in argon (Ni–TiO 2 ) or ammonia (Ni,N–TiO 2 ) atmosphere with different Ni:TiO 2 ratios is presented. New materials were characterized by means of: XRD, XPS, elemental analysis, UV–Vis/DR spectroscopy, SEM, EPR and N 2 adsorption at 77 K. The photocatalytic activity of the materials was studied during decomposition of acetic acid under irradiation with UV or Vis light with wavelengths longer than 400 nm or 450 nm. The obtained results suggest the occurrence of a charge transfer between TiO 2 and NiTiO 3 phases resulting in a relatively high activity of XNi–TiO 2 materials under the irradiation up to 400 nm. A band-gap narrowing of TiO 2 after ammonia treatment was proved on the basis of UV–Vis/DR spectra for all the co-modified samples. The influence of Ti 3+ ions on the band-gap narrowing and consequently photocatalytic activity of XNi,N–TiO 2 and possible electron transfer from rutile conduction band to metallic Ni is here discussed.

In this paper, studies of the mechanical properties and photocatalytic activity of new photoactive cement mortars are presented. The new building materials were obtained by the addition of 1, 3, and 5 wt % (based on the cement content) of nitrogen-modified titanium dioxide (TiO2/N) to the cement matrix. Photocatalytic active cement mortars were characterized by measuring the flexural and the compressive strength, the hydration heat, the zeta potential of the fresh state, and the initial and final setting time. Their photocatalytic activity was tested during NOx decomposition. The studies showed that TiO2/N gives the photoactivity of cement mortars during air purification with an additional positive effect on the mechanical properties of the hardened mortars. The addition of TiO2/N into the cement shortened the initial and final setting time, which was distinctly observed using 5 wt % of the photocatalyst in the cement matrix.

A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials.

A simple method of preparation of visible-light active rutile-TiO2 photocatalysts is presented. New materials were obtained by modification of a commercial amorphous titanium dioxide via impregnation followed by calcination at 800 C processes. Series of Fe-modified TiO2 with different Fe:TiO2 ratios (1, 5 and 10 wt.% of Fe) were obtained by impregnation with Fe(NO3)3 followed by calcination in argon atmosphere. Nitrogen-modified TiO2 was prepared by calcination of the commercial titania in ammonia atmosphere at 800 C. Finally (Fe,N) co-modified samples were prepared by combining impregnation with calcination in ammonia atmosphere. The materials were characterized by the following methods: Xray power diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis, UV-Vis/DR spectroscopy, scanning electron microscopy (SEM) and N2 adsorption at 77 K. The photocatalytic activity of the new materials was studied during oxidative decomposition of acetic acid under visible light irradiation using mercury lamp and a cut-off filter providing wavelength longer than 400 nm. Additionally, the so-called action spectra measurements of photocatalytic activity as a function of irradiation wavelength were conducted. The results revealed an excellent increase in the visible light photoactivity of the co-modified samples in comparison with the single-modified ones, which was ascribed to the synergistic effect of the N,Fe rutile co-modification. Nitrogen caused a band-gap narrowing allowing absorption of longer wavelengths from visible light region, whereas iron increased the efficiency of charge separation. As a result, a significantly improved photocatalytic performance of the materials was observed.

Porous carbons loaded with CaO and MgO were prepared through a one-step process from mixtures of poly(ethylene terephthalate) and dolomite mineral. Obtained hybrid materials were examined as sorbents for CO2 gas contained in air. The influence of pore structure, loadings of the oxides, moisture, and temperature on the efficiency of gas removal is presented and discussed. Performance of the materials during CO2 capture was confirmed to be influenced by all mentioned factors. As a rule, efficiency of CO2 removal increased along with loading of the oxides. CO2 uptake increased also with moisture content and temperature of the bed. On the basis of attained results, optimal parameters for operational use are suggested and probable mechanisms of the CO2 removal from dry and humid air are proposed. Cyclic sorption–desorption experiments confirmed capability of the material for several-times use. Superior performance of the hybrid materials over a mixture of CaO and MgO is confirmed and discussed.

Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288 K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most important pollution intensifying greenhouse effect is anthropogenic carbon dioxide. This particular gas absorbs secondary infrared radiation, which in the end leads to an increase of average temperature of Earth’s atmosphere. Main source of CO2 is burning of fossil fuels, like oil, natural gas, and coal. Therefore, to reduce its emission, a special CO2 capture and storage technology is required. Carbonaceous materials are promising materials for CO2 sorbents. Thus multiwalled carbon nanotubes, due to the lack of impurities like ash in activated carbons, were chosen as a model material for investigation of acid treatment impact on CO2 uptake. Remarkable 43% enhancement of CO2 sorption capacity was achieved at 273 K and relative pressure of 0.95. Samples were also thoroughly characterized in terms of texture (specific surface area measurement, transmission electron microscope) and chemical composition (X-ray photoelectron spectroscopy).

An easy way of preparing highly N-doped rutile photocatalysts (N–TiO2/R) in tubular furnace in a constant ammonia (NH3) flow at 800–1000 °C temperature range is presented. New materials were compared to TiO2 samples prepared at the same temperatures in air atmosphere as well as to the starting material. Complete transformation of amorphous and anatase phases to rutile was confirmed by XRD method. Successful incorporation of relatively high amounts of nitrogen (up to 17% at.), in form of either TiO2(N), TiOxNy or TiN, on photocatalysts’ surface and in their lattice was confirmed using XPS and XRD analysis. Also presence of Ti3+ was revealed by EPR studies. In contrast to pristine TiO2, the UV–vis/DR absorption spectra of N-modified photocatalysts extended significantly into the visible light region. Whereas nitrogen concentration as well as visible light absorption were found to increase with increasing modification temperature, photocatalytic activity was, on the contrary decreasing. This may be due to the very high nitrogen concentration, obtained at higher modification temperature, as well as the presence of small amount of conductive TiN phase on the N–TiO2/1000 °C photocatalyst surface. The artificial solar light activity of new photocatalysts after thermal treatment in NH3 increased in comparison to starting material, due to nitrogen modification and presence of Ti3+ ions. Activity under UV(-vis) light, though, decreased after modification procedure, probably due to smaller surface areas of new photocatalysts and complete anatase to rutile transformation.

Photoactivities of TiO 2 based photocatalysts towards dyes decomposition was studied by consider their adsorption abilities. It was proved that zeta potential and PZC (point zero charge) of photocatalyst surface as well as pH of solution strongly influenced adsorption of tested dyes, Methylene Blue (MB) and Reactive Red 198 (RR198). These dyes underwent the photocatalytic decomposition by two ways, OH radicals attack and direct oxidation with photogenerated holes. The latter one is more efficient in case of better contact of pollutant with the photocatalysts surface and is dominant under visible light irradiation, where insignificant amount of OH radicals is formed. The former one is powerful under UV irradiation and is a key factor in decomposition of dyes regardless of their adsorption abilities.

In this work photocatalytic properties of TiO2 thin fi lms doped with 8.51 at. % of Nd were described. The self-cleaning phenomenon of thin fi lms was discussed together with the structural, optical and surface properties of prepared thin fi lms. Transparent coatings based on titanium dioxide were manufactured by high-energy reactive magnetron sputtering process. Incorporation of Nd during sputtering process results in amorphous behavior, without a signifi cant infl uence on transparency and colour as compared to the undoped TiO2-rutile matrix. Nevertheless, doping with neodymium doubles the photocatalytic activity of the matrix due to higher quantity of photo-generated charge carriers and more effi cient mechanism of energy transfer.

MgO-containing porous carbon material prepared from natural magnesite and poly(ethylene terephthalate) was examined in cyclic CO2 sorption and thermal regeneration, using thermogravimetric method. Adsorption capacity toward the gas and porous structure of the sorbent after two cycles remained practically unchanged. However, a small mass loss of the hybrid material was noticed during each regeneration step. Reason of the loss is explained on the basis of thermogravimetric and temperature-programmed desorption measurements.

New preparation method of rutile phase TiO2 revealing photocatalytic activity under visible light is described. The photocatalysts were prepared using sol–gel synthesis followed by a flash combustion at 850 °C. As found, addition of glycerol to the titanium isopropoxide during sol–gel synthesis strongly influences size of TiO2 crystallites. Rutile-type TiO2 obtained showed ability to degrade photocatalytically phenol under visible light. Effectiveness of the mineralisation of phenol was comparable or insignificantly higher than these of commercial TiO2 samples: Evonik P25 and R-001.