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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.

This paper examines the synthesis of the ZnO/carbon spheres composites using resorcinol—formaldehyde resin as a carbon source and zinc nitrate as a zinc oxide source in a solvothermal reactor heated with microwaves. The influence of activation with potassium oxalate and modification with zinc nitrate on the physicochemical properties of the obtained materials and CO2 adsorption capacity was investigated. It was found that in the case of nonactivated material as well as activated materials, the presence of zinc oxide in the carbon matrix had no effect or slightly increased the values of CO2 adsorption capacity. Only for the material where the weight ratio of carbon:zinc was 2:1, the decrease of CO2 adsorption capacity was reported. Additionally, CO2 adsorption experiments on nonactivated carbon spheres and those activated with potassium oxalate with different amounts of zinc nitrate were carried out at 40 °C using thermobalance. The highest CO2 adsorption capacity at temperature 40 °C (2.08 mmol/g adsorbent) was achieved for the material after activation with potassium oxalate with the highest zinc nitrate content as ZnO precursor. Moreover, repeated adsorption/desorption cycle experiments revealed that the as-prepared carbon spheres were very good CO2 adsorbents, exhibiting excellent cyclic stability with a performance decay of less than 10% over up to 25 adsorption-desorption cycles.

Titanium dioxide mixed with reduced graphene oxide (rGO) has been tested in the photoproduction of hydrogen using UV light from water-ethanol combination in gas phase. The presence of the reduced graphene oxide in TiO2/rGO nanocomposites affects the physicochemical properties of hybrid materials, thus enhancing the photocatalytic activity. The obtained catalysts have been characterized for physical-chemical properties using X-ray diffraction (XRD), UV–vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM)/high-resolution transmission electron microscopy (HRTEM), and Brauner Emmett Teller (BET). The best photocatalyst has been obtained by mixing anatase and rGO (10 wt%) after calcination at 700 °C. This TiO2-rGO composite exhibited the highest performance with a hydrogen photogeneration rate of 9.5 mmol h-1 g-1.

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 study presents a simple method of titanium dioxide modification by carbon. Monosaccharide (fructose) was used as the carbon source. The pressure modification using fructose caused enhancement of antibacterial efficiency. It was found that prepared photocatalysts were capable of total Escherichia coli and Staphylococcus epidermidis inactivation under the UV-A and artificial solar light, which was attributed to the changes of the surface characteristics, i.e. zeta potential. The best results were observed for the TiO2-F-1%-100 photocatalyst, containing 0.51 wt% of carbon with less negative zeta potential (−18.08 mV). The two-stage photocatalytic mechanism of bacteria destruction by OH radicals was found. Obtained data suggest that fructose-modified photocatalysts may be useful in the development of alternative water disinfectants.

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.

Selenium is one of the trace elements playing a crucial role in a proper function of living organisms. Selenium intake varies, largely based on the selenium content of food. The daily Se intake recommended for adults amounts to 55 μg per day. The mean level of selenium in the population varies considerably between countries. Recent studies on the selenium dietary intakes in Poland showed that it is not sufficient to meet the daily requirement for this microelement so it is strongly recommended to employ selenium supplementation. The commercial product SEL-BRCA1® being a selenium diet supplement was subjected to chemical and microbial analysis to determine its stability in storage time and conditions. Basing on the obtained results it can be stated that the stability of studied supplement, stored in the closed bottles, can be confirmed for the period of time up to 45 months after the production date and it is not recommended to store opened bottles for the period of time longer than 12 months. The studied supplement showed a very high microbial stability what underscores its usefulness as human medicines.

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.

This work reports on the preparation and examination of biomass-derived activated carbons featuring high CO 2 adsorption capacity. A detailed micropore structure analysis and surface characterization were performed using nitrogen adsorption isotherms at 77 K and carbon dioxide isotherms at 273 K. At 273 K and 1 bar only micropores in the range of 0.30–0.86 nm were mainly effective for CO 2 adsorption. When the temperature increased to 298 K, the ranges of effective micropores for CO 2 adsorption at 1 bar decreased to 0.30–0.33 nm. For the typical flue gas conditions (partial pressure of CO 2 0.15 bar), micropores in the range of 0.30–0.57 nm were mainly effective for CO 2 adsorption. The precursor had a strong effect on the textural properties of the resulting carbon and CO 2 adsorption. Activated carbon prepared from pomegranate peels showed the highest CO 2 adsorption and selectivity (CO 2 /N 2 ). The experimental isotherm data of activated carbon produced from pomegranate peels were analysed using Langmuir, Freundlich, Sips, and Toth isotherm equations. The fitting details showed that the multitemperature Toth equation is a powerful tool to mathematically represent CO 2 isotherms on activated carbon produced from pomegranate peels. The isosteric heat of adsorption was calculated by fitting the Toth equation to the adsorption isotherms and applying the Clausius–Clapeyron equation. The value of the heterogeneity coefficient and isosteric heat of adsorption suggested heterogeneous interactions between CO 2 and sorbent surface.

Three commercial activated carbons (ACs) supplied by Carbon, Norit and Desotec were modified by acid treatments. A significant CO 2 capacity improvement of up to 36% was achieved. It was found that higher CO 2 uptakes were related to removal of inorganic impurities i.e. mineral matter and increase of the submicropores volume i.e. smaller than 0.8 nm. Sorbents were thoroughly characterized in terms of texture and chemical composition. CO 2 uptake was determined by BET isotherm measurement carried out at 273 K and pressure of up to 0.95 bar. The enhancement of CO 2 uptake was observed especially for ACs with the highest initial mineral matter content. It was found that mineral matter in ACs plays the role of a ballast and additionally blocks adsorption places and submicropores volume thus lowers CO 2 uptake. On the other hand it was proven that mineral matter may prevent the structure from collapsing and thus can stabilize high SSA. The AC surface oxidation effect on CO 2 uptake was determined by comparison of ACs treated with HCl and HNO 3 . Both acids remove mineral matter content to the same degree, but detailed X-ray photoelectron spectroscopy (XPS) study revealed that in case of HNO 3 treatment, AC surface was more oxidized which correlated with higher CO 2 uptake. However observed uptake increase was attributed to increase of the submicropores volume.

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.

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.

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.

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.

The conducted studies were focused on the development of the gypsum material exhibiting self-cleaning properties. To this end, the raw gypsum was mixed with unique TiO2-based photocatalysts, previously modified by nitrogen and/ or carbon doping. The photocatalytic activity of the obtained gypsum plasters was evaluated trough the degradation of model organic compound (Reactive Red 198) under UV-vis irradiation. The impact of the photocatalysts presence on the physicochemical properties of the obtained gypsum plasters was evaluated. Furthermore, the role of non-metals presence on the photocatalytic properties of the TiO2 was determined. It was confirmed that the addition of N,C co-modified titanium dioxide into gypsum bestows this material with self-cleaning properties. The highest dye removal rate was displayed by the gypsum plaster containing optimal amount (10 wt%) of co-modified TiO2/N,C photocatalyst, after 20 hours of UV-vis irradiation.

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.

Aim of this research is to obtain effective, molasses based activated carbon, which would adsorb big amounts of CO2. Molasses was mixed with KOH. Weight ratio of dry materials was 1:1 (AC1, AC3) and 1:2 (only AC2). Homogeneous mixture was obtained. Material was left for 3 h at 25 ◦C. Drying lasted for 12 h at 200 ◦C, and the material was grounded. The mixture was pyrolysed at 750 ◦C, under constant flow (18 dm/min) of nitrogen. The material was grounded again. Then, powder was washed with water, until filtrate was neutral, which took about 5 dm of water. AC3 was washed with 1 dm of water. After drying, materials were soaked in HCl (0.1 mol/dm) for 19 h, and washed with water, until filtrate was neutral. CO2 adsorption was performed under high pressure up to 40 atm, at 40 ◦C. Specific surface area (according to the Brunauer–Emmett–Teller equation) was calculated for AC1, AC2 and AC3 and it is respectively 1985, 1967, and 2026 m/g, micropore volume — 0.714, 0.707, and 0.728 cm/g and it was between 75% and 89% of total pore volume. The excess uptake at 40 atm pressure was as follows: AC1 — 14.02 mmol/g, AC2 — 12.75 mmol/g, and AC3 — 15.79 mmol/g.

A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of "green energy" production.

In this study, sorption of gaseous SO2 on nitrogen-modified titanium dioxide (TiO2/N) materials was investigated. The TiO2/N materials were prepared by thermal modification of commercial TiO2 in gaseous ammonia flow. First, TiO2 was calcined at 100-700 °C (Δt = 200 °C). The obtained samples were then rinsed with water to remove the residual ammonium groups adsorbed on the TiO2 surface. The influence of modification temperature, BET surface area, pore volume and nitrogen content on the efficiency of SO2 sorption on TiO2 surface was discussed. The best result was obtained for nitrogen-modified material that is heat treated at 100 °C. The total sorption capacity calculated for this sample was 20.96 mg SO2/1 g TiO2. It was shown that TiO2 modified with nitrogen at low temperature can be a very effective sorbent in capturing SO2 particles.

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.

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.

Nanoparticles of nitrogen-modified TiO2 (N-doped TiO2) calcined at 300°C and 350°C, have been prepared with and without water rinsing. Samples were characterized by x-ray diffractrometry (XRD) and optical spectroscopy. The electron paramagnetic resonance (EPR) spectra from centers involving oxygen vacancies were recorded for all samples. These could be attributed to paramagnetic surface centers of the hole type, for example to paramagnetic oxygen radicals O−, O2−etc. The concentration of these centers increased after water rising and it further increased for samples annealed at higher temperature. Additionally, for samples calcined at 300°C, and calcined at 350°C and rinsed, the EPR spectra evidenced the presence of magnetic clusters of Ti3+ ions. The photocatalytic activity of samples was studied towards phenol decomposition under unltraviolet-visible (UV-Vis) irradiation. It was found that, in comparison to the starting materials, the rinsed materials showed increased photocatalytic activity towards phenol oxidation. The light absorption (UV-Vis/DRS) as well as surface Fourier transform infrared/diffuse reflectance spectroscopy (FTIR/DR) studies confirmed a significantly enhanced light absorption and the presence of nitrogen groups on the photocatalysts surfaces, respectively. A significant increase of concentration of paramagnetic centers connected with oxygen vacancies after water rising has had an essential influence on increasing their photocatalytic activity.

Three different methods of modification (impregnation, photodeposition and mechanical alloying) were used to obtain a series of novel Cu/TiO2 photocatalysts. Two Cu(II) salts: (Cu(NO3)2 and Cu(CH3COO)2) as well as metallic copper were applied as modifying agents. The influence of the modification procedure and copper precursor on the physico-chemical properties and photoactivity of the photocatalysts towards formation of useful hydrocarbons from acetic acid were especially investigated. Various gaseous products were identified during the photocatalytic process: CH4, CO2, C2H6, C3H8 and H2. The amounts of those compounds were strongly dependent on the photocatalyst type. Crucial features affecting the photoactivity of the obtained materials were the amount of Cu and phase composition of the samples. Nonetheless, most of the Cu/TiO2 photocatalysts revealed significantly improved activity in the photocatalytic generation of useful aliphatic hydrocarbons and hydrogen compared to the crude TiO2 or commercial TiO2 P25.

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.

Porous carbons obtained from poly(ethylene terephtalate) contained in a mixture with either MgCO3 or Mg(OH)2 were examined as adsorbents for removal of humic acid from water. Adsorption of the model contaminants is discussed in relation to the textural parameters of the obtained carbon materials. Pore structure parameters of the carbonaceous materials were strongly influenced by preparation conditions including temperature and relative amounts of the inorganics used during preparations as template. Porous carbons prepared revealed a potential to purify water from the model contaminant of high molecular weight. The results presented confirmed a key role of mesoporosity in the adsorption of humic acid. Fluorescence spectroscopy was confirmed to be an useful method to evaluate concentration of humic acid in water.

Samples of TiO 2 , calcined at 350 °C, 400 °C, 450 °C and 500 °C, have been prepared without and with water rinsing. The crystallite sizes were determined to be below 32 nm for all types of samples. Temperature dependence of magnetic resonance spectra of the obtained samples has been investigated. The electron paramagnetic resonance (EPR) spectra of free radicals were recorded for all samples, non-rinsed and water-rinsed, centered between g eff = 2.0027(3) and g eff = 2.0032(3) with linewidths Δ H pp = 5(1) G and Δ H pp = 8(1) G. The temperature dependence of the EPR integrated intensities has shown the presence of different relaxation processes operating in high temperature range, which could have arisen due to different concentrations of conducting electrons. For the water-rinsed sample annealed at 400 °C the ferromagnetic resonance (FMR) spectrum of magnetic agglomerates was recorded. Very intense reorientation processes of a correlated spin system have been observed in different temperature ranges. The EPR spectra of trivalent titanium ions were registered in all samples. The number of oxygen vacancies could have increased, possibly involving complexes and agglomerates containing trivalent titanium ions.

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.

In this work photoluminescence together with photocatalytic activity of nanocrystalline TiO2 thin films doped with different amount of Tb are described. Thin films were manufactured by high energy reactive magnetron sputtering process. Structural investigation has shown that all as-deposited films had rutile structure. Doping of the matrix resulted in decrease of the average crystallite sizes from 8.7 nm to 6.6 nm for undoped and doped films, respectively. This testifies about densification of the matrix structure by Tb-doping. Photoluminescence measurements of TiO2:Tb films have revealed light emission in wide spectral range (from 350 up to 700 nm) with a strong green luminescence at 545 nm. In order to explain Tb3+ luminescence phenomenon in TiO2-rutile matrix possible energy transfer mechanisms are discussed. The photocatalytic activity of nanocrystalline films was determined based on phenol decomposition during UV-light irradiation. Results showed that all manufactured films were photocatalytically active and their activity was growing with increase of terbium amount. The highest decomposition rate was observed for the TiO2 thin films with Tb amount of 2.6 at. %.

This study reports the generation of combustible C1–C4 hydrocarbons and hydrogen via photocatalytic decomposition of acetic acid in N2 atmosphere. A new photoreactor design based on a hybrid suspended/supported photocatalytic system was proposed. The TiO2 photocatalyst was immobilized on a glass fabric which was mounted in the photoreactor containing additionally TiO2 suspended in the reaction solution. The photodecomposition took place in both liquid and gaseous phases. The configuration allowed for the diffusion of CH3COOH molecules from the reaction solution to the upper part of the fabric where the photoreaction proceeded. Moreover, decomposition of acetic acid molecules which evaporated from the solution took place. An improvement of the effectiveness of methane generation for about 90% compared to the suspended system and for about 50% in comparison with the immobilized system alone was observed. The amounts of the gases evolved after 27 h of the process conducted in the novel photoreactor were equal to 1.95, 1.66, 0.304, 0.059, 0.0014 and 0.007 mmol (5.57, 4.74, 0.87, 0.17, 0.004 and 0.02 mmol/mol CH3COOH) for CH4, CO2, C2H6, C3H8, C4H10 and H2, respectively. The observed improvement of the process efficiency was attributed to: (i) simultaneous CH3COOH decomposition in liquid and gaseous phases and (ii) photoreduction of CO2 to CH4.

Porous carbons loaded with MgO, prepared through one-step process from mixtures of poly(ethylene terephthalate) and natural magnesite, were examined as sorbents for SO 2 gas contained in air at low temperature. Influence of pore structure, inorganics loading, humidity, and temperature, on the efficiency of the gas removal is presented and discussed. Performance of the hybrid sorbent materials increased along with MgO loading, temperature of the bed, and moisture content. As found, removal of SO 2 by the prepared sorbents is due to synergic effect involving adsorption on porous material and chemical interaction between the gas and MgO. Possible mechanism of the SO 2 removal process is proposed on the basis of XPS spectroscopy measurements.

a b s t r a c t A one-step, hydrothermal method for the synthesis of nitrogen, carbon co-doped titanium dioxide (N,C TiO2) photocatalysts is demonstrated. The incorporation of nitrogen from ammonia and car- bon from alcohols with different chain length (methanol, ethanol, isopropanol, 1-butanol, 2-butanol, tert-butanol) used as carbon precursors was confirmed by FTIR/DRS and XPS analyses. The UV-vis/DR absorption spectra of the modified photocatalysts extended into the visible. XRD, BET and Zeta Sizer- Nano techniques were used for the characterization of the modified photocatalysts. The crystallite size of N,C TiO2 was not affected by the nature of the alcohol or the pressure acquired during the modification process but surface area, particle size (crystal agglomerate) and anatase content increased with synthesis pressure. In contrast with other studies in literature, the photoactivity of the different synthesized mate- rials was evaluated at a constant volumetric rate of photon absorption (VRPA) in an annular photoreactor. This innovative method allows the evaluation of the intrinsic photoactivity of each material. As a result, the effect of N,C-co-modification on the TiO2 photoactivity was evaluated without interference from the amount of radiation absorbed by each suspended powder since the total radiant energy absorbed by each slurry suspension was kept constant. Phenol decomposition confirmed that activity increased with the chain length of the alcohol precursor. The highest intrinsic photoactivity was for N,C TiO2 pre- pared from 2-butanol, and 1-butanol as carbon precursor which also exhibited much stronger resistance to deactivation during multiple catalyst reuse compared to pristine TiO2 and commercial Degussa P25 photocatalysts.

Photocatalytic activity of nitrogen modified TiO 2 calcined at temperatures of 100–350 °C toward 3-chlorophenol (3-CP) degradation was studied. In the experiments the fluorescent UV lamp and the incandescent lamp emitting mainly Vis light were applied. The degradation efficiency was evaluated on a basis of changes of 3-CP, total organic carbon and Cl − concentration. A significant improvement of the photoactivity of the N-modified photocatalysts compared to the reference sample was observed. The rate of 3-CP degradation increased with the calcination temperature, and the highest efficiency was achieved for TiO 2 annealed at 350 °C. After 5 h of UV irradiation in the presence of TiO 2 /N-350 and reference TiO 2 the 3-CP concentration decreased for 77% and 36%, respectively. The 3-CP removal after 24 h of Vis irradiation was 30% and 12% for the N-modified and reference samples, respectively. The 3-CP decomposition and mineralization were greatly influenced by pH of the solution, achieving the highest rate at pH 7 for the modified photocatalysts. An increase of the calcination temperature resulted in an increase of the rate of OH formation. The photocatalytic activity of the N-modified TiO 2 remained unchanged during repeated photocatalytic degradation cycles.

Samples of TiO2, calcined at 100 °C (type 1) and 200 °C (type 2), have been prepared without and with water rinsing. The crystallite sizes determined by XRD method were smaller than 15 nm for both types of samples. Magnetic resonance spectra of the obtained samples have been studied in 230–300 K temperature range. Before rinsing no magnetic spectra were observed but after rinsing the magnetic response appeared in form of a resonance line centered at geff ∼ 2.54 with linewidth ΔHpp ∼ 460 G in type 1 samples and geff ∼ 2.26 with linewidth ΔHpp ∼ 220 G in type 2 samples. The integrated intensity of the observed spectrum was two times greater in the type 1 sample. The resonance line could be attributed to the localized magnetic moments in the correlated spin system formed during rinsing. The rinsing resulted also in higher photocatalytic properties under UV–VIS irradiation. It is suggested that the number of oxygen vacancies increases after rinsing and as they are involved in the formation of low oxidation states of titanium ions, they could be responsible for the appearance of the observed magnetic properties.

Photocatalytic mineralisation of humic acids using TiO2 modified by tungsten dioxide/ hydrogen peroxide TiO2 of anatase structure was modified by tungsten dioxide and H2O2 in order to obtain WO3-TiO2 photocatalyst with enhanced photocatalytic activity under both, UV and artificial solar light irradiations. WO2 was dissolved in 30% H2O2 and mixed with TiO2 in a vacuum evaporator at 70°C. Such modified TiO2 was dried and then calcinated at 400 and 600°C. The prepared samples and unmodified TiO2 were used for the photocatalytic decomposition of humic acids (Leonardite standard IHSS) in the aqueous solution under irradiations of both, UV and artificial solar light. Modification of TiO2 with tungsten dioxide and H2O2 improved separation of free carriers in TiO2 which resulted in the increase of OH radicals formation. Calcination caused an increase of anatase crystals and higher yield in OH radicals. The uncalcined samples showed high abilities for the adsorption of HA. Combination of adsorption abilities and photocatalytic activity of photocatalyst caused that the uncalcined TiO2 modified with WO2/H2O2 showed the shortest time of HA mineralisation. The mineralisation of HA under the artificial solar light was much lower than under the UV. It was proved that, although OH radicals are powerful in the decomposition of HA, adsorption can facilitate the contact of the adsorbed molecules with the photocatalyst surface and accelerate their photocatalytic decomposition.

Carbon modified TiO 2 was used for Methylene Blue (MB) dye decomposition under artificial solar light irradiation. TiO 2 /C photocatalysts were prepared by modification of commercial anatase TiO 2 (Z.Ch. POLICE Company, Poland) in different alcohols atmosphere at 120 °C for 4 h under elevated pressure. Termogravimetric analyses shown that the amount of carbon present in TiO 2 depends on amount of carbon in used alcohols. Modification does not change the specific surface area of photocatalysts. Used low temperature and elevated pressure conducted to change the amorphous phase presented in pristine material to anatase structure and also conducted to increasing of crystalline size of anatase. The optimal amounted of carbon needed to increasing the activity of photocatalyst under visible light irradiation amounted 0.02% of mass.

Mixtures of poly(ethylene terephthalate) (PET) with magnesium compounds including carbonate, hydroxide, and oxide, with different weight ratios of the components, were subjected to thermogravimetric measurements up to 850 °C in argon atmosphere. For reference, pure components of the examined mixtures were analyzed at the same conditions. During the heating, PET underwent carbonization and magnesium carbonate and hydroxide decomposed to MgO with evolution of gaseous products (CO2 and/or H2O). As found, carbon yields calculated from the residual masses depended on the qualitative and quantitative composition of the starting mixture. Yields of carbon obtained from PET mixed with MgO did not depend on MgO/PET ratio. However, yields of carbon formed through pyrolysis of PET contained in the mixture with either magnesium carbonate or magnesium hydroxide were in general higher and depended on the weight ratio of components in the starting material. Reasons of these inconsistent results are discussed and explained. An influence of gasification of char on the carbon yield is explained.

Photocatalysis is often used for the decomposition of organic compounds in water, e.g., for dye decomposition. There are many problems with calculating the photocatalytic activity of photocatalysts during dye decomposition, especially in the case of photocatalysts with a high adsorption capacity because it is difficult to say whether a dye is photocatalytically decomposed or whether it is only adsorbed on photocatalyst surface. In both cases, the dye disappears from the water, but the optimal situation is when the dye is both adsorbed and decomposed on photocatalyst surface. Moreover, it is problematic to compare the photocatalytic activity of different photocatalysts when they have strong adsorption capacity. In this study a new method of measuring photocatalytic activity of photocatalysts with high adsorption capacity is presented. Reactive Red (monoazo) and Direct Green (poliazo) dyes were used to determine adsorption capacity and photocatalytic activity of commercial TiO2 Degussa P25, anatase TiO2 and carbon modified anatase TiO2.

A photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid under N2 atmosphere is presented. The photocatalysts were prepared from a crude TiO2 modified with Fe(NO3)3 and calcinated at the temperatures of 400–600 °C in argon atmosphere. The main gaseous products of CH3COOH decomposition were CH4 and CO2. Moreover, ethane, propane and hydrogen were also detected. The most active photocatalyst towards CH4 generation was TiO2 containing 20 wt.% of Fe calcinated at 500 °C. The optimum loading of this photocatalyst was 1 g/dm3. After 5 h of the process the amount of CH4, CO2, C2H6, C3H8 and H2 evolved was 0.458, 0.450, 0.025, 0.003 and 0.013 mmol, respectively. An increase of CH3COOH concentration from 0.01 to 1 mol/dm3 resulted in an increase of methane production. A further increase of CH3COOH concentration up to 10 mol/dm3 led to a decrease of the process efficiency. The stability of the prepared photocatalysts against photocorrosion was very high. The amount of dissolved Fe did not exceed 0.17 wt.% of the total Fe present in a catalyst sample.

In this work photocatalytic properties of TiO2 thin films doped with different amount of Tb have been described. Thin films were prepared by high energy reactive magnetron sputtering process. Comparable photocatalytic activity has been found for all doped TiO2 thin films, while different amounts of Tb dopant (0.4 and 2.6 at. %) results in either an anatase or rutile structure. It was found that the terbium dopant incorporated into TiO2 was also responsible for the amount of hydroxyl groups and water particles adsorbed on the thin film surfaces and thus photocatalytic activity was few times higher in comparison with results collected for undoped TiO2 thin films.

The present study was focused on the photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid under N 2 atmosphere. The photocatalysts applied in the study were prepared from a crude TiO 2 modified with Fe(CH 3 COO) 2 and calcinated at the temperatures of 400, 500 or 600 °C in argon atmosphere. In order to compare the results, the commercially available photocatalyst AEROXIDE ® P25 (Evonik, former Degussa, Germany) was also used in the experiments. The photocatalysts were characterized by UV–vis/DR and FTIR spectroscopy, N 2 adsorption–desorption at 77 K and XRD measurements. The crystallite size of anatase was in the range of 7–28 nm and the anatase over rutile ratio was from 82:18 to 95:5. The main gaseous products of CH 3 COOH decomposition were CH 4 and CO 2 . Moreover, ethane, propane and hydrogen were detected in the gaseous reaction mixtures. The most active photocatalyst towards CH 4 generation was TiO 2 containing 20 wt.% of Fe calcinated at 500 °C. After 27 h of the process conducted with this catalyst the amount of CH 4 , CO 2 , C 2 H 6 , C 3 H 8 and H 2 evolved was 3.36, 2.97, 0.13, 0.01 and 0.14 mmol/mol CH 3 COOH, respectively. It was concluded that photocatalytic decomposition of organic compounds, such as acetic acid, under N 2 atmosphere could be regarded as a method of production of environmentally friendly “photo-biogas”; however, since the yield of hydrocarbons formation was very low, deep and extensive investigations are still necessary in order to improve the efficiency of the process.

Nanoporous carbons with a high surface area were directly prepared from various carbon precursors without any stabilization and activation processes. Various carbon precursors, including poly(vinyl alcohol), poly(ethylene terephthalate), polyimide, coal tar pitch, were used and MgO itself, Mg acetate, Mg citrate, Mg gluconate and Mg hydroxy-carbonate were employed as MgO precursor. Carbon precursor was mixed with MgO precursor in different ratios either in powder (powder mixing) or in solution (solution mixing), and heat-treated at 900 °C in inert atmosphere. MgO formed in the carbonization products was dissolved out using a diluted acid. BET surface area of the carbons obtained could be reached to high value, as high as 2000 m2/g, even though any activation process was not applied. Most carbons prepared through this method were rich in mesopores. Size of mesopores in the resultant carbons was tunable by selecting MgO precursor and relative volume between mesopores and micropores was controlled by carbon precursor.

The process of removal of two azo dyes (Reactive Red 198 and Direct Green 99) from water was investigated. The adsorption of azo dyes onto surfaces of pristine TiO2, P25 and carbon-modified TiO2 (at 120 °C for 24 h) was presented. The Freundlich model of adsorption isotherm was found for pristine TiO2 and TiO2-P25. Modification of TiO2 by carbon lead to the change from the Freundlich model to the Langmuir model of adsorption isotherm. For the TiO2-C photocatalyst the adsorption capacity was determined, which was almost two times higher for Direct Green 99 than Reactive Red 198 dyes. As a result we observed the increase of photocatalytic activity of carbon-modified TiO2 photocatalyst.

Porous carbon materials were prepared by heating of a PET [poly(ethylene terephtalate)] and magnesium carbonate (3MgCO3·Mg(OH)2·3H2O) mixture under Ar gas flow, followed by acid washing. The inorganic component of the mixture underwent thermal decomposition with formation of MgO and evolution of gaseous products including CO2 and H2O. Influence of the magnesium compound mixed with PET, and carbonization temperature on the pore structure of carbonaceous material is presented. As found, porosity of prepared materials depended on magnesium carbonate loading in the starting mixture and on heating temperature. The impact of CO2 and H2O evolved during heating on the pore structure is discussed, and a mechanism of pore formation is proposed.

Carbon-modified photocatalyst was obtained by modification of the commercial anatase TiO2 (Police, Poland) in a pressure reactor in an ethanol atmosphere at 120 °C for 4 h. The activity was tested during monoazo dye decomposition under UV light irradiation (Reactive Red 198 with λmax = 516 nm). The reusability aspect of carbon-modified TiO2 photocatalysts was predominantly studied. Using the additional aeration process caused to stabilization the “decolourisation time” of aqueous solution of Reactive Red 198. To compare the activity of obtained material the commercial TiO2 P25 was used and only on its surface the presence of carbon deposits were observed.

A new photocatalyst was obtained by modification of commercial anatase TiO2 (Police, Poland) in a pressure reactor in an ethanol atmosphere at 120 °C for 4 h. The photocatalytic activity of the new material was tested during three azo dyes decomposition: monoazo (Reactive Red 198), diazo (Reactive Black 5) and poliazodye (Direct Green 99). The obtained photocatalyst had new bands at 1,440 cm−1 attributed to CO groups. UV–Vis/DR spectra of the photocatalyst also were changing and had an insignificant decrease in the visible region of the spectra. The amount of hydroxyl radicals produced on carbon-modified TiO2 was a little higher than for the pristine one. The carbon modification also changes the Freundlich model of dyes adsorption to Langmuir model of adsorption. Additionally, it increases the monolayer capacity of modified TiO2. As a result we observed a clear increase of the photocatalytic activity of carbon-modified TiO2 sample.

Carbon modified TiO2 photocatalysts for water purification Carbon can form different structures with TiO2: carbon-doped TiO2, carbon coated TiO2 and composites of TiO2 and carbon. The presence of carbon layer on the surface of TiO2 as well as the presence of porous carbon in the composites with TiO2 can increase the concentration of organic pollutants on the surface of TiO2, facilitating the contact of the reactive species with the organic molecules. Carbon-doped TiO2 can extend the absorption of the light to the visible region by the narrowing of the band gap and makes the photocatalysts active under visible light irradiation. TiO2 loaded carbon can also work as a photocatalyst, on which the molecules are adsorbed in the pores of carbon and then they undergo the photocatalytic decomposition with UV irradiation. Enhanced photocatalytic activity for the destruction of some organic compounds in water was noticed on the carbon coated TiO2 and TiO2 loaded activated carbon, mostly because of the adsorptive role of carbon. However, in carbon-doped TiO2, the role of carbon is somewhat different, the replacement of carbon atom with Ti or oxygen and formation of oxygen vacancies are responsible for extending its photocatalytic activity towards the visible range.