H2 Gas Production Research Articles

One-pot fabrication of open-spherical shapes based on the decoration of copper sulfide/poly-O-amino benzenethiol on copper oxide as a promising photocathode for hydrogen generation from the natural source of Red Sea water

Abstract Harnessing green hydrogen production from natural Red Sea water offers an innovative solution to address energy challenges. A one-pot fabrication method is used to create novel nanocomposite thin films with open-spherical shapes, utilizing copper sulfide/poly-O-amino benzenethiol decorated on copper oxide as a promising photocathode. After thorough analysis, a unique morphology characterized by open spherical shapes is projected, which contributes to improved optical absorption. The bandgap of the nanocomposite is 1.17 eV, enabling efficient absorption of light across the entire optical spectrum, extending up to 950 nm. Utilizing Red Sea water as an electrolyte, the generated J ph serves as an indicator of H2 gas production. The substantial J ph value of −0.82 mA cm−2 is achieved at −0.85 V under light illumination. Furthermore, J ph values exhibit variability, starting at −0.58 mA cm−2 (at 730 nm) and increasing to −0.75 mA cm−2 at a wavelength of 340 nm. The estimated hydrogen gas production rate reaches 1.5 µmole h−1 cm−2, translating to an impressive 15 µmole h−1 for every 10 cm². This remarkable rate underscores the effectiveness of the photocathode, especially given its fabrication through a single-step process that is suitable for mass production. In addition, its cost-effectiveness further enhances its appeal as a viable solution for renewable energy production for hydrogen gas generation from seawater.

Exploring the potential of cobalt-based catalysts in the methane dry reforming for sustainable energy applications

Cobalt-based powder catalysts with different Co loadings were synthesized via wet impregnation using MgAl2O4 spinel as support. The catalytic properties of the solids were evaluated in the dry-reforming methane at different reaction temperatures and two CH4:CO2 ratios. The catalyst with higher cobalt content (13 %) presented superior performance due to increased Co0 species availability, confirmed by XPS analysis. Besides, this catalyst displayed remarkable resistance to carbon deposition at 550 °C and CH4:CO2 1: 1 ratio. In-situ DRIFT measurements demonstrated the formation and transformation of carbonate and hydrogen carbonate species during the DRM reaction, highlighting efficient CO2 and CH4 activation on the catalyst surface. Based on this data, a structured catalyst was deposited on top of the FeCrAlloy monolith, which was active, stable, selective for H2, and resistant against on/off cycles. Compared with the powder catalyst, the structured system displayed higher catalytic activity, possibly due to higher reducibility of metal species and improved heat transfer provided by the FeCrAlloy substrate. The results highlight the potential of Co-based structured catalysts for H2 or synthesis gas production processes.

Eminent Red Sea water hydrogen generation via a Pb(ii)-iodide/poly(1H-pyrrole) nanocomposite photocathode

Abstract The development of a photocathode based on a Pb(ii)-iodide/poly(1H-pyrrole) porous spherical (PbI2/P1HP PS) nanocomposite has been successfully achieved in the efficient production of H2 gas from Red Sea water. The distinguishable spherical and porous shapes of these nanocomposites are characterized by a minimum surface measuring approximately 25 nm. This structural configuration, coupled with the nanocomposite’s substantial light absorbance, results in a modest bandgap of 2.4 eV. This turns the nanocomposite into a highly promising candidate for renewable energy applications, particularly for H2 gas generation from natural sources like Red Sea water. The economic viability of the PbI2/P1HP PS nanocomposite, relying on a glass substrate, mass production, and straightforward fabrication techniques, adds to its promising profile for H2 gas evolution. The photocathode exhibits significant potential for H2 gas production, with a notable current density (J ph) value of 1.0 mA·cm−2 in a three-electrode cell configuration. The IPCE reaches 3.1%, reflecting the successful evolution of 24 µmol·h−1 10 cm2 of the photocathode. Importantly, the use of natural Red Sea water as an electrolyte underscores a key feature for H2 gas production: utilizing freely available natural resources. This aspect holds considerable promise for industrial applications, emphasizing the environmentally sustainable nature of the photocathode.

Data-driven models for the prediction of H2 generation through chemical reaction and performance evaluation of on-board hydrogen fuelled sintering tube furnace

Hydrogen is emerging as a sustainable fuel for the future. In this present work, data-driven modelling tools viz. Radial Basis Function Neural Network (RBFNN) and Least Square Fit (LSF) method, are employed to determine the rate of production of H2 gas by the chemical reaction between aluminium and water in the presence of aq. NaOH. Reactions are carried out at NaOH concentrations of 1M–5M, water temperatures 303K–333K. Hydrogen gas obtained at 333K/4M is found to have a yield of ⁓88 % of the theoretical yield. The activation energy of the reaction is found to be 57.62 kJ mol−1. The fitted models are validated with experimental results for two unknown conditions. The correlation coefficient obtained for the RBFNN model is 0.999, which indicates the high reliability of the model. On-board production of H2 gas by the chemical reaction was used for heating a sintering tube furnace. The hot products of the combustion of hydrogen and air at various fuel-air ratios were used to heat the sintering tube furnace. The maximum thermal efficiency obtained for the furnace is 76.22 % at a fuel-air ratio of 1:60 corresponds to a fuel-air equivalent ratio (λ) of 0.57.

Numerical investigation to predict the impact of pre-heated air on the tar formation of cocoa pod husk gasification in a fixed bed downdraft gasifier

Tar production is a critical aspect of gasification thermochemistry, and it hinders the widening of biofuel utilisation in several applications. Both the gasifier configuration and the operating conditions influence the quantity of tar in PG. Since temperature plays a major role, this study examines the performance parameters of a gasifier across a spectrum of input air temperatures, from 27 to 627 °C, utilising computational fluid dynamics with species transport and porous media models. Since the deviation of numerical predictions from experimental results is within 10 %, the model's validity is confirmed. CO and H2 gas production increased from 19.23 % to 27.12 % and 9.23 %–16.2 %, respectively, over the tested air temperature range; however, the variation in methane content was not significant. Furthermore, the higher heating values of PG and cold gas efficiency were found to be 5–6.8 MJ/Nm3 and 65–69 %, respectively. The study also investigates reaction rates for gasification, combustion, and volatiles' breakdown under various operating conditions. Among the tar species studied, benzene is the most concentrated at 1.6 g/Nm3, followed by toluene at 0.9 g/Nm3, with naphthalene and phenol present in comparatively smaller amounts. Furthermore, the research indicates that an appropriate temperature of gasifying medium can control tar in PG.

Exploring the potential of surface-modified alginate beads for catalytic removal of environmental pollutants and hydrogen gas generation

In this study, hydrogel beads were fabricated using alginate (Algt) polymer containing dispersed nickel phthalocyanine (NTC) nanomaterial. The viscous solution of Algt and NTC was poured dropwise into a divalent Ca2+ ions, resulting in the formation of hydrogel beads known as NTC@Algt-BDs. The surface of the NTC@Algt-BDs was further modified by coating them with different types of metal ions, yielding metal-coated M+/NTC@Algt-BDs. The adsorbed metal ions i.e., Cu+2, Ag+, Ni+2, Co+2, and Fe+3 were subsequently reduced to zero-valent metal nanoparticles (M0) by NaBH4. The prepared beads were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Initially, M0/NTC@Algt-BDs were examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among them, Cu0/NTC@Algt-BDs catalyst exhibited the highest reduction rate and therefore, investigated for reduction of different nitrophenols (NPs) and dyes, including 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), potassium ferrocyanide (PFC), congo red (CR), and acridine orange (ArO). The highest reduction rates of 2.019 and 1.394 min−1 were observed for MO and 2-NP, respectively. Furthermore, the fabricated catalysts were employed for the efficient production of H2 gas by NaBH4 methanolysis. Among which the Ag0/NTC@Algt-BDs catalyst showed excellent catalytic production of H2 gas, exhibiting the lowest activation energy (Ea) of 25.169 kJ/mol at ambient temperature. Furthermore, the impact of NaBH4 amount, and catalyst dosage on the reduction of 2-NP and H2 gas production was conducted whereas the effect of temperature on methanolysis of NaBH4 for evolution of H2 gas was studied. The amount of H2 gas was confirmed by GC-TCD system. Additionally, the recyclability of the catalyst was investigated, as it garnered significant research interest.

The Impact of Temperature on the Production of High Calorific Value Syngas using Cogasification Technology

Cogasification represents a thermochemical reaction employed to transform by combining biomass or fossil carbonaceous materials into combustible matters. Widely acknowledged as the most appealing approach among various combustible material to useful energy. This method offers significant potential for environmentally friendly energy production, boasting low carbon emissions. This study conducted gasification tests utilizing an updraft gasifier, incorporating parameters variable at 650°C to 850°C. The materials utilized consisted of a blend of Municipal-Solid-Waste (MSW) and coconut shells, maintaining a steam to biomass at 1.3. Optimum temperature at 750°C, the syngas revealed 41.30% mol CO, 20.90 mol% CO2 37.25 mol% H2, and 0.55 mol% CH4. Notably. The highest H2 gas production was achieved at this temperature. Furthermore, the net caloric value at this temperature, surpassed other variations, reaching 374.67 kJ/mol, accompanied by the generation of 11.38% of tar and 21.1% char.

The effects of synthesis gas feedstocks and oxygen perturbation on hydrogen production by Parageobacillus thermoglucosidasius

BackgroundThe facultatively anaerobic thermophile Parageobacillus thermoglucosidasius is able to produce hydrogen gas (H2) through the water–gas shift (WGS) reaction. To date this process has been evaluated under controlled conditions, with gas feedstocks comprising carbon monoxide and variable proportions of air, nitrogen and hydrogen. Ultimately, an economically viable hydrogenogenic system would make use of industrial waste/synthesis gases that contain high levels of carbon monoxide, but which may also contain contaminants such as H2, oxygen (O2) and other impurities, which may be toxic to P. thermoglucosidasius.ResultsWe evaluated the effects of synthesis gas (syngas) mimetic feedstocks on WGS reaction-driven H2 gas production by P. thermoglucosidasius DSM 6285 in small-scale fermentations. Improved H2 gas production yields and faster onset towards hydrogen production were observed when anaerobic synthetic syngas feedstocks were used, at the expense of biomass accumulation. Furthermore, as the WGS reaction is an anoxygenic process, we evaluated the influence of O2 perturbation on P. thermoglucosidasius hydrogenogenesis. O2 supplementation improved biomass accumulation, but reduced hydrogen yields in accordance with the level of oxygen supplied. However, H2 gas production was observed at low O2 levels. Supplementation also induced rapid acetate consumption, likely to sustain growth.ConclusionThe utilisation of anaerobic syngas mimetic gas feedstocks to produce H2 and the relative flexibility of the P. thermoglucosidasius WGS reaction system following O2 perturbation further supports its applicability towards more robust and continuous hydrogenogenic operation.

Indirect H2O2 synthesis without H2

Industrial hydrogen peroxide (H2O2) is synthesized using carbon-intensive H2 gas production and purification, anthraquinone hydrogenation, and anthrahydroquinone oxidation. Electrochemical hydrogenation (ECH) of anthraquinones offers a carbon-neutral alternative for generating H2O2 using renewable electricity and water instead of H2 gas. However, the H2O2 formation rates associated with ECH are too low for commercialization. We report here that a membrane reactor enabled us to electrochemically hydrogenate anthraquinone (0.25 molar) with a current efficiency of 70% at current densities of 100 milliamperes per square centimeter. We also demonstrate continuous H2O2 synthesis from the hydrogenated anthraquinones over the course of 48 h. This study presents a fast rate of electrochemically-driven anthraquinone hydrogenation (1.32 ± 0.14 millimoles per hour normalized per centimeter squared of geometric surface of electrode), and provides a pathway toward carbon-neutral H2O2 synthesis.

Stabilizing Zn metal anodes by 4-hydroxybenzaldehyde as the H* scavenger

The conventional wisdom of Zn metal anodes suggests avoiding the hydrogen evolution reactions (HER) in aqueous electrolytes since it leads to H2 production, irregular by-product precipitation, and then the quick failure of batteries. However, the HER process is thermodynamically inevitable during cycling, especially when water is the main solvent. Herein, we propose a novel H* scavenger strategy to properly utilize the HER process instead of blocking it. By coupling experimental and theoretical analysis, we reveal the positive role of 4-hydroxybenzaldehyde (HB) additives, which consume the H* produced by the Volmer step and thus suppress the Heyrovsky or Tafel step of HER. The former produces a uniform organic/inorganic solid electrolyte interphase (SEI), while the latter eliminates H2 gas production. As a consequence, HB additives enable a stable cycle life of 120 h at 30 mA cm−2 with a depth of discharge (DOD) of 51.3 % in Zn|Zn symmetric cells and an average Coulombic efficiency of 99.8 % at 2 mA cm−2 for 2460 cycles in Zn|Cu half cells. The versatility of this H* scavenger strategy is also demonstrated by extending it to other zinc salts and electrolyte additives.

Microscopic mechanism for CO2-assisted co-gasification of polyethylene and softwood lignin: A reactive force field molecular dynamics study

Co-gasification of biomass and waste plastic to produce syngas and value-added products is an attractive technology for renewable energy utilization and waste disposal. CO2 as a gasifying agent has received much attention as it can act as carbon source and oxidant in the reaction. In this paper, the feasibility and characteristics of CO2-assisted co-gasification of polyethylene and softwood lignin were explored. Simulation results showed that the lignin macromolecule began to decompose through C–O–C bond breaking and the PE chain gradually decomposed through C–C bond breaking. CO2-assisted co-gasification showed a negative synergistic effect on gas yield at the early stage, which delayed the reaction, but showed a positive synergistic effect at the late stage. The reaction between CO2 and carbon-containing fragments greatly promoted CO production. The hydrogen and hydrocarbon radicals from PE were actively involved in H2 and hydrocarbon gas production. Compared with O2-assisted co-gasification, the CO2-assisted and CO2/O2-assisted co-gasification yielded more CO, hydrocarbon gases and combustible gases and increased the lower heating value of gas product. This work sheds light on the underlying mechanisms of CO2-assisted co-gasification of polyethylene and softwood, and would be helpful for the development of this technology.

Directing Group Strategy for the Isolation of Organoselenium(VI) Benzoselenonates: Metal-Free Catalysts for Hydrogen Evolution Reaction.

The exploration of fourth-period organoelements, particularly organoseleniums in their highest VI oxidation state, is limited owing to their stability and synthesis. Herein, the isolation of a new class of quinolinyl-embedded, hexavalent selenium(VI) benzoselenonates has been discussed and further evaluated for a metal-free electrocatalytic hydrogen evolution reaction (HER). The Se(VI) benzoselenonates exhibited high Faradaic efficiency (F.E.) of metal-free H2 gas production up to 86% with a very good turnover number (TON) up to 43 and moderate overpotential (η) of 500 mV; in the presence of mild acetic acid source in a less deprotonating DMF solvent. Taken together with various (NMR, UV-vis, and EPR) spectroscopic and DFT computation studies, a plausible HER pathway is proposed, which suggests that the electrochemical reduction of quinolinyl ring is the initiation step and Se(VI) acts as the reaction site by involving a hydridic type of intermediate for the electrochemical H2 gas generation.

Hydrogen-rich syngas production from acetic acid as bio-oil model compound: Effect of intermediate phases (La2NiO4, La2O3 and Ni) of LaNiO3 catalyst

In biomass gasification, bio-oil is the main component of the condensable by-products. It is considered an attractive source for H2 production via steam reforming. This study conducted acetic acid as a bio-oil model compound with LaNiO3 perovskite catalyst due to its high oxygen vacancies and active sites. However, the perovskite structure of LaNiO3 catalysis can be destroyed by produced H2 gas, forming additional phases, including La2NiO4, La2O3 and Ni. The LaNiO3 and different phases were synthesized via a sol-gel method to probe its contribution and interaction with the H2 gas produced from steam reforming of acetic acid. Through 300 min of reaction in steam to carbon (S/C) ratio of 3, the results showed that reduced-LaNiO3 has stable H2 gas production, while the other phases decrease with time. In particular, CH4 is the main composition with the La2O3 phase. A series of characterization techniques, such as XRD, BET, XPS, SEM, TG, H2-TPR and (CO2 and O2)-TPD, were utilized to investigate fresh and used samples. The results showed that the LaNiO3-reduced phase has high oxygen storage capacity, oxygen mobility, oxygen vacancies and surface area, preventing coke deposition. In contrast, the LaNiO3 and La2NiO4 phases have poor coke deposition resistance.

Enhanced H2 gas production from steam gasification of a winery waste through CO2 capture by waste concrete fines and use of alkali catalysts

This study focused on production of a high yield of hydrogen as a clean energy source from a winery waste, through steam gasification. The experiments were conducted in a fixed bed system and a thermal analysis-mass spectrometer unit. Quarry dust waste from cement industry was used to capture carbon dioxide emissions and alkali carbonates of K, Li and Na were used as catalysts. Based on the optimum conditions derived in a previous work, the effects of sorbent/biomass ratio, catalyst loading and temperature on conversion, gas composition and quality, cold gas efficiency and yield of high purity hydrogen were investigated. The amount of carbon dioxide captured up to 700 °C was 92–97 % and at 750 °C about 83 %. At Ca/C = 1 the molar fraction of hydrogen in the product gas was 74.8 %. Sodium carbonate exhibited a better overall catalytic activity at a loading of 20 % wt. In this case, hydrogen yield and concentration were 4.7 m3/kgchar and 95.9 %, respectively and char conversion 98.1 % on a dry ash-free basis. The proposed method was proved advantageous for high purity hydrogen gas production and environmental management of wastes.

Bionic Mineralization toward Scalable MOF Films for Ampere-Level Biomass Upgrading.

With significant advances in metal-organic framework (MOF) nanostructure preparation, however, the facile synthesis of large-scale MOF films with precise control of the interface structure and surface chemistry is still challenging to achieve with satisfactory performance. Herein, we introduce a universal strategy bridging metal corrosion chemistry and bionic mineralization to synthesize 16 MOF films on 7 metal supports under ambient conditions. The robustness to explore unlimited libraries of MOF films (e.g., carboxylate-, N-heterocycle-, phenolic-, and phosphonate-MOFs) on supports is evoked by independently regulating the metal redox behavior, electrolyte properties, and organic ligands along with hydrogen evolution or oxygen reduction, which offers the basic guidelines for regulating the microstructure and composition of MOFs on the Pourbaix diagram. In conjunction with multiple manufacturing methods, we demonstrated proof of concept for "printing" a large variety of MOF patterns from micrometer to meter scales. Furthermore, a large-area electrolyzer (64 cm2) devised enables 5-hydroxymethylfurfural oxidation to achieve a record-breaking current of 3.0 A at 1.63 V with 2,5-furandicarboxylic acid production, leading to the simultaneous production of H2 gas and valuable feedstocks. The improved electrocatalytic activity for significantly boosting the 5-hydroxymethylfurfural oxidation exemplifies one of the functional MOF films for given applications beyond biomass upgrading.

Addition of torrefied algal biomass to improve land-based biomass gasification for hydrogen-rich gas production

Steam co-gasification of two kinds of biomass with different activities could generate synergetic effect on the fuel gas production. In this study, steam co-gasification of torrefied biochar from seaweed with land-based biomass, i.e., cedar wood and rice husk, was performed for the production of hydrogen(H2)-rich fuel gas, in which seaweed was torrefied at different temperatures (i.e., 200, 250 and 300 °C), and the performance of co-gasification was evaluated at three different gasification temperatures (i.e., 650, 700 and 750 °C) under atmospheric condition with three different steam flow rates (i.e., 0.05, 0.10 and 0.15 g/min) in a fixed bed reactor with a feed biomass and torrefied biochar weight ratio of 1:1. Taguchi's orthogonal array of L9 (34) was used to determine the importance of each parameter on the amount of H2 produced. It is found that the optimum parameters resulting in the highest H2 gas were the co-gasification cedarwood with the torrefied seaweed obtained at a torrefaction temperature of 300 °C at a co-gasification temperature of 750 °C with a steam flow rate of 0.10 g/min. Especially, at this condition, the produced H2 gas was nearly twice higher than that from cedarwood individual gasification and 11 % less tar produced than the calculated result.

Analysis of Hydrogen Gas Production Results in Water Electrolysis Process on Genset Characteristics

Hydrogen gas is a type of alternative fuel for transportation that can serve a number of other potential needs. Water electrolysis is one way to get hydrogen gas. This study aims to determine the results of water electrolysis with three catalysts and mixed metal electrodes which are then applied to generator motor engines. The research method used was an experimental method with variations in electrolysis using KOH and NaOH base catalysts, H2SO4 acid catalysts, and stainless steel 316 electrodes. The best results for H2 gas production in this study were obtained with a 2M H2SO4 catalyst with a gas yield of 244.9mL H2 gas, while The lowest yield in this study was the 1M concentration of 1M NaOH catalyst of 12.5mL. The best results for H2 gas production were varied with pertalite fuel and then tested with a generator engine. Testing the generator motor engine is measured arm length and mass with a machine dynamometer. After testing, the data is obtained which is then analyzed to obtain the value of torque (Nm) and electric motor power (kW), and driving motor power (HP). The maximum energy produced pertalite + H2 gas has increased by 2.27kW on the electric motor and power of 4.13HP on the driving motor, while for pertalite fuel alone the power generated is 1.44kW on the electric motor and power of 2.62HP on the driving motor.[1] S. A. Grigoriev, V. N. Fateev, D. G. Bessarabov, and P. Millet, “Current status, research trends, and challenges in water electrolysis science and technology,” Int. J. Hydrogen Energy, vol. 45, no. 49, pp. 26036–26058, 2020, doi: 10.1016/j.ijhydene.2020.03.109.[2] Y. Song, X. Zhang, K. Xie, G. Wang, and X. Bao, “High-Temperature CO2 Electrolysis in Solid Oxide Electrolysis Cells: Developments, Challenges, and Prospects,” Adv. Mater., vol. 31, no. 50, pp. 1–18, 2019, doi: 10.1002/adma.201902033.[3] A. Nechache and S. 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Improvements in performance and durability through surface modification of aluminum micro-pulsating heat pipe using water as working fluid

PHPs (pulsating heat pipes) using water are typically made of Cu and Si. Although Al is more sustainable than Cu and cheaper than Si (in addition to weight and durability advantages), water–Al PHPs have not been extensively investigated because noncondensable H2 gas is generated during Al–water reactions at high temperatures, stopping the flow in PHPs and degrading the thermal performance. In this study, a nontoxic micro-nano surface treatment method that is cheaper and simpler than the only reported method for water–Al PHPs was applied to the internal surface of an Al PHP. This prevented H2 gas production by forming Al(OH)3, thereby eliminating possible reaction sites on the surface. The internal two-phase flows, which significantly affected the thermal performance of PHPs, were compared using a flow visualization technique. The dry-out region gradually expanded in the original PHP with increasing operation time. In contrast, the modified surface PHP exhibited flow regeneration, preventing dry-out, as well as a thermal resistance 45.8% lower than that of the original surface PHP. Further, the critical heat flux of the PHP remained at 4.57 W/cm2 with the modified surface. Therefore, the proposed method improved the performance and durability of water–Al PHPs.

Experimental Investigation and Modelling by Machine Learning Techniques for Hydrogen Generation by Reacting Aluminium with Aqueous NaOH Solution

Hydrogen gas is projected as the future fuel for energy generation due to high energy density, and almost zero COx and NOx emissions during combustion. Production of H2 gas by the chemical reaction of aluminium and aqueous NaOH solution appears to be a simple and cost effective technique. Accurate forecasting of the reaction kinetics based on multi-variable interactions is necessary for large scale in-situ production and control of hydrogen gas. In the present study, the kinetics of the reaction between Al and aq. NaOH to produce H2 at different temperatures and concentrations of NaOH is investigated. Data obtained from these investigations are used to predict the reaction rate and correlate the simulated and experimental results using Machine Learning Techniques, viz, Artificial Neural Network (ANN) and Multiple Linear Regression (MLR). The simulation model obtained by the MLR technique is found to be less accurate in terms coefficient of correlation than the ANN model while comparing with the experimental results. The coefficient of correlations (Rcc) and average absolute relative error % are found to be 0.998 and 1.377% respectively during simulation by ANN. During the ANN simulation, 97.8 % of data points lie within a 95 % level of confidence indicating very good simulation capability. The results of the investigation reveal the application of Machine learning technique for the accurate prediction of hydrogen gas generation by a chemical reaction.

Titania nanoparticles for photocatalytic degradation of ethanol under simulated solar light.

TiO2 nanoparticles were synthesized by laser pyrolysis from TiCl4 vapor in air in the presence of ethylene as sensitizer at different working pressures (250-850 mbar) with and without further calcination at 450 °C. The obtained powders were analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. Also, specific surface area and photoluminescence with optical absorbance were evaluated. By varying the synthesis parameters (especially the working pressure), different TiO2 nanopowders were obtained, whose photodegradation properties were tested compared to a commercial Degussa P25 sample. Two series of samples were obtained. Series "a" includes thermally treated TiO2 nanoparticles (to remove impurities) that have different proportions of the anatase phase (41.12-90.74%) mixed with rutile and small crystallite sizes of 11-22 nm. Series "b" series represents nanoparticles with high purity, which did not require thermal treatment after synthesis (ca. 1 atom % of impurities). These nanoparticles show an increased anatase phase content (77.33-87.42%) and crystallite sizes of 23-45 nm. The TEM images showed that in both series small crystallites form spheroidal nanoparticles with dimensions of 40-80 nm, whose number increases with increasing the working pressure. The photocatalytic properties have been investigated regarding the photodegradation of ethanol vapors in Ar with 0.3% O2 using P25 powder as reference under simulated solar light. During the irradiation H2 gas production has been detected for the samples from series "b", whereas the CO2 evolution was observed for all samples from series "a".