Decomposition Of Acetic Acid Research Articles

Difference and similarity of coke from thermal decomposition or steam reforming of acetic acid

Polymerization/cracking and the reaction of intermediates with steam are the main routes by which the coke of very different properties might formed in steam reforming of acetic acid. This was investigated herein by conducting the steam reforming and decomposition of acetic acid on Ni/SBA-15 at 400, 550 and 700 °C, with particular focus on investigating the nature of resulting coke. Decomposition generated more coke than steam reforming at 400 °C (79.1% versus 24.6%), 550 °C (73.0% versus 45.6%) or 700 °C (39.0% versus 6.8%). More carbonaceous species like *CHx and *CC were the main intermediates, precursors of aromatic coke in decomposition, and their concentration on the catalyst surface let to serious coking at 550 °C, however, in steam reforming, oxygen-containing species like CO or C-O-C where the main intermediates precursors of coke. While larger outer diameter of carbon nanotube was formed in the reaction at 550 °C, smooth surface was formed at 700 °C.

Pt-O-Ce interaction enhanced by Al substitution to promote the acetone degradation through accelerating the breaking of C[sbnd]C bond in acetic acid intermediate

The reaction rate of volatile organic compounds (VOCs) oxidation is controlled by the rate-limiting step in the total reaction process. This study proposes a novel strategy, by which the rate-limiting step of acetone oxidation is accelerated by enhanced chemical bond interaction with more electrons transfer through Al-substituted CeO2 loaded Pt (Pt/Al-CeO2). Results indicate that the rate-limiting step in the process of acetone oxidation is the decomposition of acetic acid. Al substitution enhances the Pt-O-Ce interaction that transfers more electrons from Pt/Al-CeO2 to acetic acid, promoting the breaking of its CC bond with a lower free energy barrier. Attributing to these, the reaction rate of Pt/Al-CeO2 is 13 times as high as that of Pt/CeO2 and its TOFPt value is 11 times as high as that of Pt/CeO2 at 150 °C. Moreover, the CO2 selectivity of Pt/Al-CeO2 also increases by 22 %. This work establishes the relationship between Pt-O-Ce interaction and acetone oxidation that provides novel perspectives on the development of efficient materials for VOCs oxidation.

Low-temperature degradation of waste epoxy resin polymer improved by swelling-assisted pyrolysis

The disposal of waste epoxy resin matrix composite becomes an urgent issue, and pyrolysis is an effective method to decompose the epoxy resin polymer, but the high operating temperature hinders its application. In this study, a swelling-assisted pyrolysis method was proposed for the low-temperature decomposition of epoxy resin. It was found that the degradation ratio of epoxy resin increased from 59.13 % to 79.10 % at 300 °C after the swelling treatment with acetic acid. Compared with traditional pyrolysis, the cracking of epoxy resin was promoted in the swelling-assisted pyrolysis, increasing the yields of pyrolysis gas and oil, as well as enriching the light components in pyrolysis oil and raising the graphite degree of pyrolysis char. Following the characterizations and reactive force field molecular dynamics (ReaxFF-MD) simulation, the key mechanisms of swelling-assisted pyrolysis were determined as the interaction of the enhanced heat transfer and the accelerated ring-open reactions. After the swelling treatment, epoxy resin became porous, improving the heat transfer in the pyrolysis process. Meanwhile, abundant O radicals were generated with the decomposition of acetic acid, accelerating the ring-open reactions of benzene rings. The results could provide promising guidance for the pyrolysis recovery of epoxy resin matrix composites towards the circular economy.

Hydrogen tunneling with an atypically small KIE measured in the mediated decomposition of the Co(CH3COOH)+ complex.

Quantum mechanical tunneling (QMT) is a well-documented phenomenon in the C-H bond activation mechanism and is commonly identified by large KIE values. Herein we present surprising findings in the kinetic study of hydrogen tunneling in the Co+ mediated decomposition of acetic acid and its perdeuterated isotopologue, conducted with the energy resolved single photon initiated dissociative rearrangement reaction (SPIDRR) technique. Following laser activation, the reaction proceeds along parallel product channels Co(CH4O)+ + CO and Co(C2H2O)+ + H2O. An energetic threshold is observed in the energy dependence of the unimolecular microcanonical rate constants, k(E). This is interpreted as the reacting population surmounting a rate-limiting Eyring barrier in the reaction's potential energy surface. Measurements of the heavier isotopologue's reaction kinetics supports this interpretation. Kinetic signatures measured at energies below the Eyring barrier are attributed to H/D QMT. The below-the-barrier tunneling kinetics presents an unusually linear energy dependence and a staggeringly small tunneling KIE of ∼1.4 over a wide energy range. We explain this surprising observation in terms of a narrow tunneling barrier, wherein the electronic structure of the Co+ metal plays a pivotal role in enhanced reactivity by promoting efficient tunneling. These results suggest that hydrogen tunneling could play important functions in transition metal chemistry, such as that found in enzymatic mechanisms, even if small KIE values are measured.

Ag Nanoparticle and Ti-MOF Cooperativity for Efficient Inactivation of E. coli in Water.

Because of the limitations of traditional chlorine-based bactericidal water treatment, such as the formation of disinfection byproducts (DBPs) and resistance to chlorine, novel approaches and materials are required for effective disinfection of water. This study focuses on the development of a new sterilization material, Ag/NH2-MIL-125(Ti), which was designed to effectively inactivate Escherichia coli in water. The effectiveness of the as-designed material stems from the synergistic interactions between Ag nanoparticles (NPs) and photoactive metal-organic frameworks (MOFs). In this complex material, the MOFs play a critical role in dispersing and isolating the Ag NPs, thus preventing undesirable aggregation during bacterial inactivation. Simultaneously, Ag NPs enhance the photocatalytic performance of the MOFs. Sterilization experiments demonstrate the remarkable rapid E. coli inactivation performance of Ag/NH2-MIL-125(Ti) under illuminated and nonilluminated conditions. Within 25 min of visible light exposure, the as-prepared material achieves a >7-log E. coli reduction. In addition, Ag/NH2-MIL-125(Ti) efficiently decomposes acetic acid, which is the main DBP precursor, under visible light irradiation. Mechanistic investigations revealed that •O2- and h+ were the primary active substances responsible for the inactivation of E. coli and the decomposition of acetic acid, respectively.

(Invited) True Particle-Size Dependence of Photocatalytic Activity of Octahedral-Shaped Anatase Titania

Here, attempts to prepare octahedral-shaped anatase titanium(IV) oxide (titania) particles (OAPs) of uniform bulk structure (anatase with negligible non-crystalline components), surface structure (only exposing {101} facets) and particle size are reported as the first and sole example of a "pure" metal-oxide powder. The OAP samples were prepared by sonication-hydrothermal (HT) reaction of potassium-titanate nanowires through the process modified from the previous report [1]. Characterization of the samples by Rietveld analysis of XRD patterns (including non-crystalline phases using an internal standard) [2], reversed double-beam photoacoustic spectroscopy (RDB-PAS; a method measuring energy-resolved distribution of electron traps mainly located on the surface of metal-oxide and the other semiconducting samples) [3,4] and SEM observations revealed the homogeneousness of crystalline bulk, surface and particle size, respectively, to indicate the samples "pure". By controlling the preparation conditions, several OAP samples with different average size ranging of ca. 60–260 nm keeping the purity of the OAP shape. Roughly speaking, the particle-size distribution of those samples was the size of ca. 80% particles in the range of +20% of the average. Photocatalytic activities of those samples in (a) methanol dehydrogenation with in-situ deposited platinum to yield hydrogen, (b) oxidative decomposition of acetic acid under aerobic conditions to yield carbon dioxide and (c) oxygen evolution from deaerated aqueous silver sulfate were examined under ultraviolet-light (> 290 nm) irradiation to find that there seemed no particle-size dependence for the systems (a) hydrogen evolution and (b) carbon-dioxide evolution, while the activity in system (c) to liberate oxygen was almost linearly increased with the particle size [5]. These particle-size dependences of photocatalytic activity seem strange but could be "true" considering the purity of those samples, i.e., almost pure bulk crystal component exposing only anatase{101} facets. The previously reported particle-size dependence might be incorrectly derived due to the unknown effects by the other structural parameters.[1] Molecules 19, 19573 (2014). [2] Catal. Today 313, 218 (2018). [3] Chem. Commun. 52, 12096 (2016). [4] Electrochim. Acta 264, 83 (2018). [5] To be submitted.

Ambient-Pressure X-ray Photoelectron Spectroscopy Study of Acetic Acid Thermal Decomposition on Pd(111)

Acetic acid on Pd(111) is an excellent model system to study the effect of water on thermal decomposition of fatty acids and other oxygenates. Acetic acid is a simple molecule that has both methyl and acid groups, where its decomposition involves many of the key bond-breaking steps involved in more complex chemical decompositions. Here, we use ambient-pressure X-ray photoelectron spectroscopy and mass spectrometry supported by density functional theory (DFT) calculations of the core-level binding energies to study the effect of co-adsorbed water on the decomposition of acetic acid. The addition of water to acetic acid results in an increased acetic acid/acetate coverage and a decreased CO coverage. Moreover, when water is co-dosed with acetic acid, the gas phase composition from the reaction shows an approximately 30% increase in the CO2/CO ratio, suggesting a shift toward CO2 production in the presence of water. These observations are supported by previous DFT calculations, which show that the presence of co-adsorbed water lowers the barriers for O–H bond breaking but increases the barriers for C–O bond breakage, leading to increased CO2 production.

STUDY OF THE KINETICS OF MILK KEFIR USING SOY GERM AS SUBSTRATE

The main objective of this study was to analyze the growth kinetics of milk kefir on bean sprouts (Glycine max) as a germinated substrate for 4 days by the glass jar method followed by extracts. Ratio 1:3 (soy: water). 3% kefir grains (activated) inoculated with soluble bud extracts. The soluble extract of bean sprouts has a total sugar content of 5.57% and a fermentable carbohydrate of 3.37 g / L (sucrose), which is a source of nutrition and energy reserves; 1.40% of lipids are used for catabolic grain activity, while protein increases the amount of soluble nitrogen by 6.66%. The pH is 6.67 and the acidity is 0.17%, inversely proportional to lactic acid. The number of microbial populations of soluble extracts of kefirada sprouts reached the logarithmic stage of development after 24 hours for lactic acid bacteria and 48 hours for acetic acid bacteria and yeast, consuming the nutrients of the beverage, influencing its metabolites on the pH of the medium; The period of decomposition of lactic acid bacteria, acetic acid and yeast is 72 hours, and the medium lacks nutrients. The symbiotic action of milk kefir using soluble sprouted extracts is mutual, as the microorganisms it contains grow synergistically and create favorable changes in pH and acidity, depletion of nutrients and the creation of an appropriate environment. To improve the texture it is recommended to combine with fruits or vegetables that contain a lot of sugar.

Tuning the Surface Mn/Al Ratio and Crystal Crystallinity of Mn–Al Oxides by Calcination Temperature for Excellent Acetone Low-Temperature Mineralization

Here, Mn–Al oxides with the strengthened synergistic effect of Mn and Al species were fabricated by facilely adjusting the calcination temperature with the hydrolysis-driven redox-precipitation method. Results demonstrated that the surface Mn/Al ratio and KMn8O16 phase can be effectively tamed under different calcination temperatures, which obviously alter the CO2 selectivity, reaction rate, and stability of Mn–Al oxides for catalytic oxidation of acetone, among which the Mn5Al-350 catalyst exhibits the best catalytic performance (90% of acetone converted at 159 °C) with CO2 selectivity higher than 99.5%, mainly owing to its higher surface Mn/Al ratio and weaker Mn–O bond with more Mn3+ as compared to Mn5Al-250, Mn5Al-450, and Mn5Al-550. Although a decrease in the consumption rate of acetic acid in the presence of 3.0 vol % H2O leads to the slight reduction of acetone conversion and CO2 yield, Mn5Al-350 still exhibits a superior catalytic stability. The reaction intermediates including acetaldehyde, ethanol, acetic acid, and formic acid species before total mineralization are determined by proton transfer reaction–mass spectrometry, theoretical calculations, and in situ DRIFTS. Theoretical calculations also reveal that the p-orbital interaction of C with a certain anisotropy leads to a weak catalytic effect in the process of acetic acid decomposition as the rate-limiting step.

Adsorption, surface reactions and hydrodeoxygenation of acetic acid on platinum and nickel catalysts

Acetic acid adsorption and surface reactions were studied on Pt(111) and Ni(110) with infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption as well as computationally on the same well-defined single-crystal surfaces with density functional theory calculations. Additional calculations were performed for Ni(111) for comparison with Pt(111). At high acetic acid exposures at the dosing temperature of 90 K, acetic acid forms a chemisorbed layer covered by a physisorbed multilayer. The chemisorbed layer at 90 K for both Pt and Ni contains a mixture of molecularly adsorbed acetic acid as well as acetate. The physisorbed multilayer desorbs at 157–172 K. At 200 K, while a mixture of molecular acetic acid and acetate remains on Pt(111), acetic acid almost completely decomposes into acetate and, furthermore, produces some CO on Ni(110). Due to the almost complete decomposition of acetic acid on Ni at 200 K, only a small fraction of the chemisorbed acetic acid desorbs molecularly at 220 K. Unlike on Ni(110), most of the chemisorbed acetic acid desorbs molecularly from Pt(111) at a similar temperature of 218 K. Recombinative desorption of acetic acid is observed as a broad peak at 345 K for Pt(111) and as a tail peak at 220–300 K for Ni(110). At 450 K, the decomposition of acetic acid is almost complete on both metals. In contrast with acetic acid surface reactions where Ni is equally or even more reactive than Pt, a 1.5 wt % Ni/SiO2 catalyst is less active than a 5 wt % Pt/SiO2 catalyst in vapor-phase acetic acid hydrodeoxygenation at 473 and 573 K. Hydrogen temperature programmed reduction measurements for calcined catalysts show that Ni requires a higher temperature of 622 K for its reduction than 564 K for Pt. Therefore, the lower catalytic activity of Ni in hydrodeoxygenation can be attributed to the lower reducibility of Ni and not the differences in acetic acid adsorption or surface reactions.

A computational investigation of the decomposition of acetic acid in H-SSZ-13 and its role in the initiation of the MTO process

The zeolite-catalyzed reaction of acetic acid is important in the direct utilization of biomass and also plays a role in the reactivity of oxygenates in the methanol-to-olefins (MTO) process.

Is Black Titania a Promising Photocatalyst?

Five different (commercial and self-synthesized) titania samples were mixed with NaBH4 and then heated to obtain black titania samples. The change in synthesis conditions resulted in the preparation of nine different photocatalysts, most of which were black in color. The photocatalysts were characterized by various methods, including X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), photoacoustic and reverse-double beam photoacoustic spectroscopy (PAS/RDB-PAS). The photocatalytic activity was tested for oxidative decomposition of acetic acid, methanol dehydrogenation, phenol degradation and bacteria inactivation (Escherichia coli) under different conditions, i.e., irradiation with UV, vis, and NIR, and in the dark. It was found that the properties of the obtained samples depended on the features of the original titania materials. A shift in XRD peaks was observed only in the case of the commercial titania samples, indicating self-doping, whereas faceted anatase samples (self-synthesized) showed high resistance towards bulk modification. Independent of the type and degree of modification, all modified samples exhibited much worse activity under UV irradiation than original titania photocatalysts both under aerobic and anaerobic conditions. It is proposed that the strong reduction conditions during the samples’ preparation resulted in the partial destruction of the titania surface, as evidenced by both microscopic observation and crystallographic data (an increase in amorphous content), and thus the formation of deep electron traps (bulk defects as oxygen vacancies) increasing the charge carriers’ recombination. Under vis irradiation, a slight increase in photocatalytic performance (phenol degradation) was obtained for only four samples, while two samples also exhibited slight activity under NIR. In the case of bacteria inactivation, some modified samples exhibited higher activity under both vis and NIR than respective pristine titania, which could be useful for disinfection, cancer treatment and other purposes. However, considering the overall performance of the black titania samples in this study, it is difficult to recommend them for broad environmental applications.

Decomposition of Formic Acid and Acetic Acid into Hydrogen Using Graphitic Carbon Nitride Supported Single Metal Catalyst

In a combination of generation and storage of hydrogen gas, both formic acid (FA) and acetic acid (AA) have been notified as efficient hydrogen carriers. This study was conducted to synthesize the monometallic catalysts namely palladium (Pd), copper (Cu), and zinc (Zn) on graphitic-carbon nitride (g-C3N4) and to study the potential of these catalysts in FA and mixed formic acid (FA)-acetic acid (AA) decomposition reaction. Several parameters have been studied in this work such as the type of active metals, temperature, and metal loadings. The mass percentage of Pd, Cu, and Zn metal used in this experiment are 1, 3, and 5 wt%, respectively. At low temperature of 30 °C, 5 wt% Pd/g-C3N4 catalyst yielded higher volume of gas with 3.3 mL, instead of other Pd percentage loadings. However, at higher temperature of 70 °C and 98% FA concentration, Pd with 1 wt%, 3 wt%, and 5 wt% of loading over g-C3N4 has successfully produced optimum gas (H2 and CO2) of 4.3 mL, 7.4 mL, and 4.5 mL in each reaction, respectively. At higher temperature, Pd metal showed high catalytic performance and the most active element of monometallic system in ambient condition. Meanwhile, at higher percentage of Pd metal, the catalytic decomposition reaction also increased thus producing more gas. However, it can be seen the agglomeration of the particles formed at higher loadings of Pd (5 wt%), and remarkably lowering the catalytic activity at higher temperature, while higher activity at low temperature of 30 °C. The result also showed low catalytic decomposition reaction for Cu and Zn catalyst, due to the small formation of Cu and Zn metal, but presence of high metal oxide (CuO) and (ZnO) promotes the passive layer formation on the catalyst surface.

Highly Active Rutile TiO2 for Photocatalysis under Violet Light Irradiation at 405 nm

Anatase TiO2 is a widely investigated photocatalyst; however, it can only work under ultraviolet (UV) light with wavelengths less than 390 nm (band gap 3.2 eV). Rutile TiO2 can absorb visible light at wavelengths less than 410 nm (band gap 3.0 eV); however, its photocatalytic activity is not high. Herein, we activated rutile TiO2, which was prepared from Evonik TiO2 P 25 through calcination at 800 °C using hydrogen reduction treatment at 700 °C. The photocatalytic activity of the hydrogen-treated TiO2 was as high as P 25 under UV irradiation at 380 nm, which was significantly higher than P 25 under violet light irradiation at 405 nm for the oxidative decomposition of acetic acid in water. Electron spin resonance studies indicate that charge separation is enhanced in reduced TiO2, and their oxygen reduction pathways differ between anatase and rutile. The formation of H2O2 was observed on rutile TiO2; however, it was consumed during photocatalysis to accelerate acetic acid decomposition.

Bi12O17Cl2 with a Sextuple BiO Layer Composed of Rock‐Salt and Fluorite Units and its Structural Conversion through Fluorination to Enhance Photocatalytic Activity

AbstractLayered bismuth oxyhalides with bilayered (Bi2O2) fluorite (FL) slabs are promising visible‐light photocatalysts because of their excellent stability and the ability to adjust band levels depending on the layers combined. It is interesting to manipulate the Bi2O2 slab itself, but only trilayered FL blocks (e.g., Bi3O4) are reported so far. Here, a structurally uncharacterized Bi12O17Cl2, which is extensively studied as a photocatalyst for a variety of reactions, has a sextuple Bi6O8.5 block separated by Cl is shown. Unlike double and triple layered cases, the inner region of the Bi6O8.5 block contains 1D rock‐salt (RS) units in the FL matrix along the a‐axis, causing in‐plane corrugation. A topochemical reaction involving anion‐exchange gives Bi12O17–0.5xFxCl2 (x ≤ 6) with alternate FL and RS slabs along the c‐axis. The elimination of the structural corrugation increases higher photo‐conductivity and improves photocatalytic activity against acetic acid decomposition under visible light irradiation. This study paves new opportunities of controlling the properties of layered bismuth oxyhalides by the thickness of Bi–O block, FL/RS configuration, and structural modulation.

TiO2/Au/TiO2 Plasmonic Photocatalysts: The Influence of Titania Matrix and Gold Properties

Plasmonic photocatalysts have gained more and more attention because of possible applications for solar energy conversion, environmental decontamination, and water treatment. However, the activity under visible light is usually very low, and the property-governed activity as well as the mechanisms are not fully understood yet. Accordingly, this study examines four different titania photocatalysts (anatase and rutile with fine and large crystallites) modified with gold by photodeposition. Three kinds of samples were prepared, as follows: (i) gold-modified titania (Au/TiO2), (ii) physically mixed Au/TiO2 samples (Au/TiO2(1) + Au/TiO2(2)), and (iii) Au/(TiO2(1) + Au/TiO2(2)) samples, prepared by subsequent deposition of gold on the mixture of bare and gold-modified titania. In total, twelve samples were prepared and well characterized, including diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM). The photocatalytic activity was examined in three reaction systems: (i) methanol dehydrogenation during gold photodeposition under UV/vis irradiation, (ii) oxidative decomposition of acetic acid (UV/vis), and (iii) oxidation of 2-propanol to acetone under visible light irradiation (λ > 450 nm). It was found that during subsequent deposition, gold is mainly formed on the surface of pre-deposited Au nanoparticles (NPs), localized on fine titania NPs, through the electrostatic attractions (negatively charged gold resulting from photogenerated electrons’ accumulation). This gold aggregation, though detrimental for UV activity (many “naked” large titania with low activity), is highly beneficial for vis activity because of efficient light harvesting and increased interface between gold and titania (gold deposits surrounded by fine titania NPs). Moreover, it was found that rutile is more active than anatase for plasmonic photocatalysis, probably due to easier electron transfer from gold via titania to adsorbed oxygen (more negative conduction band), which might hinder the back reaction (electron transfer: Au→TiO2→Au).

The property-governed activity of silver-modified titania photocatalysts: The influence of titania matrix.

Commercial titania photocatalysts were modified with silver nanoparticles (NPs) by the photodeposition method in the presence/absence of methanol. The obtained photocatalysts were characterized by XRD, XPS, diffuse reflectance spectroscopy, STEM, and time-resolved microwave conductivity (TRMC) methods. The photocatalytic activity was tested under UV/vis irradiation for (i) methanol dehydrogenation (during silver deposition), (ii) oxygen evolution with in situ silver deposition, and (iii) oxidative decomposition of acetic acid, as well as under vis irradiation for 2-propanol oxidation. The action spectra of 2-propanol oxidation were also performed. It has been confirmed that modification of titania with silver causes significant improvement of photocatalytic activity under both UV and vis irradiation as silver works as an electron scavenger (TRMC data) and vis activator (possibly by an energy transfer mechanism). The obtained activities differ between titania samples significantly, suggesting that the type of crystalline phase, particle/crystallite sizes, and electron traps' density are crucial for both the properties of formed silver deposits and resultant photocatalytic activity. It might be concluded that, under UV irradiation, (i) high crystallinity and large specific surface area are recommended for rutile- and anatase-rich samples, respectively, during hydrogen evolution, (ii) mixed crystalline phases cause a high rate of oxygen evolution from water, and (iii) anatase phase with fine silver NPs results in efficient decomposition of acetic acid, whereas under vis irradiation the aggregated silver NPs (broad localized surface plasmon resonance peak) on the rutile phase are promising for oxidation reactions.

Antimicrobial properties of pristine and Pt-modified titania P25 in rotating magnetic field conditions

Effective and cheap water purification is one of the most important tasks facing humanity. Among various methods of water treatment, heterogeneous photocatalysis is probably most recommended. However, the application of artificial sources of irradiation results in high investment and operating costs. Accordingly, either vis-responsive photocatalysts or different ways of photocatalyst activation should be developed. In the present study, rotating magnetic field (RMF) has been tested to inactivate gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria in the presence of pristine and Pt-modified titania P25 photocatalyst. Liquid cultures of the bacteria have been exposed to the titania and RMF (RMF frequency of 1–50 Hz, RMF magnetic induction of ca. 19.92 mT, 180 min exposure time, temperature of incubation at 37 °C). It has been found that highly active titania photocatalyst might also work in the absence of photoirradiation but under RMF. Moreover, its modification with platinum besides highly improved photocatalytic activity (tested for two model reactions of oxidative decomposition of acetic acid and anaerobic dehydrogenation of methanol under UV/vis irradiation) results in significant enhancement of antimicrobial effect under RMF. Additionally, photocatalysts with larger content of oxidized forms of platinum show higher antimicrobial activity, and thus it is proposed that platinum oxides are more active than zero-valent platinum under RMF. This study provides evidence of antimicrobial effect of titania without photoirradiation, indicating that RMF might efficiently activate photocatalyst.

Effects of Co-adsorbed Water on Different Bond Cleavages of Oxygenates on Pd (111)

Experimental studies have shown that co-adsorbates and solvents affect both the activity and selectivity of heterogeneous catalysts, but how they affect different bond cleavages and a network of parallel reactions is not well understood. Here we present a density functional theory (DFT) calculation of how co-adsorbed water affects different bond cleavages of oxygenates on metal surface, using decomposition of acetic acid over Pd (111) as a model system for oxygenates, with application in biomass conversion. The presence of co-adsorbed water generally enhances O–H bond cleavage while generally inhibiting the OC–O, C–C, and OC–OH bond cleavage. The influence of co-adsorbed water on C–H bond cleavage varies the most and depends on the nature of the transition state and how co-adsorbed water stabilizes the initial and final state. Although these trends are useful as general guidance, they are not sufficient to predict the effect on a complex reaction network such as acetic acid decomposition that has several parallel reaction paths. In the absence of co-adsorbed water, the two lowest energy pathways are decarboxylation and decarbonylation pathways through a common CH2COO intermediate. But through an inhibition of OC–O bond cleavage but enhancement of C–C bond cleavage of CH2COO, one of three exceptions to the general trend of C–C inhibition in the presence of water, the two lowest free energy pathways are decarboxylation forming CO2 in the presence of water. This illustrates how a single reaction step can affect a complex reaction network with many parallel, energetically similar paths. This suggests that the presence of co-adsorbed water makes acetic acid decarboxylation (formation of carbon dioxide) more favorable than acetic acid decarbonylation (formation of carbon monoxide) over Pd (111).

Does Symmetry Control Photocatalytic Activity of Titania-Based Photocatalysts?

Decahedral anatase particles (DAPs) have been prepared by the gas-phase method, characterized, and analyzed for property-governed photocatalytic activity. It has been found that depending on the reaction systems, different properties control the photocatalytic activity, that is, the particle aspect ratio, the density of electron traps and the morphology seem to be responsible for the efficiency of water oxidation, methanol dehydrogenation and oxidative decomposition of acetic acid, respectively. For the discussion on the dependence of the photocatalytic activity on the morphology and/or the symmetry other titania-based photocatalysts have also been analyzed, that is, octahedral anatase particles (OAP), commercial titania P25, inverse opal titania with and without incorporated gold NPs in void spaces and plasmonic photocatalysts (titania with deposits of gold). It has been concluded that though the morphology governs photocatalytic activity, the symmetry (despite its importance in many cases) rather does not control the photocatalytic performance.