Carbon Monoxide Yield Research Articles

Valorizing spent mushroom substrate into syngas by the thermo-chemical process

This study investigated the conversion of agricultural biomass waste (specifically, spent mushroom substrate) into syngas via pyrolysis. Carbon dioxide was used to provide a green/sustainable feature in the pyrolysis process. All the experimental data highlight the mechanistic role of carbon dioxide (CO2) in the process, demonstrated by the enhanced carbon monoxide (CO) yield from pyrolysis under CO2. Carbon dioxide was indeed reactive at ≥ 500 ˚C. Carbon dioxide was reduced and subsequently oxidized volatiles stemming from the thermolysis of spent mushroom substrate via the gas-phase reaction, thereby resulting in the enhanced formation of CO. Carbon dioxide radically diverted the carbon distribution patterns of the pyrogenic products, as more carbon in the oil was allocated to syngas by the gas-phase reaction of volatiles and CO2. To enhance the mechanistic role of CO2, a Ni-based catalyst was added to the pyrolysis process, which greatly accelerated the gas-phase reaction of volatiles and CO2.

Sustainable hydrogen production through coupling isopropanol-butanol-ethanol with enhanced heat recirculation

The utilization of isopropanol-butanol-ethanol (IBE) to clean energy effectively mitigated the problems of environmental pollution and sustainable energy regeneration. In order to improve the utilization efficiency of ethanol and isopropanol in IBE, a liquid double-layer porous media burner was designed. And the combustion characteristics with different porous pellets and isopropanol ratios were studied. The results indicated that the mole fraction of hydrogen decreased with the increasing pellet diameter, and the lower heating value of syngas reached the highest value of 82.0 MJ/Nm3 when the pellets possessed two holes. Meanwhile, the peak temperature reached the maximum of 1009 K when the water content was 20% due to the sufficient combustion. And the isopropanol was conducive to the improvement of the total energy conversion efficiency. In addition, the yields of hydrogen and carbon monoxide were improved by 23.7% and 30.5% when the velocity increased from 10 to 12 cm/s. These results showed that the combustion of ethanol and isopropanol in porous media burners achieved the sustainable production of hydrogen and efficient utilization of IBE biofuels.

Comprehensive assessment of transparent wood degradation

Transparent wood includes a group of composite materials consisting of a renewable component (various wood species) and a refractive-matching index polymer (petroleum or bio-based) with a wide range of applications. There are various types of polymers used for transparent wood preparation Due to their favourable optical, mechanical, and carbon-storing properties, transparent wood is ideal for use in, e.g., the automobile industry, construction, packaging, or electronics. In this study, acrylic-based transparent wood was prepared by deactivating chromophore groups in natural basswood (Tilia cordata, L.), followed by a subsequent vacuum-assisted 2-hydroxyethyl-methacrylate polymer infiltration. Fire characteristics, UV and biological resistance of this wood-polymer system were investigated. Transparent wood prepared for this study shows high resistance to wood decay fungi. Fire performance test shows higher resistance to initiation (higher time to ignition and critical heat flux)compared to natural wood and lower yields of carbon monoxide. When exposed to UV irradiation, colour, and transmittance change intensively only in the first hours of exposure, then only very gradually. On the other hand, transparent wood shows higher values of heat release rate and derived parameters.

Sn and dual-oxygen-vacancy in the Z-scheme Bi2Sn2O7/Sn/NiAl-layered double hydroxide heterojunction synergistically enhanced photocatalytic activity toward carbon dioxide reduction

Photocatalytic conversion of carbon dioxide (CO2) into high value-added chemicals is an attractive yet challenging process, primarily due to the readily recombination of hole-electron pairs in photocatalysts. Herein, dual-oxygen-vacancy mediated Z-scheme Bi2Sn2O7/Sn/NiAl-layered double hydroxide (VO,O-20BSL) heterojunctions were hydrothermally synthesized and subsequently modified with Sn monomers to enhance photocatalytic activity toward CO2 reduction. The abundance of oxygen vacancies endowed the VO,O-20BSL with extended optical adsorption, enhanced charges separation, and superior CO2 adsorption and activation. The interfacial charges transfer of the VO,O-20BSL was demonstrated to follow a Z-scheme mechanism via photochemical deposition of metal/metal oxide. Under visible light irradiation, the VO,O-20BSL exhibited the highest yields of carbon monoxide (CO) and methane (CH4), with values of 72.03 and 0.85 umol·g−1·h−1, respectively, which were 2.66 and 1.57 times higher than that of the VO-NiAl-layered double hydroxide (VO-1LDH). In situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) revealed that carboxylic acid groups (COOH*) and aldehyde groups (CHO*) were the predominant intermediates during CO2 reduction, and accordingly, possible CO2 reduction pathways and mechanism were proposed. This study presents a feasible approach to incorporate dual vacancies into Z-scheme heterojunctions for CO2 reduction.

Experimental investigation and numerical modelling of CO and HCN release during the combustion of flexible polyurethane foam

The combustion of flexible polyurethane foam (FPUF) in fires releases relatively large amounts of carbon monoxide (CO) and hydrogen cyanide (HCN), threatening the lives of those exposed thereto. It is therefore necessary to use computational fluid dynamics method to explore the distribution of CO and HCN in a fire involving the combustion of FPUF. However, the release of CO and HCN varies significantly with the combustion conditions, which makes the numerical modelling challenging. In the present research, the yields of CO and HCN during the combustion of a non-flame-retardant FPUF were determined using a steady-state tube furnace (SSTF) facility, considering the effect of the ventilation condition. Meanwhile, a pyrolysis and combustion model of FPUF was constructed based on the fire dynamics simulator (FDS), and a four-step chemistry model was proposed to deal with the reactions in the gas phase. The experimental results showed that the yields of CO and HCN both increased with the limitation of ventilation, which was more pronounced in under-ventilated conditions. Meanwhile, the numerical simulation applying the four-step chemistry model predicted the variations in the yields of CO and HCN under ventilated conditions. In addition, when the appropriate kinetic parameters were applied to the reactions governing the oxidation of CO and HCN, the comparative results indicated that the global average deviations between the predicted and experimental yields could be reduced to 13.61 % (CO) and 8.19 % (HCN), respectively.

Triangular silver nanoplates-BiVO4 composite for the photocatalytic CO2 reduction under irradiating LED light source

In this study, triangular silver nanoplates (TagNPts)/BiVO4 nanomaterials were prepared by hydrothermal method and are used as a photocatalyst in a photoreaction system to convert carbon dioxide into methane and carbon monoxide. The as prepared material was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and ultraviolet–visible spectrometer (UV–vis). The absorbance increases in the visible light region due to the incorporation of nano-silver (triangular plate) metal and pulls electrons, reduces the recombination rate of electron-hole pairs, and improves the photoreduction activity. The transmittance ratio is measured and the specific wavelengths of blue LED 412–505 nm and green LED 427–622 nm are measured. It shows that the irradiation of targeted wavelength bands will increase the absorbance and effectively reduces the recombination of electron-hole pairs. The best performance in this study was achieved after irradiating blue light source with 0.9% TAgNPts/BiVO4. The cumulative production of photoreduced carbon monoxide is 30.11 μmol g−1 and the quantum yield is 0.07%. After a green light source, the cumulative carbon monoxide yield using 0.9 wt% TAgNPts/BiVO4 is 24.77 μmol g− and the quantum yield is 0.06%.

Modelling carbon monoxide transport and hazard from smouldering for building fire safety design analysis

Smouldering produces massive toxic smoke and carbon monoxide (CO) that is responsible for the majority of fire deaths, but current building fire safety design rarely considers smouldering hazards. This work investigates the transport and hazards of CO from smouldering fire for the building performance-based design practice. The numerical model is firstly validated by reproducing two flat-scale fire experiments, revealing the characteristic surface temperature and CO yield of smouldering sources. The smouldering fire scenario is then designed in an atrium to review the evolution of CO concentration and its associated Available Safe Egress Time (ASET). Results show that a smouldering fire of the same burning rate as a flaming fire not only can provide a similar ASET, but also present a greater threat to occupants and rescue teams by forming a cold layer of lethal CO on the ground. Hence, the smouldering fire scenarios and their CO hazards should be considered in the performance-based design of building fire safety. Simulations also reveal that the smouldering fire can be more dangerous as the atrium height decreases, and ceiling ventilation is particularly effective in extracting CO emissions from smouldering fires.

Hydrogenation of calcium carbonate to carbon monoxide and methane

The current cement, steel, refractory and calcium carbide industries rely on thermal decomposition of calcium carbonate (CaCO3) that forms calcium oxide (CaO) and carbon dioxide (CO2). Hydrogenation of CaCO3 may reduce or eliminate CO2 in CaO generation and simultaneously generate carbon monoxide (CO) and/or methane (CH4). This work mainly investigates CaCO3 hydrogenation conditions for CO and CH4 and establishes the kinetics for these reactions. It is found that CH4 forms at temperatures lower than that of CO2 but higher than that of CO. The rates of CO and CH4 formation increase with increasing hydrogen pressure (PH2) but that of CO peaks at PH2 of 0.05–0.10 MPa. The CO2, CO and CH4 yields are 17.7%, 81.4% and 0.9% at the PH2 of 0.10 MPa while 1.2%, 20.0% and 78.8% at the PH2 of 6.00 MPa. The kinetics of CaCO3 conversion and CO and CH4 formation can be better modeled by the shrinking core model (SCM) than the volume reaction model (VRM) and the gas reaction model (GRM). The activation energy (Ea) for CaCO3 conversion and CO and CH4 formation by SCM is 165.8, 156.4 and 211.9 kJ·mol−1, respectively, with the order of PH2 of 0.108, 0.005 and 0.673, respectively.

Experimental investigation and optimization of the gasification parameters of macadamia nutshells in a batch-fed bubbling fluidized bed gasifier with air preheating

Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas, which is considered as renewable energy. This work investigated the gasification of macadamia nutshells in air-preheated, batch-fed fluidized bed gasifier. The study conducted a parametric analysis to assess the effect of equivalence ratio (ER) and air temperature on the gasifier temperature profile and its performance based on gas composition, higher heating value (HHV), and gas yield. The research was conducted within the range of 0.15–0.35 for the ER and 25–825 °C for the air temperature. Multi-objective numerical optimization was conducted using response surface methodology (RSM). From the parametric study, a distinct temperature profile was observed along the gasifier height, with the peak temperature near the top of the fluidized bed section and the lowest temperature at the top of the gasifier. Air preheating mostly favored gasification temperature at the lower part of the gasifier and showed rare significance at the top. No improvement in gasifier performance was observed beyond an air temperature of 620 °C, which was identified as the ideal air-preheating temperature. Analysis of variance (ANOVA) revealed that the ER was the most influential parameter in the production of combustible gasses, syngas HHV and gas yield. Air preheating did not have a significant effect on methane production and gas yield. The most optimal values for ER and air temperature were obtained as 0.195 °C and 620 °C, respectively, producing optimal values of 9.54, 14.65%, 2.03, 4.02 MJ·Nm−3, and 1.82 Nm3·kg−1 for hydrogen, carbon monoxide, methane, HHV, and gas yield, respectively.

Co-partial oxidation of acetic acid, methanol, and ethanol in an integrated porous media with efficient heat recirculation: Green hydrogen production and its expansion method

Green energy from biomass contributed to substituting the traditional fossil fuels and environmental protection. To explore the hydrogen production from bioethanol with the industrial by-products, a porous media burner integrated with a heat-recirculating tube was designed to realize the efficient vaporization of ethanol. Then the partial oxidation characteristics of ethanol were investigated with the acetic acid and methanol addition at different operating conditions. The results indicated that the acetic acid and methanol addition inhibited hydrogen production but promoted methane production. Compared with pure ethanol, the heating values of syngas were decreased by 3.41 and 0.64 MJ/Nm3 with the acetic acid or methanol content of 20%. The highest yields of hydrogen and carbon monoxide were achieved at 43.94% and 66.45% respectively when the ratio of acetic acid content to methanol was 5:15. Nevertheless, blended fuels achieved more syngas production at higher equivalence ratios and velocities. The hydrogen concentration of the blended fuel reached the maximum of 21%, exceeding that of pure ethanol by 1.6% when the velocity was 22 cm/s. The corresponding results provided a theoretical reference for the industrial application of bioethanol.

Novel Samarium Cobaltate/Silicon Carbide Composite Catalyst for Dry Reforming of Methane into Synthesis Gas

The paper describes a specifically developed novel samarium cobaltate/silicon carbide composite that transforms into a high-performance carbon-resistant catalyst for dry reforming of methane into syngas (DRM). This 30%SmCoO3/70%SiC composite without hydrogen prereduction was tested in DRM at atmospheric pressure and GHSV 15 L g–1 h–1 (of an equimolar CH4–CO2 mixture). During the test, the yields of hydrogen and carbon monoxide reached 92 and 91 mol %, respectively, at 900°C, and 20 and 28 mol % at 700°C. Using XRD, TGA, and SEM examination, zero carbonization of the catalyst surface was demonstrated. It was found that, in the course of DRM, the initial composite transformed into a material that contained silicon carbide, samarium silicate, and samarium oxide, as well as metallic cobalt nanoparticles (20 nm).

Novel Samarium Cobaltate/Silicon Carbide Composite Catalyst for Dry Reforming of Methane into Synthesis Gas

The paper describes a specifically developed novel samarium cobaltate/silicon carbide composite that transforms into a high-performance carbon-resistant catalyst for dry reforming of methane into syngas (DRM). This 30%SmCoO3/70%SiC composite without hydrogen prereduction was tested in DRM at atmospheric pressure and GHSV 15 L g–1 h–1 (of an equimolar CH4–CO2 mixture). During the test, the yields of hydrogen and carbon monoxide reached 92 and 91 mol %, respectively, at 900°C, and 20 and 28 mol % at 700°C. Using XRD, TGA, and SEM examination, zero carbonization of the catalyst surface was demonstrated. It was found that, in the course of DRM, the initial composite transformed into a material that contained silicon carbide, samarium silicate, and samarium oxide, as well as metallic cobalt nanoparticles (<20 nm).

La-Ce-hexaaluminate doped by multivalent metal ion as the oxygen carrier for the optimization of hydrogen production

The efficiency of porous media combustion was greatly improved by combining the high-temperature catalyst of hexaaluminate. In this paper, a double-layer porous media burner filled with cylinders was built with the loading of La0.8Ce0.2MAl11O19 (M = Fe, Co, Cu). The effects of hexaaluminate and cylinders parameters on the products concentration and temperature distribution were studied at different working conditions. Results indicated that the La0.8Ce0.2CuAl11O19 obtained the excellent catalytic performance with the most adsorbed oxygen and oxygen channels, so that the maximum hydrogen mole fraction was achieved. With the increasing of the 13 mm cylinders volume ratio from 0 to 1, the hydrogen and carbon monoxide yield increased by 53.3 % and 50.9 %, respectively. Meanwhile, the increased heat releasing of the higher velocity contributed to improving the combustion temperature and syngas production. These results provided theoretical guidance for the catalytic porous media reactor in energy utilization and environmental protection.

An improved plastination method for strengthening bamboo culms, without compromising biodegradability

Biomaterials are increasingly being designed and adapted to a wide range of structural applications, owing to their superior mechanical property-to-weight ratios, low cost, biodegradability, and CO2 capture. Bamboo, specifically, has an interesting anatomy with long tube-like vessels present in its microstructure, which can be exploited to improve its mechanical properties for structural applications. By filling these vessels with a resin, e.g. an applied external loading would be better distributed in the structure. One recent method of impregnating the bamboo is plastination, which was originally developed for preserving human remains. However, the original plastination process was found to be slow for bamboo impregnation application, while being also rather complicated/methodical for industrial adaptation. Accordingly, in this study, an improved plastination method was developed that is 40% faster and simpler than the original method. It also resulted in a 400% increase in open-vessel impregnation, as revealed by Micro-X-ray Computed Tomography imaging. The improved method involves three steps: acetone dehydration at room temperature, forced polymer impregnation with a single pressure drop to − 23 inHg, and polymer curing at 130 °C for 20 min. Bamboo plastinated using the new method was 60% stronger flexurally, while maintaining the same modulus of elasticity, as compared to the virgin bamboo. Most critically, it also maintained its biodegradability from cellulolytic enzymes after plastination, as measured by a respirometric technique. Fourier transform infrared-attenuated total reflection, and thermogravimetric analyses were conducted and showed that the plastinated bamboo’s functional groups were not altered significantly during the process, possibly explaining the biodegradability. Finally, using cone calorimetry, plastinated bamboo showed a faster ignition time, due to the addition of silicone, but a lower carbon monoxide yield. These results are deemed as a promising step forward for further improvement and application of this highly abundant natural fiber in engineering structures.

Influence of pressure and sunflower husks ash as catalyst on tire-char steam gasification

Catalytic gasification of low-reactive waste fuels, like tire-char, with the use of a different type of waste as a cheap and efficient catalyst seems to be an up-and-coming solution; however, requiring selecting appropriate process conditions. Therefore, this study aimed to assess the effect of various amounts (0, 5, 10, 15 wt%) of waste-based catalyst (sunflower husks ash, SHA) and pressure on tire-char gasification with steam. Feedstock and catalyst were characterised, then physically mixed, and the prepared samples were subjected to steam gasification. The gasification measurements were performed at 800, 850, 900 and 1000 °C and the pressures of 0.5 and 1 MPa, using the thermovolumetric method based on an analysis of the composition of the resulting gas (this research focused on the main gas components, i.e. CO and H2). The obtained results showed that the selected tire-char was characterised by a high calorific value; however, it contained a high content of carbon and catalytically inert ash, which may affect its reactivity. In turn, sunflower husk ash selected as catalyst consisted mainly of catalytically active compounds of alkali and alkaline earth metals (in particular K2O), while at the same time a low content of acid components that inhibit the process. The gasification measurements proved that the character of curves of formation rates of CO and H2 differed, indicating different formation mechanisms. Moreover, pressure and catalyst addition affected the gasification process, especially at low temperatures (∼800–850 °C). In this temperature range, an increase in pressure, catalyst addition, and increasing its loading improved the conversion reaction rate and maximum carbon conversion, as well as hydrogen yields. In turn, an increase in pressure and the addition of catalyst positively affected the yield of carbon monoxide in almost the entire range of analysed temperatures, whereas the effect of catalyst was not significant. Finally, the analysis of kinetic parameters of carbon conversion reaction during steam gasification showed that the addition of catalyst reduced both activation energy and pre-exponential factor (the most significant reduction was observed when using 5 wt% of SHA), while the increase in pressure had an inverse effect on these parameters. Nevertheless, the obtained results show that steam gasification of tire-char at low temperatures, the pressure of 1 MPa and in the presence of 15 wt% of SHA may be an attractive way to efficiently obtain gas rich in hydrogen — one of the most promising future fuels.

Plane Parallel Barrier Discharges for Carbon Dioxide Splitting: Influence of Discharge Arrangement on Carbon Monoxide Formation

A planar volume dielectric barrier discharge (DBD) in pure carbon dioxide (CO2) for the formation of carbon monoxide (CO) is examined by combined electrical and CO density measurements. The influence of the type of electrode, the barrier material, the barrier thickness, and the discharge gap on the plasma power and the CO formation is analyzed systematically. The electrical characterization by means of charge-voltage plots is based on the simplest equivalent circuit model of DBDs, extended by the so-called partial surface discharge effect and the presence of parallel parasitic capacitances. The stackable discharge arrangement in this study enables one to elucidate the influence of parasitic capacitances, which can be overlooked in the application of such plasma sources. The determination of the discharge voltage from charge-voltage plots and the validity of the so-called Manley power equation are revised by taking into account non-uniform coverage as well as parasitic capacitances. The energy yield (EY) of CO is analyzed and compared with the literature. No correlations of EY with the mean reduced electric field strength or the geometric parameters of the DBD arrangement are observed.

Second stage porous media burner for syngas enrichment

The syngas production from hydrocarbons by porous media combustion (or conventional gasification) processes has been intensively and extensively studied due its calorific value and its applications in the energy sector. However, the syngas produced in a first stage gasifier can still have concentrations of light hydrocarbons (e.g., methane) which can be post-processing for further enrichment of hydrogen and carbon monoxide. The present work numerically investigates the performance of a second stage porous media burner to enrich the syngas content, mainly hydrogen and carbon monoxide. A one-dimensional model based on a two-temperature approximation is implemented, based on the PREMIX code, and supported by CHEMKIN and GRI-MECH 3.0 database and routines. From hybrid porous bed reactor experiments, five types of mixtures in the equivalence ratio range between 0.4 and 2.4 are tested: pure methane as baseline, pure Eucalyptus nitens syngas, pure Pinus radiata syngas, and two mixtures of methane with each of the biomass syngas in equal volume quantities, as transition points. The results obtained show that in the enriched syngas, in comparison to the first content after the first stage reactor, the concentrations of hydrogen and carbon monoxide increase, due to the partial oxidation of methane, however part of the hydrogen is consumed in the process. The intermediate species present in methane processing for pure syngas mixtures have broader reaction zones and in lower concentrations compared to the use of pure methane. For equivalence ratios greater than 1.9, pure syngas mixtures show higher conversion efficiencies compared to the baseline. At the equivalence ratio of 2.4, the pure syngas from Eucalyptus nitens and Pinus radiata has an energy return over energy invested (EROI) of 58.27% and 53.95%, respectively, and a maximum hydrogen and carbon monoxide yields of 31.66% and 48.40%, respectively. In the case of the Pinus radiata, the outlet syngas concentrations of the hydrogen and carbon monoxide on dry basis expose an increment about two times in comparison to the initial concentrations.

Architecting fire safe hierarchical polymer nanocomposite films with excellent electromagnetic interference shielding via interface engineering

Integrating high flame retardancy and excellent electromagnetic interference (EMI) shielding into polymetric materials is extremely necessary, and well dispersing conductive fillers into polymeric materials is still a great challenge because of incompatible interfacial polarity between polymer matrix and conductive fillers. Therefore, under the premise of maintaining integral conductive films in the process of hot compression, constructing a novel EMI shielding polymer nanocomposites where conductive films closely adhere to polymer nanocmposites layers should be a fascinating stratety. In this work, salicylaldehyde-modified chitosan decorated titanium carbide nanohybrid (Ti3C2Tx-SCS) was combined with piperazine-modified ammonium polyphosphate (PA-APP) to fabricate thermoplastic polyurethane (TPU) nanocomposites, which were used for construction of hierarchical nanocomposite films by inserting reduced graphene oxide (rGO) films into TPU/PA-APP/Ti3C2Tx-SCS nanocomposite layers through our self-developed air assisted hot pressing technique. The total heat release, total smoke release and total carbon monoxide yield for TPU nanocomposite containing 4.0 wt% Ti3C2Tx-SCS nanohybrid were 58.0%, 58.4% and 75.8% lower than those of pristine TPU, respectively. Besides, the hierarchical TPU nanocomposite film containing 1.0 wt% Ti3C2Tx-SCS presented an averaged EMI shielding effectiveness of 21.3 dB in X band. This work provides a promising strategy for fabricating fire safe and EMI shielding polymer nanocomposites.

Photooxidation of 2-Pentanone in the Gas Phase: Photo-Products, Reaction Mechanism, OH Reaction Kinetics, and Atmospheric Implication

Photooxidation of 2-pentanone (2PN, C3H7C(O)CH3), an atmospherically abundant volatile linear carbonyl compound and a proposed second-generation fuel, was studied in a laboratory reactor under simulated tropospheric conditions under the exposure of ultraviolet (UV) light of wavelength of 311 nm, which is abundant in the troposphere. Formic acid (HC(O)OH), acetic acid (CH3C(O)OH), formaldehyde (HCHO), methanol (CH3OH), and carbon dioxide (CO2) were identified as the photooxidation products using FTIR spectroscopy as the detection method. Photodissociation of 2PN resulted in the formation of acetone (CH3C(O)CH3) and ethylene (C2H4) by Norrish type-2 reaction, while carbon monoxide (CO) was found to be formed by both photodissociation and photooxidation. The yields of CH3C(O)CH3, C2H4, CO, CH3OH, HC(O)OH, and HCHO were determined to be (54.0 ± 2.7), (61.7 ± 3.4), (47.7 ± 4.7), (8.1 ± 0.7), (4.4 ± 0.3), and (2.7 ± 0.7) %, respectively. The yield of CH3C(O)OH cannot be measured due to its low absorbance and spectral interferences by other species in the probe FTIR spectra. A reaction mechanism involving photodissociation and subsequent reactions of the produced radicals is presented for the formation of different photooxidation products. A reaction modeling study was performed for further corroboration of the proposed mechanism of photooxidation reaction. Reinvestigated here also was the reaction kinetics of 2PN with OH by the relative rate method using FTIR detection, and a rate constant of (5.1 ± 0.8) × 10–12 cm3 molecule–1 s–1 at room temperature was estimated, which agrees well with previous reports. The estimated tropospheric lifetime of 2PN by a UV photooxidation channel (∼3.2–7.2 days) is comparable with that for reaction with the OH (∼2.3 days). Carboxylic acids formed in the photooxidation of 2PN can be significant for atmospheric acidity and secondary organic aerosol (SOA) formation.

Tailoring Copper Chemical Status and Hydrophobicity of Biomimetic Photocatalytic Films for Carbon Dioxide Conversion.

Naturally hierarchical nanostructures of leaves were successfully replicated on thermally stable polyimide (PI) films to obtain biomimetic substrates for the grafting of p-type semiconductor, cuprous oxide (Cu2O). The chemical states of Cu2O and the hydrophobicity on the photocatalytic films were tunable by altering the process time of ion-exchange or chemical reduction. The obtained photocatalytic films showed activity to photocatalytically convert carbon dioxide (CO2) into carbon monoxide (CO) under visible light illumination. The yield of CO was initially improved with the increasing hydrophobicity on the film but then leveled off. The photocatalytic activity could be further improved by tailoring the amount or composition of copper oxides. An optimum ratio of Cu2O and moderate basicity on the surface, as well as more metallic Cu from the bulk, will achieve more efficient interfacial charge transfer, resulting in a higher CO production rate.