Oxidation Of Carbon Monoxide Research Articles

Potential Effects in Electrochemical Oxidation of Carbon Monoxide Catalyzed by Rh-N-Doped Graphene

Potential Effects in Electrochemical Oxidation of Carbon Monoxide Catalyzed by Rh-N-Doped Graphene

Model simplification and sensitivity analysis of chemical species for oxidation behavior in multi route complex chemical mechanism

This study employs a Model Reduction Technique (MRT) to simplify the four-step catalytic carbon monoxide (CO) oxidation reaction. The C-matrix method identifies key elements, key/non key components, and key reactions, while the Intrinsic Low-Dimensional Manifold (ILDM) pinpoints a Slow-Invariant Manifold (SIM) important for understanding key species behavior. Sensitivity analysis can be considered for measuring the efficiency of the chemical species in detailed mechanism. This systematic approach contributes to optimizing and controlling complex reactions offering broad application potential. In addition to the mathematical proof, the validation of the given chemical model is rectified. The comparison between the slow invariant manifold of both reaction routes is reported and the computational based results performed in this study are obtained through MATLAB.

Synthesis of ultrastable silver catalyst supported on alumina nanofibers for carbon monoxide combustion

A catalyst consists of fine aggregates nanoflowers of alumina as support and uniform coating of silver as active component was fabricated to oxidize carbon monoxide. The alumina nanofibers synthesized via a simple electrochemical method. XRD and FE-SEM analysis showed that the thickness of silver deposit was in the range of subnanometer. Elemental mapping also showed a uniform distribution of silver. Also, BET and EDX tests were performed to measure the specific surface area and elemental composition of the catalyst, respectively. Its catalytic activity was measured, and at GHSV equal to 60000 ml/h.g, the end temperature of the oxidizing reaction was 175°C. By increasing the GHSV to 120,000 ml/h.g, the end temperature of the reaction reached 190°C. The thermal stability of the catalyst was also high, as the specific surface area of the catalyst changed from 87m2/g to 51m2/g by increasing the temperature from ambient temperature to 900°C. Due to the high stability of alumina, the structure of the catalyst is always stable. On the other hand, feasibility studies have been given special attention to the advancement of the project. Therefore, for the synthesis of nanocatalyst, available precursors and a simple method have been used, so there will be no problem in the mass production of the catalyst. It is hoped to be able to synthesize nanocatalysts with similar structure and mass production capability for other chemical reactions with this method.

CO Oxidation Mechanism of Silver-Substituted Mo/Cu CO-Dehydrogenase - Analogies and Differences to the Native Enzyme.

The aerobic oxidation of carbon monoxide to carbon dioxide is catalysed by the Mo/Cu-containing CO-dehydrogenase enzyme in the soil bacterium Oligotropha carboxidovorans, enabling the organism to grow on the small gas molecule as carbon and energy source. It was shown experimentally that silver can be substituted for copper in the active site of Mo/Cu CODH to yield a functional enzyme. In this study, we employed QM/MM calculations to investigate whether the reaction mechanism of the silver-substituted enzyme is similar to that of the native enzyme. Our results suggest that the Ag-substituted enzyme can oxidize CO and release CO2 following the same reaction steps as the native enzyme, with a computed rate-limiting step of 10.4 kcal/mol, consistent with experimental findings. Surprisingly, lower activation energies for C-O bond formation have been found in the presence of silver. Furthermore, comparison of rate constants for reduction of copper- and silver-containing enzymes suggests a discrepancy in the transition state stabilization upon silver substitution. We also evaluated the effects that differences in the water-active site interaction may exert on the overall energy profile of catalysis. Finally, the formation of a thiocarbonate intermediate along the catalytic pathway was found to be energetically unfavorable for the Ag-substituted enzyme. This finding aligns with the hypothesis proposed for the wild-type form, suggesting that the creation of such species may not be necessary for the enzymatic catalysis of CO oxidation.

Oxygen vacancies promote the activation of O2 in transition metal oxide doped ε-MnO2 for low-temperature CO oxidation

Carbon monoxide (CO), a toxic pollutant usually formed from incomprehensive combustion especially at low temperature, has harmful effects on human health. Therefore, the catalytic oxidation of CO always receives widespread attention. Herein, we reported transition metal (Cu, Co, Ni, Fe) doped ε-MnO2 as CO catalysts using a hydrothermal-deposition method. Physiochemical properties for CO oxidation were meticulously analyzed employing characterization techniques such as SEM, XRD, BET, XPS, EPR, CO-TPR. The doped ε-MnO2 catalyst showed expanded BET surface area, increased oxygen vacancy defects, more active sites, enhanced adsorption, and faster electron transfer. Catalytic activity tests indicated that the ε-MnO2 catalyst doped with transition metals exhibited exceptionally high catalytic activity, with the Cu-doped catalyst showing the fastest chemical reaction rate and the lowest complete conversion reaction temperature (TOF of 9.92 × 10−3 s−1, at 65℃). Density Functional Theory (DFT) calculations indicated that Cu doping more effectively induced oxygen vacancy defects compared to Co, Ni, Fe, and raw ε-MnO2 catalysts. It identifies the CO oxidation reaction and improved the CO adsorption capacity of the catalyst. Furthermore, a novel potential reaction pathway for the M-vK mechanism in transition metal oxides was proposed.

Variability in the properties of the distribution of the relative humidity with respect to ice: implications for contrail formation

Abstract. Relative humidity with respect to ice (RHi) is a key variable in the formation of cirrus clouds and contrails. We document its probability density function (PDF) using long-term Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft (MOZAIC) and the In-service Aircraft for a Global Observing System (IAGOS) observations over the period 1995–2022 in the upper troposphere (UT) and the lower stratosphere (LS) between 325 and 175 hPa. The characteristics of the RHi PDF differ in the UT and in the LS of the high-latitude regions (HLs) and mid-latitude regions (MLs) of the Northern Hemisphere. In the LS, this PDF decreases exponentially with increasing RHi. In the UT, it first increases exponentially in subsaturated conditions and then decreases exponentially in supersaturated conditions. Because of these different behaviors, the PDF for the combined UT and LS is bimodal. In contrast to the HLs and the MLs, the RHi PDF in the tropical troposphere decreases exponentially with increasing RHi. The different forms of PDF, in the tropics and in the higher-latitude regions, lead to a global PDF of RHi in subsaturated tropospheric conditions that is almost uniform. These findings invite caution when using MOZAIC and IAGOS measurements to calibrate large-scale simulations of RHi. The variability in RHi properties associated with that of temperature also has implications for the formation of contrails. We examined the impact of switching fuel (from kerosene to bioethanol or liquid hydrogen) on the frequency of contrail formation using the Schmidt–Appleman criterion. We show that bioethanol and, to a larger extent, liquid hydrogen would produce more contrails. The impact of a potential change from kerosene to these alternative fuels decreases with decreasing pressure but increases when moving from the higher latitudes of the Northern Hemisphere to the tropics. Finally, we emphasize that investigations of the impact on contrail occurrence frequency as a result of switching from fossil kerosene to more sustainable fuels must be carried out in various meteorological conditions.

Catalytic oxidation of carbon monoxide at low temperature using AuRh/TiO2 bimetallic catalysts: Effect of the synthesis method

AuRh nanoparticles supported on TiO2 P25 were synthesized by two sequential deposition methods: sequential deposition-precipitation with urea (DPU) and impregnation (IMP)-DPU. Segregated nanoparticles (RhcoreAushell ball-cup-type, and Janus-type arrangements) were observed in gold-rhodium bimetallic catalysts, but mainly ball-cup-type and Janus-type nanoparticles were found on catalysts prepared by IMP-DPU. XPS analysis of gold-rhodium bimetallic catalysts, before and after reaction allowed concluding that gold-rhodium interaction on metallic state was an important factor to avoid the oxidation of rhodium during CO oxidation. However, this effect of stabilization of the rhodium metallic phase by gold does not fully explain the promoting effect observed for some bimetallic catalysts on CO oxidation. Some structural aspects such as the atomic arrangement of the bimetallic nanoparticles and the type of active sites, determined by DRIFTS-CO, were also considered. TPR and UV–visible DR spectroscopy characterizations also showed differences in the gold-rhodium interactions.

Enhancing sulfur resistance of oxides in carbon monoxide oxidation by a high‐entropy‐stabilized strategy

AbstractIndustrial chemical processes require sulfur‐resistant catalysts, which reduce catalyst replacement costs and simplify process operations. Herein, a high‐entropy‐stabilized strategy was put forward for sulfur‐resistant catalysis. A spinel high entropy (Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4) was introduced by ball milling process with aluminum isopropoxide as the main precursor. Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4 possessed a high surface area of 171.2 m2 g−1, higher than typical high‐entropy oxides (HEOs). The high‐entropy spinel catalyst exhibited better SO2‐resistance performance in the oxidation of carbon monoxide, better than the simple oxides. The SO2‐resistance of Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4 was primarily improved by reinforcing the stability of the oxide using a high‐entropy structure to decrease the absorption of SO2 on its surface. Any adsorbed SO2 on the surface of the HEO was then selectively trapped by sacrificial metal ions with stronger electron‐withdrawing ability, protecting the active center (Cu2+, Co2+) from poisoning. This work reveals the significance of high‐entropy structures in sulfur resistance.

Urban air pollution evaluation in downtown streets of a medium-sized Latin American city using AERMOD dispersion model.

The transport sector is considered the largest contributor of air pollutants in urban areas, mainly on-road vehicles, affecting the environment and human health. Bahía Blanca is a medium-sized Latin American city, with high levels of traffic in the downtown area during peak hours. In this regard, it is necessary to analyze air pollution using an air quality model considering that there are no air pollutant measurements in the central area. Furthermore, this type of study has not been carried out in the region and since the city is expected to grow, it is necessary to evaluate the current situation in order to make effective future decisions. In this sense, the AERMOD model (US-EPA version) and the RLINE source type were used in this work. This study analyzes the variations of pollutant concentrations coming from mobile sources in Bahía Blanca's downtown area, particularly carbon monoxide (CO) and nitrogen oxides (NOx) during the period Jul-2020 to Jun-2022. It is interesting to note the results show the maximum concentration values detected are not directly associated with maximum levels of vehicle flow or emission rates, which highlights the importance of meteorological parameters in the modeling. In addition, alternative scenarios are proposed and analyzed from a sustainable approach. Regarding the scenario analysis, it can be concluded that diesel vehicles have a large influence on NOx emissions. Moreover, restrictions as strict as those proposed for a Low Emission Zone would be less applicable in the city than alternative temporary measures that modify traffic at peak hours.

Assessing the Intrinsic Activity of Pt‐Group Electrocatalysts for Carbon Monoxide Oxidation: Best Practices and Benchmarking Parameters

AbstractPt‐group elements are the state‐of‐the‐art electrocatalysts for various fuel cells. However, their CO‐poising is a critical hitch for large‐scale applications, so the researchers are exerting huge efforts to solve this issue. The exponentially increasing attention in this field pressures the researchers to publish their findings quickly, leading to unavoidable flawed evaluation parameters for the intrinsic activity of electrocatalysts. The CO oxidation (COOxid) is highly sensitive to various factors. Thus, it is urgent to afford a deeper understanding of the inherent COOxid activity of state‐of‐the‐art electrocatalysts and adopt accurate guidelines for researchers to test, optimize, and compare their electrocatalysts. This review provides exactitude in the evaluation and precise assessment of the key descriptors related to electrocatalysts (i. e., effect of both size, shape, and support) and CO oxidation (i. e., effect of electrolyte, working electrode, and CO surface diffusion). This is besides the fundamental aspects (i. e., COOxid Process, mechanism, measurements, calculations, thermodynamics, and kinetics). Various experimental results from our group and others besides in‐situ analysis were provided to support our deep discussion. Finally, we provide a brief synopsis of the relevant milestones of the up‐to‐date challenges and perspectives.

Validation and analysis of the Polair3D v1.11 chemical transport model over Quebec

Abstract. Air pollution is a major health hazard, and while air quality overall has been improving in industrialized nations, pollution is still a major economic and public health issue, with some species, such as ozone (O3), still exceeding the standards set by governing agencies. Chemical transport models (CTMs) are valuable tools that aid in our understanding of the risks of air pollution both at local and regional scales. In this study, the Polair3D v1.11 CTM of the Polyphemus air quality modeling platform was set up over Quebec, Canada, to assess the model's capability in predicting key air pollutant species over the region, at seasonal temporal scales and at regional spatial scales. The simulation by the model included three nested domains, at horizontal resolutions of 9 km by 9 km and 3 km by 3 km, as well as two 1 km by 1 km domains covering the cities of Montréal and Québec. We find that the model captures the spatial variability and seasonal effects and, to a lesser extent, the hour-by-hour or day-to-day temporal variability for a fixed location. The model at both the 3 km and the 1 km resolution struggled to capture high-frequency temporal variability and showed large variabilities in correlation and bias from site to site. When comparing the biases and correlation at a site-wide scale, the 3 km domain showed slightly higher correlation for carbon monoxide (CO), nitrogen dioxide (NO2), and nitric oxide (NO), while ozone (O3), sulfur dioxide (SO2), and PM2.5 showed slight increases in correlation at the 1 km domain. The performance of the Polair3D model was in line with other models over Canada and comparable to Polair3D's performance over Europe.

CO-tolerance behaviors of proton exchange membrane fuel cell stacks with impure hydrogen fuel

Carbon monoxide poisoning poses a significant challenge for proton exchange membrane (PEM) fuel cells operating with CO-containing hydrogen. One established solution involves air bleeding, a process that enhances the oxidation of carbon monoxide at the anode side of the fuel cell by blending a small quantity of air with the impure hydrogen before its introduction into the fuel cell. However, researchers have raised concerns regarding durability issues about catalyst sintering and membrane decomposition induced by air bleeding. The effects and underlying mechanisms of air bleeding on PEM fuel cells have yet to be comprehensively elucidated. To address this, this study conducts a detailed durability test to quantitatively evaluate the effects of air bleeding on the CO-containing hydrogen-fueled PEM fuel cells via the micro-current excitation method. The investigation substantiates that the PtRu/C catalysts significantly enhance both the performance and durability of fuel cells when air bleeding is employed, exhibiting different CO-tolerance and decay behaviors compared to the Pt/C anode catalyst. Furthermore, the evolution of MEA parameters indicates that the advantageous behaviors of PtRu/C catalysts can be attributed to their CO-tolerance capabilities, alleviated anodic catalyst sintering and loss, and decreased chemical carbon support corrosion and membrane decomposition through diminished hydrogen peroxide generation. This study contributes critical insights and empirical evidence for researchers focusing on CO-tolerant catalyst materials, the durability of PEM fuel cells, and the conversion and utilization of impure hydrogen energy derived from fossil fuels.

Investigation of nanoparticle (Fe3O4) addition to 3rd generation biodiesel (spirulina microalgae)/diesel mixture as an innovative fuel according to different engine variables: An RSM optimization

In order to reduce dangerous air pollution and lessen the hazards associated with climate change, biofuels made from vegetable biomass can be utilized as fuel in diesel engines. However, feedstocks and the crop space needed for their cultivation are unavoidable barriers that hinder its adoption and result in a shortage of farmland for increasing food profits. Nevertheless, microalgae are the most reliable and competent biodiesel supply because they are not edible and do not require cropland. Additionally, the addition of nanoparticles has become popular to improve the negative aspects of biodiesel. Based on these, in this study, multi-purpose optimization research was conducted on the addition of iron oxide (Fe3O4) nanoparticles in three different amounts (25, 50, and 75 ppm) to 20 % synthesized spirulina microalgae biodiesel (SSMB)/80 % diesel mixtures. Tests were conducted at three different compression ratios (14.5:1, 15.5:1, and 16.5:1) (CoR) and four different engine loads (25 %, 50 %, 75 %, and 100 %). The response surface methodology (RSM) optimization process was performed with the test results. According to RSM, a desirability coefficient of 0.8299, 15.80:1 CoR, 68 ppm AoN, and 45 % LoE were the ideal conditions. The optimum responses under these circumstances were 421.9653 g/kWh, 19.4014 %, 0.0939 %, 4.0785 %, 73.1716 ppm and 253.0620 ppm for brake-specific fuel consumption (BSFC), brake-thermal efficiency (BTHE), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon (HC), and nitrogen oxide (NOx), respectively. RSM could be used successfully because the error rates (maximum 6.5 %) when comparing the test results with the RSM optimization outcomes were within reasonable bounds.

Performance and Emission Analysis of Ethanol-Petrol Blends in Single-Cylinder Engines: A Sustainability Perspective

This study investigates the blending of ethanol and petrol in the Indian subcontinent, addressing the urgent need for sustainable fuel alternatives amid rising energy demands and environmental concerns. Ethanol, as a renewable biofuel, presents a viable option for enhancing the efficiency of internal combustion engines while reducing harmful emissions. Given the significant air pollution issues prevalent in urban areas of India, optimizing fuel blends can substantially improve engine performance and contribute to cleaner air. The primary objectives of this research include analyzing the impact of different ethanol-petrol blends on the performance of a single-cylinder petrol engine, assessing key performance metrics such as brake power, Indicated Mean Effective Pressure (IMEP), Brake Mean Effective Pressure (BMEP), and Brake Thermal Efficiency (BTHE). Emission analysis was conducted to measure hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO₂), oxygen (O₂), and nitrogen oxides (NOₓ) across various blends, quantifying the environmental impact of each. Grey Relation Analysis (GRA) was employed to rank the fuel blends based on their performance and emissions, helping identify the most effective blend for optimal engine operation. Additionally, the sustainability of ethanol blending as an alternative fuel solution in the Indian automotive sector was assessed. The study recorded key performance indicators and emissions using standardized techniques, with GRA calculating Grey relational coefficients to measure the degree of similarity between observed data and desired outcomes. This approach facilitated the ranking of blends, ultimately identifying the optimal ethanol-petrol blend. The findings revealed significant variations in both performance and emissions across different blends, indicating that ethanol blending holds substantial promise as a sustainable solution for the Indian automotive sector. These insights align with recent studies on the benefits of biofuels in enhancing engine performance and reducing emissions, providing valuable guidance for optimizing ethanol-petrol blends to improve sustainability in energy consumption.

Performance of Transition Metal Supported Al2O3 Coated on Honeycomb Catalysts and Its Segmentation on Exhaust Gasses Oxidation

The oxidation of carbon monoxide (CO) and unburnt hydrocarbons (HC) under segmented honeycomb catalysts was investigated using actual exhaust gas mixtures from a gasoline-fueled internal combustion engine of a motorcycle. The honeycomb catalysts were prepared through a wet process, resulting in four types coated with transition metals (Cu, Cr, Fe, and Ni) supported on Al2O3. The oxidation of CO and HC was monitored using an exhaust gas analyzer across a range of air-to-fuel ratios (AFR), from lean to rich, under stationary conditions. The results demonstrate that the honeycomb catalysts effectively decreased CO and HC concentrations in the exhaust gas. Among the transition metal oxide honeycomb catalysts, Cr and Ni exhibited high CO and HC conversion rates, surpassing those observed with Cu. The average CO and HC conversion calculations, spanning from lean to rich air-to-fuel ratios, were consistent with the actual conversion rates achieved. Furthermore, the study investigated the effect of honeycomb segmentation on CO and HC conversion. Surprisingly, the catalytic performance of Cr and Ni remained high even with longer gaps in the honeycomb. Interestingly, the conversion of CO and HC over the iron oxide honeycomb catalyst increased as the gap in the honeycomb became longer. This is likely due to an increase in the gap size and enhanced re-mixing of reactants (CO, HC, and O2) caused by recirculation. Thus, this study provides valuable elucidation on the potential application of segmented honeycomb catalysts for reducing CO and HC emissions in exhaust gases.

Optimal planning and designing of microgrid systems with hybrid renewable energy technologies for sustainable environment in cities.

Although hybrid wind-biomass-battery-solar energy systems have enormous potential to power future cities sustainably, there are still difficulties involved in their optimal planning and designing that prevent their widespread adoption. This article aims to develop an optimal sizing of microgrids by incorporating renewable energy (RE) technologies for improving cost efficiency and sustainability in urban areas. Diverse RE technologies such as photovoltaic (PV) systems, biomass, batteries, wind turbines, and converters are considered for system configuration to obtain this goal. Net present cost (NPC) is this study's objective function for optimal sizing microgrid configuration. For demonstration, we assess the technical, economic factors, and atmospheric emissions of optimal hybrid renewable energy systems for Putrajaya City in Malaysia. The required solar radiation data, temperature, and wind speeds are collected from the NASA surface metrological database. From the quantitative analysis of simulations, the biomass-battery-based system has optimal economic outcomes compared to other systems with an NPC of around 1.07M$, while the cost of energy (COE) is 0.118 $/kWh. Moreover, environmentally safe nitrogen oxide emissions, carbon monoxide, and carbon dioxide concentrations exist. The grid-tied RE technology boasts cost-effectiveness, with an NPC of 348,318 $ and a COE of 0.0112 $/kWh. This study aids decision-makers in formulating policies for integrating hybrid RE systems in urban areas, promoting sustainable energy generation.

Dynamic trend of lung fluid movement during exercise in heart failure: From lung imaging to alveolar-capillary membrane function

BackgroundIn chronic heart failure (HF), exercise-induced increase in pulmonary capillary pressure may cause an increase of pulmonary congestion, or the development of pulmonary oedema. We sought to assess in HF patients the exercise-induced intra-thoracic fluid movements, by measuring plasma brain natriuretic peptide (BNP), lung comets and lung diffusion for carbon monoxide (DLCO) and nitric oxide (DLNO), as markers of hemodynamic load changes, interstitial space and alveolar-capillary membrane fluids, respectively. Methods and resultsTwenty-four reduced ejection fraction HF patients underwent BNP, lung comets and DLCO/DLNO measurements before, at peak and 1 h after the end of a maximal cardiopulmonary exercise test. BNP significantly increased at peak from 549 (328–841) to 691 (382–1207, p < 0.0001) pg/mL and almost completely returned to baseline value 1 h after exercise. Comets number increased at peak from 9.4 ± 8.2 to 24.3 ± 16.7, returning to baseline (9.7 ± 7.4) after 1 h (p < 0.0001). DLCO did not change significantly at peak (from 18.01 ± 4.72 to 18.22 ± 4.73 mL/min/mmHg), but was significantly reduced at 1 h (16.97 ± 4.26 mL/min/mmHg) compared to both baseline (p = 0.0211) and peak (p = 0.0174). DLNO showed a not significant trend toward lower values 1 h post-exercise. ConclusionsModerate/severe HF patients have a 2-step intra-thoracic fluid movement with exercise: the first during active exercise, from the vascular space toward the interstitial space, as confirmed by comets increase, without any effect on diffusion, and the second, during recovery, toward the alveolar-capillary membrane, clearing the interstitial space but worsening gas diffusion.

Synthesis and Catalytic Performance of High-Entropy Rare-Earth Perovskite Nanofibers: (Y0.2La0.2Nd0.2Gd0.2Sm0.2)CoO3 in Low-Temperature Carbon Monoxide Oxidation.

This study investigated the catalytic properties of low-temperature oxidation of carbon monoxide, focusing on (Y0.2La0.2Nd0.2Gd0.2Sm0.2)CoO3 synthesized via a glycothermal method using 1,4-butanediol and diethylene glycol at 250 °C. This synthesis route bypasses the energy-intensive sintering process at 1200 °C while maintaining a high-entropy single-phase structure. The synthesized material was characterized structurally and chemically by X-ray diffraction and SEM/EDX analyses. The material was shown to form nanofibers of (Y0.2La0.2Nd0.2Gd0.2Sm0.2)CoO3, thereby increasing the active surface area for catalytic reactions, and crystallize in the model Pbnm space group of distorted perovskite cell. Using a custom setup to investigate catalytic properties of (Y0.2La0.2Nd0.2Gd0.2Sm0.2)CoO3, the CO oxidation behavior of those high-entropy perovskite oxide was investigated, showing an overall conversion of 78% at 50 °C and 97% at 100 °C. These findings highlight the effective catalytic activity of nanofibers of (Y0.2La0.2Nd0.2Gd0.2Sm0.2)CoO3 under mild conditions and their versatility in various catalytic processes of robust CO neutralization. The incorporation of rare-earth elements into a high-entropy structure could impart unique catalytic properties, promoting a synergistic effect that enhances performance.

CO and O2 Interaction with Kinked Pt Surfaces.

We investigate the chemical interaction of carbon monoxide (CO) and oxygen (O2) with kink atoms on steps of platinum crystal surfaces using a specially designed Pt curved sample. We aim at describing the fundamental stages of the CO oxidation reaction, i.e., CO-covered/poisoned stage and O-covered/active stage, at the poorly known kinked Pt facets by probing CO uptake/saturation and O2 saturation, respectively. Based on the systematic analysis that the curved surface allows, and using high-resolution X-ray photoemission, a diversity of terrace and step/kink species are straightforwardly identified and accurately quantified, defining a smooth structural and chemical variation across different crystal planes. In the CO-saturated case, we observe a preferential adsorption at step edges, where the CO coverage reaches a CO molecule per step Pt atom, significantly higher than their close-packed analogous steps with straight terrace termination. For the O-saturated surface, a significantly higher O coverage is observed in kinked planes compared to the Pt(111) surface. While the strong adsorption of CO at the kinked edges points toward a higher ignition temperature of the CO oxidation at kinks as compared to terraces, the large O coverage at steps may lead to an increased reactivity of kinked surfaces during the active stage of the CO oxidation.

Comparative Experimental Assessment of Pollutant Emission Behavior in Combustion of Untreated and Thermally Treated Solid Biofuels from Spruce Chips and Rapeseed Straw

Biomass energy for heating is going to be part of the spectrum of renewable energy sources. However, biomass combustion produces emissions of various pollutants with negative effects at both local and global scales. To reduce some of the locally important pollutant load, thermally treated biomass fuels may offer a partial solution. In this study, two biomass feedstocks, i.e., spruce chips and rapeseed straw, were thermally treated at 300 °C to produce biochars. Subsequently, both original materials and biochars were burned in a 25 kW retort combustion device. In both cases, the biochar showed lower emissions of carbon monoxide and nitrogen oxides, usually almost across the whole range of tested combustion conditions. In total, for the emission production per unit of net calorific value, the spruce biochar showed reductions in CO and NOx productions of 10.8% and 14.5%, respectively. More importantly, in rapeseed straw biochar, the difference was more pronounced. The total production was reduced by 28% and 42%, again in CO and NOx emissions, respectively.