NOx Storage on BaTi0.8Cu0.2O3 Perovskite Catalysts: Addressing a Feasible Mechanism.
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ABSTRACT:
SUBMITTER: Albaladejo-Fuentes V
PROVIDER: S-EPMC8401998 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Pt/K2CO3/MgAlOx-reduced graphene oxide (Pt/K/MgAlOx-rGO) hybrids were synthesized, characterized and tested as a promising NOx storage and reduction (NSR) catalyst. Mg-Al layered double hydroxides (LDHs) were grown on rGO via in situ hydrothermal crystallization. The structure and morphology of samples were thoroughly characterized using various techniques. Isothermal NOx adsorption tests indicated that MgAlOx-rGO hybrid exhibited better NOx trapping performance than MgAlOx, from 0.44 to 0.61?mmol?·?g-1, which can be attributed to the enhanced particle dispersion and stabilization. In addition, a series of MgAlOx-rGO loaded with 2?wt% Pt and different loadings (5, 10, 15, and 20?wt%) of K2CO3 (denoted as Pt/K/MgAlOx-rGO) were obtained by sequential impregnation. The influence of 5% H2O on the NOx storage capacity of MgAlOx-rGO loaded with 2?wt% Pt and 10% K2CO3 (2Pt/10?K/MgAlOx-rGO) catalyst was also evaluated. In all, the 2Pt/10?K/MgAlOx-rGO catalyst not only exhibited high thermal stability and NOx storage capacity of 1.12?mmol?·?g-1, but also possessed excellent H2O resistance and lean-rich cycling performance, with an overall 78.4% of NOx removal. This work provided a new scheme for the preparation of highly dispersed MgAlOx-rGO hybrid based NSR catalysts.
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Project description:NOx is a notorious emission from motor vehicles and chemical factories as the precursor of acid rain and photochemical smog. Although zirconia-based NOx sensors have been developed and showed high sensitivity and selectivity at a high temperature of above 800?°C, they fail to show good performance, and even don't work at the typical work temperature window of the automotive engine (<500?°C). It still is a formidable challenge for development of mild-temperature NOx detector or sensor. Herein, a novel amperometric solid-state NOx sensor was developed using perovskite-type oxide Gd1-xCaxAlO3-?(GCA) as the electrolyte and NiO as the sensing electrode. NOx sensing properties of the device were investigated at the temperature region of 400-500?°C. The response current value at -300?mV was almost linearly proportional to the NOx concentration between 300 and 500?ppm at 500?°C. At such a temperature, the optimal sensor gave the highest NO2 sensitivity of 20.15?nA/ppm, and the maximum response current value reached 5.57??A. Furthermore, a 90% response and 90% recover time to 500?ppm NO2 were about 119 and 92?s, respectively. The excellent selectivity and stability towards NOx sensing showed the potential application of the sensor in motor vehicles.
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Project description:Exsolution of metal nanoparticles from perovskite-type oxides is a very promising approach to obtain catalysts with superior properties. One particularly interesting property of exsolution catalysts is the possibility of electrochemical switching between different activity states. In this work, synchrotron-based in-situ X-ray diffraction experiments on electrochemically polarized La0.6Sr0.4FeO3-δ thin film electrodes are performed, in order to simultaneously obtain insights into the phase composition and the catalytic activity of the electrode surface. This shows that reversible electrochemical switching between a high and low activity state is accompanied by a phase change of exsolved particles between metallic α--Fe and Fe-oxides. Reintegration of iron into the perovskite lattice is thus not required for obtaining a switchable catalyst, making this process especially interesting for intermediate temperature applications. These measurements also reveal how metallic particles on La0.6Sr0.4FeO3-δ electrodes affect the H2 oxidation and H2O splitting mechanism and why the particle size plays a minor role.
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Project description:The two-dimensional (2D) temporal evolution of the NO-concentration over a NOx-storage catalyst is investigated in situ with planar laser-induced fluorescence (PLIF) in an optically accessible parallel wall channel reactor. Signal accumulated phase-correlated 2D-recordings of repetitive adsorption/desorption cycles are obtained by synchronizing the switching of the NO gas flow (on/off) with the laser and detection system, thereby significantly increasing the signal-to-noise ratio. The gas compositions at the reactor outlet are additionally monitored by ex-situ analytics. The impacts of varying feed concentration, temperature and flow velocities are investigated in an unsteady state. Transient kinetics and the mass transfer limitations can be interpreted in terms of the NO concentration gradient changes. The technique presented here is a very useful tool to investigate the interaction between surface kinetics and the surrounding gas flow, especially for transient catalytic processes.
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Project description:Whilst the highest power conversion efficiency (PCE) perovskite solar cell (PSC) devices that have reported to date have been fabricated by high temperature sintering (>500 °C) of mesoporous metal oxide scaffolds, lower temperature processing is desirable for increasing the range of substrates available and also decrease the energy requirements during device manufacture. In this work, titanium dioxide (TiO2) mesoporous scaffolds have been compared with metal oxide oxidation catalysts: cerium dioxide (CeO2) and manganese dioxide (MnO2). For MnO2, to the best of our knowledge, this is the first time a low energy band gap metal oxide has been used as a scaffold in the PSC devices. Thermal gravimetric analysis (TGA) shows that organic binder removal is completed at temperatures of 350 °C and 275 °C for CeO2 and MnO2, respectively. By comparison, the binder removal from TiO2 pastes requires temperatures >500 °C. CH3NH3PbBr3 PSC devices that were fabricated while using MnO2 pastes sintered at 550 °C show slightly improved PCE (η = 3.9%) versus mesoporous TiO2 devices (η = 3.8%) as a result of increased open circuit voltage (Voc). However, the resultant PSC devices showed no efficiency despite apparently complete binder removal during lower temperature (325 °C) sintering using CeO2 or MnO2 pastes.
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Project description:Nitric oxide (NO) signaling in mammals controls important processes such as smooth muscle relaxation and neurotransmission by the activation of soluble guanylate cyclase (sGC). NO binding to the heme domain of sGC leads to dissociation of the iron-histidine (Fe-His) bond, which is required for enzyme activity. The heme domain of sGC belongs to a larger class of proteins called H-NOX (Heme-Nitric oxide/OXygen) binding domains. Previous crystallographic studies on H-NOX domains demonstrate a correlation between heme bending and protein conformation. It was unclear, however, whether these structural changes were important for signal transduction. Subsequent NMR solution structures of H-NOX proteins show a conformational change upon disconnection of the heme and proximal helix, similar to those observed in the crystallographic studies. The atomic details of these conformational changes, however, are lacking in the NMR structures especially at the heme pocket. Here, a high-resolution crystal structure of an H-NOX mutant mimicking a broken Fe-His bond is reported. This mutant exhibits specific changes in heme conformation and major N-terminal displacements relative to the wild-type H-NOX protein. Fe-His ligation is ubiquitous in all H-NOX domains, and therefore, the heme and protein conformational changes observed in this study are likely to occur throughout the H-NOX family when NO binding leads to rupture of the Fe-His bond.
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Project description:Mn-based oxides are promising for the selective catalytic reduction (SCR) of NOx with NH3 at temperatures below 200 °C. There is a general agreement that combining Mn with another metal oxide, such as CeOx improves catalytic activity. However, to date, there is an unsettling debate on the effect of Ce. To solve this, here we have systematically investigated a large number of catalysts. Our results show that, at low-temperature, the intrinsic SCR activity of the Mn active sites is not positively affected by Ce species in intimate contact. To confirm our findings, activities reported in literature were surface-area normalized and the analysis do not support an increase in activity by Ce addition. Therefore, we can unequivocally conclude that the beneficial effect of Ce is textural. Besides, addition of Ce suppresses second-step oxidation reactions and thus N2O formation by structurally diluting MnOx. Therefore, Ce is still an interesting catalyst additive.
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Project description:BackgroundSelf-management is recommended for patients with chronic conditions, but its use with cancer survivors is underexplored. Optimal strategies for achieving lifestyle changes in cancer survivors are not known.ObjectiveWe aimed to determine feasibility, acceptability and preliminary efficacy of self-management-based nutrition and physical activity interventions for cancer survivors.Design, setting and participantsAdult survivors (n = 25) during (Group 1 , n = 11) or post (Group 2, n = 14)-curative chemotherapy for solid tumours, most (n = 20, 80%) with breast cancer, were recruited prospectively from a single clinical centre.InterventionThe Flinders Living Well Self-Management Program, a generic self-management care planning programme, was utilized to establish patient-led nutrition and exercise goals within a tailored 12-week intervention. Fortnightly progress reviews occurred with assessments at baseline, 6 and 12 weeks.ResultsMost participants (84%) found the intervention acceptable/very acceptable. Both groups showed a trend towards significant improvement in the self-management capability 'knowledge about changing risk factors' (P = 0.047); Group 2 showed a trend towards significantly improved 'psychological impacts' (P = 0.007). Goal ratings improved for both groups (P = 0.001). Quality of life improved for both groups for emotional functioning (P = 0.03). Physical functioning improved for Group 2 (P = 0.05); however, most symptom domains worsened for Group 1, as expected given their treatment stage.Discussion and conclusionsSelf-management interventions are feasible for this population. In particular, building self-management capacity during the active phase of patients' cancer treatment provides health and psychosocial benefits. Larger randomized controlled trials are required to further determine efficacy. Further translational research is also needed to determine acceptability,feasibility, enablers and barriers for clinicians embedding this approach into routine cancer survivorship care.
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Project description:Symbolic regression (SR) is an approach of interpretable machine learning for building mathematical formulas that best fit certain datasets. In this work, SR is used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. A simple descriptor, ?/t, where ? and t are the octahedral and tolerance factors, respectively, is identified, which accelerates the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesise five new oxide perovskites and characterise their OER activities. Remarkably, four of them, Cs0.4La0.6Mn0.25Co0.75O3, Cs0.3La0.7NiO3, SrNi0.75Co0.25O3, and Sr0.25Ba0.75NiO3, are among the oxide perovskite catalysts with the highest intrinsic activities. Our results demonstrate the potential of SR for accelerating the data-driven design and discovery of new materials with improved properties.
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