To reduce air pollution worldwide, regulations on exhaust gas emissions from ships are becoming increasingly stringent. One fuel that is being considered as an alternative to replace the heavy fuel ...oil used in existing ship engines and thereby reduce harmful emissions, such as NOx, SOx, and greenhouse gases, is sulfur-free liquefied petroleum gas (LPG). To assess the viability of this alternative, it is necessary to understand propane reactivity, the main component of LPG, and develop after-treatment devices applicable to LPG engines. This research evaluated the performance of three prototype Pd-based three-way catalysts (TWCs) with varying Pd loadings (6.5, 4.1, and 1.4 g/L), focusing on their effectiveness concerning propane reactivity in LPG engines. For the fresh samples, catalysts with 4.1 g/L Pd demonstrated performance that was comparable to, or even surpassed, those containing 6.5 g/L Pd. Notably, the temperature of 50% conversion (T50) for NO and C3H8 in the fresh Pd-4.1 was lower by 14 °C and 10 °C, respectively, compared to the fresh Pd-6.5 sample, despite having 37% less precious-metal loading. However, after hydrothermal aging at 900 °C for 100 h, the performance of the 4.1 g/L Pd catalyst significantly deteriorated, exhibiting lower efficiency than the 6.5 g/L Pd catalyst. The study also delved into various probe reactions, including the water–gas shift and propane steam reforming. Advanced analytical techniques, such as N2 physisorption and scanning transmission electron microscopy, were employed to elucidate the texture and structural characteristics of the catalyst, providing a comprehensive understanding of its behavior and potential applications. Through this research, within the efforts of the maritime sector to address challenges posed by emission regulations and rising costs associated with precious metals, this study has the potential to contribute to the development of cost-effective emission control solutions.
► Novel thiolated carbon nanostructures – platinum nanoparticles t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt have been synthesized, and t-GO-C(O)-pt and t-MWCNT-C(O)-S-pt denotes as t-GO-pt and t-MWCNT-Pt in ...manuscript, respectively. ► The modified electrode denoted as PDDA/t-GO-pt/GCE was used for the electrochemical determination of H2O2 for the first time. ► The results show that PDDA/t-GO-pt nanoparticles have the promising potential as the basic unit of the electrochemical biosensors for the detection of H2O2. ► The proposed H2O2 biosensors exhibited wide linear ranges and low detection limits, giving fast responses within 10s.
Glassy carbon electrodes were coated with thiolated carbon nanostructures – multi-walled carbon nanotubes and graphene oxide. The subsequent covalent addition of platinum nanoparticles and coating with poly(diallydimethylammonium chloride) resulted in biosensors that detected hydrogen peroxide through its electrocatalytic reduction. The sensors were easily and quickly prepared and showed improved sensitivity to the electrocatalytic reduction of H2O2. The Pt nanoparticles covalently bonded to the thiolated carbon nanostructures were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. Cyclic voltammetry and amperometry were used to characterize the biosensors’ performances. The sensors exhibited wide linear ranges and low detection limits, giving fast responses within 10s, thus demonstrating their potential for use in H2O2 analysis.
Thermal rectification in defect-engineered graphene with asymmetric hole arrangements is assessed via molecular dynamics simulations. Asymmetry in two different configurations (triangular and ...rectangular hole arrangements) is controlled by manipulating geometrical parameters, such as hole size; effects of geometry on the resultant rectification are investigated. Filtering of phonon propagation directions by geometrical confinement, and asymmetric relaxation distance induce a difference in heat transfer depending on transport direction, or thermal rectification. Increase in porosity, which results in additional confinement and larger difference in relaxation, produces more significant thermal rectification. While a rectangular arrangement of holes results in 70% of the maximum thermal rectification, up to 78% of rectification was achieved using a triangular arrangement within 47.5 nm of graphene, which can be attributed to more effective phonon-hole boundary scattering with a triangular arrangement. This study suggests a feasible approach to create thermal rectification and enables its fine control, contributing to the development of phononic devices and enhancement of thermal system design for electronics.
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With increasing concerns about global warming, the push for sustainable and eco-friendly fuels is accelerating. Propane, recognized as liquefied petroleum gas or LPG, has garnered research interest ...as an alternative fuel due to its notable advantages, including a high-octane rating, reduced greenhouse gas emissions, and potential cost-effectiveness. However, to realize its full potential as an alternative fuel it is essential to develop catalysts that efficiently handle emissions at low temperatures. In our research, we investigated three distinct palladium (Pd)-based three-way catalyst (TWC) formulations (PdRh, Pd-only, and Pd-OSC) to investigate the influence of typical TWC components rhodium (Rh) and oxygen storage components (OSC) in exhaust scenarios relevant to propane-fueled engines. Among these, the formulation containing oxygen storage components (Pd-OSC) showed the highest reactivity for both NO and C3H8 while minimizing performance degradation from hydrothermal aging (HTA). Notably, the temperature of 50% conversion (T50) for propane in the Pd-OSC fresh and HTA sample was lower by 30 °C and 13 °C, respectively, compared to the Pd-only sample, highlighting the role of oxygen storage materials in enhancing catalyst performance, even without dithering. Additionally, N2 physisorption showed that the Pd-OSC sample has a higher surface area and increased pore volume. This underscores the idea that OSC materials not only augment the catalyst’s porosity but also optimize reactant accessibility to active sites, thus elevating catalytic efficiency. In addition to evaluating performance, we further explored the performance and characteristics of the catalysts using catalytic probe reactions, such as water–gas shift and steam reforming reactions.
In the present study, two industry primary and secondary zinc dialkyldithiophosphate standards, ZDDP1 and ZDDP2, respectively, are evaluated for their impact on the performance of Pd-based three-way ...catalyst and bench-marked against two mixed lubricant additives formed from either ZDDP1 or ZDDP2 with a second-generation oil-miscible phosphoric-containing ionic liquid (IL). The three-way catalysts (TWCs) are exposed to the lubricant additives in an engine bench under four different scenarios: a base case with no additive (NA), ZDDP1, IL+ZDDP1, ZDDP2, and IL+ZDDP2. The engine-aged TWC samples are characterized through a variety of analytical techniques, including evaluation of catalyst reactivity in a bench-flow reactor. With respect to the water–gas shift reaction and the oxygen storage capacity, the ZDDP2- and IL+ZDDP2-aged TWC samples are more degraded than the ZDDP1- and IL+ZDDP1-aged TWC samples. X-ray diffraction (XRD) patterns indicate that phosphorus in the form of CePO4 was found to be present in the washcoat of all TWC samples, with the highest amount found in the ZDDP2-aged TWC sample. The results obtained from XRD are further confirmed by those from inductively coupled plasma-optical emission spectroscopy (ICP-OES), which show that more phosphorus is detected in the washcoat of ZDDP2- and IL+ZDDP2-aged TWC samples than in the ZDDP1- and IL+ZDDP1-aged TWC samples.
Boron-containing compounds are one of the lubricant additive options due to their suitable properties for additives and have been used as commercial lubricant additives. In the present study, the ...impact of a boron-containing lubricant oil additive, AR9100 (BR), on Pd/Rh-based three-way catalyst (TWC) performance is investigated, and the results are compared with the baseline no-additive (NA) case and the industry standard zinc dialkyl-dithiophosphate (ZDDP) results. Accelerated engine aging is performed using a genset to expose the catalysts to lubricant additives at high temperatures. All aged TWC samples are investigated for reactivity in a bench-flow reactor and characterized using a variety of analytical techniques. Compared with the no-additive case, the temperatures of 90% conversion (T90) of NO, CO, C3H6, and C3H8 for the ZDDP-aged TWC sample increased by 34, 30, 37, and 48 °C. However, the T90 of all gas species for the BR-aged TWC sample are similar to the NA-aged TWC sample. Additionally, a significant decrease in water–gas shift reactivity and oxygen storage capacity is observed in the ZDDP-aged sample, but not in the BR-aged sample. Inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis and electron probe microanalysis (EPMA) maps of accelerated engine aging samples show the presence of phosphorus and boron in ZDDP- and BR-aged TWC samples, respectively. However, no boron-related peaks are observed in the X-ray diffraction (XRD) pattern of the BR-aged TWC sample, which may exist in the form of an amorphous phase.
Graphene nanosheets can be produced from easily available starting materials. We synthesized several chemically different types of graphene nanosheet for use as electrocatalysts and characterized ...their electrochemical properties. We evaluated the surface morphologies of the graphene nanosheets via X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (SEM), and examined their electrocatalytic activities using electrochemical impedance spectroscopy (EIS). The results were compared with those for other graphene nanosheets, and the efficiency for the electrochemical detection of serotonin, known as an important neurotransmitter, was also studied. Electrocatalytic activities were verified by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). A wide variation of results was observed for each of the graphene nanosheets prepared by using three different reductants. Among these graphene nanosheets, RGO1, that was reduced by hydrazine and ammonia solution as a reductant, exhibited high sensitivity, good selectivity, low detection limit, fast response time, and stability.
Rh single atom catalysts (SACs) have been insensitively investigated recently due to the maximum utilization efficiency of Rh, one of the most expensive precious metals. Although great efforts have ...been made in the development and application of Rh SACs, there are few reports on the precise control of the local coordination environment of Rh single sites on CeO2 and their catalytic performance for N2O decomposition. Herein, Rh/CeO2 catalysts with different Rh–O coordination numbers (CNs) were successfully prepared using different CeO2 supports and a simple incipient wetness impregnation (IWI) method. It is observed that the Rh/CeO2 catalyst with slightly higher CN of Rh–O (Rh/CeO2-H) prepared from CeO2 shows much higher N2O decomposition activity than the catalyst with lower CN of Rh–O (Rh/CeO2-L) obtained from Ce(OH)x. The Rh species within Rh/CeO2-H are found to be more reactive than those within Rh/CeO2-L, which can better facilitate the O2 desorption once formed during N2O decomposition. In addition, more surface oxygen vacancies are present on Rh/CeO2-H than on Rh/CeO2-L, well explaining the superior N2O adsorption and activation capability on the former catalyst. It is concluded that more abundant oxygen vacancies and reactive Rh single atom sites with slightly higher CN of Rh–O and significantly higher reducibility altogether contribute to the superior N2O decomposition activity on the Rh/CeO2-H catalyst.
Rh/CeO2 single-atom catalysts with different Rh–O coordination numbers (CNs) were successfully prepared. The catalyst with higher CN of Rh–O shows higher N2O decomposition activity due to its more abundant oxygen vacancies and more reactive Rh single-atom sites. Display omitted
•Rh/CeO2 single atom catalysts with different Rh–O coordination numbers (CNs) were successfully prepared.•Rh/CeO2 catalyst with slightly higher CN of Rh–O (Rh/CeO2–H) showed much higher N2O decomposition activity than the one with lower CN of Rh–O (Rh/CeO2-L).•Rh species within Rh/CeO2–H was more reactive than that within Rh/CeO2-L in terms of reducibility.•More surface oxygen vacancies were present on Rh/CeO2–H than on Rh/CeO2-L.
► Covalently grafting Pt to MWCNT via sulfur atom (MWCNT–S–Pt). ► Enhancement of the catalyst activity via covalent bonding. ► Better catalysis with reduced Pt use in MWCNT–S–Pt. ► Enhanced four ...electron ORR with minimal H2O2 production.
A carbon nanostructure has fabricated from covalently grafted platinum (Pt) to multi walled carbon nanotube (MWCNT) with the assistance of sulfur atom on the MWCNT's sidewall, MWCNT–S–Pt. The MWCNT–S–Pt displays an excellent electrocatalytic performance for oxygen reduction reaction (ORR) than that of an unbonded Pt to MWCNT, MWCNT/Pt. Here we describe a comparative study of the ORR on two MWCNT-supported Pt-based catalysts in aqueous acidic electrolyte. Both MWCNT–S–Pt and MWCNT/Pt catalysts have the compositions of 1.03 and 2.18at% Pt, respectively. For the characterization, the bonding features have confirmed by the X-ray photoelectron spectroscopic (XPS) and electron microscopy have used to determine the size and shape as well as the distribution of the particle on both catalysts. Electrochemical measurements have performed using the cyclic voltammetry and hydrodynamic voltammetry methods in 0.1moll−1 HClO4 solution. Kinetic analysis in comparison to unbonded MWCNT/Pt a significant enhancement for the covalently bonded MWCNT–S–Pt has been found. The MWCNT/Pt is unstable at electrode potentials for long term use than that of MWCNT–S–Pt. Ring-current collection measurements for peroxide indicate MWCNT–S–Pt catalyst has a less peroxide yield.
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