Group Metals Research Articles

Advanced approach for active and durable proton exchange membrane fuel cells: Coupling synergistic effects of MNC nanocomposites

AbstractAtomically dispersed metal and nitrogen co‐doped carbon (MNC) is a promising oxygen reduction reaction (ORR) catalyst for electrochemical energy storage and conversion applications but typically suffers from low durability and activity under the acidic conditions of practical polymer electrolyte exchange membrane fuel cells (PEMFCs). Recently, the performance of MNC nanocomposites under acidic ORR conditions has been enhanced by exploiting the synergistic coupling effects of their constituents (single‐atom sites, nanoclusters, and nanoparticles). The unique geometric structures formed by the coupling of diverse sites in these nanocomposites provide optimal electronic structures and efficient reaction pathways, thus resulting in high activity and long‐term durability. This work provides an overview of MNC nanocomposites as ORR electrocatalysts under practical PEMFC conditions, focusing on activity and durability enhancement methods and highlighting the strategies used to prepare electrocatalytically efficient MNC nanocomposites containing no or low amounts of platinum group metals. Progress in the development of advanced MNC nanocomposites as acidic ORR catalysts is discussed, and the pivotal role of synergistic effects resulting from the coupling sites within the nanocomposites is explored together with the characterization methods used to elucidate these effects. Finally, the challenges and prospects of developing MNC nanocomposites as next‐generation electrocatalysts are presented.image

Multivariate Analysis of Geochemical Data to Determine Critical Minerals in Prigi Beach Sand, Trenggalek

Abstract Critical minerals are essential elements mainly for industry. As technological advancements, the demand for critical minerals also increases. Critical minerals include Rare Earth Elements (REE), Lithium (Li), Gallium (Ga), Germanium (Ge), Platinum Group Metals (PGM), Indium (In), Beryllium (Be), Tungsten (W), Cobalt (Co), Molybdenum (Mo), Niobium (Nb), Antimony (Sb), Vanadium (V), Nickel (Ni), Chromium (Cr), Tellurium (Te), Tin (Sn), Thorium (Th), Zirconium (Zr), Hafnium (Hf), Selenium (Se), Rhenium (Re), Phosphate (P), Potassium (K), and others. This study aims is to figure out the distribution of critical minerals in the sand of Prigi Beach, Trenggalek. Chemical elements are determined using X-Ray Fluorescence (XRF). Based on data analysis, critical minerals were detected with the presence of elements such as Al, K, Ca, Si, Ti, P, V, Mn, Cr, Zn, Fe, Sr, Eu, and Cu. Using the Pearson Correlation and Principal Component Analysis (PCA) methods. Significant correlations were found between (Al-Zn), (Si with K-Ti-V-Fe-Cu-Eu), (K with Ti-V-Fe-Cu-Eu), (Ca-Sr), (Ti with V-Mn-Fe-Cu-Eu), (V with Fe-Cu-Eu), (Fe-Eu), and (Cu-Eu). The elements that dominate the critical minerals based on geochemical data analysis of the sand revealed three highest concentrations consisting of Fe (41.44%), Si (35.32%), and Ca (10.96%). Base on several previous studies on critical minerals in beach sands, including a study by Endang (2023) it is know that Fe is a dominant element compared to others such Ca, Al, and K. This is due to the influence of various geological conditions and human activities.

Mechanochemical Thioglycolate Modification of Microscale Zero‐Valent Iron for Superior Heavy Metal Removal

Microscale zero‐valent iron (mZVI) is widely used for water pollutant control and environmental remediation, yet its reactivity is still constrained by the inert oxide shell. Herein, we demonstrate that mechanochemical thioglycolate (TG) modification can dramatically enhance heavy metal (NiII, CrVI, CdII, PbII, HgII, and SbIII) removal rates of mZVI by times of 16.7 to 88.0. Compared with conventional impregnation (wet chemical process), this dry mechanochemical process could construct more robust covalent bonding between TG and the inert oxide shell of mZVI through its electron‐withdrawing carboxylate group to accelerate the electron release from the iron core, and more effectively strengthen the surface heavy metal adsorption through metal(d)‐sulfur(p) orbital hybridization between its thiol group and heavy metal ions. Impressively, this mechanochemically TG‐modified mZVI exhibited an unprecedented NiII removal capacity of 580.4 mg Ni g−1 Fe, 17.1 and 9.5 times those of mZVI and wet chemically TG‐modified mZVI, respectively. Its application potential was further validated by more than 10 days of stable groundwater NiII removal in a column flow reactor. This study offers a promising strategy to enhance the reactivity of mZVI, and also emphasizes the importance of the modification strategy in optimizing its performance for environmental applications.

Mechanochemical Thioglycolate Modification of Microscale Zero-Valent Iron for Superior Heavy Metal Removal.

Microscale zero-valent iron (mZVI) is widely used for water pollutant control and environmental remediation, yet its reactivity is still constrained by the inert oxide shell. Herein, we demonstrate that mechanochemical thioglycolate (TG) modification can dramatically enhance heavy metal (NiII, CrVI, CdII, PbII, HgII, and SbIII) removal rates of mZVI by times of 16.7 to 88.0. Compared with conventional impregnation (wet chemical process), this dry mechanochemical process could construct more robust covalent bonding between TG and the inert oxide shell of mZVI through its electron-withdrawing carboxylate group to accelerate the electron release from the iron core, and more effectively strengthen the surface heavy metal adsorption through metal(d)-sulfur(p) orbital hybridization between its thiol group and heavy metal ions. Impressively, this mechanochemically TG-modified mZVI exhibited an unprecedented NiII removal capacity of 580.4 mg Ni g-1 Fe, 17.1 and 9.5 times those of mZVI and wet chemically TG-modified mZVI, respectively. Its application potential was further validated by more than 10 days of stable groundwater NiII removal in a column flow reactor. This study offers a promising strategy to enhance the reactivity of mZVI, and also emphasizes the importance of the modification strategy in optimizing its performance for environmental applications.

Leaching Platinum Group Metals from Simulated Spent Auto-Catalyst Material Using Ozone and Hydrochloric Acid

This paper reports the development of a process for leaching Pt, Pd, and Rh from simulated spent auto-catalyst material using ozone and hydrochloric acid in order to produce a pregnant leach solution that could be fed to an industrial precious metal refinery. The effects of O3 mass flow, initial acid concentration, and temperature were investigated using a Box–Behnken experimental design with three centre-point runs and a total leach time of 6 h. Set points of 3.34, 5.01, and 6.68 g/h; 1.0 M, 3.0 M, and 5.0 M; and 30, 60, and 90 °C were used for O3 mass flow, hydrochloric acid concentration, and temperature, respectively. The optimal extractions for Pt, Pd, and Rh were 80%, 85%, and 42%, respectively, at 5.01 g/h O3, 5.0 M HCl, and 90 °C. Statistical analyses indicated high dependencies of Pd and Rh on hydrochloric acid concentration and temperature, with only Pt displaying a significant dependence on O3 mass flow.

Mineralogical Impact on the Compaction of Residual Gabbro Soils in the Construction of Platinum Tailings Storage Facilities

AbstractOver the past decade, there have been 45 tailings storage facility (TSF) disasters worldwide resulting in fatalities, serious environmental damage, and the destruction of entire ecosystems. These failures often stem from substandard design or operational practices. Many TSFs are constructed in regions associated with intrusive mafic rocks such as gabbro, norite, pyroxenite, and anorthosite, which are commonly found alongside platinum group metals in areas like the Bushveld Igneous Complex in South Africa and the Great Dyke in Zimbabwe. The stability of these structures can be significantly influenced by the residual soils present at the construction sites. Residual soils, both cohesive and non-cohesive, contain varying quantities of different minerals, which can impact the compaction characteristics and, consequently, the stability of the TSF foundations. Cohesive soils rich in clay minerals, such as kaolinite and smectite, exhibit properties that can hinder effective soil compaction. The expansive nature of smectite due to its ability to absorb large amounts of water and host free exchangeable cations counteracts the compaction process, reducing soil stability. Soil compaction is a complex process influenced by several factors, including compaction effort, method, water content, particle size distribution, and mineralogy. This study aimed to analyse these factors using a series of laboratory tests, including foundation indicators, MOD AASHTO compaction testing, and X-ray diffraction analysis, on residual soils from two TSF construction sites. The findings revealed that soils with high clay content tend to retain more water and have a higher optimum water content, adversely affecting their compaction properties. This study highlights the critical need to consider the mineralogical composition and weathering effects of residual soils in the design and construction of TSFs. By improving our understanding of these factors, we can enhance the stability of TSF foundations, reducing the likelihood of future failures. The insights gained from this research highlight the importance of thorough geotechnical assessments in the successful design and maintenance of TSFs.

Risk assessment of heavy metals (Zn, Cu, Pb, and Ni) in the edible tissue of Oncorhynchus mykiss trout in the rivers of the southern Caspian Sea and the northern and southeast coast of Iran

The study aims to monitor and compare the concentration of heavy metals viz., zinc, copper, lead and nickel in the edible tissue of Oncorhynchus mykiss trout in the southern coast of Caspian Sea and the rivers of Khash city in the north-southeast coast of Iran. The average concentrations of zinc, copper, lead and nickel for the Stations in the north of Iran and the southeast of Iran were found 10.1, 8.1, 5.9, 4.7 and 6.5, 6.1, 3.5, 3.2 μg/g dry weight, respectively. Lead exceeded was the recommended standard limits by WHO, FAO, NHMRC, EC and UKMAFF. Based on the results, the average nickel metal was higher than the allowed concentration of international standards in all the studied stations, which indicates that more control should be done on the sources producing this metal around the target areas. furthermore, the daily intake (EDI) of the studied metals in all age groups were lower than the reference dose determined by the EPA organization and the tolerable intake (TI) provided by the FAO/WHO organization. The lowest frequency of daily consumption of Oncorhynchus mykiss was reported for the group of adult males and based on nickel metal (1.67 μg/g) and lead metal (1.14 μg/g) in the rivers located in the south of the Caspian Sea and the rivers of Khash city located in the southeast of Iran, respectively. The risk potential and risk index for non-cancerous diseases for all age groups in the muscle tissue of this fish was less than one, which shows that the consumption of this type of fish for human consumption will not cause a problem from the point of view of health and public health. However, management measures are necessary to prevent and control pollutants, especially in the southern shores of the Caspian Sea.

Diphosphonic ionic liquids as anion-exchangers for palladium(II) and platinum(IV): Synthesis, complexation and selective extraction from hydrochloric solutions

The demand for platinum group metals (PGMs) continues to grow. To reduce the negative environmental impact, it is necessary to switch to secondary sources of PGMs and to improve the separation and purification processes of these metals. In this work, new phosphonium-based ionic liquids (diphosphonium salts) were synthesized as extractants for the selective recovery of palladium(II) and platinum(IV) from hydrochloric acid solutions. Substances synthesized contain a doubly-charged cation, which significantly affects the selectivity of extraction compared to singly charged phosphonium extractants. It was found that diphosphonium salts have a high extraction efficiency of metallic ions that form stable doubly-charged chloride anionic complexes. Thus, solutions of synthesized ionic liquids in 3-nitrobenzotrifluoride can selectively extract palladium(II) and platinum(IV) in the presence of all d‐metal ions studied, which are contained in PGMs secondary sources. The extraction efficiency under optimal conditions is 99.6 % and 98.5 % for palladium(II) and platinum(IV), respectively. The extraction mechanism has been investigated by X-ray diffraction, DFT calculations and 31P, 111Cd NMR spectroscopy. Extraction proceeds through the anion-exchange mechanism, however, in the case of the studied compounds, the significant role of bromide as a counterion of ligands was shown. It was found that bromide is likely included in the extracted ion pair, displacing chloride ions from anionic metal complexes during extraction.

Iron capture mechanism for harmless recovering platinum group metals from spent automobile catalyst

ABSTRACT Automotive catalysts are the largest consumption source of platinum group metals (PGMs). When it exceeds its useful life, spent automotive catalysts (SACs) are the most important secondary PGMs resource and are classified as hazardous solid waste. Recycling SAC is a promising solution to alleviate the shortage of PGMs resources for projects and reduce environmental pollution. The technology for recovering PGMs by iron-melting collection can obtain Fe-PGMs alloy and harmless glass slag. In this paper, the spontaneous aggregation and growth behaviour of Fe and PGMs in slag at melting temperature were studied, and the settling velocity of Fe-PGMs particles in the slag was calculated to be 6.68 × 10−3 m/s. The effects of melting time, melting temperature and Fe dosage on PGMs recovery were determined, and the optimal conditions were 10 wt% Fe, 1500°C and 40 min. The toxicity test verifies that the slag obtained is a clean slag harmless to the environment. This work explains the mechanism of Fe collection of PGMs and provides a pathway for efficient and harmless recovery of PGMs from SAC.

Fabrication of Highly Dispersed Ru Catalysts on CeO2 for Efficient C3H6 Oxidation.

Emissions of volatile organic compounds (VOCs) threaten both the environment and human health. To realize the elimination of VOCs, Ru/CeO2 catalysts have been intensively investigated and applied. Although it has been widely acknowledged that the catalytic performance of platinum group metal catalysts was highly determined by their dispersion and coordination environment, the most reactive structures on Ru/CeO2 catalysts for VOCs oxidation are still ambiguous. In this work, starting from Ce-BTC (BTC = 1,3,5-benzenetricarboxylic acid) materials, atomically dispersed Ru catalysts and agglomerated Ru catalysts were successfully created via one-step hydrothermal method (Ru-CeO2-BTC) and conventional incipient wetness impregnation method (Ru/CeO2-BTC), respectively. In a typical model reaction of C3H6 oxidation, atomically dispersed Ruδ+ species with the formation of abundant Ru-O-Ce linkages on Ru-CeO2-BTC were found to perform much better than agglomerated RuOx species on Ru/CeO2-BTC. Further characterizations and mechanism study disclosed that Ru-CeO2-BTC catalyst with atomically dispersed Ru ions and more superior low temperature redox performance compared to Ru/CeO2-BTC could better facilitate the adsorption/activation of C3H6 and the decomposition/desorption of intermediates, thus exhibiting superior C3H6 oxidation activity. This work elucidated the reactive sites on Ru/CeO2 catalysts in the C3H6 oxidation reaction and provided insightful guidance for designing efficient Ru/CeO2 catalysts to eliminate VOCs.

Particle-Solid Transition Architecture for Efficient Passive Building Cooling.

Electricity consumption for building cooling accounts for a significant portion of global energy usage and carbon emissions. To address this challenge, passive daytime radiative cooling (PDRC) has emerged as a promising technique for cooling buildings without electricity input. However, existing radiative coolers face material mismatch issues, particularly on cementitious composites like concrete, limiting their practical application. Here, we propose a cementitious radiative cooling armor based on a particle-solid transition architecture (PSTA) to overcome these challenges. The PSTA design features an asymmetric yet monolithic morphology and an all-inorganic nature, decoupling radiative cooling from building compatibility while ensuring UV resistance. In the PSTA design, nanoparticles on the surface serve as sunlight scatterers and thermal emitters, while those embedded within a cementitious substrate provide build compatibility and cohesiveness. This configuration results in enhanced interfacial bonding strength, high solar reflectance, and strong mid-infrared emittance. Specifically, the PSTA delivers an enhanced interfacial shear strength (0.93 MPa), several-fold higher than that in control groups (metal, glass, plastic) along with a cooling performance (a subambient temperature drop of ∼6.6 °C and a cooling power of ∼92.8 W under a direct solar irradiance of ∼680 W/m2) that rivals or outperforms previous reports. Importantly, the design concept of the PSTA is applicable to various particles and solids, facilitating the practical application of PDRC technology in building scenarios.

Repurposing discarded porphyrin waste as electrocatalysts for the oxygen reduction reaction

The oxygen reduction reaction (ORR), presently known as the key bottleneck in the mass-scale implementation of fuel cells (FCs), typically relies on the exploitation of scarce and expensive platinum group metals (PGMs). Meanwhile, as a substitute for PGMs, transition metal-nitrogen carbons (TM-Nx-C) are proving to be reliable electrocatalysts (ECs) in which atomically dispersed TMs coordinated with nitrogen are integrated into the carbon matrix. Such TM-Nx coordination already exists in metal-porphyrins making them suitable precursors for TM-Nx-C. Adler-Longo method is the standard recipe for meso‑tetraphenyl porphyrin realizes ca. 20 % yield whereas the residual polypyrromethenes, structurally resembling open porphyrin rings, are often wasted. Herein, the possibility of upcycling waste polypyrromethenes into efficient TM-Nx-C for ORR is demonstrated. A comprehensive structural and morphological characterization is provided, and the electrocatalytic activity towards ORR in an alkaline environment is discussed using Fe and Mn as TMs. The EC synthesized from pure porphyrin precursor at 600 °C (FeTPP_600) had the best performance recording 0.972 and 0.852 V vs RHE for Eonset and E1/2. Mixing porphyrins with their synthetic waste (ratio of 1:4) and pyrolyzing it at 800 °C (FeTPP/Waste(1:4)_800) still exhibits appreciable kinetics with similar results (0.977 and 0.853 V vs RHE for Eonset and E1/2).

One-pot synthesis of FeNi3/FeNiOx nanoparticles for PGM-free anion exchange membrane water electrolysis

Low-temperature anion exchange membrane water electrolysis (AEMWE) is one of the most promising technologies to produce green hydrogen. To date, membrane-electrode assembly (MEA) based on platinum group metal (PGM) electrocatalysts shows higher performance than PGM-free ones. Here, a single and easy synthesis for non-noble metal electrocatalysts (PGM-free) for both hydrogen and oxygen evolution reactions (HER and OER) was developed. Both electrocatalysts consist of FeNi3/FeNiOx nanoparticles obtained through chemical reduction using hydrazine. The electrocatalyst exhibits an overpotential of 210 mV and 234 mV for HER and OER respectively, at a current density of 10 mA cm−2 in 1 M KOH electrolyte, allowing a comparison between mass activity and geometric activity compared to PGM catalysts. In addition to a preliminary electrochemical characterization of the FeNi3/FeNiOx, the electrocatalyst were integrated into a pilot-scale AEMWE at both anode and cathode, which reaches (without iR-correction) 1.72 V and 1.94 V at a current density of 0.4 A cm−2 and 1 A cm−2 respectively at 60 °C. This PGM-free MEA outperforms the one based on Pt/C at cathode and RuO2 at anode with a voltage gap of 284 mV at 1 A cm−2. The aforementioned MEA was tested for 150 h with a discontinuous power profile, in order to get an idea of the possible degradation trends for a future industrial application, the reversible and irreversible voltage losses were calculated resulting in a degradation rate of 886 µV/h. This work demonstrates a simple and scalable synthesis of earth-abundant electrocatalytic materials for high-efficiency AEM water electrolysis.

Understanding the Roles and Regulation Methods of Key Adsorption Species on Ni‐Based Catalysts for Efficient Hydrogen Oxidation Reactions in Alkaline Media

This review focuses on recent advancements in the development and understanding of nickel‐based catalysts for the hydrogen oxidation reaction in alkaline media. Given the economic and environmental limitations associated with platinum group metals , nickel‐based catalysts have emerged as promising alternatives due to their abundance, lower cost, and comparable catalytic properties. The review begins with an exploration of the fundamental HOR mechanisms, emphasizing the key roles of the reactive species in optimizing the catalytic activity of Ni‐based catalysts. Thermodynamic and stability optimizations of nickel‐based catalysts are thoroughly examined, focusing on alloying strategies, heteroatom incorporation, and the use of various support materials to enhance their catalytic performance and durability. The review also addresses the challenge of catalyst poisoning, particularly by carbon monoxide, and evaluates the effectiveness of different approaches to improve poison resistance. Finally, the review concludes by summarizing the key findings and proposing future research directions to further enhance the efficiency and stability of nickel‐based catalysts for practical applications in anion exchange membrane fuel cells. The insights gained from this comprehensive analysis aim to contribute to the development of cost‐effective and sustainable catalysts and facilitate the broader adoption of AEMFCs in the quest for clean energy solutions.

Kinetics of Iron Collector Leaching in HCl and HF Media

Automotive catalysts containing Platinum Group Metals (PGMs) are valuable secondary raw materials for refineries. Hydrometallurgical processing of catalysts is ineffective due to the low PGMs content—0.15–0.3%. Therefore, such raw materials are melted into an iron collector containing 1.5–5% PGMs. However, when leaching a collector containing 10–20% Si in both HCl and H2SO4, the recovery of PGMs does not exceed 40%. The latter indicates incomplete destroying of the PGM-encapsulating ferrosilicon matrix. To completely destroy the ferrosilicon matrix, it is proposed to carry out the leaching process in a mixture of HCl and HF. In this case, the extraction of Fe into solution and Si into the gas phase (in the form of SiF4) exceeds 90%. This should be sufficient to completely destroy the ferrosilicon matrix and release PGMs. The current work presents the results of studies of the leaching kinetics of the iron collector containing ferrosilicon in a mixture of HCl and HF using the Shrinking Core Model (SCM). It was found that the greatest positive effect on Fe extraction into solution is exerted by HCl concentration and temperature, while Si release into the gas phase is only influenced by HF concentration. In addition, during the destroying of ferrosilicon, FeF2 is formed and deposited on the surface of the material in the form of thin-film conglomerates. This leads to diffusion difficulties and a gradual decrease in the intensity of the iron collector leaching 30 min after the start of process. After 120 min, there may be a decrease in Fe recovery into solution.

Iron Chloride Vapor Treatment for Leaching Platinum Group Metals from Spent Catalysts

AbstractAn efficient and environmentally friendly recovery of platinum group metals (PGMs) from secondary sources is necessary to ensure a sustainable supply of PGMs. In this study, contact with FeCl2 vapor in the presence of metallic Fe was investigated as a useful pretreatment for leaching PGMs from spent automobile catalysts. Fe-PGM alloys were efficiently formed when Pt, Pd, and Rh wires and Rh2O3 powder were subjected to FeCl2 vapor treatment at 1050 K (777 °C) for approximately 40 min. Further, the leachability of the PGMs in spent automobile catalyst samples increased after a similar vapor treatment was applied. When the pulverized spent catalyst sample without pretreatment was leached with aqua regia at 333 K (60 °C) for 60 min, 88% of Pt, 91% of Pd, and 37% of Rh were extracted. Meanwhile, after vapor treatment at 1050 K, 98% of Pt, 97% of Pd, and 87% of Rh were extracted under the same leaching conditions. Thus, the pretreatment with FeCl2 vapor, followed by leaching, is a feasible and effective technique for recovering PGMs from spent catalysts. Graphical Abstract

Effect of the Addition of Platinum Group Metals on Mechanical Properties of Cemented Carbide

Effect of the Addition of Platinum Group Metals on Mechanical Properties of Cemented Carbide

The key role of Sn in enhancing Rh recovery from spent automotive catalysts

The recovery of platinum group metals (PGMs) from spent automotive catalysts (SACs) is a promising solution to alleviate PGMs resource shortage and reduce environmental pollution caused by SACs. Nevertheless, the traditional iron capture method requires high smelting temperatures for effective PGMs recovery, leading to significant energy consumption. Therefore, experimenting with lower temperatures to achieve efficient recovery is both beneficial and challenging. The introduction of Sn for the Fe-Sn co-capture of Pt and Pd has been proven to be effective. However, the unique behavior and mechanism of Sn in capturing Rh remain unclear. In this paper, we conduct a detailed study on Sn's behavior in capturing Rh. Rh exhibits a different trend compared to Pt/Pd. Specifically, Sn demonstrates a significantly stronger ability to capture Rh than Pt/Pd, and its effectiveness surpasses that of Fe. Under optimized slag types and smelting conditions, the recovery efficiencies for Pt, Pd, and Rh increased by 20.55 %, 13.04 %, and 21.57 % respectively, compared to traditional single metal iron trapping, reaching 94.14 %, 93.42 %, and 93.76 %. DFT calculations indicate that the lattice substitution energy for PGMs entering the Sn lattice is lower than that for Fe, thus the introduction of Sn enhances the metal trap's ability to capture PGMs. This work provides an in-depth understanding of how the introduction of Sn enhances the recovery of PGMs, particularly Rh. It offers new theoretical guidance for efficiently recovering PGMs from SACs, benefiting the comprehensive recovery and utilization of PGMs.

Boron nitride nanotube confining selected platinum group metal (PGM=Pd and Pt) single atoms catalysts for efficient CO oxidation: Theoretical insight into confinement effect

Despite platinum group metal have been widely used in catalytic converters, high cost and reaction temperature hindered their application. Inspired by the single-atom catalysts and confinement effect, selected PGM confined on the boron nitride nanotube with vacancy defects for CO oxidation have been systematically investigated. For PGM–BNNT catalysts, CO oxidation would proceed competitively in Eley–Rideal and Langmuir–Hinshelwood pathways. With N vacancy, Pd/Pt-BNNT(6,6) needs 0.33 and 0.28 eV to overcome the reaction barriers through the LH mechanism. The internal of BNNT will provide a more favorable nano-confinement environment than exterior surface, with the more activated adsorbed gases andelectron transfer.

The effect of supported metal Species on soot oxidation over PGM/CeO2-ZrO2

Abstract Herein is studied the soot oxidation over platinum group metal oxide/CeO2–ZrO2 (PGM/CZ) catalysts. The ability to capture gas-phase oxygen was in sequence of Ru/CZ > Rh/CZ > Ir/CZ > Pt/CZ > Pd/CZ. A soot oxidation test by TG-DTA showed that Ru/CZ, Rh/CZ, and Ir/CZ are highly active catalysts. It was found that there is a good correlation between the ability to capture gas-phase oxygen and soot oxidation activity. TEM observation revealed that soot oxidation mainly occurs at the interface between soot and CZ surfaces. The Ea values and soot oxidation test using labelled oxygen suggest that highly active catalysts oxidize soot by CZ lattice oxygen. For Ir/CZ, soot oxidation at 270 °C occurred due to the reduction by soot. Ru/CZ and Rh/CZ captured gas-phase oxygen spontaneously below 250 °C, resulting in soot oxidation at 270 °C. H2-TPR results suggest that the reactivity of lattice oxygen in the CZ surface, improved by PGM, is also related to soot oxidation activity. This suggests that the ability to capture gas-phase oxygen and the reactivity of lattice oxygen in the CZ surface determine the soot oxidation activity, and that Ru, Rh, and Ir have the effect of enhancing these properties.