Catalyst Samples Research Articles

Hydrogenation of Simulated Bio-Syngas in the Presence of GdBO3 (B = Fe, Co, Mn) Perovskite-Type Oxides

Direct light olefin synthesis from bio-syngas hydrogenation is a promising pathway to decarbonize the chemical industry. The present study is devoted to the investigation of co-hydrogenation of carbon oxides in the presence of complex systems with the perovskite structure GdBO3 (B = Fe, Mn, Co). The catalyst samples were synthesized by sol-gel technology and characterized by XRD, XPS, BET and TPR. It was found that the Fe/Mn-containing samples exhibited efficient catalysis of the hydrogenation of simulated bio-syngas to light hydrocarbons. The GdMnO3 catalyst exhibits selectivity for C2–C3 light olefins of up to 37% among C1+ hydrocarbons, with a maximum olefin/paraffin ratio. GdMnO3 also exhibits high conversion of CO and CO2, reaching up to 70–75% at 723 K. However, the GdFeO3 catalyst shows a lower selectivity of (C2−3= = 22%, while it exhibits a higher conversion of CO2, up to 95%, at the same temperature. Herein, we established a catalyst structure–performance relationship as a function of chemical composition. Oxygen mobilities and ratios of surface (Os) to lattice (Ol) oxygen, forms of hydrogen adsorption, formation of -CHx- radicals and their subsequent recombination to olefins are influenced by the nature of the element in the B position. This work provides valuable insights for the rational design of bimetallic catalysts for bio-syngas hydrogenation.

The Effect of H2O2 Pretreatment on TiO2-Supported Ruthenium Catalysts for the Gas Phase Catalytic Combustion of Dichloromethane (CH2Cl2)

In the study presented herein, a series of TiO2-supported Ru catalysts were prepared through over-impregnation with different amounts of H2O2 and applied to the catalytic combustion of dichloromethane (DCM). The experimental results show that the optimal (1 H2O2)-Ru@TiO2 catalyst sample yields 90% DCM conversion at 301 °C, which is 40 °C lower than the temperature required by the (0 H2O2)-Ru@TiO2 catalyst. This good activity is related to its high number of acid sites (especially Brønsted acid sites), an appropriate amount of uniformly dispersed RuO2 particles, and strong interaction between RuO2 and the TiO2 support. In addition, excessive H2O2 leads to the growth and phase segregation of RuO2, which weakens the interaction between RuO2 and the TiO2 support and decreases catalytic activity. Moreover, H2O2 addition also contributes to the stability of catalysts, which possibly results from the re-dispersion of RuO2 on the TiO2 support during the reaction.

Thermal and Structural Characterization of Coke Deposition on Spent NiMo Catalyst Used During Catalytic Upgrading of Heavy Oil

Catalyst deactivation has become a major concern in the refining industry globally. The deactivation of hydroprocessing catalyst by coke deposition reduces its useful life, the on-stream time of the process involved and the profitability of upgrading heavy oils to useful products. There are various methods used in thermal and structural characterization but for the purpose of this research journal, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) were carried out on both fresh and spent NiMo catalyst. The TGA results of the spent catalyst samples indicates the presence of coke species with the major portion of the species being ‘medium’ and ‘hard’ coke (second and third stage). There was also no significant change in loss of weight with change in heating rate. In comparison to the fresh catalyst, the SEM micrograph of the used catalyst indicates the formation of poor porous-structure and block-shaped crystallites depicting the sintering of particles because of the higher calcination temperature. O–C–O bond stretching vibrations with an anatase morphology were observed using FTIR on the spent catalyst sample confirming the presence of the coke species while the XRD results showed the formation and nature of carbonaceous deposits on the spent catalyst’s surfaces. A rutile phase with a tetragonal symmetry was detected for spent NiMo diffraction peaks, with the major phase indicating the presence of Carbon with a hexagonal phase.

Calcination Temperature Impacting the Structure and Activity of CuAl Catalyst in Aqueous Glycerol Hydrogenolysis to 1,2-Propanediol

AbstractThis study investigated the impact of calcination temperature on the structural properties of CuAl catalyst which was found to be a robust nano-structured catalyst calcined directly without ramping at 400 °C and performed exceedingly well for aqueous phase hydrogenolysis of glycerol. Various samples of CuAl catalysts were prepared by co-precipitation at Cu: Al molar ratio 1:1 and were calcined at different temperatures (300–1000 °C). The obtained catalysts were reduced at 200 °C before their activity testing for glycerol hydrogenolysis reaction. To correlate the structure-activity, the catalysts were thoroughly characterized by XRD, XPS, BET, TEM, H2-TPR, NH3-TPD, and pyridine FTIR. It was observed that with an increase in calcination temperature from 300 to 700 °C, the glycerol conversion also increased from 47 to 55% with 93% selectivity to 1,2-PDO. The better performance of these catalysts was mainly related to the predominant presence of Brønsted acid sites, an appropriate ratio of the Cu0 to CuAl2O4 + CuO (0.33) and CuAl2O4 to CuO phases (0.35), the existence of Cu2O phase and the smaller Cu0 particle size. It was shown that altering the ramping rate for the calcination temperature of 400 °C impacted the catalytic activity. The CuAl-400 (DC) (direct calcined) catalyst exhibited a maximum glycerol conversion of 60%.

Tailoring Electrolyzer Catalyst Layer Morphology Via Pore Network Modelling

Polymer electrolyte membrane (PEM) water electrolysis is a key technology to produce clean, high purity hydrogen, which can serve as an alternative to carbon-based fuels. However, PEM electrolyzer uptake has been sluggish due to high catalyst costs, which can contribute to up to 47% of total stack costs [1]. Thus, to lower stack costs, the morphology of the catalyst layer must be optimized towards lower precious metal loadings. However, catalyst layer morphology optimization remains a challenge, as the mechanisms linking catalyst morphology to mass and charge transport remain ambiguous in the literature [2], [3]. While the morphology of porous transport layer (PTL) has been extensively explored via stochastic material generation and pore network modelling techniques [4], such an analysis must also be extended to the catalyst layer to design efficient, low-cost materials.In this work, we introduce a method to replicate the pore structure of commercially available PEM electrolyzer catalyst layers using stochastic generation techniques. Our method employs a custom divider to combine regions of varying pore sizes and effectively replicate the range of catalyst layer pore sizes observed in commercial materials. Moreover, we demonstrate that the pore size distribution of stochastically generated materials is statistically indistinguishable from imaged catalyst samples. Pore network modelling techniques were further applied to stochastically generated morphologies to evaluate electrical and mass transport properties. We not only reveal that the transport properties of our stochastically generated materials fall within experimentally measured ranges, but also reveal how tailoring pore size distributions can enhance these properties. The findings from our analysis can be used to identify desirable catalyst morphology targets for manufacturing and enhance the accuracy of electrolyzer transport models via the estimation of catalyst layer transport properties.[1] A. Mayyas, M. Ruth, et al., Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, United States (2019).[2] Z. Taie, X. Peng, et al., ACS Appl. Mater. Interfaces, 12, 47, 52701–52712 (2020).[3] J. Lopata, Z. Kang, et al., J. Electrochem. Soc., 167. 064507 (2020).[4] J. K. Lee, C. H. Lee, and A. Bazylak, J. Power Sources, 437, 226910 (2019).

High Performance Bifunctional Catalysts Using RuCoOx Composite Oxide System for Alkaline Water Electrolysis

In recent years, the importance of sustainable energy has rapidly escalated due to increasingly severe environmental concerns and the exhaustion of fossil fuels. Among these, renewable energy sources such as hydrogen, solar, and wind energy have garnered growing attention and research interest as crucial pathways to achieving zero carbon emissions. Hydrogen, being the most plentiful element in the universe, boasts rich resources and widespread sources. Hydrogen gas is also one of the highest energy density fuels and, upon combustion, produces only water, making it clean and non-polluting1. Among the methods for hydrogen production, water electrolysis stands out as the most efficient and cleanest approach, representing a promising direction for breakthroughs in energy technology. In the water electrolysis reaction, oxygen evolution reaction (OER) occurs at the anode while hydrogen evolution reaction (HER) takes place at the cathode. However, due to their involvement in multi-electron transfer processes, both reactions exhibit sluggish kinetics, requiring substantial overpotentials to drive them forward. This necessity has prompted the development of efficient electrocatalysts to expedite the reactions. Catalysts based on Ru and Ir are considered benchmark catalysts for water electrolysis due to their excellent OER activity and long-term stability2. Among them, Ru-based catalysts offer significant advantages in resource abundance and cost, with catalytic activity higher than Ir-based catalysts. Nonetheless, the poor stability and corrosion resistance hinder the development of this type of material.Recent studies have indicated that introducing transition metal elements into conventional Ru-based oxide catalysts can alter the catalyst's electronic structure and bonding situations to some extent, potentially enhancing the catalytic activity and long-term stability of Ru-based water electrolysis catalysts3. Furthermore, Ru-based catalysts can exhibit excellent HER catalytic performance through appropriate modifications, making them potential bifunctional water electrolysis catalysts. In this study, we synthesized a series of RuCoOx catalysts using a simple glucose-blowing method at different temperatures and heating times (heating for 5 hours at 350 °C, heating for 5 hours at 500 °C, heating for 7 hours at 350 °C, and heating for 7 hours at 500 °C), and focused on investigating the catalytic performance of these catalysts for OER and HER (Figure 1.) in an alkaline environment (1.0 mol·L-1 KOH solution). The X-ray diffraction (XRD) patterns indicate the coexistence of RuO2 and Co3O4 in the catalyst samples describing the successful synthesis (Figure 2.). Linear sweep voltammetry (LSV) results demonstrated the relationship between the catalytic performance of the RuCoOx series catalysts and the heating temperature and duration during synthesis. The electrocatalytic performance of the RuCoOx series catalysts generally exhibited a negative correlation with the calcination time. Among them, the sample heated at 500 °C for 5 hours achieved overpotentials of 268 mV for OER and 92 mV for HER at a current density of 10 mA·cm-2. Additionally, we analyzed the changes in the electronic structure of the catalysts during the water electrolysis reaction using in situ or operando X-ray absorption spectroscopy (XAS) to track active structures for understanding catalytic mechanisms.Figure 1.: (a) XRD patterns of RuCoOx composite under different conditions (b) LSV curves of OER for RuCoOx; (c) LSV curves of HER for RuCoOx. Acknowledgment This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Morphology Changes of Pt Supported on an Ordered Mesoporous Carbon with Network-Structure: In Situ TEM Observation of a PEFC Electrocatalyst

Development of highly durable and active electrocatalysts for polymer electrolyte fuel cells (PEFCs) is an important research topic for future hydrogen energy applications. In PEFCs used for fuel cell vehicles (FCVs), it is known that the high cathode potential causes corrosion of the catalyst support carbon, especially during startup and shutdown operations. It is also known that PFSA-based ionomers directly contacting the Pt surface cause poisoning and deactivation of catalytic activity for the oxygen reduction reaction. There has been interest in immobilization of Pt particles inside nanopores at adequate depth regions (accessible region) at which direct contact with ionomers is suppressed, without any significant limitation of mass transport of reactants and products1). We have recently developed a new Pt/C electrocatalyst using an ordered mesoporous carbon having a network-structure (Net-OMC) with a three-dimensional macrostructure and ordered nanopore (several-nm size) arrangement with ca. 5 nm diameter2)3). In this study, morphologic changes of a Pt/Net-OMC electrocatalyst were studied using in situ TEM/STEM at elevated temperatures and in various gas atmospheres. The Net-OMC was prepared as previously reported2). In this study, the annealing temperature of the Net-OMC sample was 1000 °C. Loading of Pt on the Net-OMC support was carried out using a colloidal technique2)3). The loading amounts of Pt for Pt/Net-OMC were 20 to 30 wt.%. The high-resolution analytical TEM (H-9500, Hitachi High-Tech) was used to observe the characteristics of the catalyst samples at elevated temperatures in various gas atmospheres. The sample was mounted on a heating element of a direct-heating type sample heating holder equipped with a gas supply injector4). During TEM measurements, the total pressure in the vicinity of the catalyst sample was controlled to around 0.2 Pa, and, in order to minimize damage caused by electron beam irradiation, the latter was limited to a short period of time. After sample measurement and cooling down to room temperature, the sample was transferred to the high-resolution STEM with a cs-corrector lens system (HD-2700, Hitachi High-Tech), without detaching the sample from the sample holder in order to observe secondary electron (SE) images at identical locations of the samples. In situ TEM observations were performed from room temperature to 200 °C under various gas atmospheres. At the initial stage, highly dispersed Pt particles were predominantly located at the near outermost surface of nanopores of the Net-OMC support particles. It was found that most Pt particles in the nanopores of Net-OMC migrated 2-5 nm from their original depth positions with increasing temperature. Figure 1 shows the results of SE images for the Pt/Net-OMC catalyst after in situ TEM observations. SE images observed after heating in oxygen (Fig. 1(b) and hydrogen (Fig. 1(c)) flow revealed that Pt particles in the nanopores migrated from the surface to greater depths. Although corrosion of the Net-OMC support progressed to some extent, it was found that agglomeration and growth of Pt nanoparticles hardly progressed. When this carbon support is used as an electrocatalyst, even if catalyst deterioration progresses, it is expected to suppress aggregation of Pt particles due to the feature of accessible nanopores of the Net-OMC support. In the previous study by our group, the Pt/Net-OMC catalyst exhibited remarkably higher durability than a commercial Pt/C during potential step cycling measurement2)3). These results suggest that the more stable characteristics of the catalyst can be easily created by pre-heat treatment in the appropriate atmosphere, and indicate that the Net-OMC is a particularly effective support to combat Pt migration and aggregation. This work was partially based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO) Japan.References1) V. Yarlagadda, M. Carpenter, T. Moylan, R Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand, ACS Energy Lett., 3, 618 (2018).2) T. Miyao, H. Nishino, H. Yamazaki, S. Sato, K. Tamoto, M. Uchida, A. Iiyama, K. Shibanuma, N. Koizumi, 242nd ECS meeting , #I01D-1578(2022).3) S. Sato, H. Yamazaki, H. Nishino, K. Tamoto, M. Uchida, A. Iiyama, K. Shibanuma, M. Sodeno, N. Koizumi, Y. Hoshikawa, T. Miyao, 244th ECS meeting , #I01D-1999(2023).4) T. Kamino, H. Saka, Micros. Microanal. Microstructure, Y4, 219 (1993). Figure 1

Propane Dehydrogenation on PtxZny Active Sites in Silicalite‐1

AbstractThe improvement of Pt‐based catalysts for propane dehydrogenation (PDH) has progressed by recent investigations that have identified Zn as a promising promoter for Pt subnanometer catalysts. It is desirable to gain insights into the structure, stability, and activity of such active sites and the factors that influence them, such as Zn : Pt ratio, Pt coordination and nuclearity. Here, we employ density functional theory and microkinetic simulations to investigate the stability of PtxZny (x=1–3, y=0–3) active sites grafted on silanols of Silicalite‐1 and the PDH activity of Pt. We find that the coordination of a Pt atom to a nest of grafted Zn(II) atoms increases the stability of the Pt1Zny sites, whose activity is similar for y=0–2 and drops dramatically for y>2. We further demonstrate, via linear scaling relations and microkinetic simulations, that the turnover frequency obeys a volcano law as a function of propylene binding strength. The Pt2Zn1 and Pt3Zn1 sites are stable and exhibit activity similar to Pt1Zn2, but only Pt1Zn2 manifests reaction kinetics consistent with experimental data, strongly suggesting the active site composition in the synthesized catalyst samples. The methodology presented here suggests a general strategy for deducing active site information such as composition through simple kinetic experiments.

Propane Dehydrogenation on PtxZny Active Sites in Silicalite-1.

The improvement of Pt-based catalysts for propane dehydrogenation (PDH) has progressed by recent investigations that have identified Zn as a promising promoter for Pt subnanometer catalysts. It is desirable to gain insights into the structure, stability, and activity of such active sites and the factors that influence them, such as Zn:Pt ratio, Pt coordination and nuclearity. Here, we employ density functional theory and microkinetic simulations to investigate the stability of PtxZny (x=1-3, y=0-3) active sites grafted on silanols of Silicalite-1 and the PDH activity of Pt. We find that the coordination of a Pt atom to a nest of grafted Zn(II) atoms increases the stability of the Pt1Zny sites, whose activity is similar for y=0-2 and drops dramatically for y>2. We further demonstrate, via linear scaling relations and microkinetic simulations, that the turnover frequency obeys a volcano law as a function of propylene binding strength. The Pt2Zn1 and Pt3Zn1 sites are stable and exhibit activity similar to Pt1Zn2, but only Pt1Zn2 manifests reaction kinetics consistent with experimental data, strongly suggesting the active site composition in the synthesized catalyst samples. The methodology presented here suggests a general strategy for deducing active site information such as composition through simple kinetic experiments.

Enhanced photocatalytic degradation of antiviral drugs lopinavir and ritonavir by Ni doped ZnO/SiO2 nanocomposites

A series of silica-based Ni doped ZnO nanocomposites were successfully synthesized by the co-precipitation of zinc and nickel acetate salts in the presence of urea on the surface of amorphous silica using thermo-oxidative degradation at 600 °C with a concentration of 3, 6 and 9 mmol ZnO per 1 g SiO2. The effects of the dopants and SiO2 matrix on the structure, morphology and optical properties of the composites were investigated using N2 adsorption-desorption, Raman, XRD, UV-Vis, PL, FT-IR, SEM, and TEM analyses. XRD indicated the formation of a hexagonal ZnO wurtzite structure, while Ni2+ ions substituted Zn2+ sites in the host lattice. The size of nanoparticles was in the range of 10–100 nm and showed a broad fluorescence emission at 442–433 nm. The specific surface area was 110–171 m2 g−1. The materials showed high efficiency in removing the antiviral SARS-CoV-2 drugs lopinavir (LOPI) and ritonavir (RITO) from water. The comparative photocatalytic activity showed 100 % removal of LOPI by 3-, 6- and 9-Ni-ZnO/SiO2 photocatalysts after 60, 30 and 45 min of ultraviolet light irradiation, respectively, and 60 min for RITO for all catalyst samples. The effects of inorganic ions, dissolved organics and reusability on photocatalytic degradation were also described in terms of practical applications.

Role of Ca in Ni-Ca/Fumed-SiO2 Catalysts for CO2 Catalytic Conversion to Methane

AbstractThis study investigates the role of calcium in facilitating the carbon dioxide methanation reaction over nickel supported on fumed-SiO2 catalysts. The wet impregnation method was used to prepare Ni/fumed-SiO2 catalysts with three different Ca loadings for CO2 conversion. As part of the investigation into the effects of Ca concentration and reaction conditions on the structural and morphological properties of the catalysts, various techniques including XRD, BET, SEM, TPR and TEM were used for both fresh and used catalyst samples. The findings showed that the addition of 0.5% Ca increases the catalyst reducibility, promotes dispersion of Ni sites on the surface of fumed SiO2 support and prevents the metal from agglomerating. Evaluation of catalytic results showed that the performance of 10%Ni-0.5Ca/fumed-SiO2 was superior to the other tested catalysts, with CO2 conversion and CH4 yield of 76% and ~ 40% at 650 °C, respectively.

Synergistic role of indium doping and g-C3N4 reinforcement in boosting the visible light-triggered rhodamine B and diclofenac sodium salt degradation over rare earth molybdate

Designing and fabricating cost-efficient and eco-friendly photocatalysts for removing organic pollutants from wastewater streams is a crucial research objective for effectively managing industrial effluents to tackle environmental sustainability issues. In this study, we prepared bare cerium molybdate (Ce2(MoO4)3, M1) and indium-doped cerium molybdate (In- Ce2(MoO4)3, M2) photocatalysts via a hydrothermal method. We then synthesized a nanocomposite of In- Ce2(MoO4)3 (M3) with the promising material graphitic carbon nitride (g-C3N4) using an ultrasonication approach. The synthesized photocatalysts were effectively applied to degrade the Rhodamine B dye and diclofenac sodium salt (a drug) from synthetic industrial wastewater through a photocatalysis approach. The impact of indium (In3+) doping on the bare (Ce2(MoO4)3 and the strong interaction between the (In-Ce2(MoO4)3 and g-C3N4 nanosheets were analyzed through physical and electrochemical techniques, including SEM, EDS, XRD, FTIR, UV–Vis spectroscopy, and EIS analysis. The comprehensive photocatalytic degradation of dye and the drug via first-order kinetic parameters under visible light irradiation for all the prepared catalyst samples was evaluated. The nanocomposite In-Ce2(MoO4)3/g-C3N4 exhibited excellent photocatalytic activity, degrading the maximum amount of RhB dye and drug (RhB:96 %, drug:87 %) in 90 min with a higher rate constant (k) compared to In-Ce2(MoO4)3 (RhB:69 %, drug:56 %) and Ce2(MoO4)3 (RhB:56 %, drug:38 %). Furthermore, the In-Ce2(MoO4)3/g-C3N4 samples produced a 7-fold and 3-fold increase in transient photogenerated current response compared to pristine Ce2(MoO4)3 and In-Ce2(MoO4)3 samples, respectively. These findings pave the way for synthesizing an economical, versatile, and efficient In-Ce2(MoO4)3/g-C3N4 photocatalyst to eliminate pollutants from industrial wastewater streams and boost environmental sustainability.

Hydrothermal Catalytic Transformations of Polymeric Wastes over Zeolite Catalysts Modified with Molybdenum and Tungsten

The article is devoted to the study of the adsorption properties and morphology of new composite catalysts based on acid-activated zeolite heulandite-clinoptilolite of the Kazakhstan Taizhuzgen deposit modified with molybdenum salts (NH4)MoO·4H2O and tungsten (NH4)5H5[H2(WO4)6]·H2O, for the process of thermocatalytic hydrogenation of plastic waste. The study of the developed catalyst by the method of adsorption nitrogen porometry demonstrated the presence of typical type IV isotherms, which indicated the formation of a porous adsorbent by multilayer nitrogen adsorption in the mesopores of the catalyst. The adsorption capacity of the structure formed by the catalyst based on zeolite modified with molybdenum and tungsten, due to the presence of predominantly mesoporous cavities, is able to selectively influence the process of hydrothermocatalytic processing of waste polymers based on polyethylene and polypropylene. The pore size distribution indicates the presence of mesopores and an insignificant number of micropores at low pressure. The catalyst samples were tested in the thermocatalytic hydrogenation reaction of polymer waste. Significant gas formation and predominant content of alkanes, isoalkanes, alkenes and aromatic hydrocarbons in liquid products are shown. It is obviously that the main contribution to the transformations made by mesoporous inclusions in the cavities of the zeolite under study formed during their treatment with molybdenum and tungsten salts.

Initial investigation of catalyst pack for 98 %+ hydrogen peroxide satellite monopropellant thruster

This study aimed to assess the decomposition rate of highly concentrated hydrogen peroxide on catalyst samples, based on the various materials and the geometry of the supporting structures. The drop test method was used and involved delivering a droplet of hydrogen peroxide to a catalyst sample in a sealed chamber, and then measuring the pressure rise. Different sample groups showed various pressure increase rates, indicating differences in catalytic performance. The drop tests were followed by a material investigation to compare the morphology of the active layer produced on various substrates and the effects of the high-test peroxide (HTP) interaction with the surface after the tests. Qualitative tests of phase composition and chemical composition were also performed. Different substrates resulted in varying morphology based on material type, chemical composition, and porosity. The study was treated as a screening test to choose the best catalytic pack option for testing under thruster-like conditions.

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

An 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

Highly efficient Co-added Ni/CeO2 catalyst for co-production of hydrogen and carbon nanotubes by methane decomposition

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO2 emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO2 catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni8Co2/CeO2 catalyst was approximately twice that of the Ni10/CeO2 catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni8Co2/CeO2 catalyst was 4.38 mmol/min∙gcat at 600 °C with WHSV of 36 L/gcat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (ID/IG) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.

Highly Efficient Catalyst for Methyl Formate Decomposition Through KOH Activation of Carbon Material Supports

AbstractIn this research, we utilized potassium hydroxide (KOH) to re‐activate activated carbon and subsequently loaded zinc oxide to obtain a more efficient catalyst for the decomposition of methyl formate. The objective of KOH activation was to augment the catalytic activity of the original ZnO/AC catalyst. Various techniques were used to characterize the prepared catalyst samples, including BET, FT‐IR, SEM, XRD, XPS, and CO2‐TPD. We found that KOH re‐activation of AC can increase the carrier's specific surface area and alkaline sites, significantly improving the catalyst's performance.

Advanced Alkaline Amine Fuel Cell Development

Today, perhaps the most pressing issue is that of power generation. It is important that a source which is inexpensive, reliable, efficient, sustainable, and carbon free be developed and implemented. The hydrogen fuel cell is one possibility. Fuel cells meet many of the requirements listed above save one, current designs are expensive. The catalysts used in most modern hydrogen fuel cells are often platinum group metals, which significantly increases the cost of manufacturing. The high price has proved a significant barrier to adoption. Alkaline fuel cells are comparatively cheap as the catalysts are inexpensive, but they suffer from reliability issues. For one, they form carbonates, which are produced when carbon dioxide reacts with the potassium hydroxide electrolyte. Carbonates build up on the catalytic sites, rendering the fuel cell inoperable. With this project, the chemistry is being manipulated to eliminate this failure. The standard electrolyte is being replaced with an organic amine. Carbonates are soluble in amines and will not precipitate out of solution. This will prevent the buildup and may clean catalytic sites. This project is also testing low-cost production processes. We are using electrochemical synthesis methods to deposit nickel and silver onto carbon cloth to build the fuel cell electrodes. These are then characterized via SEM, EDAX, and x-ray fluorescence. The purpose of this is to establish what size of particles will afford the maximum catalytic activity. Optimizing particle size will help to improve efficiency and reduce costs. Prototypes will be built to identify the best amine and catalyst samples. By the end of 2024, the first cell will be built and tested. Next year, a full-scale alkaline amine fuel cell system will be built. It will be tested as a twelve-volt system for current density, lifetime and total costs.

Optimizing post-treatment strategies for enhanced oxygen reduction/evolution activity in Co–N–C electrocatalyst

Uncovering the origin of bifunctional oxygen reduction/evolution reaction (ORR/OER) activity of M-N-C type electrocatalysts is essential for their extensive usage in fuel cells and metal-air batteries. The electrochemical properties of heterogeneous M-N-C catalysts depend on the surface structure, which can be modified via different synthetic methods. Herein, we investigate the effect of structure on the activity of Co–N–C electrocatalyst material derived from an amorphous metal-organic framework TAL-2. Specifically, TAL-2 served as the sole precursor for the synthesis of a range of Co–N–C catalysts via various carbonization and acid-leaching modes. Co–N–C catalysts were prepared by carbonizing TAL-2 at different temperatures (700, 800, 900, and 1000 °C) and subsequent acid-leaching using different acids, namely HCl, H2SO4, and HNO3, either individually or in various combinations. This resulted in the generation of 36 distinct catalyst samples, each exhibiting unique morphological characteristics. By systematically varying these parameters, we aimed to unravel the intricate relationship between post-synthetic treatment and the resulting electrocatalytic properties, shedding light on the rational design of Co–N–C catalysts for enhanced ORR/OER.

Direct Epoxidation of Hexafluoropropene Using Molecular Oxygen over Cu-Impregnated HZSM-5 Zeolites

This study explores a novel method of directly epoxidizing hexafluoropropene with molecular oxygen under gaseous conditions using a Cu/HZSM-5 catalytic system (Cu/HZ). An in-depth investigation was conducted on the catalytic performance of Cu-based catalysts on various supports and Cu/HZ catalysts prepared under different conditions. Cu/HZ catalysts exhibited better catalytic performance than other porous medium-supported Cu catalysts for the epoxidation of hexafluoropropene by molecular oxygen. The highest propylene oxide yield of 35.6% was achieved over the Cu/HZ catalyst prepared under conditions of 350 °C with a Cu loading of 1 wt%. By applying characterization techniques including XRD, BET, NH3-TPD, and XPS to different catalyst samples, the relationship between the interaction of Cu2+ and HZSM-5 and the reactivity of the catalyst was studied, thereby elucidating the influence of calcination temperature and loading on the reactivity. Finally, we further proposed the possible mechanism of how isolated Cu2+ and acid sites improve catalytic performance.