Dispersed Catalysts Research Articles

Vitalizing Perovskite Oxide-Based Acetone Sensors with Metal-Organic Framework-Derived Heterogeneous Oxide Catalysts.

Perovskite oxides are promising candidates for chemiresistive-type gas sensors owing to their exceptional thermal and chemical stability during solid-gas reactions. However, perovskites suffer from critical issues such as low surface area and poor surface activity, which negatively influence the sensing characteristics. While metal nanoparticles can be incorporated in perovskites to improve their reactivity, the fundamental incompatibility between catalytic metals and perovskite oxides often leads to substantial structural degradation as well as phase instability. Herein, we overcome this challenge through the introduction of an intermediary phase that forms coherent interfaces with both the perovskite phase and catalyst metals. Specifically, we present the case study of p-type La0.8Ca0.2Fe0.98Pt0.02O3 perovskite, whose hole accumulation layer was modulated by the incorporation of metal-organic framework (MOF)-derived n-type α-Fe2O3 nanoparticles decorated with highly dispersed Pt catalysts. The resulting composite exhibited significantly improved surface activity over the nonmodified La0.8Ca0.2FeO3 perovskite, leading to exceptional chemiresistive sensing performance toward acetone gas (Rg/Ra = 39.8 toward 10 ppm of acetone at 250 °C) with high cross-sensitivity against interfering gases. Importantly, our findings reaffirm the critical influence of interfacial engineering in facilitating surface chemical reactions on perovskite oxides and, by doing so, effectively provide a general synthetic guideline to the design of perovskite-based chemiresistors.

Partial upgrading of heavy oils by catalytic aquathermal visbreaking with dispersed iron oxide catalysts

The impact of water and red mud-like Fe oxide catalysts on aquavisbreaking (AVB) of heavy-oils was studied under various circumstances. Vacuum residue (VR) was employed as a good substitute for low-viscous bitumen grades. The reaction products were separated into SARA fractions using open-column liquid chromatography (OCLC), and boiling point groups were classified using thermogravimetric analysis (TGA). In addition, Fourier-transform infrared (FTIR) spectroscopy was used to study the structural features of VR and its derivatives. It was observed that the thermal visbreaking of VR led to a severe coke formation with asphaltene (ASP) to coke selectivity over 130 %, while the addition of water and Fe catalyst could increase the conversion of ASP to liquid oil products while inhibiting coke formation, resulting in improved conversion of ASP. Furthermore, the structural properties of spent catalysts recovered after reactions were analyzed using X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD) to identify the active phase, confirming that the Fe precursor is converted to a 20–30 nm Fe2O3 and Fe3O4 during VR AVB. Moreover, the addition of carbon additives to AVB further improved the dispersion of ASP and catalyst particles, contributing to the decrease of the selectivity for ASP conversion to coke by 50 %.

Prussian Blue-Derived Atomic Fe/Fe3C@N-Doped C Catalysts Supported by Carbon Cloth as Integrated Air Cathode for Flexible Zn-Air Batteries.

The development of an integrated air cathode with superior oxygen reduction reaction (ORR) performance is fundamental to flexible zinc-air batteries (ZABs) for wearable electronics. Herein, a self-assembled metal-organic framework (MOF)-derived strategy is proposed to prepare a atomic Fe/Fe3C@N-doped C catalysts supported by carbon cloth (CC) catalyst for use as an air cathode of flexible ZABs. The Prussian Blue precursor, which self-assembles on the surface of the carbon cloth due to electrostatic attraction, is critical in achieving the uniform dispersion of catalysts with high density loading on carbon cloth substrates. The hollow cubic structure, N-doped carbon layer coating, and the integrated electrode design can provide more accessible active sites and facilitate a rapid electron transfer and mass transport. Density functional theory (DFT) calculation reveals that the electronic interactions between the Fe-N4 and Fe3C dual active sites can optimize the adsorption-desorption behavior of oxygen intermediates formed during the ORR. Consequently, the Fe/Fe3C@N-doped C/CC exhibits an excellent half wave potential (E1/2 = 0.903V) and superior long-term cycling stability in alkaline environments. With excellent ORR performance, ZABs and flexible ZABs based on Fe/Fe3C@N-doped C/CC air cathode demonstrate excellent overall electrochemical performance in terms of open circuit voltage, maximum power density, flexibility, and cycling stability.

Atomically Dispersed Cobalt Anchored on Hollow Tubular Carbon Nitride Mediates Direct Electron Transfer and Oxygen-Related Active Species Path for Activation of Permonosulfate.

Atomically dispersed catalysts anchored on nitrogen-rich substrates present promising application potential for the persulfate-based advanced oxidation process. Nevertheless, efficient activation efficiency and a clear activated mechanism of persulfate remain challenging in carbon nitride-based single-atom catalysts (SACs). To these, combined with the regulation strategy of metal-ligand section and carrier's architecture, an atomically dispersed Co single-atom catalyst anchored on regular hollow tubular carbon nitride (Co/TCN SAC) herein was devised and utilized to activate permonosulfate. As a result, Co/TCN SACs show excellent catalytic performance for the degradation of common antibiotics. Combined with X-ray absorption fine structure and theory calculation, it is confirmed that superficially anchored CoO3 sites of the Co2N2O2-CoO3 unit are the catalytic active center for peroxymonosulfate (PMS) activation. The electrochemical test and in situ electron paramagnetic resonance results demonstrate radical (SO4•- and •OH) and nonradical (electron transfer process and 1O2) paths contributing to the superior catalytic performance. In addition, the catalyst exhibits high reaction efficiency and structural stability considering water quality parameters. Finally, a continuous and efficient device was operated on a laboratory scale, which exhibited satisfactory efficiency in continuously removing electron-rich antibiotics such as tetracycline. This work reveals the atomic-level modulation of cobalt atomic sites on hollow tubular carbon nitride and their structure-activity relationship with persulfate activation.

CH4 Carbonylation to Acetic Acid Using H2O as an Oxidant on a Rh-Functionalized UiO-67 Combined with Oriented External Electric Fields: Selectivity and Mechanistic Insights from DFT Calculations.

Acetic acid (CH3COOH), as an industrially important petrochemical product, is predominantly produced via multistep energy-intensive processes. The development of a rhodium single-site heterogeneous catalyst has received considerable attention due to its potential to transform CH4 into CH3COOH in a single step. Herein, the reaction mechanism for the generation of CH3COOH from CH4, CO, and H2O catalyzed by Rh-functionalized metal-organic framework (MOF) UiO-67 and the selectivity of products CH3COOH, formic acid (HCOOH), methanol (CH3OH), and acetaldehyde (CH3CHO) under the oriented external electric fields (OEEFs) were systematically explored by density functional theory (DFT) calculations. The results reveal that the insertion of CO into Rh-CH3 is the rate-determining step with a free energy barrier of 21.0 kcal/mol in CH4 carbonylation to CH3COOH. Upon applying an OEEF of Fx = +0.0050 au along the C-C bond, the rate-determining step shifts toward H2O decomposition with the barrier of 19.6 kcal/mol, significantly improving the selectivity for CH3COOH production, compared to the major competitive HCOOH route. The Brønsted-Evans-Polanyi (BEP) relationships between key transition states, field strength, and NPA charge transfer were established. This study may guide the rational design of atomically dispersed MOF catalysts for the selective coconversion of CH4 and CO to CH3COOH using H2O as the oxidant under the OEEF.

Atomically dispersed ruthenium single-atom alloy catalysts enabling efficient iodide oxidation reaction electrolysis in acidic media

Single-atom catalysts exhibit immense potential across diverse reactions, yet their synthesis and stability in acidic environments pose significant challenges. Herein, we introduce a facile one-step hydrothermal approach to fabricate Ru single-atom alloy catalysts (Ru SAAC) through the reaction of Ru and Ti precursors, followed by annealing in an argon atmosphere. Analysis via extended X-ray absorption fine structure spectroscopy and aberration-corrected scanning transmission electron microscopy confirms the atomically dispersed Ru alloy catalyst anchored on a TiO2 support. Remarkably, Ru SAAC demonstrates exceptional electrocatalytic performance in the iodide oxidation reaction (IOR), achieving a benchmark current density of 10 mA/cm2 at a mere voltage of 0.64 V in acidic conditions within a three-electrode electrolyzer setup. Surpassing nanoscale Ru/TiO2 and RuO2/TiO2 counterparts, Ru SAAC exhibits the highest voltage efficiency (84.4%), lowest Tafel slope (36 mV/dec), and lowest overpotential (100 mV) under identical experimental conditions. This method enables facile control over Ru morphology. It enhances the kinetics and thermodynamic favorability of Ru SAAC in acidic media, opening avenues for synthesizing diverse transition metal-based single-alloy catalysts for varied applications.

Ordered Mesoporous Nitrogen Dope Carbon Synthesized from Aniline for Stabilization of Ruthenium Species in CO2 Hydrogenation to Formate

The hydrogenation of CO2 to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as the silica template, while aniline served as the nitrogen–carbon precursor. The resultant MNC-An exhibits cubic Ia3D geometry, possesses significant mesoporosity, and has a high nitrogen content, which is essential for stabilizing ruthenium single atoms. The catalyst exhibited a specific activity of 252 mmolFAgcat−1 following a 2 h reaction at 120 °C. Moreover, the catalyst exhibited exceptional relative activity during five recycling experiments while preserving its catalytic efficacy. The atomically dispersed ruthenium and its Ru3+ oxidation state demonstrated perseverance both before and after the treatment. The results indicated that the synthesized catalyst possesses potential for the expedited commercialization of CO2 hydrogenation to produce formic acid. The elevated carbon yield, along with excellent thermal stability, renders it a viable substrate for attaching and stabilizing atomically dispersed ruthenium catalysts.

Ru Nanoparticles Encapsulated by Defective TiO2 Boost the Hydrogen Oxidation/ Evolution Reaction.

The development of efficient and durable electrocatalysts for the alkaline hydrogen oxidation/evolution reaction is crucial for anion exchange membrane fuel cells/water electrolyzers. However, designing such electrocatalysts poses a challenge due to the need for optimizing various adsorbates. Herein, highly dispersed Ru nanoparticles catalysts is reported encapsulated and supported by defective anatase phase of titanium dioxide (named as Ru NPs/def-TiO2(A)) for boosting hydrogen-cycle electrocatalysis with robust anti-CO-poisoning in alkaline conditions. The Ru NPs/def-TiO2(A) achieves a high-quality activity of 7.65 A mgRu -1, which is 23.2 and 9.5-fold higher than commercial Ru/C and Pt/C in alkaline HOR. Moreover, this catalyst exhibits an outstanding overpotential of 21mV at 10mAcm-2 in alkaline HER. Hydrogen underpotential deposition (Hupd) and CO stripping experiments demonstrate that Ru NPs/def-TiO2(A) has the optimized H*, OH*, and CO* adsorption strength, enabling the Ru NPs/def-TiO2(A) catalyst to display excellent and robust HOR/HER performance under alkaline conditions. Using density functional theory calculations, the enhanced HOR performance mechanism for the Ru NPs/def-TiO2(A) catalyst originates from the TiO2 step face in contact with the Ru nanoparticles, indicating that the kinetics of water formation are considerably more favorable at the Ru NPs/def-TiO2(A) interface.

Renaissance of Chlorine Evolution Reaction: Emerging Theory and Catalytic Materials.

Chlorine (Cl2) is one of the most important commodity chemicals that has found widespread utility in chemical industry. Most Cl2 is currently produced via the chlorine evolution reaction (CER) at the anode of chlor-alkali electrolyzers, for which precious group-metal-based mixed metal oxides (MMOs) have been used for more than half a century. However, MMOs suffer from the use of platinum-group metals, which are costly and scarce, and the selectivity issue arises from the parasitic oxygen evolution reaction. Over the last decade, the field of CER catalysis has seen dramatic advances in both the theory and discovery of new catalysts. Theoretical approaches have enabled a fundamental understanding of CER mechanisms and provided catalyst design principles. The exploration of new materials has led to the discovery of CER catalysts other than MMOs, including non-PGM-based oxides, atomically dispersed single-site catalysts, and organic molecules, with some of which following novel reaction pathways. This minireview provides an overview of the recent advances in CER electrocatalyst research and suggests future directions for this revitalized field.

Asymmetrically Coordinated Cu Dual-Atom-Sites Enables Selective CO2 Electroreduction to Ethanol.

Electrochemical reduction of CO2 (CO2RR) to value-added liquid fuels is a highly attractive solution for carbon-neutral recycling, especially for C2+ products. However, the selectivity control to preferable products is a great challenge due to the complex multi-electron proton transfer process. In this work, a series of Cu atomic dispersed catalysts are synthesized by regulating the coordination structures to optimize the CO2RR selectivity. Cu2-SNC catalyst with a uniquely asymmetrical coordinated CuN2-CuNS site shows high ethanol selective with the FE of 62.6% at -0.8V versus RHE and 60.2% at 0.9V versus RHE in H-Cell and Flow-Cell test, respectively. Besides, the nest-like structure of Cu2-SNC is beneficial to the mass transfer process and the selection of catalytic products. In situ experiments and theory calculations reveal the reaction mechanisms of such high selectivity of ethanol. The S atoms weaken the bonding ability of the adjacent Cu to the carbon atom, which accelerates the selection from *CHCOH to generate *CHCHOH, resulting in the high selectivity of ethanol. This work indicates a promising strategy in the rational design of asymmetrically coordinated single, dual, or tri-atom catalysts and provides a candidate material for CO2RR to produce ethanol.

Enhancing Ni oxidation reconstruction in Ni3Fe nanoalloy for efficient Electro-Oxidation of 5-Hydroxymethylfurfural

Herein, a novel ball milling-pyrolysis strategy was proposed for preparing a highly dispersed Ni3Fe nanoalloy catalyst (Ni3Fe@NC) used for 5-hydroxymethylfurfural (HMF) electro-oxidation reaction. The Ni3Fe@NC delivered a high current density of 100 mA cm−2 at a low potential of 1.467 V vs RHE, with a HMF conversion rate of over 99.6 %, 2,5-furan dicarboxylic acid (FDCA) selectivity of 97.1 % and a Faraday efficiency of 96.7 %. Theoretical calculations, in-situ EIS, quasi-in-situ XRD and XPS demonstrated that Fe-doping optimizes the electronic structure of Ni3Fe@NC and regulates its d-band center, which not only promoted the reconstruction of Ni3Fe@NC to form high-oxidation-activity Ni2+δ and Ni3+δ species but also reduced the reaction barrier of the key rate-determining step (*5-Hydroxymethyl-2-furancarboxylic acid (HMFCA)→*5-formyl-2-furancarboxylic acid (FFCA)) during HMFOR. Based on this interesting work, we provided a facile macroscopic preparation strategy on highly dispersed nanoalloy catalyst for efficient electro-oxidation of HMF.

High activity of cobalt-atomically dispersed catalyst on mesoporous carbon for rechargeable Zn-air batteries via effective removal of the hard template

The use of oxygen from air in Zn-air batteries requires the smart design of materials with bifunctional activity for oxygen reduction and evolution reactions (ORR/OER), and with a porous structure to facilitate the diffusion of oxygen gas to active sites. Kit-6 template-assisted porous structures have been proposed to this end; however, traditional methods for the removal of Kit-6 templates are highly aggressive and environmentally harmful. In this study, we present the synthesis of a cobalt atomically dispersed catalyst (Co-ADC) with interlayer engineering using mesoporous Kit−6 templates, focusing on two removal strategies: sodium hydroxide (0.5, 1, and 2 M) and hydrofluoric acid (15, 30, and 45 %). Physicochemical results indicated that Co-ADC-containing nanoparticles were obtained using the proposed methodology, while the use of HF promoted the loss of cobalt in the catalyst. During the activity evaluation for the ORR, and it was found that 0.5 M NaOH and HF at 15 % displayed similar activity, which could be related to the effect of carbon material as co-catalyst, but the first enabled a close 4e− pathway, and thus, the Co-ADC presented a ΔEOER-ORR of 640 mV. This optimized ADC displayed improved functionality owing to diffusion improvements by the mesoporous structure, presenting a maximum power density of 130.6 mW cm−2 and 30 % higher specific activity than the Pt + IrO2/C reference material. Rechargeability was evaluated, yielding a ΔV = 0.87 V at 5.175 mA cm−2 with a round-trip efficiency of 57.5 %. Nonetheless, the optimized material presented higher rechargeability, displaying no significant round-trip changes after 100 cycles, while Pt + IrO2/C presented changes due to OER issues after only 48 cycles.

Recent Achievements in Heterogeneous Bimetallic Atomically Dispersed Catalysts for Zn-Air Batteries: A Minireview.

Rechargeable Zn-air batteries (ZABs) hold promise as the next-generation energy-storage devices owing to their affordability, environmental friendliness, and safety. However, cathodic catalysts are easily inactivated in prolonged redox potential environments, resulting in inadequate energy efficiency and poor cycle stability. To address these challenges, anodic active sites require multiple-atom combinations, that is, ensembles of metals. Heterogeneous bimetallic atomically dispersed catalysts (HBADCs), consisting of heterogeneous isolated single atoms and atomic pairs, are expected to synergistically boost the cyclic oxygen reduction and evolution reactions of ZABs owing to their tuneable microenvironments. This minireview revisits recent achievements in HBADCs for ZABs. Coordination environment engineering and catalytic substrate structure optimization strategies are summarized to predict the innovation direction for HBADCs in ZAB performance enhancement. These HBADCs are divided into ferrous and nonferrous dual sites with unique microenvironments, including synergistic effects, ion modulation, electronic coupling, and catalytic activity. Finally, conclusions and perspectives relating to future challenges and potential opportunities are provided to optimise the performance of ZABs.

Catalytic degradation of stable benzene molecules under room temperature conditions over Pt-loaded boron-carbon-nitride (Pt/BCN) catalysts

The catalytic degradation of volatile organic compounds (VOCs) such as benzene via ring-opening at room temperature is challenging due to the presence of π-bonds in the ring-forming carbon atoms. This study involved the preparation of a novel Pt-loaded boron-carbon-nitride (Pt/BCN) catalyst containing single-atom active sites for efficient catalysis of benzene degradation at room temperature in air. The micromorphology, surface structure, and coordination environment of the catalyst were analyzed using characterization techniques including aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC–HAADF–STEM) and X-ray absorption fine structure (XAFS). The degradation mechanism was investigated using electron paramagnetic resonance (EPR) and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). The experimental results demonstrate that Pt/BCN contains many Pt-N4 single-atom active sites that can generate hydroxyl radicals under room-temperature air conditions, leading to the oxidation of benzene to CO2 and H2O. Containing atomically dispersed active-site catalysts developed in this study offer a theoretical foundation for designing catalyst active centers in related fields and advancing the industrial application of room-temperature, low-carbon VOCs treatment technologies.

Efficient atomically dispersed Fe catalysts with robust three-phase interface for stable seawater-based zinc-air batteries

The use of seawater-based electrolytes in zinc-air batteries (S-ZABs) presents significant economic and social benefits and mitigates the demand for scarce freshwater resources. However, it is challenging to achieve a metal-nitrogen-carbon (M-N-C) catalyst that exhibits high resistance to corrosive Cl- in seawater-based electrolytes and possesses a strengthened binding affinity with O2, which enables catalysts with an optimized oxygen reduction reaction (ORR) and enhances the applicability of S-ZABs. Herein, we propose a combined wet chemistry-pyrolysis strategy to obtain atomically dispersed Fe-decorated nitrogen-doped mesoporous carbon spheres (N-MCS-Fe-900). Benefiting from the capacity of the Fe decorations to form the edge-hosted aerophilic FeN4-O2 sites at the optimized three-phase interface, N-MCS-Fe-900 affords the enhanced resistance of the active Fe sites to corrosive Cl-, as well as improved interaction with O2, thereby facilitating the ORR process. As expected, the N-MCS-Fe-900 delivers high half wave potential of 0.90V and kinetic current density of 18.61mAcm−2 at 0.85V in seawater-based 0.1M KOH. More importantly, the S-ZABs equipped with N-MCS-Fe-900 exhibited long-term stability under a high current density for over 140h without voltage decay. Theoretical calculations and electrochemical performance evaluations collectively revealed the superior catalytic efficacy and genesis of this activity in N-MCS-Fe-900, which features edge-hosted FeN4-O2 sites at the stable three-phase interface in seawater electrolytes. This study provides new insights for the advancement of ORR catalysts in sustainable energy conversion technologies for seawater-based electrolytes.

Atomically dispersed bimetallic FeZn-N-C with oxidase-like performance: Synthesis, characterization, calculation and activity

The burgeoning interest in single atom catalysts (SACs) stems from their exceptional oxidase-mimicking capabilities, driving substantial advancements in this field. Nevertheless, a critical knowledge gap remains regarding the influence of Zn incorporation on the oxidase-like activity of atomically dispersed Fe-N-C catalysts. This study successfully synthesized and comprehensively characterized three distinct SACs (FeZn SAC-N@C, Fe SAC-N@C, and Zn SAC-N@C) using TEM, HAADF-STEM, XRD, XPS, BET, ICP-MS, and XAFS techniques. Activity assays revealed that FeZn SAC-N@C exhibited the highest oxidase-mimicking activity, with Fe SAC-N@C displaying moderate activity, whereas Zn SAC-N@C did not exhibit oxidase-like behavior. The superior oxidase-like activity of FeZn SAC-N@C is attributed to its enhanced O2 activation capacity, characterized by a high free energy of 0.90 eV in the rate-determining reaction step, surpassing those of Fe SAC-N@C (0.85 eV) and Zn SAC-N@C (0.71 eV). EPR and DFT calculations elucidated the catalytic mechanism of FeZn SAC-N@C, involving the generation of O2− radicals. As a proof-of-concept, FeZn SAC-N@C demonstrates potential as a colorimetric sensor for detecting ascorbic acid and nitrite, achieving a limit of detection of 0.77 μM for ascorbic acid and 0.16 μM for nitrite. These findings open a new avenue for configuring bimetallic atomically dispersed catalysts with oxidase-like activity in future research.

Organic and Metal–Organic Polymer-Based Catalysts—Enfant Terrible Companions or Good Assistants?

This overview provides insights into organic and metal–organic polymer (OMOP) catalysts aimed at processes carried out in the liquid phase. Various types of polymers are discussed, including vinyl (various functional poly(styrene-co-divinylbenzene) and perfluorinated functionalized hydrocarbons, e.g., Nafion), condensation (polyesters, -amides, -anilines, -imides), and additional (polyurethanes, and polyureas, polybenzimidazoles, polyporphyrins), prepared from organometal monomers. Covalent organic frameworks (COFs), metal–organic frameworks (MOFs), and their composites represent a significant class of OMOP catalysts. Following this, the preparation, characterization, and application of dispersed metal catalysts are discussed. Key catalytic processes such as alkylation—used in large-scale applications like the production of alkyl-tert-butyl ether and bisphenol A—as well as reduction, oxidation, and other reactions, are highlighted. The versatile properties of COFs and MOFs, including well-defined nanometer-scale pores, large surface areas, and excellent chemisorption capabilities, make them highly promising for chemical, electrochemical, and photocatalytic applications. Particular emphasis is placed on their potential for CO2 treatment. However, a notable drawback of COF- and MOF-based catalysts is their relatively low stability in both alkaline and acidic environments, as well as their high cost. A special part is devoted to deactivation and the disposal of the used/deactivated catalysts, emphasizing the importance of separating heavy metals from catalysts. The conclusion provides guidance on selecting and developing OMOP-based catalysts.

CO Oxidation at Low Temperatures over the Au Cluster Supported on Crystalline Silicotitanate.

Crystalline silicotitanate (CST) with a sitinakite structure has attracted considerable attention as an ion exchanger because of its anionic surface owing to SiO4 tetrahedral and TiO6 octahedral linked structures. In particular, the anionic surface of CST is advantageous in immobilizing single Au atoms derived from a cationic precursor such as Au(en)2Cl3 (en = ethylenediamine). In this study, a Au/CST catalyst was prepared and evaluated for CO oxidation. The transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that Au single atoms and clusters (Auδ+, 0 < δ < 1) were supported on Na+-CST particles. The 1.0 wt % Au/CST catalyst yielded high catalytic activity for CO oxidation, where 50% CO oxidation was achieved at a low temperature of -13 °C. In the low-temperature region (from -84 to 20 °C), CO oxidation over Au/CST may progress through the well-known Langmuir-Hinshelwood mechanism. Conversely, the experimental results of CO oxidation without O2 confirmed that the reaction proceeded according to the Au-assisted Mars-van Krevelen mechanism using the lattice oxygens of the CST particles at temperatures above 20 °C. Therefore, this work contributes to the design of highly dispersed single-atom or cluster catalysts using the anionic surface of the microporous CST.

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.

Harnessing the Potential of Hollow Graphitic Carbon Nanocages for Enhanced Methanol Oxidation Using PtRu Nanoparticles.

Direct Methanol Fuel Cell (DMFC) is a powerful system for generating electrical energy for various applications. However, there are several limitations that hinder the commercialization of DMFCs, such as the expense of platinum (Pt) at market price, sluggish methanol oxidation reaction (MOR) due to carbon monoxide (CO) formation, and slow electrooxidation kinetics. This work introduces carbon nanocages (CNCs) that were obtained through the pyrolysis of polypyrrole (Ppy) as the carbon source. The CNCs were characterized using BET, XRD, HRTEM, TEM, SEM, and FTIR techniques. The CNCs derived from the Ppy source, pyrolyzed at 750 °C, exhibited the best morphologies with a high specific surface area of 416 m2g-1, allowing for good metal dispersion. Subsequently, PtRu catalyst was doped onto the CNC-Ppy750 support using chemical reduction and microwave-assisted methods. In electrochemical tests, the PtRu/CNC-Ppy750 electrocatalyst demonstrated improved CO tolerance and higher performance in MOR compared to PtRu-supported commercial carbon black (CB), with values of 427 mA mg-1 and 248 mA mg-1, respectively. The superior MOR performance of PtRu/CNC-Ppy750 was attributed to its high surface area of CNC support, uniform dispersion of PtRu catalyst, and small PtRu nanoparticles on the CNC. In DMFC single-cell tests, the PtRu/CNC-Ppy750 exhibited higher performance, approximately 1.7 times higher than PtRu/CB. In conclusion, the PtRu/CNC-PPy750 represents a promising electrocatalyst candidate for MOR and anodic DMFC applications.