Kinetics Of Elementary Reactions Research Articles

High-Resolution Crossed-Beam Dynamics Studies of the D + Para-H2 → HD + H Reaction at 1.21 eV.

Understanding kinetic isotope effects is important in the study of the reaction dynamics of elementary chemical reactions, particularly those involving hydrogen atoms and molecules. As one of the isotopic variants of the hydrogen exchange reaction, the D + para-H2 reaction has attracted much attention. However, experimental studies of this reaction have been limited primarily due to its strong experimental background noise. In this study, by using the velocity map ion imaging method and the near-threshold ionization technique, together with improvements on the vacuum condition in the vicinity of the collision zone, background noise was reduced significantly, and quantum state-resolved differential cross sections (DCSs) for the D + para-H2 reaction at a collision energy of 1.21 eV were acquired in a crossed molecular beams experiment. Interestingly, clear rotational state-dependent angular distributions were noticed in the quantum state-resolved DCSs. The most intense peak's positions for HD (v', j') products shift to different scattering directions as the product's ro-vibrational quantum number increases. Two different microscopic reaction mechanisms are found to be involved in this reaction for HD products in different vibrational states. The results show a direct correlation between the scattering angle and the product's rotational quantum number, revealing that the contributions of impact parameters are strongly influenced by the corresponding centrifugal barrier.

A detailed kinetic submechanism for OH[formula omitted] chemiluminescence in hydrogen combustion revisited. Part 2

In this series of two papers, we present a novel physically sound kinetic submechanism aimed at modeling the formation and decay of chemiluminescent (electronically excited) OH∗ molecules in the ignition and combustion of hydrogen and hydrogen-based mixtures over a wide range of temperatures and pressures. The present Part describes the construction of this detailed reaction submechanism based on the groundwork and findings of the preceding paper. In so doing, we relied both on critical evaluation of known and at times conflicting experimental and theoretical data on the elementary reaction kinetics of OH∗ and on our quantum chemical calculations and rate constant estimates for the key processes. The kinetic model under development was validated against the representative dataset of the observed OH(A2Σ+→X2Π) chemiluminescent emission accompanying the high-temperature (post-shock) oxidation of various H2-containing mixtures. To improve its performance against the collected OH∗ emission data, the rate constants of some reactive and quenching processes, to which the OH∗ kinetics is the most sensitive and for which there is a particular uncertainty, were jointly varied within the limits imposed by theoretical considerations and/or the scatter in the available experimental evidence. Thus, by refining the rate constants of these elementary processes, we obtained a reasonable reaction submechanism for OH∗ that describes the known experimental data better than previous models.Novelty and significance statement Although ultraviolet OH∗ chemiluminescence as an optical signature of the combustion process and the underlying chemistry is known to provide unique capabilities for combustion diagnostics, the development of the detailed reaction mechanisms intended for quantitative interpretation of the OH∗ emission measurements has now almost stagnated. Indeed, existing kinetic models contain a discouragingly small number of elementary processes and, apparently, do not account for the full variety of possible reaction pathways of OH∗ formation and depletion. Therefore, in this serial work, we have intended to revise the current ideas about the kinetics of OH∗ production and consumption during ignition and combustion and focused first on the OH∗ kinetics in a reacting H2/O2/Ar/N2 mixture. The principal outcome of this Part of the series is a new physically based kinetic submechanism aimed at modeling the formation and decay of electronically excited OH∗ molecules in the ignition and combustion of hydrogen and hydrogen-containing mixtures. Its incorporation into any conventional kinetic model of hydrogen oxidation enables quantitative interpretation of the OH(A2Σ+−X2Π) chemiluminescent emission observed experimentally in flames and shock-heated reacting flows with an accuracy higher than that of previous analogous mechanisms. No less importantly, the rate constant approximations for a number of individual elementary processes with OH∗, recommended here based on the critical review of literature data and on our quantum chemical calculations, are also of independent interest for the kinetics of electronically excited OH∗ particles. Finally, the OH∗ reaction subset we suggested for hydrogen flames can form the basis of more complex OH∗ chemiluminescence modeling reaction mechanisms for other fuels and fuel compositions.

Investigations of the reaction mechanism of sodium with hydrogen fluoride to form sodium fluoride and the adsorption of hydrogen fluoride on sodium fluoride monomer and tetramer.

The reaction between Na and HF is a typical harpooning reaction which is of great interest due to its significance in understanding the elementary chemical reaction kinetics. This work aims to investigate the detailed reaction mechanisms of sodium with hydrogen fluoride and the adsorption of HF on the resultant NaF as well as the (NaF)4 tetramer. The results suggest that the reaction between Na and HF leads to the formation of sodium fluoride salt NaF and hydrogen gas. Na interacts with HF to form a complex HF···Na, and then the approaching of F atom of HF to Na results in a transition state H···F···Na. Accompanied by the broken of H-F bond, the bond forms between F and Na atoms as NaF, then the product NaF is yielded due to the removal of H atom. The resultant NaF can further form (NaF)4 tetramer. The interaction of NaF with HF leads to the complex NaF···HF; the form I as well as II of (NaF)4 can interact with HF to produce two complexes (i.e., (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF), but the form III of (NaF)4 can interact with HF to produce only one complex (NaF)4(III)···HF. These complexes were explored in terms of noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. NCI analyses confirm the existences of attractive interactions in the complexes HF···Na, NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF. QTAIM analyses suggest that the F···Na interaction forms in the HF···Na complex while the F···H hydrogen bonds form in NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF complexes. Natural bond orbital (NBO) analyses were also applied to analyze the intermolecular donor-acceptor orbital interactions in these complexes. These results would provide valuable insight into the chemical reaction of Na and HF and the adsorption interaction between sodium fluoride salt and HF. The calculations were carried out at the M06-L/6-311++G(2d,2p) level of theory which were performed using the Gaussian16 program. Intrinsic reaction coordinate (IRC) calculations were carried out at the same level of theory to confirm that the obtained transition state was true. The molecular surface electrostatic potential (MSEP) was employed to understand how the complex forms. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analysis was used to know the topology parameters at bond critical points (BCPs) and intermolecular interactions in the complex and intermediate. The topology parameters and the BCP plots were obtained by the Multiwfn software.

Unraveling the mechanism and kinetics of aerobic Baeyer–Villiger oxidation of cyclohexanone

AbstractThis study explores the aerobic Baeyer–Villiger oxidation of cyclohexanone into ε‐caprolactone using metalloporphyrin and benzaldehyde, a greener process to replace hazardous concentrated peroxyacid. The reaction mechanism involves a series of free radical reactions, identified through in situ EPR. In this complex three‐component reaction, we developed an intrinsic kinetic model based on the proposed mechanism. Utilizing a hyperbolic equation, the model well fits experimental data, describing biomimetic catalytic behavior of the aerobic Baeyer–Villiger oxidation. The reaction orders for the three reactants corroborate the kinetic model, with the activation energy of oxygen (130.27 kJ/mol) surpassing cyclohexanone (94.85 kJ/mol) and benzaldehyde (40.73 kJ/mol), implying slow initial oxygen activation while rapid subsequent benzaldehyde oxidation, making oxygen transfer and activation key steps. This unified approach to elementary reaction, mechanism, and intrinsic kinetics provides robust forecasts and lays the groundwork for additional studies, such as side reactions control and mass transfer enhancement and reactor design.

Active-site isolation in intermetallics enables precise identification of elementary reaction kinetics during olefin hydrogenation

Active-site isolation in intermetallics enables precise identification of elementary reaction kinetics during olefin hydrogenation

Direct ammonia protonic ceramic fuel cell: A modelling study based on elementary reaction kinetics

As an efficient energy carrier with high volumetric energy density, ammonia can be effectively utilized by protonic ceramic fuel cells (PCFCs) for power generation at an intermediate temperature (IT) (500–600 °C). The pioneering modelling studies in the literature on NH3-PCFC usually simplify the reaction processes and neglect the current leakage through the electrolyte. A NH3-PCFC model is developed to fully consider the elementary reaction kinetics in the anode and different charges’ transport including electronic holes in the electrolyte. Results suggest the operating potential to be < 0.7 V to minimize the current leakage. When the transport of electronic holes is slowed down by 10%, the Faraday efficiency increases by 11.5%. It is also found that chemical reactions can be the limiting factor for PCFC performance. By increasing inlet steam fraction, while cell performance and proton uptake are improved, electronic hole formation is enhanced by 80%. Importantly, NH3-PCFC performance at an IT is sensitive to temperature distribution. Introducing 5% H2 can occupy surface reaction sites and inhibit ammonia decomposition, thereby decreasing temperature-gradient by 22% and improving cell performance by 3%. Increasing nitrogen desorption by 20% results in a 3% decrease in cell performance due to the enhanced endothermic effect.

Experimental and chemical kinetic modeling study of trimethoxy methane combustion

The use of oxymethylene ethers (OMEs) as alternative fuels or fuel-additives has motivated the present study on the combustion behavior of trimethoxy methane (TMM), which is a branched version of OMEs. A detailed chemical kinetic model for TMM combustion is provided, which is based on a recent model for the structurally similar dimethoxy methane (DMM) and recent elementary reaction kinetics studies. This model is validated against TMM ignition delay times measured in a shock tube at 20 and 40 bar, under fuel lean, stoichiometric, and fuel rich conditions. Further, the TMM model is validated against laminar burning velocities, which were measured in a heat flux setup for a variation of fuel/air ratios. A good agreement between the TMM model predictions and the measured ignition delay times and laminar burning velocities is observed. At fuel rich conditions in the shock tube, however, the model underestimates the reactivity of TMM by up to 60%, which could not be compensated by physically meaningful modifications of the TMM model. The analysis of the TMM model shows that at low temperatures, TMM is primarily consumed via H-atom abstraction by ȮH radicals, followed by classical β-scission and low-temperature chemistry. At higher temperatures, a significant fraction of TMM is consumed via unimolecular decomposition, leading to a higher reactivity compared to OME2. The present model and experiments lay the foundation for future kinetic modeling of TMM and other branched OME-like compounds.

Numerical study of carbon monoxide poisoning effect on high temperature PEMFCs based on an elementary reaction kinetics coupled electrochemical reaction model

High-temperature proton exchange membrane fuel cells have received lots of attention due to their high tolerance of impurities in the fuel gas. Many researchers have conducted experimental and numerical investigations to study the influence of carbon monoxide on performance of the high-temperature proton exchange membrane fuel cell. However, most numerical models use an empirical formula to consider the effect of adsorption and desorption of hydrogen and carbon monoxide. To more accurately study the influence mechanism of carbon monoxide as an impurity, a novel three-dimensional non-isothermal model considering elementary reactions of hydrogen and carbon monoxide for high-temperature proton exchange membrane fuel cells is developed in this study. The elementary reaction kinetics of the anodic catalytic layer adopts a six-step global reaction, and the adsorption processes, desorption processes, as well as electrochemical reactions are taken into account. This model is able to accurately predict the steady polarization curve of a high-temperature proton exchange membrane fuel cell fed by hydrogen containing different amounts of carbon monoxide. The sensitivities of elementary reaction rates in the voltage range of 0.4–0.9 V for the fuel cell fed by pure hydrogen or a mixture of hydrogen and carbon monoxide are analyzed. The rate-determination step is studied at different voltages. In addition, the distributions of gaseous species, surface species and reaction rates of all elementary reactions along different directions of the anode catalytic layer are presented. Finally, the influences of carbon monoxide content in the fuel gas and the operating temperature of a high-temperature proton exchange membrane fuel cell fed by a mixture of hydrogen and carbon monoxide are numerically studied.

Mode- and Bond-Selected Reaction of H with Local Mode Molecule HDS.

Understanding mode- and bond-selected dynamics of elementary chemical reactions is of central importance in molecular reaction dynamics. The initial state-selected time-dependent wave packet method is employed to study the mode and bond selectivity, isotopic branching ratio, and temperature dependence of rate constants of the two-channel reaction of H with local mode molecule HDS. For the abstraction channel, fundamental excitation of the HS (DS) bond of the reactant HDS significantly enhances the H-abstraction (D-abstraction) reaction, whose efficacy is higher than the same amount of translational energy except at low energies just above the energy threshold. This is in sharp contrast to the prediction of Polanyi rules: translational energy is more efficient than vibrational energy in enhancing a reaction with an early barrier. The recent sudden vector projection model is then applied to rationalize the observed mode specificity, which, however, shows that the translational mode vector has a larger coupling with the reaction coordinate than the stretching vector of the active bond, implying a reversed relative efficacy on promoting the reaction as well. In contrast, the mode and bond specificity for the exchange channel is not as strong as for the abstraction channel due to the regulation of the shallow well along the reaction path.

Catalytic oxidation of CO over V2O5/TiO2 and V2O5-WO3/TiO2 catalysts: A DFT study

Vanadium‑titanium based selective catalytic reduction (SCR) catalysts are commercially applied for the denitrification of nitrogen oxides (NOx) in flue gas. Meanwhile, they are also catalytically effective to the abatements of many contaminants including carbon monoxide (CO) catalytic oxidation. Understanding the catalytic performance on CO oxidation is of great significance to develop modified SCR catalysts for the synergetic control of nitrogen oxides and CO. Two SCR catalyst models were constructed, i.e., V2O5/TiO2(001) and V2O5-WO3/TiO2(001). The mechanisms of CO oxidation over the above two catalyst surfaces were analyzed by density functional theory (DFT) calculations. The results show that the whole oxidation cycle of CO includes two reaction stages. In the first stage, CO reacts with terminal oxygen of VO site, following MvK mechanism, which is also the rate-determining step of the whole reaction process. In the second stage, the redundant oxygen Oe of the absorbed O2 molecule reacts with another CO molecule, which follows E-R mechanism. The activation energy barriers of the CO oxidation on V2O5/TiO2 surface are lower than those on V2O5-WO3/TiO2, indicating that WO3 doping inhibits CO oxidation. Moreover, the established reaction kinetics of elementary reactions would be helpful to model CO catalytic oxidation over the real SCR catalysts.

Ammonia electro-oxidation mechanism on the platinum (100) surface

The catalytic electrochemical oxidation of ammonia is a structure-sensitive reaction that will potentially play a role in future energy systems, including portable fuel cells and the elimination of harmful pollutants. Platinum is an ideal catalyst for this reaction because of its selectivity toward the formation of nitrogen gas. The Pt (100) facet shows much faster ammonia electroxidation than other facets of Pt, however the elementary reaction steps responsible for this phenomenon are not understood. Density functional theory (DFT) calculations are used to determine elementary reaction thermodynamics and kinetics. Absorbed NH2* formation is rapid and this intermediate is very stable on Pt (100). High coverage NH2* binds at atop sites, enabling favorable NN bond formation. The faster rate of ammonia oxidation on Pt (100) results from the low barrier of N2H4* formation resulting from NH2* dimerization at high coverage. Understanding the reactivity of ammonia oxidation of Pt (100) can aid in electrochemical reaction mechanism development and catalyst design.

Extracellular Electron Shuttling Mediated by Soluble c-Type Cytochromes Produced by Shewanella oneidensis MR-1.

How metal-reducing bacteria transfer electrons during dissimilatory energy generation under electron acceptor-limited conditions is poorly understood. Here, we incubated the iron and manganese-reducing bacterium Shewanella oneidensis MR-1 without electron acceptors. Removal of soluble extracellular organic compounds (EOCs) dramatically retarded transfer of electrons to an experimental electron acceptor, Cr(VI), by MR-1. However, the return of either high MW (>3000 Da) or low MW (<3000 Da) soluble EOCs produced by MR-1 to washed cells restored Cr(VI) reduction though Cr(VI) reduction was fastest when both size fractions were added together. Spectral and electrochemical characterization of EOCs indicated the presence of flavins and c-type cytochromes (c-Cyts). A model of the kinetics of individual elementary reactions between cells, flavins, released c-Cyts, and Cr(VI), including the direct reduction of flavins, released c-Cyts, and Cr(VI) by cells and the indirect reduction of Cr(VI) by reduced forms of flavins and released c-Cyts, was developed. Model results suggest that released c-Cyts could act as electron mediators to accelerate electron transfer from cells to Cr(VI), and the relative contribution of this pathway was higher than that mediated by flavins. Hence, extracellular c-Cyts produced by MR-1 likely play a role in extracellular electron transfer under electron acceptor-limited conditions. These findings provide new insights into extracellular electron shuttling and the metabolic strategy of metal-reducing bacteria under electron acceptor-limited conditions.

Reevaluation of the reaction rate of H + O2 (+M) = HO2 (+M) at elevated pressures

The rate coefficients for H + O2 (+M) = HO2 (+M) at high-pressure conditions were re-evaluated using the reported experimental shock tube data of Davidson et al. (1996), Bates et al. (2001), Shao et al. (2019) and Choudhary et al. (2019), and based on an updated mechanism of Hong et al. (2011). The major updates of the Hong et al. Mechanism compared to the originally used GRI-Mech in the works of Davidson et al. (1996) and Bates et al. (2001) were the interfering reactions of H + O2, H + HO2 and OH + HO2 as well as NOx-related reactions. After applying the updates of the elementary reaction kinetics, the revised rates of H + O2 (+M) = HO2 (+M) for Davidson et al. (1996) and Bates et al. (2001) showed improved agreement with each other, and consequently led to a more reliable Troe formula of H + O2 (+M) = HO2 (+M) with M = Ar and N2 covering the pressure range of 1–150 bar and temperature range of 300–1800 K. The new Troe formula is expected to facilitate kinetic model development and high-pressure combustion studies.

The kinetics of elementary thermal reactions in heterogeneous catalysis

The kinetics of elementary reactions is fundamental to our understanding of catalysis. Just as microkinetic models of atmospheric chemistry provided the predictive power that led to the Montreal Protocol reversing loss of stratospheric ozone, pursuing a microkinetic approach to heterogeneous catalysis has tremendous potential for societal impact. However, the development of this approach for catalysis faces great challenges. Methods for measuring rate constants are quite limited, and the present predictive theoretical methods remain largely unvalidated. Here, we present a short Perspective on recent experimental advances in the measurement of rates of elementary reactions at surfaces that rely on a stroboscopic pump–probe concept for neutral matter. We present the principles behind successful measurement methods and discuss a recent implementation of those principles. The topic is discussed within the context of a specific but highly typical surface reaction, CO oxidation on Pt, which, despite more than 40 years of study, was only clarified after experiments with velocity-resolved kinetics became possible. This deceptively simple reaction illustrates fundamental lessons concerning the coverage dependence of activation energies, the nature of reaction mechanisms involving multiple reaction sites, the validity of transition-state theory to describe reaction rates at surfaces and the dramatic changes in reaction mechanism that are possible when studying reactions at low temperatures. In this Perspective, recent advances in measuring rates of elementary reactions at model catalyst surfaces are presented. A recent ion-imaging-based technique — velocity-resolved kinetics — is discussed in the context of a typical surface reaction, CO oxidation on Pt.

Computational Investigation of Aqueous Phase Effects on the Dehydrogenation and Dehydroxylation of Polyols over Pt(111)

Prediction of solvation effects on the kinetics of elementary reactions occurring at metal–water interfaces is of high importance for the rational design of catalysts for the biomass and electrocat...

Particle-Based Simulation Reveals Macromolecular Crowding Effects on the Michaelis-Menten Mechanism

Many computational models for analyzing and predicting cell physiology rely on in vitro data collected in dilute and controlled buffer solutions. However, this can mislead models because up to 40% of the intracellular volume—depending on the organism, the physiology, and the cellular compartment—is occupied by a dense mixture of proteins, lipids, polysaccharides, RNA, and DNA. These intracellular macromolecules interfere with the interactions of enzymes and their reactants and thus affect the kinetics of biochemical reactions, making in vivo reactions considerably more complex than the in vitro data indicates. In this work, we present a new, to our knowledge, type of kinetics that captures and quantifies the effect of volume exclusion and other spatial phenomena on the kinetics of elementary reactions. We further developed a framework that allows for the efficient parameterization of these kinetics using particle simulations. Our formulation, entitled generalized elementary kinetics, can be used to analyze and predict the effect of intracellular crowding on enzymatic reactions and was herein applied to investigate the influence of crowding on phosphoglycerate mutase in Escherichia coli, which exhibits prototypical reversible Michaelis-Menten kinetics. Current research indicates that many enzymes are reaction limited and not diffusion limited, and our results suggest that the influence of fractal diffusion is minimal for these reaction-limited enzymes. Instead, increased association rates and decreased dissociation rates lead to a strong decrease in the effective maximal velocities Vmax and the effective Michaelis-Menten constants KM under physiologically relevant volume occupancies. Finally, the effects of crowding were explored in the context of a linear pathway, with the finding that crowding can have a redistributing effect on the effective flux responses in the case of twofold enzyme overexpression. We suggest that this framework, in combination with detailed kinetics models, will improve our understanding of enzyme reaction networks under nonideal conditions.

Coupling ammonia catalytic decomposition and electrochemical oxidation for solid oxide fuel cells: A model based on elementary reaction kinetics

Ammonia (NH3) is a carbon-free Hydrogen carrier with the advantages of high volumetric energy density, developed infrastructure, as well as easy and safe storage. The coupling of NH3 catalytic decomposition with electrochemical oxidation in an anode of solid oxide fuel cells leads to the field of direct Ammonia-fueled solid oxide fuel cell. However, the related coupling mechanism needs clarification. In the present study, by developing a mechanistic model and a library of elementary reaction kinetics, we attempt to have an overview on the synergism of heterogeneous reactions, charge-transfer reactions, bulk diffusion, and charge-transfer processes of direct Ammonia-fueled solid oxide fuel cell. We describe charge-transfer reactions based on hydrogen spillover mechanism as well as oxygen spillover mechanism, and find that only the hydrogen spillover mechanism fits with experimental data. With this validated model, we identify the rate-determining steps as well as the main surface species in H2-fueled and NH3-fueled solid oxide fuel cells. We define the region of NH3 catalytic decomposition and that of electrochemical oxidation to quantify the coupling within the anode. Based on the quantification results, we study the effects of temperature and content of inlet NH3 on cell performance.

Platinum/Nickel Bicarbonate Heterostructures towards Accelerated Hydrogen Evolution under Alkaline Conditions.

Heterostructured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO3 )2 ) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO3 )2 are substantially improved compared to the bare Pt nanoparticles (NPs). The Ni(HCO3 )2 provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO3 )2 nanoplates offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO3 )2 is an effective catalyst promoter for alkaline HER.

Platinum/Nickel Bicarbonate Heterostructures towards Accelerated Hydrogen Evolution under Alkaline Conditions

AbstractHeterostructured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO3)2) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO3)2 are substantially improved compared to the bare Pt nanoparticles (NPs). The Ni(HCO3)2 provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO3)2 nanoplates offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO3)2 is an effective catalyst promoter for alkaline HER.

Catalytic activity of different sizes of Ptn/Co3O4 in the oxidative degradation of Methylene Blue with H2O2

In this work, we demonstrate the catalytic activity and kinetic analyses of generation six poly(amido-amine) hydroxyl-terminated (PAMAM), G6-OH(Ptn) (n = 55, 140, 225) dendrimer-encapsulated nanoparticles (DENs) immobilized onto mesoporous cobalt oxide (Co3O4) for the catalytic oxidation of methylene blue (MB). Ultra-Violet Visible (UV–Vis) spectrophotometry showed the ligand to metal charge transfer (LMCT) band of metal precursor ions coordinated to the tertiary amines of the dendrimer. The size of fully reduced Pt DENs and supported Pt nanoparticles were investigated using High-Resolution Transmission Electron Microscopy (HR-TEM). The mesoporous Co3O4 was synthesized by inverse micelle method, prior to Ptn DENs being supported on the Co3O4 via wet impregnation procedure. The crystallite structure and size of Co3O4 was investigated by powder X-ray diffraction (p-XRD) spectroscopy. Immobilized Ptn/Co3O4 structural analysis was investigated for the pore size and pore volume using N2 sorption techniques. Thermal gravimetric analyses (TGA) also indicated the dendrimer decomposition on the G6-OH(Ptn)/Co3O4 materials to be 550 °C. Hydrogen temperature programmed reduction (H2-TPR) analyses were conducted and the reducibility of the supported cobalt oxide showed only one temperature peak that was ascribed to the reduction of surface lattice oxygens. The experimental kinetic data was analyzed and fitted to the Langmuir-Hinshelwood model using elementary first-order reaction kinetics and the thermodynamic parameters were calculated. Catalyst Pt55/Co3O4 showed stability during the reusability investigation of up to 8 cycles. The G6-OH(Ptn) were immobilized on silica and tested for catalytic oxidation of MB as a control experiment.