Sluggish Oxidation Research Articles

Bifacial Modulation of Carrier Transport in BiVO4 Photoanode for Stable Photoelectrochemical Water Splitting via Interface Engineering

AbstractMonoclinic bismuth vanadate photoanodes promise high efficiency‐to‐cost ratios for photoelectrochemical (PEC) water splitting owing to their suitable band structure and ease of synthesis. However, inadequate charge separation and sluggish oxidation kinetics remain a fundamental challenge. This study investigates bifacially interface engineered BiVO4 photoanodes by considering a seed‐layer and NiOOH oxygen evolution catalyst (OEC) over‐layer to regulate the charge carrier transport and improve the overall PEC water‐splitting performance. The modification of the BiVO4/FTO interface stimulates electron flow towards fluorine‐doped tin oxide (FTO) and a NiOOH over‐layer improves the facile hole transfer from BiVO4 to the electrolyte. Compared to the moderate photocurrent density of a bare BiVO4 photoanode (1.5 mA cm−2), the interface‐engineered Seed_BiVO4_NiOOH photoanode shows a remarkably high (≈3.4 times higher) photocurrent density of 5.10 mA cm−2 at 1.23 V vs reversible hydrogen electrode with impressive long‐term stability over 9 h under illumination. The optimally interface engineered Seed_BiVO4_NiOOH photoanode shows an excellent photoconversion efficiency (1.83%), with significant improvement in bulk charge separation efficiency. This work presents a promising strategy for the development of a highly stable PEC water‐splitting device and eliminates the intrinsic material shortcomings of the bare BiVO4 photoanode by modulating the carrier transport via bifacial interface engineering.

Rationally engineered BiVO4 micro-leaves as a bifunctional photocatalyst for highly durable solar water treatment and water splitting

Recently, the use of monoclinic bismuth vanadate (BiVO4) as a visible light active catalyst has continued to increase, thus minimizing major issues such as fast recombination, poor carrier mobility, and sluggish oxidation kinetics has become an increasingly crucial issue. Accordingly, we report the fabrication of phase-engineered BiVO4 micro-leaves via the facile hydrothermal route and their utilization in solar-light-driven azo dye degradation and water splitting. Notably, low-temperature calcined BiVO4 micro-leaves exhibited a monoclinic–tetragonal isotype heterostructure crystal system with highly active (110) oxidative facets that significantly improved redox chemistry, whereas exposed (040) facets facilitated charge transport from monoclinic to tetragonal crystallites. Rationally phase-engineered and (110)/(040)-oriented BiVO4 micro-leaves (mt-BiVO4) presented efficient visible-light-assisted dye-degradation efficiencies (~94%) for water treatment with high durability. Moreover, the fabricated samples displayed dominant photochemical oxygen evolution rates of 1509.62 and 1214.04 μmol h–1 g–1 in an aqueous solution of FeCl3 and AgNO3, respectively. Our results suggest that synergistic effects of exposed reactive facets, dual-phase, and morphology engineering boosted the photocatalytic activity in BiVO4 and provided a promising approach for the development of a bifunctional photocatalyst in water treatment and water-splitting devices.

Rapid Iron(III)−Fluoride‐Mediated Hydrogen Atom Transfer

AbstractWe anticipate high‐valent metal–fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H−F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII(F)−F−FeIII(F) complex (1) by reacting [FeII(NCCH3)2(TPA)](ClO4)2 (TPA=tris(2‐pyridylmethyl)amine) with difluoro(phenyl)‐λ3‐iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Brønsted acids to yield a monomeric [FeIII(TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT‐IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C−H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.

Rapid Iron(III)-Fluoride-Mediated Hydrogen Atom Transfer.

We anticipate high‐valent metal–fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H−F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII(F)−F−FeIII(F) complex (1) by reacting [FeII(NCCH3)2(TPA)](ClO4)2 (TPA=tris(2‐pyridylmethyl)amine) with difluoro(phenyl)‐λ3‐iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Brønsted acids to yield a monomeric [FeIII(TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT‐IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C−H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.

Nanometal Dust Explosion in Confined Vessel: Combustion and Kinetic Analysis.

Extensive application of metal powder, particularly in nanosize could potentially lead to catastrophic dust explosion, due to their pyrophoric behavior, ignition sensitivity, and explosivity. To assess the appropriate measures preventing accidental metal dust explosions, it is vital to understand the physicochemical properties of the metal dust and their kinetic mechanism. In this work, explosion severity of aluminum and silver powder, which can be encountered in a passivated emitter and rear contact (PERC) solar cell, was explored in a 0.0012 m3 cylindrical vessel, by varying the particle size and powder concentration. The Pmax and dP/dtmax values of metal powder were demonstrated to increase with decreasing particle size. Additionally, it was found that the explosion severity of silver powder was lower than that of aluminum powder due to the more apparent agglomeration effect of silver particles. The reduction on the specific surface area attributed to the particles’ agglomeration affects the oxidation reaction of the metal powder, as illustrated in the thermogravimetric (TG) curves. A sluggish oxidation reaction was demonstrated in the TG curve of silver powder, which is contradicted with aluminum powder. From the X-ray photoelectron spectroscopy (XPS) analysis, it is inferred that silver powder exhibited two reactions in which the dominant reaction produced Ag and the other reaction formed Ag2O. Meanwhile, for aluminum powder, explosion products only comprise Al2O3.

CH3OH selective oxidation to HCHO on Z-scheme Fe2O3/g-C3N4 hybrid: The rate-determining step of C–H bond scission

• The unique Z-scheme ZOF@CN NTs photoanode exhibits outstanding CH 3 OH oxidation activity. • ZOF@CN NTs with high selectivity provides a green and clean pathway for CH 3 OH conversion process. • The CH 3 O* via the C–H bond scission to form CH 2 O* is the rate-determining step for the reactions. Fe 2 O 3 as photoanode photoelectrocatalytic (PEC) CH 3 OH conversion is a promising approach for industrial preparation of high value-added HCHO. However, the conversion efficiency is limited by its poor charge separation and sluggish oxidation mechanism. This study reports a direct Z-scheme system consisting of 1D nanotubes oxygen-deficient a -Fe 2 O 3 and g -C 3 N 4 (ZOF@CN NTs) with great enhancement of PEC CH 3 OH oxidation to HCHO activity. The ZOF@CN NTs presents a CH 3 OH oxidation photocurrent density of 1.05 mA cm −2 at 0.6 V vs Ag/AgCl, 5.25 times than that of oxygen-deficient a -Fe 2 O 3 alone (0.20 mA cm −2 ), and HCHO selectivity of 81.5%. Combining by UV–vis, UPS, PL spectroscopy, PEC performance and density functional theory calculations, the mechanism of CH 3 OH oxidation to HCHO on Z-scheme ZOF@CN NTs photoanode was found along following pathway: CH 3 OH*–CH 3 O*- CH 2 O* –CH 2 O (g), which is starting from the O–H bond scission and then followed by C−H scission. The CH 3 O* via the C–H bond scission to form CH 2 O* is the key step for the reaction, and N atoms from g -C 3 N 4 with higher electronegativity compared with O atoms, which is useful for C–H bond scission. This work serves as a solid foundation for understanding Fe 2 O 3 -based Z-scheme system photoanodes for CH 3 OH oxidation to HCHO.

Characterization of An Oxygen Evolution Reaction Redox Mediator for Li-O2 Battery by In-Situ Differential Electrochemical Mass Spectrometry

Development of lithium-oxygen (Li-O2) batteries is hindered by large overpotentials, low energy efficiency and unsatisfactory cycling life, which are predominately caused by the oxygen evolution reaction (OER) involving sluggish oxidation of lithium peroxide (Li2O2). Herein, a highly-efficient soluble redox mediator (RM) of N,N’-Diphenyl-p-phenylenediamine (DPPD) is introduced to catalyze the oxygen evolution reaction for Li-O2 batteries. During charging process, DPPD is electrochemically oxidized into DPPD+, which can chemically decompose Li2O2 on the cathode with a much-reduced overpotential. The in-situ differential electrochemical mass spectrometry confirms that the charging process is dominated by Li2O2 decomposition. With the assistance of DPPD, Li-O2 cells can achieve lower charging potential, improved cycling stability, and prolonged lifespan (294 cycles) which is three times longer than that of tetrathiafulvalene counterpart. This work presents a credible and viable opportunity for long lifespan Li-O2 batteries.

Palladium (II)‐catalyzed homogeneous alcohol oxidations: Disclosing the crucial contribution of palladium nanoparticles in catalysis

Versatile redox catalysts play the significant roles in alcohol oxidations, in which the mechanisms for homogeneous and heterogeneous alcohol oxidations are generally different. This work introduced a Lewis acid (LA) promoted homogeneous alcohol oxidation with Pd (OAc)2 catalyst by using oxygen balloon as the oxidant source. It was found that adding Lewis acid such as Sc (OTf)3 significantly accelerated Pd (II)‐catalyzed alcohol oxidations; notably, the time courses of oxidations monitored by GC and 1H NMR disclosed that there existed two processes including the initial sluggish oxidation followed by a rapid oxidation. The promotional effect of Lewis acid was attributed to the formation of heterobimetallic Pd (II)/LA species, which improved the oxidizing power of the palladium (II) species, thus accelerating alcohol oxidation in the induction period. Correlating the sizes of in situ generated palladium nanoparticles with the time course of alcohol oxidation further disclosed that the loosely, spherically large nanoparticles, which were composed of many tiny nanoparticles having the size less than 10 nm, were responsible for the rapid oxidation, whereas those highly dispersed, tiny nanoparticles having the size less than 10 nm were not responsible for the rapid oxidation.

Modulation of Lewis acidic-basic sites for efficient photocatalytic H2O2 production over potassium intercalated tri-s-triazine materials

Photocatalytic H2O2 production (PHOP) on graphitic carbon nitride (GCN) at neutral pHs is limited by the sluggish oxidation of sacrificial alcohols and insufficient protons. In our work, the PHOP over a series of K intercalated triazine (KTCN) or tri-s-triazine units (KTTCN) reached 11–32 folds of GCN in the presence of only 0.5 vol% isopropanol, and a positive correlation between the H2O2 production and the K contents was found. The critical role of K was revealed as that K intercalation creates Lewis acidic sites for isopropanol adsorption and strengthens Lewis basic sites for hydrogen abstraction and proton release. The improved alcohol oxidation and enhanced O2 chemisorption synergistically result in dramatically accelerated PHOP over KTTCN. The findings provide the understanding of the preliminary active site dependent PHOP mechanism and bring insights for design of carbon nitride polymers with desirable photocatalytic performance.

Structure and Unprecedented Reactivity of a Mononuclear Nonheme Cobalt(III) Iodosylbenzene Complex

AbstractA mononuclear nonheme cobalt(III) iodosylbenzene complex, [CoIII(TQA)(OIPh)(OH)]2+ (1), is synthesized and characterized structurally and spectroscopically. While 1 is a sluggish oxidant in oxidation reactions, it becomes a competent oxidant in oxygen atom transfer reactions, such as olefin epoxidation, in the presence of a small amount of proton. More interestingly, 1 shows a nucleophilic reactivity in aldehyde deformylation reaction, demonstrating that 1 has an amphoteric reactivity. Another interesting observation is that 1 can be used as an oxygen atom donor in the generation of high‐valent metal‐oxo complexes. To our knowledge, we present the first crystal structure of a CoIII iodosylbenzene complex and the unprecedented reactivity of metal‐iodosylarene adduct.

Tunable Redox Temperature of a Co3–xMnxO4 (0 ≤ x ≤ 3) Continuous Solid Solution for Thermochemical Energy Storage

Heat storage technologies are well suited to improve energy efficiency of power plants and recovery of process heat. A good option for high storage capacities, especially at high temperatures, is storing thermal energy by reversible thermo-chemical reactions. In particular, the Co3O4/CoO and Mn2O3/Mn3O4 redox-active couples are known to be very promising systems. However, cost and toxicity issues for Co oxides and sluggish oxidation rate (leading to poor reversibility) for Mn oxide, hinder the applicability of these singles oxides. Considering instead binary Co-Mn oxide mixtures could mitigate the above-mentioned shortcomings. To examine this in detail, here we combine first-principles atomistic calculations and experiments to provide a structural characterization and thermal behavior of novel mixed metal oxides based on cobalt/manganese metals with spinel structure Co3-xMnxO4. We show that novel Co3-xMnxO4 phases enhance indeed the enthalpy of the redox reactions, facilitate reversibility, and mitigate energy losses when compared to pure metal oxide systems. Our results enlarge therefore the limited list of today's available thermochemical heat storage materials and pave the way towards the implementation of tunable redox temperature materials for practical applications.

Can a Mononuclear Iron(III)-Superoxo Active Site Catalyze the Decarboxylation of Dodecanoic Acid in UndA to Produce Biofuels?

Decarboxylation of fatty acids is an important reaction in cell metabolism, but also has potential in biotechnology for the biosynthesis of hydrocarbons as biofuels. The recently discovered nonheme iron decarboxylase UndA is involved in the biosynthesis of 1-undecene from dodecanoic acid and using X-ray crystallography was assigned to be a mononuclear iron species. However, the work was contradicted by spectroscopic studies that suggested UndA to be more likely a dinuclear iron system. To resolve this controversy we decided to pursue a computational study on the reaction mechanism of fatty acid decarboxylation by UndA using iron(III)-superoxo and diiron(IV)-dioxo models. We tested several models with different protonation states of active site residues. Overall, however, the calculations imply that mononuclear iron(III)-superoxo is a sluggish oxidant of hydrogen atom abstraction reactions in UndA and will not be able to activate fatty acid residues by decarboxylation at room temperature. By contrast, a diiron-dioxo complex reacts with much lower hydrogen atom abstraction barriers and hence is a more likely oxidant in UndA.

High-Spin Mn(V)-Oxo Intermediate in Nonheme Manganese Complex-Catalyzed Alkane Hydroxylation Reaction: Experimental and Theoretical Approach.

Mononuclear nonheme manganese complexes are highly efficient catalysts in the catalytic oxidation of hydrocarbons by hydrogen peroxide in the presence of carboxylic acids. Although high-valent Mn(V)-oxo complexes have been proposed as the active oxidants that afford high regio-, stereo-, and enantioselectivities in the catalytic oxidation reactions, the importance of the spin state (e.g., S = 0 or 1) of the proposed Mn(V)-oxo species is an area that requires further study. In the present study, we have theoretically demonstrated that a mononuclear nonheme Mn(V)-oxo species with an S = 1 ground spin state is the active oxidant that effects the stereo- and enantioselective alkane hydroxylation reaction; it is noted that synthetic octahedral Mn(V)-oxo complexes, characterized spectroscopically and/or structurally, possess an S = 0 spin state and are sluggish oxidants. In an experimental approach, we have investigated the catalytic hydroxylation of alkanes by a mononuclear nonheme Mn(II) complex, [(S-PMB)MnII]2+, and H2O2 in the presence of carboxylic acids; alcohol is the major product with high stereo- and enantioselectivities. A synthetic Mn(IV)-oxo complex, [(S-PMB)MnIV(O)]2+, is inactive in C-H bond activation reactions, ruling out the Mn(IV)-oxo species as an active oxidant. DFT calculations have shown that a Mn(V)-oxo species with an S = 1 spin state, [(S-PMB)MnV(O)(OAc)]2+, is highly reactive and capable of oxygenating the C-H bond via oxygen rebound mechanism; we propose that the triplet spin state of the Mn(V)-oxo species results from the consequence of breaking the equatorial symmetry due to the binding of an equatorial oxygen from an acetate ligand. Thus, the present study reports that, different from the previously reported S = 0 Mn(V)-oxo species, Mn(V)-oxo species with a triplet ground spin state are highly reactive oxidants that are responsible for the regio-, stereo-, and enantioselectivities in the catalytic hydroxylation of alkanes by mononuclear nonheme manganese complexes and terminal oxidants.

Effects of temperatures and carbon dioxide nanobubbles on superior electric storage for anodically oxidized films of AlY10 amorphous alloy

The effects of temperature and nanometer-sized bubbles (NBs) on a superior electric storage capacitor for anodically oxidized films of AlY10 amorphous alloys were determined at temperatures ranging from 275 to 298 K in 0.4 M H2SO4 solutions with NBs of ozone, oxygen, and carbon dioxide. The AAO specimen obtained by solution with carbon dioxide NBs at 278 K showed longer discharging time. The discharging time increases with increasing charging time and then saturates after around 70 s. The increment in temperature makes the structure from simple series capacitor with large capacitance to simple parallel capacitor with lower capacitance and larger resistance. The stability of NBs in water could be explained by enclosure in protonated polyhedral water clusters. The collapse of clusters with oxygen NBs result in the formation of OH− radicals and its resulting elution of Al, while carbon oxide NBs prevent the formation of OH− radicals, promoting sluggish oxidation that is required for the formation of AlO6 clusters.

Highly Selective and Catalytic Oxygenations of C−H and C=C Bonds by a Mononuclear Nonheme High‐Spin Iron(III)‐Alkylperoxo Species

The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII (t-BuLUrea )(OOCm)(OH2 )]2+ (2), generated from [FeII (t-BuLUrea )(H2 O)(OTf)](OTf) (1) [t-BuLUrea =1,1'-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C-H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C-H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O-O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.

Highly Selective and Catalytic Oxygenations of C−H and C=C Bonds by a Mononuclear Nonheme High‐Spin Iron(III)‐Alkylperoxo Species

AbstractThe reactivity of a mononuclear high‐spin iron(III)‐alkylperoxo intermediate [FeIII(t‐BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t‐BuLUrea)(H2O)(OTf)](OTf) (1) [t‐BuLUrea=1,1′‐(((pyridin‐2‐ylmethyl)azanediyl)bis(ethane‐2,1‐diyl))bis(3‐(tert‐butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C−H and C=C bonds of hydrocarbons is reported.2oxygenates the strong C−H bonds of aliphatic substrates with high chemo‐ and stereoselectivity in the presence of 2,6‐lutidine. While2itself is a sluggish oxidant, 2,6‐lutidine assists the heterolytic O−O bond cleavage of the metal‐bound alkylperoxo, giving rise to a reactive metal‐based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by2are discussed.

Electrochemical investigation of multi-fuel based low temperature nano-composite anode for solid oxide fuel cell

Extensive efforts have been made in order to develop multi-fuel-based low temperature solid oxide fuel cell for direct conversion of hydrocarbons to electric power. It is extremely difficult to operate due to the CH activation and its tremendously sluggish oxidation reduction in the low temperature range from 300 to 600 °C. The structural and electrochemical properties of novel anode material Ni0.6(Ba0.3Ce0.2Zn0.5)0.4 have been investigated in the presence of hydrogen, natural gas, ethanol, glucose, and sugar-cane at low temperature of 600 °C. Through sol-gel method the proposed oxide material is synthesized. The composite average crystalline size has been found 25–90 nm by both scanning electron microscopy and X-ray diffraction techniques. The ultraviolet– visible and Fourier transform infrared techniques are used to determine band gap and absorption spectrum respectively. The power density of the cell at various fuels has been observed and measurements indicate that it varies from 57 to 315 mWcm−2 at 600 °C among different fuels at anode side. The current study reveals that proposed anode Ni0.6(Ba0.3Ce0.2Zn0.5)0.4 is promising multi-fuel anode material for low-temperature solid oxide fuel cell, and it does not need to reform hydrocarbon fuels in order to fully utilize the advantage of these cells.

Dimethyl Ether Oxidation on an Active SnO2/Pt/C Catalyst for High‐Power Fuel Cells

AbstractDimethyl ether (DME) has been considered a potential fuel for direct‐feed proton exchange membrane fuel cells, owing to its high energy density, low toxicity, and low crossover through a Nafion® membrane in comparison to commonly reported fuels such as methanol, ethanol, and formic acid. The main hurdle in the implementation of direct DME fuel cells is the sluggish oxidation kinetics on state‐of‐the‐art Pt−based catalysts (e. g. Pt and PtRu). In this work, DME oxidation on a platinum‐coated tin oxide catalyst (Pt/SnO2) supported on carbon is reported and compared with commercial Pt/C catalysts. Our catalyst was synthesized by using the polyol method, and structural characterization was performed by using transmission electron microscopy and X‐ray diffraction. Electrochemical analysis in acid solution showed overpotentials that are 50 mV lower than commercial Pt/C, as well as a higher oxidation current ( ). The peak power obtained using a 4 cm2 laboratory prototype fuel cell (loading of 1.23 mgPt cm−2 on anode at 0.40 V) was 105 mW cm−2 at 70 °C. Online mass spectrometry analysis of the oxidation products gives insights into the new pathways of the electro‐oxidation mechanism on this promising catalyst.

Performance of quaternized poly(vinyl alcohol)‐based electrolyte membrane in passive alkaline DEFCs application: RSM optimization approach

ABSTRACTDirect ethanol fuel cells (DEFCs) have emerged as potential tools for producing sustainable energy for portable devices due to their high energy density and their safe and nontoxic fuel source. However, the main problem of DEFCs is the sluggish oxidation of ethanol and fuel crossover from the anode side to the cathode side. Nafion membranes are commonly used as the electrolyte membrane in DEFCs, but they have a high production cost and high ethanol permeability. Thus, this work studies the performance of an alternative electrolyte membrane that is based on a quaternized poly(vinyl alcohol) (QPVA) polymer in passive alkaline DEFCs. The composition of the QPVA‐based membranes was optimized with potassium hydroxide (KOH) as an ion charge carrier and by the inorganic filler graphene oxide (GO). The membrane properties were influenced by KOH and GO. The effect of these two parameters on the performance of the QPVA‐based membranes was investigated for its ion‐exchange capacity and ionic conductivity and selectivity using the response surface methodology to optimize the membrane composition. The QPVA‐based membranes were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, and field emission scanning electron microscope. The membrane properties were influenced by KOH concentration doping and GO filler loading, which affect the membrane selectivity and, consequently, the overall performance of the passive alkaline DEFCs. Finally, the maximum power density of the passive DEFCs was improved from 5.8 to 11.3 W cm−2 at 30 °C, 13.7 mW cm−2 at 60 °C, and 19.3 mW cm−2 at 90 °C, respectively, in ambient air. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47526.

Reactivity patterns of vanadium(iv/v)-oxo complexes with olefins in the presence of peroxides: a computational study.

Vanadium porphyrin complexes are naturally occurring substances found in crude oil and have been shown to have medicinal properties as well. Little is known on their activities with substrates; therefore, we decided to perform a detailed density functional theory study on the properties and reactivities of vanadium(iv)- and vanadium(v)-oxo complexes with a TPPCl8 or 2,3,7,8,12,13,17,18-octachloro-meso-tetraphenylporphyrinato ligand system. In particular, we investigated the reactivity of [VV(O)(TPPCl8)]+ and [VIV(O)(TPPCl8)] with cyclohexene in the presence of H2O2 or HCO4-. The work shows that vanadium(iv)-oxo and vanadium(v)-oxo are sluggish oxidants by themselves and react with olefins slowly. However, in the presence of hydrogen peroxide, these metal-oxo species can be transformed into a side-on vanadium-peroxo complex, which reacts with substrates more efficiently. Particularly with anionic axial ligands, the side-on vanadium-peroxo and vanadium-oxo complexes produced epoxides from cyclohexene via small barrier heights. In addition to olefin epoxidation, we investigated aliphatic hydroxylation mechanisms by the same oxidants and some oxidants show efficient and viable cyclohexene hydroxylation mechanisms. The work implies that vanadium-oxo and vanadium-peroxo complexes can react with double bonds through epoxidation, and under certain conditions also undergo hydroxylation, but the overall reactivity is highly dependent on the equatorial ligand, the local environment and the presence or absence of anionic axial ligands.