Adsorption Of O2 Molecules Research Articles

Temperature-induced evolution of CuOx clusters in CuOx/TiO2 catalyst for boosting auto-exhaust oxidation

Developing non-noble metal oxides, replacing platinum group catalysts for auto-exhaust purification, where their usage amount exceeds 40 % of global demand, remains a challenge. Herein, we presented a combined approach on the synthesis and application of robust CuOx/TiO2 catalysts with ultra-fine CuOx clusters (ca. 1 nm). The strong interaction between CuOx and TiOx induces favorable interfacial charge accumulation, facilitating the extraction of the interfacial oxygen atoms in Cu2-x-O-Ti4-y chains and the surface lattice oxygen on CuOx clusters. Isotope 18O2 experiments and DFT calculations jointly confirmed that these oxygen atoms preferentially participate in the oxidation through the Mars-van Krevelen mechanism below 250 °C. The resulted oxygen vacancies facilitate the adsorption and activation of O2 molecules, which will participate the oxidation above 250 °C through Eley-Rideal mechanism. The increase in the temperature also drives the synergy of active oxygen species in the interfacial Cu2-x-O-Ti4-y bond chains and on CuOx clusters, cooperatively promoting the conversion of NO to NO2. As a result, the CuOx/TiO2 catalyst exhibits exceptional catalytic performance in soot oxidation, with a four-fold higher reaction rate (4.17 μmol g−1 min−1) than that of single-atom Cu₁-TiO2 catalyst. Such findings provide a novel strategy for the advancement of Cu-based cluster catalysts in environmental applications.

Boosting CO oxidation performance via reaction-induced single-atom active site: DFT and microkinetic investigation of a unified CO oxidation mechanism on Gd-doped ceria supported copper catalysts

Single-atom (SA) catalysts have emerged as a pivotal area drawing extensive research interest due to their high catalytic activities. However, SA catalysts are often plagued by the aggregation and deactivation of SA sites under reaction conditions. This study focuses on CO oxidation over Gd-doped ceria supported Cu catalysts and aims to provide a new strategy to stabilize the SA site, in which a Cu SA site is “prestored” in a relatively stable Cu cluster and can be dynamically activated under reaction conditions. Three typical Cu10/CeO2 catalyst models were built with different Gd-doping contents, which are pristine Cu10/CeO2, Cu10/Gd0.125Ce0.875O2, and Cu10/Gd0.25Ce0.75O2, respectively. We performed density functional theory (DFT) calculations on the Cu10/Gd-CeO2 system to investigate the adsorption of CO and O2 molecules, the formation of surface oxygen vacancy (OV) and dynamic Cu SA site, and potential energy surfaces of CO oxidation process. Ab initio thermodynamic analysis suggests that the saturation adsorption of CO on Cu10 and high Gd-doping in CeO2 lead to a spontaneously formed single Cu−CO site and an OV defect on ceria surface. The CO oxidation process is identified as a two-paths-coupled catalytic cycle, in which Path I is activated by the terminal O atom of adsorbed O2 at surface OV site while Path II initiates with the lattice O atom of CeO2 surface. The microkinetic modeling demonstrates that the dominant pathway is Path I for the undoped and low-doping cases, and Path II for the high-doping case which exhibits a novel mechanism for CO oxidation and the highest reaction activity due to the participation of the dynamic SA site.

Mechanism study of replacing adsorbed O2 molecules in different pore sizes under different CO2/N2 inert gas conditions

Injecting inert gases into the goaf is a crucial method for inhibiting coal spontaneous combustion. Research has verified that the co-injection of CO2 and N2 provides a more effective control measure compared to a single gas, but the microscopic mechanism underlying the synergistic displacement of O2 by CO2 and N2 remains unclear. Injecting inert gases into the goaf is a crucial method for inhibiting coal spontaneous combustion. Research has verified that the co-injection of CO2 and N2 provides a more effective control measure compared to a single gas, but the microscopic mechanism underlying the synergistic displacement of O2 by CO2 and N2 remains unclear. Here, for the constructed multi-scale aperture slit model, the Grand Canonical Monte Carlo simulation (GCMC) and Molecular Dynamics (MD) simulation are used to investigate the mechanism of displacing adsorbed O2 molecules under different CO2/N2 inert gas conditions. The results indicate that CO2 and N2 aggregated on opposing sides of the coal molecules and dispersed within the slit layer, respectively. At 1 nm pore size, the relative concentration of O2 for optimal displacement was 1.054. The absolute value of the average binding energy is small when the CO2:N2 gas ratio is 80:20 and 40:60 at 2 nm and 4 nm apertures, respectively. This suggests that as the aperture size increases, the displacement effect on O2 shifts towards a higher proportion of N2, with a more conspicuous replacement effect as the aperture widens. The smaller pores ranging from 1-2 nm predominantly feature CO2 displacing adsorbed state O2, while larger pores exceeding 2 nm primarily N2 facilitate the transportation of free state O2.

Anisotropic CO adsorption and enhanced O2 activation on defective TiS2 monolayer: A DFT study

This study employs density functional theory (DFT) calculations to investigate the adsorption behaviour of CO and O2 on a defective TiS2 monolayer. The primary objective is to evaluate the potential of TiS2 for gas sensing and catalytic applications. By exploring the adsorption of CO and O2 on a monolayer with a sulfur vacancy, this study provides significant new insights into their interaction mechanisms and energetics. The DFT simulations showed that the adsorption of the CO molecule is anisotropic (i.e., orientation dependent) with higher adsorption energy for the carbon end (Ti-CO) -0.63 eV than the oxygen end (Ti-OC) -0.16 eV. In both scenarios, the CO molecule bond length does not change significantly. In contrast, the adsorption of O2 molecule is the strongest with the highest adsorption energy of -3.25 eV. The defective TiS2 monolayer exhibits notable catalytic properties through the elongation of the O-O bond from 1.21 Å to 1.47 Å, comparable to the O-O bond length in peroxides (∼ 1.45 Å). Additionally, the adsorption mechanism is explained in variation observed in Density of States (DOS), Partial Density of States (PDOS), and Mulliken charges, thus establishing its potential for gas sensing and catalytic applications.

The role of CO on initial oxidation behavior of α-U(001) surface: A first principles study

A first-principles approach based on density-functional theory has been used to investigate the corrosion resistance of alpha-U in the CO environment. Calculations show that O2 molecules spontaneously dissociate on the uranium surface, and the two O atoms formed by dissociation tend to adsorb on the hole sites and bind to the surface in the form of a U–O bond to emit a large amount of heat. The CO molecules occur on the surface of uranium as a non-dissociative chemical. The mechanism of CO inhibiting the adsorption of O2 molecules stems from the fact that CO molecules occupy the optimal adsorption sites. Another inhibition mechanism, the combination of C atoms and O atoms to form bonds and consume oxygen atoms, has little effect on uranium corrosion.

Modulated bandgap and gas adsorption behavior on two-dimensional SrAl2S4 monolayer: Potential applications for photovoltaic and energy storage

The structure of a novel two-dimensional layered material SrAl2S4 monolayer has been proposed, and its kinetic and thermodynamic stability has been confirmed. Researches have shown that SrAl2S4 monolayer is a semiconductor material with a bandgap of 1.630 eV for PBE and 2.798 eV for HSE06 at the ground state. Under biaxial strain, SrAl2S4 monolayer can complete the transition from a direct bandgap semiconductor to an indirect bandgap semiconductor, and its bandgap can vary between 0.187 eV and 1.712 eV. In addition, We have considered the adsorption behavior of SrAl2S4 monolayer for hydrogen and oxygen molecules, and the results show that SrAl2S4 monolayer adsorbed H2 molecules remains a direct bandgap semiconductor, whereas SrAl2S4 monolayer adsorbed O2 molecules show indirect bandgap semiconductor properties. At the same time, the adsorption of O2 molecules causes a flat band near the Fermi level, which increases the electrical conductivity. The few charges transfer observed between the SrAl2S4 monolayer and gas molecules confirms that the adsorption process of gas molecules on SrAl2S4 monolayer is physical adsorption. The tunable bandgap characteristics and good adsorption behavior of hydrogen and oxygen exhibited by SrAl2S4 monolayer make it a promising candidate material in the fields of photovoltaics and energy storage.

Efficient photocatalytic activity by constructing double anion defects: synergistic and process mechanism

An S-Ov co-modified double defects photocatalyst (S10 %-ZnOov) for efficient degradation of pollutants in the water environment was fabricated by introducing S and Ov into ZnO through simple hydrothermal procedures. The prepared S10 %-ZnOov exhibited enhanced photoactivity (major pollutants degradation within 60 min) and double defects synergistic co-promotion in the photocatalytic system. Experiments, characterization, and DFT calculations confirmed that the introduced S-Ov double defects not only provided stable and efficient electronic channels for electron transfer on the material surface (promoting the separation and transfer process of charges), but also provided abundant active sites (facilitated adsorption and oxide process of H2O and O2 molecules) for the surface catalytic process, which achieved the enhancement of photocatalytic performance and promoted the generation of ROS (H2O2, ·OH and O2·-). This study revealed the synergistic mechanism and catalytic properties of the double defects, providing a new idea for the development of highly active photocatalysts for environmental remediation.

ANN and DFT investigation of 55-atom icosahedral Ag-Pt nanoalloys: Understanding structure, dynamics, and [formula omitted] activation

An artificial neural network (ANN)–based interatomic potential has been constructed to examine the structural properties of Ag55−nPtn nanoalloys, where n= 0–14. We conducted molecular dynamics simulations for global-optimizations of these nanoalloys using ANN-based interatomic potential. The relative stability of the Ag-Pt nanoalloys has been studied using stability indicators such as cohesive energy, excess energy and interaction energy. Additionally, we analyse the adsorption of O2 and CO molecules on Ag55−nPtn nanoalloys using the first-principles density functional theory based (DFT) method. The presence of Pt doping has been found to increase the adsorption strength of O2 and CO on the Ag55−nPtn nanoalloys compared to the pure Ag55 nanocluster. Our investigation suggests that the presence of Pt atoms in the core of the nanoalloy has a relatively minor effect on the adsorption of O2 and CO in comparison to Pt atoms present on the surface. The adsorption of O2 and CO on Ag41Pt14 nanoalloy, in which one of the Pt atoms is present at the surface of the nanoalloy, shows strongest adsorption among all the compositions of Ag55−nPtn nanoalloys.

Theoretical study of adsorption properties and CO oxidation reaction on surfaces of higher tungsten boride

Most modern catalysts are based on precious metals and rear-earth elements, making some of organic synthesis reactions economically insolvent. Density functional theory calculations are used here to describe several differently oriented surfaces of the higher tungsten boride WB5-x, together with their catalytic activity for the CO oxidation reaction. Based on our findings, WB5-x appears to be an efficient alternative catalyst for CO oxidation. Calculated surface energies allow the use of the Wulff construction to determine the equilibrium shape of WB5-x particles. It is found that the (010) and (101) facets terminated by boron and tungsten, respectively, are the most exposed surfaces for which the adsorption of different gaseous agents (CO, CO2, H2, N2, O2, NO, NO2, H2O, NH3, SO2) is evaluated to reveal promising prospects for applications. CO oxidation on B-rich (010) and W-rich (101) surfaces is further investigated by analyzing the charge redistribution during the adsorption of CO and O2 molecules. It is found that CO oxidation has relatively low energy barriers. The implications of the present results, the effects of WB5-x on CO oxidation and potential application in the automotive, chemical, and mining industries are discussed.

Atomically dispersed magnesium enhancing reactive oxygen species generation over g-C3N4 nanosheets for efficient photocatalytic NO removal

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification.

Unveiling the oxidation mechanism of CrTaTiMo refractory medium-entropy alloys: A synergy of density functional theory and ab initio molecular dynamics

The demand for advanced materials capable of withstanding extreme high-temperature conditions has led to the development of novel High-Entropy Alloys (HEAs). Recent works indicate that forming a CrTaO4 protection layer gives HEAs excellent long-term oxidation resistance. In this study, the high-temperature oxidation resistance properties of CrTaTiMo Refractory Medium-Entropy Alloys (RMEAs) were assessed by Density Functional Theory (DFT) and ab initio Molecular Dynamics (AIMD). Through the oxygen adsorption and diffusion calculations, we demonstrated the preferential oxygen adsorption sequence on the surface of the RMEA as Ti, Ta, Cr, and Mo. Furthermore, our analysis identified the sites featuring Ta as subsurface atoms were the weakest locations for oxygen atom diffusion. The dynamic oxidation mechanism of oxygen molecules on CrTaTiMo RMEA was investigated by AIMD simulations. The results confirmed that the adsorption and dissociation of O2 molecules on the alloy surface. Additionally, the diffusion of the O atom took place at temperatures greater than 873 K and confirmed the O-attracting feature of Ta atoms. Moreover, electronic structure calculations confirmed the bonding of oxygen atoms with those four metal elements. This study could serve as a valuable reference for the strategic development of the CrTaTiMo-based RMEAs or RHEAs for high-temperature, long-term oxidation resistance applications.

DFT evaluation the photo-catalytic performance of g-C3N4 dots/ZnO with O/S doping

To develop the high-performance g-C3N4-based photo-catalysts and understand the mechanism of photo-catalytic degradation of volatile organic compounds (VOCs), we evaluated the photo-catalytic performance and corresponding catalytic mechanisms of g-C3N4 dots/ZnO (CNZO) systems using density functional theory (DFT) calculations. Our results showed that the combination of g-C3N4 dots and ZnO monolayer has a appropriate band gap and strong visible light absorption, significantly enhancing photoelectron excitation and immigration. We also observed that O/S doping exerted a significant impact on the band structure and interfacial coupling, thereby increasing the number of photoelectrons that move from the valence band (VB) of ZnO monolayer to the conduction band (CB) of g-C3N4 dots, thereby enhancing the separation of photo-generated electron-hole pairs in O/S-CNZO. Furthermore, the suitable CB and VB positions of O/S-CNZO encourage the adsorption of surface H2O and O2 molecules, leading to the generation of ·OH and ·O2− radicals crucial in VOCs degradation. This work introduces new approaches and perspectives for constructing novel photo-catalysts. Additionally, it involves a theoretical evaluation of the photo-catalytic performance of O/S-CNZO.

Tuning the adsorption of H2O, H2 and O2 molecules on diamond surfaces by B-doping

In this study, the fundamental interactions between the low Miller index (001), (110) and (111) B-doped diamond surfaces and H2O, H2 and O2 molecules, which are commonly present during growth, in ambient air and involved in electrochemical reactions, are investigated by means of ab initio simulations. The results are presented in close comparison with previous studies on undoped diamond surfaces to reveal the impact of B doping. It is demonstrated that the B dopant is preferably incorporated on the topmost carbon layer and enhances the adsorption of H2O by forming a dative bond with O. On the contrary in some cases, it seems to weaken the adsorption of O2, compared to the undoped diamond. Moreover, a noticeable displacement of the surface atoms attached to the fragment of the dissociated H2O and O2 molecules was observed, which can be associated to early stages of wear at the atomistic level. B doping was also found to reduce the energy barriers for water dissociation in most cases, with this effect being most pronounced in the C(111) surfaces. These qualitative and quantitative results aim to provide useful insights for the development of improved protective coatings and electrochemical devices.

Bio-catalyzed oxidation self-charging zinc–polymer batteries

Oxidation self-charging batteries have emerged with the demand for powering electronic devices around the clock. The low efficiency of self-charging has been the key challenge at present. Here, a more efficient autoxidation self-charging mechanism is realized by introducing hemoglobin (Hb) as a positive electrode additive in the polyaniline (PANI)-zinc battery system. The heme acts as a catalyst that reduces the energy barrier of the autoxidation reaction by regulating the charge and spin state of O2. To realize self-charging, the adsorbed O2 molecules capture electrons of the reduced (discharged state) PANI, leading to the desorption of zinc ions and the oxidation of PANI to complete self-charging. The battery can discharge for 12 min (0.5 C) after 50 self-charging/discharge cycles, while there is nearly no discharge capacity in the absence of Hb. This biology-inspired electronic regulation strategy may inspire new ideas to boost the performance of self-charging batteries.

Crystal defect engineering to construct oxygen vacancies in MXene-derived TiO2 nanocomposites for boosting photocatalytic degradation of 2,4,6-trichlorophenol

Chlorophenolic pollutants pose serious threats to the aquatic ecosystem. Photocatalysis technology has broad prospects for decontamination. In this work, MXene-derived TiO2 nanocomposites with mixed-crystal characteristics and oxygen vacancies (OVs) (E–TiO2@rGO) were successfully synthesized by atmosphere modulation. Compared with commercial TiO2 and N2–TiO2@rGO (anatase phase), the rate constants of E–TiO2@rGO (0.06874 min−1) over 2,4,6-trichlorophenol (2,4,6-TCP) degradation increased 4 and 1.3 times, respectively. The enhanced photocatalytic performance was attributed to the co-existence of anatase and rutile phases. On the one hand, the mixed-crystal phase narrowed the band gap, broadening the light absorption range. On the other hand, it induced the generation of OVs, which has been demonstrated by DFT calculation. The presence of OVs improved the adsorption and activation of O2 and H2O molecules, beneficial for the formation of active free radicals. In addition, the incorporation of rGO promoted the separation of electron-hole pairs. The Gibbs free energy of 2,4,6-TCP degradation revealed that the OVs and mixed-crystal could reduce the energy barrier of the rate-determining step, thereby boosting the dichlorination efficiency of 2,4,6-TCP. The superoxide free radical (O2−) was determined as the dominant active species. Finally, a possible mechanism of 2,4,6-TCP degradation with E–TiO2@rGO was clarified clearly. The proposed mixed-crystal defect engineering represents a novel strategy in the design and synthesis of photocatalysts.

Defects materials of Institut Lavoisier-125(Ti) materials enhanced photocatalytic activity for toluene and chlorobenzene mixtures degradation: Mechanism study

In this paper, the effect of three monocarboxylic acids on MIL-125 synthesis was systematically investigated and the results were discussed in detail. X-ray diffractometry (XRD) and nitrogen adsorption–desorption curves indicated that small molecule acids (acetic acid, propionic acid and butyric acid) affected the morphology of MIL-125 and induced lamellar pores and structural defects in the crystals. Thermogravimetric measurements confirmed the presence of acid-regulated defective metal–organic frameworks (MOFs). Electrochemical tests and density function theory calculations indicated that acid modulation could change the forbidden bandwidth of the material. The acid modification strategy effectively promoted the transfer of photogenerated electrons and enhanced the adsorption and activation of O2 and H2O molecules, generating reactive radicals. The modified MOFs also showed excellent performance in the removal of mixed toluene and chlorobenzene. The degradation pathways of the mixture were analyzed by in situ infrared (IR) and gas chromatography-mass spectrometry (GC–MS). The mixture was converted to chlorophenolic intermediates in the presence of reactive oxygen species, further decomposed to form ethers and ethanol, and finally formed small molecules such as carbon dioxide and water. A feasible method was provided for the preparation of photocatalysts for the treatment of mixed VOCs.

Effects of adsorption of O2 and H2O molecules on the corrosion behavior of the NiTi alloy surface: a DFT investigation.

The influence of O2 and H2O adsorption significantly affects the electrochemical corrosion of the NiTi alloy, with unresolved corrosion disparities between the NiTi-B2 and NiTi-B19' phases. Density functional theory (DFT) calculations are utilized in this investigation to explore the adsorption of O atoms at varying coverages on the NiTi-B2(110) and NiTi-B19'(010) surfaces. The goal is to elucidate their oxidation behavior differences. Subsequently, the effect of O adsorption on the dissolution trends of these phases is assessed by inducing Ni/Ti vacancies to simulate alloy dissolution thermodynamically. Additionally, interactions between H2O molecules and O-pre-adsorbed NiTi alloy surfaces are examined to simulate the atomic evolution of the oxidized surface under exposure to humid air and corrosive solutions. The findings indicate a propensity of the NiTi-B19' phase to react with O, forming an oxide film more readily than the NiTi-B2 phase. O adsorption facilitates Ni dissolution and retards Ti dissolution on the alloy surface. Higher O coverage promotes easier dissolution of Ni and Ti atoms on the NiTi-B2(110) surface compared to the NiTi-B19'(010) surface, underscoring the greater corrosion resistance of the NiTi-B19' phase. Both clean and O-pre-adsorbed NiTi alloy surfaces physically adsorb H2O molecules. Notably, an O monolayer substantially mitigates the detrimental effects of H2O molecules on the corrosion resistance of alloy surfaces. This research contributes to a deeper comprehension of the corrosion mechanisms in NiTi alloys.

Anchoring defective metal-free catalysts on montmorillonite nanosheets for tetracycline removal: synergetic adsorption-catalysis and mechanism insights

The hydroxyl groups on the MMT surface induced the formation of (–CN and N defects) and N defects in the composite samples, which promoted the adsorption of TC, PMS, and O2 molecules, and the generation of reactive species, improving the TC removal efficiency.

(Invited) Enhancement of Activity of Low-Pt-Content-Catalysts Toward Oxygen Reduction through Admixing with Metal Oxide Cocatalysts

The proton-exchange membrane fuel cell (PEMFC) technology is one of the most promising approaches for energy conversion in automotive applications. Despite the use of expensive noble metal electrocatalysts, the sluggish kinetics of the oxygen reduction reaction (ORR) in acid media, and formation of the undesirable hydrogen peroxide intermediate are still the main drawbacks, on top of the stability problems, when it comes to the widespread commercialization of PEMFC devices. The progress in this subject is greatly hindered by the high cost and scarcity of the state-of-the-art platinum-based materials which are regarded as the most effective cathode catalysts. Therefore, most of the current research studies have been devoted to the optimization of active centers and maximization of their utilization, which should allow the lowering of the cathode Pt loadings without loss of performance and durability. Unfortunately, the problem of electrochemical stability and the danger of generation of higher quantities of the undesirable hydrogen peroxide intermediate may become even more serious in the case of systems utilizing lower amounts of the Pt catalystAmong important strategies is hybridization, activation, and stabilization of carbon-supported Pt catalysts by functionalization through admixing with certain nanostructured and typically substoichiometric metal oxides. Special attention is paid to application of the bi- or multi-metallic Pt-based alloys in their various forms and structures. Additionally, doping of carbon carriers with heteroatoms would produce surface functional groups and active centers capable of not only improving the catalysts’ performance, but also affecting their stability. Among other important issues are such features as porosity, hydrophilicity, and degree of graphitization of carbon components, in addition to the existence of metal–support interactions, high electrochemical active surface area, electronic structure of interfacial Pt, and the feasibility of adsorptive or activating interactions with oxygen molecules.Platinum is a main catalyst for the electroreduction of oxygen, the reaction of primary importance to the technology of low-temperature fuel cells. Because of high cost of platinum. there is a need to significantly lower its loadings at interfaces. But then O2-reduction proceeds often at less positive potentials and produces higher amounts of undesirable H2O2-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, Ta2O5, Nb2O5, ZrO2), stabilize Pt and carbon nanostructures, diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction of oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. The catalytic efficiency depends on geometric (decrease of Pt–Pt bond distances) and electronic (increase of d-electron vacancy in Pt) factors, in addition to possible metal-support interactions and interfacial structural changes affecting adsorption and activation of O2-molecule.

(Keynote) Oxygen Reduction and Evolution Reactions on Faceted MnxCo1-XFe2O4 Nanoparticles Prepared By Induction-Coupled Plasma

Substantial research efforts are directed toward the development of precious metal-free catalysts for fuel cells, metal-air batteries and electrolyzers, because the deployment of these technologies requires the synthesis of low-cost catalysts with controlled properties in large quantities.Mixed spinel oxides are a promising class of catalytic materials for the oxygen evolution (OER) and oxygen reduction (ORR) reactions, and thus several works have been devoted to the understanding of the structure – composition – activity relationships. Examples include the correlation between activity of spinel oxides and the covalency of the bond formed between the oxygen species and the metal cation in the octahedral sites1, or the possible role of metal cations in the tetrahedral sites in the oxygen electrocatalysis2. However, studies highlighting the importance of the facet engineering on the electrocatalytic activity of spinel oxides3 are still rare.Here, we will present our recent work on facetted nanoparticles MnxCo1-xFe2O4 (0 ≤ x ≤ 1) prepared by thermal plasma induction; a one step4, cost-effective and scalable method allowing the synthesis of large amounts (up to 30 g h-1 for 50 kW units) of uniform and crystalline nanoparticles5.Structural characterization by X-ray diffraction and TEM-EELS analysis showed that the mixed ferrite nanoparticles are formed by individual nanocrystals with well-defined truncated octahedron shape and with {100} and {111} facets mainly exposed, have high crystallinity, a median particle size of 40 nm and a homogeneous composition down to the atomic level.Electrochemical studies conducted in 0.1M KOH using the rotating disk electrode showed the highest activity was found for carbon black + Mn0.5Co0.5Fe2O4 composite electrode: half-wave potential for oxygen reduction 140 mV more negative than that of 20 wt% Pt/C; 420 mV oxygen evolution overpotential at 10 mAcm-2 (identical to IrO2/C). These are among the best performances reported for ferrites considering the size of the nanocrystals.Computational studies using density functional theory used to study the adsorption of oxygen molecule on the {100} and {111} facets of both CoFe2O4 and Mn0.5Co0.5Fe2O4 demonstrated that the Mn0.5Co0.5Fe2O4 {111} surface appears to have a highest affinity for the O2 molecule. The sites with lowest adsorption energy on each surface were identified and further analysis of O-O bond length and frequency as well as the Mulliken charge and populations confirmed the activation of the adsorbed O2 molecule. The energy diagrams of the ORR and OER computed for both Mn0.5Co0.5Fe2O4 {100} and {111} surfaces also pointed for a higher electrocatalytic activity for the {111} facet.