Ternary Transition Metal Oxides Research Articles

Binary zinc-cobalt metal-organic framework derived mesoporous ZnCo2O4@NC polyhedron as a high-performance lithium-ion battery anode.

Ternary transition metal oxides have attracted increasing attention due to their many merits, and will enhance electrochemical performance via the synergistic effects of the different single metal oxides. Herein, ZnCo2O4 nanoparticles encapsulated in nitrogen-doped carbon (ZnCo2O4@NC) polyhedrons have been successfully prepared through a facile two-step method. The as-prepared products had a uniform size and consisted mainly of interconnected ZnCo2O4 nanoparticles (NPs), which were uniformly distributed in the materials. As a result, the ZnCo2O4@NC polyhedrons of ZnCo-700 show a superb specific capacity of approximately 1601 mA h g-1 over 50 cycles at 0.1 A g-1. A reversible capacity of 1082 mA h g-1 was retained after 300 cycles at 1 A g-1, and a superb reversible capacity of 775 mA h g-1 was attained even when the current density was increased to 5 A g-1. These distinguished electrochemical properties could be ascribed mainly to the uniquely advantageous structural and compositional features.

Synthesis of ternary metal oxides as positive electrodes for Mg-Li hybrid ion batteries.

Rechargeable magnesium-ion batteries (MIBs) have emerged as promising energy storage systems owing to their highly stable magnesiation and de-magnesiation processes and high theoretical energy density. However, MIB technology is restricted by sluggish Mg2+ ion transportation inside the host cathode due to large impedance. Herein, a rechargeable Mg-Li hybrid ion battery (MLIB) is presented to achieve fast Mg2+ ion stripping/plating at a magnesium anode and Li+ ion intercalation/de-intercalation in a ternary transition metal oxide cathode. The (NiMnCo)3O4 multi-shelled hollow spheres prepared by a one-step hydrothermal method followed by thermal treatment were employed as a positive electrode in a Mg-Li hybrid ion battery, with a magnesium metal anode and all-phenyl-complex based dual ion electrolytes. The resulting prototype MLIB delivered a reversible capacity of 550 mA h g-1 at a current density of 50 mA g-1, which is significantly higher compared with reported MLIBs. Furthermore, the prototype MLIB exhibited an affordable specific energy (368 W h kg-1) and cycle life (a capacity of 277 mA h g-1 was retained even after 100 cycles at 100 mA g-1). The significant improvement in the electrochemical performance of the MLIB is achieved via rational design of the (NiMnCo)3O4 cathode with a reduced Li+ ion diffusion length and stable deposition/dissolution of Mg at the anode without the occurrence of side reactions. Furthermore, ex situ XRD, SEM, ICP and EIS techniques were used to understand the reaction kinetics of guest ions inside the (NiMnCo)3O4 hollow sphere cathode.

Metal-organic framework-derived porous MnNi2O4 microflower as an advanced electrode material for high-performance supercapacitors

Metal-organic framework (MOF)-derived materials have attracted considerable research interest for electrochemical energy storage and conversion due to their porosity characteristics and relatively simple synthesis routes. Spinel-type ternary transition metal oxide nanomaterials are promising electrode materials in energy-related fields in view of their high reactivity. In this work, flower-like manganese nickelate (MnNi2O4) assembled with porous nanosheets building unite were successfully prepared by using a MOF-derived method. Benefiting from high specific surface area and rich active sites, the as-obtained product exhibited a remarkable electrochemical performance. When tested as an electrode material for supercapacitors, they delivered a high specific capacitance of 2848 F g−1 at 1 A g−1 and a good stability of 93.25% capacitance retention after 5000 cycles at 10 A g−1. To examine their practical application, a hybrid supercapacitor was fabricated using the as-synthesized MnNi2O4 as a positive electrode and active carbon (AC) as a negative electrode. The assembled devices exhibited a high energy density of 142.8 Wh kg−1 at a high power density of 800 W kg−1. When the power density reached 16 kW kg−1, they still delivered a high energy density of 56.8 Wh kg−1. The superior electrochemical performance can be ascribed to the unique microstructures, elemental composition and synergism of flower-like MnNi2O4.

Nature of novel criticality in ternary transition-metal oxides

There are the chains of transition-metal cations alternating with the anions of oxygen in ternary transition-metal oxides. When a p-orbital of the oxygen connects the half-filled and empty d-orbitals of adjacent transition-metal cations, double-exchange ferromagnetism takes place. Although double exchange has been well explored, the nature of novel criticality, induced by it, is yet not uncovered. We explored the magnetic-field scaling in the heat capacity of a Sm0.55Sr0.45MnO3 manganite, one of the best ternary transition-metal oxides as it is completely ferromagnetic, and found novel criticality - unordinary critical exponents which are the consequence of coherence of Coulomb lattice distortion and ferromagnetism. The coherence is caused by the trinity of the mass, the charge and the spin of an electron. When the d and p orbitals overlaps, it quickly walks from one site to the another due its lightest mass. And due to its electric charge, it equalizes the valences of the transition-metal cations in the chains and so diminishes the Coulomb lattice distortion. At last, its spin forces magnetic moments of transition-metal cations to ferromagnetically arrange. The disappearance of Coulomb distortions widens the overlap and lowers the elastic lattice energy, so that not only the spin of an electron, but also its electric charge strengthens ferromagnetism. That nonlinear effect strengthens the critical behaviour and critical exponents come off any known universality classes. Thus, the symbiotic coherence of annihilating Coulomb distortions and arising ferromagnetism is a reason of the novel criticality.

Synthesis and thermodynamics of transition metal oxide based sodium ion cathode materials

While finding sustainable renewable energy sources is of high priority, it is equally important to develop solutions for energy storage. Advances in lithium ion batteries (LIB) indeed represent a great step in this direction. However, lithium is scarce and expensive, Batteries based on more earth-abundant elements such as sodium are attractive replacements. Layered transition metal oxides with sodium in the interlayer are promising battery cathode materials. Here we report the synthesis of a series of NaMO2 (M = Mn, Fe, Co and Ni) materials and analysis of their thermodynamic stability using high temperature oxide melt solution calorimetry. Their formation enthalpies from corresponding binary oxides are highly exothermic. The NaMO2 materials are thermodynamically more stable than their LiMO2 counterparts owing to higher electropositivity of Na+ over Li+. The formation enthalpies become less exothermic in the sequence Mn, Fe, Co, Ni, a trend seen in many other ternary transition metal oxides.

MCo2O4 (M=Co, Mn, Ni, Zn) nanosheet arrays constructed by two-dimension metal-organic frameworks as binder-free electrodes for lithium-ion batteries

Metal-organic frameworks (MOFs) derived ternary transition metal oxides have attracted more attention because of their unique features of large specific surface area, high porosity, and tunable morphology. Herein, we report a synthesis route for constructing porous MOF-derived MCo2O4 (M = Co, Mn, Ni, Zn) arrays directly on the Ni foam. Among them, MnCo2O4 nanosheet arrays electrode shows a higher capacity of 848 mAh g−1 at 0.2 A g−1. Further, MnCo2O4 electrode shows a good rate capability of 544 mAh g−1 at 2 A g−1. The MnCo2O4 electrode exhibits such good electrochemical performance primarily due to the unique nanostructure, composition of electrodes, and direct growth on the conductive substrates.

Evidencing enhanced oxygen and hydrogen evolution reactions using In–Zn–Co ternary transition metal oxide nanostructures: A novel bifunctional electrocatalyst

Ternary transition metal oxides are gaining popularity for cost effective bifunctional electrocatalytic activities and to realization of novel water splitting devices. In this regard, In2O3/ZnO/Co3O4 based ternary oxide nanostructures were investigated in detail for their oxygen/hydrogen evolution reaction (OER/HER) in alkaline environment. The ternary oxides were at first processed through a simple chemical route involving hydrothermal treatment. The prepared nanostructures were then investigated by using high-resolution transmission electron microscopy (TEM/HRTEM) to ascertain their morphological traits. X-ray diffraction, Raman signals and photoluminescence data demonstrated the In2O3 phase to be prevalent in the ternary mixture on par with that of ZnO and Co3O4. The valence state of various metal ions and the In–O, Zn–O and Co–O bonding was verified using XPS. The ternary oxide coated electrodes exhibited excellent overall water splitting activity. Overpotential values of 398 and 510 mV were registered for OER and HER experiments under a current density of ±10 mA cm−2, demonstrating the material to be an ideal OER/HER electrocatalyst at room temperature. The exceptional long-term stability in ternary oxides and their Tafel slope (88 mV/dec for OER and 60 mV/dec for HER) further affirmed their unique anodic/cathodic characteristics for water splitting applications.

DFT investigation of Ca mobility in reduced-perovskite and oxidized-marokite oxides

Progress in the development of rechargeable Ca-ion batteries demands the discovery of potential cathode materials. Transition metal oxides are interesting candidates due to their theoretical high energy densities, but with the drawback of a low Ca mobility. Previous computational/experimental investigations associate the electrochemical inactivity of various oxides (CaMO3-perovskite, CaMn2O4-post-spinel and CaV2O5) to high energy barriers for Ca migration. The introduction of oxygen and/or Ca vacancies in ternary transition metal oxides is a likely way to reshape the local topology and hence improve the Ca diffusivity. In this work, the energy barriers for Ca migration are calculated and discussed for (i) oxygen-deficient perovskites within the related Ca2Fe2O5-brownmillerite and Ca2Mn2O5 structures, and (ii) tunnel CaMn4O8, a derivative of the CaMn2O4-marokite with Ca vacancies.

Hierarchical Structure MnO2 Coated PDMS−Carbon Nanotube Sponge as Flexible Electrode for Electrocatalytic Water Splitting and High Performance Supercapacitor

AbstractAs a typical transition metal oxide, MnO2 has great potential in catalysis and energy storage, but its poor conductivity greatly limits its performance. PDMS−carbon nanotube sponges have excellent electrical conductivity and flexibility. Herein, according to the principle of complementary, we propose a novel hierarchical PDMS−carbon nanotube sponge@MnO2 electrode with uniform size and morphology. In view of the structural preponderances and multifunctional of the materials, the PDMS−carbon nanotube sponge@MnO2 has been investigated as the binder−free electrode materials for both supercapacitors and electrocatalysis applications. PDMS−carbon nanotube sponge@MnO2 electrode exhibits an admirable HER property with a low onset potential of 112 mV at −30 mA cm−2, a minimal overpotential (η=258 mV), a small Tafel slope (71 mV dec−1), large anodic currents and stability for 20 h in 0.1 M H2SO4 solution. Moreover, as supercapacitor electrode, the PDMS−carbon nanotube sponge@MnO2 electrode achieves a specific mass capacitance reaching 124.7 mF cm−2 at 1 A cm−2 and good flexibility, which are better than those ternary transition metal oxides. The assembled asymmetric device with the PDMS−carbon nanotube sponge@MnO2 and CNTs respectively as positive and negative electrode has a large window voltage of 1.4 V, and thus acquires an expected specific mass capacitance (422 mF cm−3 at the current density of 1 A cm−3) and an outstanding higher energy density of 15.3 W h kg−1 (at 371 W kg−1).

A Flexible Film toward High-Performance Lithium Storage: Designing Nanosheet-Assembled Hollow Single-Hole Ni-Co-Mn-O Spheres with Oxygen Vacancy Embedded in 3D Carbon Nanotube/Graphene Network.

Ternary transition metal oxides (TMOs) are highly potential electrode materials for lithium ion batteries (LIBs) due to abundant defects and synergistic effects with various metal elements in a single structure. However, low electronic/ionic conductivity and severe volume change hamper their practical application for lithium storage. Herein, nanosheet-assembled hollow single-hole Ni-Co-Mn oxide (NHSNCM) spheres with oxygen vacancies can be obtained through a facile hydrothermal reaction, which makes both ends of each nanosheet exposed to sufficient free space for volume variation, electrolyte for extra active surface area, and dual ion diffusion paths compared with airtight hollow structures. Furthermore, oxygen vacancies could improve ion/electronic transport and ion insertion/extraction process of NHSNCM spheres. Thus, oxygen-vacancy-rich NHSNCM spheres embedded into a 3D porous carbon nanotube/graphene network as the anode film ensure efficient electrolyte infiltration into both the exterior and interior of porous and open spheres for a high utilization of the active material, showing an excellent electrochemical performance for LIBs (1595 mAh g-1 over 300 cycles at 2 A g-1 , 441.6 mAh g-1 over 4000 cycles at 10 A g-1 ). Besides, this straightforward synthetic method opens an efficacious avenue for the construction of various nanosheet-assembled hollow single-hole TMO spheres for potential applications.

Facile Preparation of Porous Rod-like Cu x Co3-x O4/C Composites via Bimetal-Organic Framework Derivation as Superior Anodes for Lithium-Ion Batteries.

To meet growing demand of energy, lithium-ion batteries (LIBs) are under enormous attention. The development of well-designed ternary transition metal oxides with high capacity and high stability is important and challengeable for using as electrode materials for LIBs. Herein, a new and highly reversible carbon-coated Cu-Co bimetal oxide composite material (CuxCo3–xO4/C) with a one-dimensional (1D) porous rod-like structure was prepared through a bimetal–organic framework (BMOF) template strategy followed by a morphology-inherited annealing treatment. During the annealing process, carbon derived from organic frameworks in situ fully covered the synthesized bimetal oxide nanoparticles, and a large number of porous spaces were generated in the MOF-derived final samples, thus ensuring high electrical conductivity and fast ion diffusion. Benefiting from the synergetic effect of bimetals, the unique 1D porous structure, and conductive carbon network, the as-synthesized CuxCo3–xO4/C delivers a high capacity retention up to 92.4% after 100 cycles, with a high reversible capacity still maintained at 900 mA h g–1, indicating an excellent cycling stability. Also, a good rate performance is demonstrated. These outstanding electrochemical properties show us a concept of synthesis of MOF-derived bimetal oxides combining both advantages of carbon incorporation and porous structure for progressive lithium-ion batteries.

In-situ synthesis of MnCo2O4.5 nanosheets on reduced graphene oxide for a great promotion in the thermal decomposition of ammonium perchlorate

In this work, ternary transition metal oxides MnCo2O4.5 nanosheets was anchored on reduced graphene oxide (RGO/MnCo2O4.5 NSs) in an in-situ way for catalyzing ammonium perchlorate (AP). XRD, FT-IR, Raman, EDX, XPS, SEM, TEM, HR-TEM, SAED and nitrogen absorption-desorption techniques were applied to characterize the structure and morphology of the catalyst. The catalytic performances for the thermal decomposition of AP were investigated using DSC and TG. The results show that the MnCo2O4.5 nanosheets are vertically grown on RGO sheets to form a hierarchically porous structure, which is remarkably effective to avoid both the aggregation of MnCo2O4.5 NSs and the re-stacking of RGO. The introduction of RGO will significantly lead to an increase in conductivity and specific surface area. Just for that reason and the synergetic effect between RGO and MnCo2O4.5 NSs, the synthesized RGO/MnCo2O4.5 NSs composites gets the low-temperature decomposition peak of AP disappeared, the high-temperature decomposition temperature reduced by as high as 124.1 °C, the activation energy decreased from 221.04 to 129.85 kJ·mol−1, and the reaction rate increased incredibly up to 186.8 times when compared with corresponding data of the pure AP. Furthermore, the catalytic mechanism of the RGO/MnCo2O4.5 NSs has been discussed either based upon the electron-transfer theory.

Influence of Spin State and Cation Distribution on Stability and Electronic Properties of Ternary Transition-Metal Oxides.

This work is a systematic ab initio study of the influence of spin state and cation distribution on the stability, dielectric constant, electronic band gap, and density of states of ternary transition-metal oxides. As an example, the chemical family of spinel ferrites MFe2O4, with M = Mg, Sc–Zn is chosen. Dielectric constant and band gap are calculated for various spin states and cation configurations via dielectric-dependent self-consistent hybrid functionals and compared to available experimental data. When choosing the most stable spin state and cation configuration, the calculated electronic properties are in reasonable agreement with measured values. The nature of the excitation is investigated through projected density of states. A pronounced dependence of band gap energy and dielectric constant on the spin state and cation configuration is observed, which is a possible explanation for the large variation of the experimental results, in particular, if several states are energetically close.

Novel ternary transition metal oxide solid solution: mesoporous Ni-Mn-Co-O nanowire arrays as an integrated anode for high-power lithium-ion batteries.

Electrochemical performances of lithium-ion batteries depend strongly on the micro-nanostructures of active materials as well as electrode configurations. A reasonable design of both active materials and electrode configuration is of great importance to improving the electrochemical properties of the batteries. Here, we present the preparation and electrochemical properties of mesoporous Ni-Mn-Co-O oxide (NMCO) nanowire arrays (NWAs) directly grown on Cu substrates, which can be used as an integrated electrode for lithium-ion batteries. The electrochemical measurements show that the NMCO/Cu NWA integrated electrodes without binder exhibit enhanced cycling stability and high specific capacity compared with the NMCO nanowire electrode prepared by a conventional coating process. In addition, the NMCO/Cu-foam NWA integrated electrode constructed from porous copper exhibits outstanding cycle stability and rate capability compared with the NMCO/Cu-foil NWA integrated electrode based on a copper foil collector.

Nanoporous CuCo2S4 Microspheres: A Novel Positive Electrode for High-Performance Hybrid Energy Storage Devices

Demands for safer, faster, and more efficient energy storage systems have motivated researchers to design and develop new electrode materials. Ternary transition metal oxides are the electrode mate...

One-Step Controllable Synthesis of Mesoporous MgCo2 O4 Nanosheet Arrays with Ethanol on Nickel Foam as an Advanced Electrode Material for High-Performance Supercapacitors.

In recent years, ternary transition metal oxides (TTMOs), especially spinel type TTMOs have attracted widespread attention as promising candidates for electrode materials. Among all of the popular TTMOs, MgCo2 O4 is an outstanding one, owing to its superior theoretical capacitance. In this work, MgCo2 O4 nanosheet arrays (NSAs) grown directly on nickel foams were fabricated through a facile hydrothermal process at 120 °C for 4 h. With a series of structural and morphological characterization techniques, it was found that the ethanol played a key role in controlling the composition and morphology during the synthesis process. The MgCo2 O4 NSAs exhibited a superior specific capacitance of 853.06 C g-1 (at 1 mA cm-2 ) and enhanced cycling performance, with 94.65 % of initial capacitance retained after 3000 cycles when used as a binder-free integrated electrode for electrochemical supercapacitors; much higher than other reported data for MgCo2 O4 as well. The excellent electrochemical properties mainly came from the unique morphology of the MgCo2 O4 NSAs. This study will demonstrate the applications of MgCo2 O4 NSAs based large-scale supercapacitors grown on low-cost nickel foams.

Highly Efficient Removal of CO in Effluent Streams from Real‐Life Propane Oxidation Process over CuO−CeO2−Based Catalysts

AbstractSelective removal of CO from the effluent streams in real‐life chemical processes is of great importance in many different fields of industry. Until now it remains challenging to use non‐precious metal oxides to selectively remove CO at low temperatures from real‐life chemical effluent with complex compositions. Herein, a series of binary and ternary transition metal oxide catalysts were prepared by co‐precipitation method and employed for the preferential removal of CO in the effluent stream (off‐gas) of propane selective oxidation. It was found that the CuO−CeO2−based mixed oxide catalyst exhibited the best CO removal performance, wider operating temperature window and higher resistance to the inhibition of hydrocarbons, H2O and CO2. The presented catalyst showed high potential for selective removal of CO in the off‐gas stream containing CO2, H2O and various hydrocarbons.

Metal-organic framework derived porous ternary ZnCo2O4 nanoplate arrays grown on carbon cloth as binder-free electrodes for lithium-ion batteries

Metal-organic frameworks (MOFs) derived ternary transition metal oxide nanostructures have attracted considerable attention for their important applications in energy-related fields. However, most of the present reports on MOFs-derived materials are in the powder form, which should be further mixed with polymer binder and conductive agents before they are coated on current conductor. In this work, we demonstrate a facile solution method to grow the bimetallic zinc/cobalt zeolitic imidazolate frameworks nanoplate arrays (Zn/Co-ZIF NPAs) on carbon cloth (CC) substrate and then they are well converted to porous ternary ZnCo2O4 NPAs on CC after an annealing treatment in air. When investigated as binder-free electrodes for lithium-ion batteries (LIBs), the ZnCo2O4 NPAs/CC electrode exhibits a high area capacity of 3.01 mA h cm−2 (corresponding to 1341.7 mA h g−1 for the ZnCo2O4 NPAs) at the current density of 0.24 mA cm−2 for 100 cycles, which is much higher than that of the Co3O4 NPAs/CC electrode (1.93 mA h cm−2). Moreover, at a high current density of 1.20 mA cm−2, the ZnCo2O4 NPAs/CC electrode can still maintain a high capacity of 2.05 mA h cm−2. The excellent electrochemical performance could be attributed to the unique morphology, structure and composition of the porous ternary ZnCo2O4 NPAs, as well as directly grown on current collector.

Hierarchical Porous NiO/β-NiMoO4 Heterostructure as Superior Anode Material for Lithium Storage.

Ternary transition metal oxides (TTMOs) have attracted considerable attention for rechargeable batteries because of their fascinating properties. However, the unsatisfactory electrochemical performance originating from the poor intrinsic electronic conductivity and inferior structural stability impedes their practical applications. Here, the novel hierarchical porous NiO/β-NiMoO4 heterostructure is fabricated, and exhibits high reversible capacity, superior rate capability, and excellent cycling stability in Li-ion batteries (LIBs), which is much better than the corresponding single-phase NiMoO4 and NiO materials. The significantly enhanced electrochemical properties can be attributed to its superior structural characteristics, including the large surface area, abundant pores, fast charge transfer, and catalytic effect of the intermediate product of metallic nickel. The NiO/β-NiMoO4 heterostructure delivers a high capacity of 1314 mA h g-1 at 0.2 A g-1 after 100 cycles. Furthermore, even after 400 cycles at 1 A g-1 , the reversible capacity remains at around 500 mA h g-1 . These results indicate that the NiO/β-NiMoO4 heterostructure shows great potential as an anode material for high-performance LIBs.

(Invited) Experimental and Theoretical Approaches to High Performance, Robust HER and Oxygen Evolution Reaction (OER) Electrocatalysts for Proton Exchange Membrane Based Water Electrolysis

Water electrolysis is a well-known approach for the generation of clean and sustainable hydrogen via acid, alkaline and neutral mediated systems. Proton exchange membrane (PEM) based acid mediated water electrolysis is considered highly advantageous and one of the most reliable technologies for hydrogen generation and oxygen evolution among all other conventional hydrogen production approaches. However, the systems have yet to reach commercialization levels due to the use of highly expensive precious metal or platinum group metal (PGM) based electro-catalysts such as Pt, RuO2, and IrO2, all well-known for their excellent electrocatalytic activity and stability for both hydrogen and oxygen evolution reactions. There is a considerable need for the identification of non-noble metal based electrocatalysts for acid mediated water electrolysis. Over the years, we have focused our efforts at generation of novel transition metal based oxide solid solutions containing reduced amounts of noble metal oxide species. First principles density functional theoretical (DFT) based calculations largely aided by the use of the Vienna ab-initio simulation package (VASP) have been utilized to identify these novel solid solutions largely mimicking the electronic structure of the noble metal electrocatalyst systems. These theoretical calculations formed the basis for the identification of various reduced noble metal oxide containing solid solutions. These initial studies and theoretical understanding of the reaction mechanisms formed the basis for eventually identifying completely non-noble metal containing compositions. All of these systems display electrochemical activity comparable or even superior to the noble metal counterparts. Chronoamperometry studies in fact, indicate the systems to show even more robust electrocatalytic performance under primarily acid mediated conditions while being equally effective under basic and neutral pH conditions as well. This presentation will outline and summarize the collective efforts undertaken by my group over the years to identify low noble metal containing electrocatalysts as well as our recent findings of a completely non-noble metal based ternary transition metal oxide solid solution containing electronegative anion such as fluorine and its promising electrocatalytic response for water electrolysis and oxygen evolution reactions. Results of the studies conducted over the years will be presented while outlining future plans and strategies for the identification of such non-noble metal and non PGM based electrocatalysts for acid mediated water electrolysis.