Co/CoO heterojunction rich in oxygen vacancies introduced by O_(2) plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc-air battery

Herein,Co/CoO heterojunction nanoparticles(NPs)rich in oxygen vacancies embedded in mesoporous walls of nitrogen-doped hollow carbon nanoboxes coupled with nitrogen-doped carbon nanotubes(P-Co/CoOV@NHCNB@NCNT)are well designed through zeolite-imidazole framework(ZIF-67)carbonization,chemical vapor deposition,and O_(2) plasma treatment.As a result,the threedimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P-Co/CoOV@NHCNB@NCNT,and they display exceedingly good electrocatalytic performance for oxygen reduction reaction(ORR,halfwave potential[EORR,1/2=0.855 V vs.reversible hydrogen electrode])and oxygen evolution reaction(OER,overpotential(η_(OER,10)=377mV@10mA cm^(−2)),which exceeds that of the commercial Pt/C+RuO_(2) and most of the formerly reported electrocatalysts.Impressively,both the aqueous and flexible foldable all-solid-state rechargeable zinc-air batteries(ZABs)assembled with the P-Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long-term cycling stability.First-principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity,reduces reaction energy barriers,and accelerates reaction kinetics rates.This work opens up a new avenue for the facile construction of highly active,structurally stable,and cost-effective bifunctional catalysts for ZABs.

Ca and Sr co-doping induced oxygen vacancies in 3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.

Tuning the crystalline and electronic structure of ZrO_(2)via oxygen vacancies and nano-structuring for polysulfides conversion in lithium-sulfur batteries

The recent emergence of tetragonal phases zirconium dioxide(ZrO_(2))with vacancies has generated significant interest as a highly efficient and stable electrocatalyst with potential applications in trapping polysulfides and facilitating rapid conversion in lithium-sulfur batteries(LSBs).However,the reduction of ZrO_(2)is challenging,even under strong reducing atmospheres at high temperatures and pressures.Consequently,the limited presence of oxygen vacancies results in insufficient active sites and reaction interfaces,thereby hindering practical implementation.Herein,we successfully introduced abundant oxygen vacancies into ZrO_(2)at the nanoscale with the help of carbon nanotubes(CNTs-OH)through hydrogen-etching at lower temperatures and pressures.The introduced oxygen vacancies on ZrO_(2-x)/CNTs-OH can effectively rearrange charge distribution,enhance sulfiphilicity and increase active sites,contributing to high ionic and electronic transfer kinetics,strong binding energy and low redox barriers between polysulfides and ZrO_(2-x).These findings have been experimentally validated and supported by theory calculations.As a result,LSBs assembled with the ZrO_(2-x)/CNTs-OH modified separators demonstrate excellent rate performance,superior cycling stability,and ultra-high sulfur utilization.Especially,at high sulfur loading of 6 mg cm^(-2),the area capacity is still up to 6.3 mA h cm^(-2).This work provides valuable insights into the structural and functional optimization of electrocatalysts for batteries.

Engineering oxygen vacancies on Tb-doped ceria supported Pt catalyst for hydrogen production through steam reforming of long-chain hydrocarbon fuels

Steam reforming of long-chain hydrocarbon fuels for hydrogen production has received great attention for thermal management of the hypersonic vehicle and fuel-cell application.In this work,Pt catalysts supported on CeO_(2)and Tb-doped CeO_(2)were prepared by a precipitation method.The physical structure and chemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction,scanning electron microscopy,transmission electron microscopy,Raman spectroscopy,H_(2)temperature programmed reduction,and X-ray photoelectron spectroscopy.The results show that Tb-doped CeO_(2)supported Pt possesses abundant surface oxygen vacancies,good inhibition of ceria sintering,and strong metal-support interaction compared with CeO_(2)supported Pt.The catalytic performance of hydrogen production via steam reforming of long-chain hydrocarbon fuels(n-dodecane)was tested.Compared with 2Pt/CeO_(2),2Pt/Ce_(0.9)Tb_(0.1)O_(2),and 2Pt/Ce_(0.5)Tb_(0.5)O_(2),the 2Pt/Ce_(0.7)Tb_(0.3)O_(2)has higher activity and stability for hydrogen production,on which the conversion of n-dodecane was maintained at about 53.2%after 600 min reaction under 700℃at liquid space velocity of 9 ml·g^(-1)·h^(-1).2Pt/CeO_(2)rapidly deactivated,the conversion of n-dodecane was reduced to only 41.6%after 600 min.

Increased Oxygen Vacancies in CuO-ZnO Snowflake-like Composites Drive the Hydrogenation of CO_(2) to Methanol

Cu/ZnO is widely used in the hydrogenation of carbon dioxide (CO_(2)) to methanol (CH_(3)OH) to improve the lowconversion rate and selectivity generally observed. In this work, a series of In, Zr, Co, and Ni-doped CuO-ZnO catalysts wassynthesized via a hydrothermal method. By introducing a second metal element, the activity and dispersion of the activesites can be adjusted and the synergy between the metal and the carrier can be enhanced, forming an abundance of oxygenvacancies. Oxygen vacancies not only adsorb CO_(2) but also activate the intermediates in methanol synthesis, playing a keyrole in the entire reaction. Co3O4-CuO-ZnO had the best catalytic performance (a CO_(2) conversion rate of 9.17%;a CH_(3)OHselectivity of 92.77%). This study describes a typical strategy for multi-component doping to construct a catalyst with anabundance of oxygen vacancies, allowing more effective catalysis to synthesize CH_(3)OH from CO_(2).

Effect of Calcination Temperature on Surface Oxygen Vacancies and Catalytic Performance Towards CO Oxidation of Co3O4 Nanoparticles Supported on SiO2

Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were char- acterized with X-ray diffraction （XRD）, laser Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, temperature-programmed reduction （TPR） and X-ray absorption fine structure （XAFS） spectroscopy. Both XRD and Raman spectroscopy only detect the existence of Co3O4 crystallites in all catalysts. However, XPS results indicate that excess Co2＋ ions are present on the surface of Co3O4 in Co3O4（200）/Si02 as compared with bulk Co3O4. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co3O4 in Co3O4（200）/SiO2, and XAFS results demonstrate that Co3O4 in Co3O4（200）/SIO2 contains excess Co2＋. Increasing calcination temperature results in oxidation of excess Co2＋ and the decrease of the concentration of surface oxygen vacancies, consequently the for- mation of stoichiometric Co3O4 on supported catalysts. Among all Co3O4/SiO2 catalysts, Co3O4（200）/SiO2 exhibits the best catalytic performance towards CO oxidation, demonstrating that excess Co2＋ and surface oxygen vacancies can enhance the catalytic activity of Co3O4 towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silicasupported Co3O4 catalysts and highlight the important role of surface oxygen vacancies on Co3O4.

Porous LaFeO3 nanofiber with oxygen vacancies as an efficient electrocatalyst for N2 conversion to NH3 under ambient conditions

Electrocatalytic N2 reduction to NH3 under ambient conditions is an eco-friendly and sustainable alternative to the traditional Haber-Bosch process. However, inhibited by the high activation barrier of N2, this process needs efficient electrocatalysts to adsorb and activate the N2, enabling the N2 reduction reaction(NRR). Herein, we report that porous LaFeO3 nanofiber with oxygen vacancies acts as an efficient NRR electrocatalyst with abundant active sites to enhance the adsorption and activation of N2. When tested in 0.1 M HCl, such electrocatalyst achieves a high Faradaic efficiency of 8.77% and a large NH3 yield rate of 18.59 μg h–1 mgcat–1.at-0.55 V versus reversible hydrogen electrode. This catalyst also shows high long-term electrochemical stability and excellent selectivity for NH3 formation. Density functional theory calculations reveal that, by introducing oxygen vacancy on LaFeO3, the subsurface metallic ions are exposed with newly localized electronic states near the Fermi level, which facilitates the adsorption and activation of N2 molecules as well as the subsequent hydrogenation reactions.

Enhanced photocatalytic NO removal and toxic NO2 production inhibition over ZIF‐8‐derived ZnO nanoparticles with controllable amount of oxygen vacancies

The controlled introduction of oxygen vacancies(OVs)in photocatalysts has been demonstrated to be an efficient approach for improving the separation of photogenerated charge carriers,and thus,for enhancing the photocatalytic performance of photocatalysts.In this study,a two‐step calcination method where ZIF‐8 was used as the precursor was explored for the synthesis of ZIF‐8‐derived ZnO nanoparticles with gradient distribution of OVs.Electron paramagnetic resonance measurements indicated that the concentration of OVs in the samples depended on the temperature treatment process.Ultraviolet–visible spectra supported that the two‐step calcined samples presented excellent light‐harvesting ability in the ultraviolet‐to‐visible light range.Moreover,it was determined that the two‐step calcined samples presented superior photocatalytic performance for the removal of NO,and inhibited the generation of NO2.These properties could be attributed to the contribution of the OVs present in the two‐step calcined samples to their photocatalytic performance.The electrons confined by the OVs could be transferred to O2 to generate superoxide radicals,which could oxidize NO to the final product,nitrate.In particular,the NO removal efficiency of Z 350‐400(which was a sample first calcined at 350℃ for 2 h,then at 400℃ for 1 h)was 1.5 and 4.6 times higher than that of Z 400(which was one‐step directly calcined at 400℃)and commercial ZnO,respectively.These findings suggested that OV‐containing metal oxides that derived from metal‐organic framework materials hold great promise as highly efficient photocatalysts for the removal of NO.

Zn‐doping mediated formation of oxygen vacancies in SnO2 with unique electronic structure for efficient and stable photocatalytic toluene degradation

To optimize the electronic structure of photocatalyst,a facile one‐step approach is developed for the simultaneous realization of Zn‐doping and surface oxygen vacancies(SOVs)formation on SnO_(2).The Zn‐doped SnO_(2)with abundant SOVs exhibits efficient and stable performance for photocatalytic degradation of toluene under both low and high relative humidity.Experimental and theoretical calculations results show that the synergistic effects of Zn‐doping and SOVs on SnO_(2)can considerably boost the charge transfer and separation efficiency.Utilizing the in situ DRIFTS and theoretical calculations methods,it is revealed that the benzene ring of toluene is opened at benzoic acid on the SnO_(2)surface and selectively at benzaldehyde on the Zn‐doped SnO_(2)surface.This implies that Zn‐doped SnO_(2)photocatalysts shorten the pathway of toluene degradation,and toxic intermediates can be significantly inhibited.This work could provide a promising and sustainable route for safe and efficient removal of aromatic VOCs with photocatalytic technology.

Oxygen vacancies engineering by coordinating oxygen-buffering CeO_(2) with CoO_(x) nanorods as efficient bifunctional oxygen electrode electrocatalyst

CeO_(2)decorated CoOx rod-like hybrid,supported onto holey reduced graphene(CoOx/CeO_(2)/RGO)composite,was fabricated via a surfactant-assisted route.Its corresponding electrocatalytic performance towards oxygen reduction/evolution reactions(ORR and OER)was systematically investigated in alkaline electrolyte.Structural,morphological and compositional studies revealed changes in electronic and surface properties when CeO_(2)was introduced as an oxygen buffer material.The oxygen vacancies effectively enhanced the electrocatalytic activity,while the synergistic effect of co-catalyst CeO_(2),CoOx activecenters,and defective graphene with many voids facilitate the charge/mass transfer,making CoOx/CeO_(2)/RGO an efficient and stable bifunctional electrocatalyst for OER/ORR with△E=0.76 V(△E=E10mAcm.-2OER-E_(1/2).ORR).This parameter is 70 mV and 270 mV lower than CoOx/RGO and the benchmark Pt/C,respectively.In addition,the OER/ORR bifunctionality of CoOx/CeO_(2)/RGO composite outperforms that of Pt/C catalyst in a H2-O_(2)micro fuel cell platform.

Improving visible-light-driven photocatalytic NO oxidation over BiOBr nanoplates through tunable oxygen vacancies

In this work,a series of BiOBr nanoplates with oxygen vacancies(OVs)were synthesized by a solvothermal method using a water/ethylene glycol solution.The number of OVs and facets of BiOBr were tuned by changing the water/ethylene glycol ratio.Although the role of OVs in photocatalysis has been investigated,the underlying mechanisms of charge transfer and reactant activation remain unknown.To unravel the effect of OVs on the reactant activation and photocatalytic NO oxidation process,in situ diffuse reflectance infrared Fourier transform spectroscopy,so‐called DRIFTS,and theoretical calculations were performed and their results combined.The photocatalytic efficiency of the as‐prepared BiOBr was significantly increased by increasing the amount of OVs.The oxygen vacancies had several effects on the photocatalysts,including the introduction of intermediate energy levels that enhanced light absorption,promoted electron transfer,acted as active sites for catalytic reaction and the activation of oxygen molecules,and facilitated the conversion of the intermediate products to the final product,thus increasing the overall visible light photocatalysis efficiency.The present work provides new insights into the understanding of the role of OVs in photocatalysts and the mechanism of photocatalytic NO oxidation.

Solvothermal fabrication of Bi_(2)MoO_(6) nanocrystals with tunable oxygen vacancies and excellent photocatalytic oxidation performance in quinoline production and antibiotics degradation

Novel Bi_(2)MoO_(6) nanocrystals with tunable oxygen vacancies have been developed via a facile low-cost approach with the assistance of a glyoxal reductant under solvothermal conditions.With the introduction of oxygen vacancies,the optical absorption of Bi_(2)MoO_(6) is extended and its bandgap narrowed.Oxygen vacancies not only lead to the appearance of a defect band level in the forbidden band but can also result in a minor up-shift of the valence band maximum,promoting the mobility of photogenerated holes.Moreover,oxygen vacancies can act as electron acceptors,temporarily capturing electrons excited by light and reducing the recombination of electrons and holes.At the same time,oxygen vacancies help to capture oxygen,which reacts with the captured photogenerated electrons to generate more superoxide radicals(·O_(2)-)to participate in the reaction,thereby significantly promoting the redox performance of the photocatalyst.From Bi_(2)MoO_(6) containing these oxygen vacancies(OVBMO),excellent photocatalytic performance has been obtained for the oxidation of 1,2,3,4-tetrahydroquinoline to produce quinoline and cause antibiotic degradation.The reaction mechanism of the oxidation of 1,2,3,4-tetrahydroquinoline to quinoline over the OVBMO materials is elucidated in terms of heterogeneous Catal.via a radical pathway.

Introducing oxygen vacancies in TiO_(2) lattice through trivalent iron to enhance the photocatalytic removal of indoor NO

The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.

Controllable oxygen vacancies and morphology engineering:Ultra-high HER/OER activity under base–acid conditions and outstanding antibacterial properties

Introducing vacancy defects and unique morphology is an effective strategy to improve the catalytic performance of transition metal compounds.However,precisely controlling the amount of vacancy defects remains challenging.Here,we propose a facile and efficient hydrothermal accompanying an annealing method to synthesize a series of Mn-doped CoO nanomaterials with controllable oxygen vacancies and unique morphology.The oxygen vacancies amount can be precisely controlled by adjusting the Mndoping content and is positively correlated with catalytic performance.It was found that the oxygen vacancies amount can reach up to 38.2%over the Mn-doped CoO nanomaterials,resulting in ultra-high hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalytic activity(HER:25.6 and 37 m V at 10 m A cm^(-2);OER:301 and 322 m V at 50 m A cm^(-2))under both basic and acidic conditions,while reaching 10 m A cm^(-2) for an ultra-low cell voltage of only 1.52 V,which exceeds that of Pt/C/RuO_(2) and all reported non-noble metal oxide catalysts.The DFT calculations reveal oxygen vacancies can optimize H*and HOO*intermediates adsorption free energy,thus improving the HER and OER performance.Interestingly,the Mn-doped CoO with rich oxygen vacancies exhibits excellent antibacterial properties in vitro of biomedicine.This work provides new ideas and methods for the rational design and precise control of vacancy defects in transition metal compounds and explores their potential application value in electrochemical water splitting and biomedical fields.

Engineering heterointerfaces coupled with oxygen vacancies in lanthanum–based hollow microspheres for synergistically enhanced oxygen electrocatalysis

The development of high–efficiency and low–cost bifunctional oxygen electrocatalysts is critical to enlarge application of zinc–air batteries(ZABs). However, it still remains challenges due to their uncontrollable factor at atomic level during the catalysts preparation, which requires the precise regulation of active sites and structure engineering to accelerate the reaction kinetics for both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Herein, a novel Co–doped mixed lanthanum oxide and hydroxide heterostructure(termed as Co–La MOH|OV@NC) was synthesized by pyrolysis of La–MOF–NH_(2) with spontaneous cobalt doping. Synergistic coupling of its hollow structure, doping effect and abundant oxygen vacancies creates more active sites and leads to higher electroconductivity, which contribute to the better performance. As employed as a bifunctional oxygen electrocatalyst, the resulting 3 Co–La MOH|OV@NC exhibits superior electrocatalytic activity for both ORR and OER. In assembled ZAB, it also demonstrates an excellent power density of 110.5 m W cm^(-2), high specific capacity of 810 m Ah g_(Zn)^(-1), and good stability over 100 h than those of Pt/C + RuO_(2). Density functional theory(DFT) calculation reveals that the heterointerfaces coupled with oxygen vacancies lead to an enhanced charge state and electronic structure, which may optimize the conductivity, charge transfer, and the reaction process of catalysts.This study provides a new strategy for designing highly efficient bifunctional oxygen electrocatalysts based on rare earth oxide and hydroxides heterointerface.

Enhanced ambient ammonia photosynthesis by Mo-doped Bi_(5)O_(7)Br nanosheets with light-switchable oxygen vacancies

The fabrication of efficient catalysts to reduce nitrogen(N_(2))to ammonia(NH3)is a significant challenge for artificial N_(2) fixation under mild conditions.In this work,we demonstrated that the simultaneous introduction of oxygen vacancies(OVs)and Mo dopants into Bi_(5)O_(7)Br nanosheets can significantly increase the activity for photocatalytic N_(2) fixation.The 1 mol% Mo-doped Bi_(5)O_(7)Br nanosheets exhibited an optimal NH_(3) generation rate of 122.9μmol g^(-1) h^(-1) and durable stability,which is attributed to their optimized conduction band position,suitable absorption edge,large number of light-switchable OVs,and improved charge carrier separation.This work provides a promising approach to design photocatalysts with light-switchable OVs for N_(2) reduction to NH_(3) under mild conditions,highlighting the wide application scope of nanostructured BiOBr-based photocatalysts as effective N_(2) fixation systems.

Optimized CeO_(2) Nanowires with Rich Surface Oxygen Vacancies Enable Fast Li-Ion Conduction in Composite Polymer Electrolytes

Low-cost and flexible solid polymer electrolytes are promising in all-solid-state Li-metal batteries with high energy density and safety.However,both the low room-temperature ionic conductivities and the small Li^(+)transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery.Here,we introduce Gd-doped CeO_(2) nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd-doped CeO_(2) nanowires and polymer electrolytes,which promotes the Li-salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes.The optimized composite polymer electrolyte has a high Li-ion conductivity of 5×10^(-4)4 S cm^(-1) at 30℃ and a large Li+transference number of 0.47.Moreover,the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high-voltage LiNi_(0.8)Mn _(0.1)Co_(0.1)O_(2)(NMC)cathode,providing the stable cycling of all-solid-state batteries at high current densities.

Negative thermal expansion of Ca2RuO4 with oxygen vacancies

Oxygen vacancies have a profound effect on the magnetic,electronic,and transport properties of transition metal oxides but little is known about their effect on thermal expansion.Herein we report the effect of oxygen defects on the structure formation and thermal expansion properties of the layered perovskite Ca2RuO4(CRO).It is shown that the CRO containing excess oxygen crystallizes in a metallic L-CRO phase without structure transition from 100 K to 500 K and displays a normal thermal expansion behavior,whereas those with oxygen vacancies adopt at room temperature an insulating S-CRO phase and exhibit an enormous negative thermal expansion(NTE)from 100 K to about 360 K,from where they undergo a structure transition to a high temperature metallic L-CRO phase.Compared to the L-CRO containing excess oxygen,the S-CRO structure has increasingly large orthorhombic strain and distinctive in-plane distortion upon cooling.The in-plane distortion of the RuO6 octahedra reaches a maximum across 260 K and then relaxes monotonically,providing a structure evidence for the appearance of an antiferromagnetic orbital ordering in the paramagnetic phase and the A_g phonon mode suppression and phase flip across the same temperature found recently.Both the L-and S-CRO display an antiferromagnetic ordering at about 150-110 K,with ferromagnetic ordering components at lower temperature.The NTE in S-CRO is a result of a complex interplay among the spin,orbital,and lattice.

Phase separation-hydrogen etching-derived Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies boosting superior sodium-ion storage kinetics

Understanding the crystal phase evolution of bimetallic oxide anodes is the main concern to profoundly reveal the conversion reaction kinetics and sodium-ion storage mechanisms.Herein,an integrated selfsupporting anode of the Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies(Ov-BMO-Cu)are in-situ generated by phase separation and hydrogen etching using nanoporous Cu-Mn alloy as selfsacrificial templates.On this basis,we have elucidated the relationship between the phase evolution,oxygen vacancies and sodium-ion storage mechanisms,further demonstrating the evolution of oxygen vacancies and the inhibition effect of manganese oxides as an“anchor”on grain aggregation of copper oxides.The kinetic analyses confirm that the expanded lattice space and increased oxygen vacancies of cycled Ov-BMO-Cu synergistically guarantee effective sodium-ion diffusion and storage mechanisms.Therefore,the Ov-BMO-Cu electrode exhibits higher reversible capacities of 4.04 mA h cm^(-2)at 0.2 mA cm^(-2)after 100 cycles and 2.20 m A h cm^(-2)at 1.0 mA cm^(-2)after 500 cycles.Besides,the presodiated Ov-BMO-Cu anode delivers a considerable reversible capacity of 0.79 m A h cm^(-2)at 1.0 mA cm^(-2)after 60 cycles in full cells with Na_(3)V_(2)(PO_(4))_(3)cathode,confirming its outstanding practicality.Thus,this work is expected to provide enlightenment for designing high-capacity bimetallic oxide anodes.

Adjusting oxygen vacancies in perovskite LaCoO_(3)by electrochemical activation to enhance the hydrogen evolution reaction activity in alkaline condition

Developing highly-active,earth-abundant non-precious-metal catalysts for hydrogen evolution reaction(HER)in alkaline solution would be beneficial to sustainable energy storage.Perovskite oxides are generally regarded as low-active HER catalysts,due to their inapposite hydrogen adsorption and water dissociation.Here,we report a detailed study on perovskite LaCoO_(3)epitaxial thin films as a model catalyst to significantly enhance the HER performance via an electrochemical activation process.As a result,the overpotential for the activation films to achieve a current density of 0.36 m A/cm^(2)is 238 m V,reduced by more than 200 m V in comparison with that of original samples.Structural characterization revealed the activation process dramatically increases the concentration of oxygen vacancies(Vo)on the surface of LaCoO_(3).We established the relationship between the electronic structure induced by Vo and the enhanced HER activity.Further theoretical calculations revealed that the Vo optimizes the hydrogen adsorption and dissociation of water on the surface of LaCoO_(3)thin films,thus improving the HER catalytic activity.This work may promote a deepened understanding of perovskite oxides for HER mechanism by Vo adjusting and a new avenue for designing highly active electrochemical catalysts in alkaline solution.