Electrocatalytic Characteristics Research Articles

Voltammetric Detection of Dihydroxybenzene Isomers By Modified Graphite Paste Electrode with Prussian Blue-Nanosized Polyaniline Hybrid

The dihydroxybenzene isomers (DHB); catechol (1, 2-dihydroxybenzene, CC), resorcinol (1, 3-dihydroxybenzene, RC) and hydroquinone (1,4-dihydroxybenzene, HQ) are well-known organic pollutants and are widely distributed in the environment. DHB isomers are frequently used as starting materials and industrial reagents in various industries for production of plastic, tanning, pharmaceuticals, paint, paper, cosmetics and rubber.1–4 Furthermore, these isomers are also found as important side products from the industrial effluents of photo-processing companies, oil refineries, coal-tar, steel, paper and pulp mills in concentrations ranging between 1 to 1000 ppm.4,5 Due to their toxicity and the health risks associated with their use, national environmental agencies from United States and European Union have categorized them as primary wastewater pollutants.6 In addition, Health Canada has also listed them under the List of Prohibited and Restricted Cosmetic Ingredients (Cosmetic Ingredient Hotlist).7 As an electroactive polymer, polyaniline (PANI) is known to have good environmental stability, conductivity and redox properties. It has also been recently used in electrochemical biosensors due to the ease of synthesis, cheap cost and simple doping mechanisms. Prussian blue (PB) is another redox substance which also possesses good conductivity and unique electrocatalytic characteristics. In this study, modified graphite paste electrode (GPE) with PB doped nanosized-PANI hybrid (PB@n-PANI/GPE) was used for simultaneous detection of DHB isomers using differential pulse voltammetry (DPV). Prussian blue doped nanosized-polyaniline (PB@n-PANI) was synthesized in two-steps, firstly, aniline and ferric (III) chloride salt reacted through in situ mechano-chemical reactions to produce nanosized-PANI polymer. Secondly, potassium hexacyanoferrate (II) solution was added to the product of step one and the polymer was doped by PB in a solid-state and template-free technique to generate PB@n-PANI. The synthesized hybrid was then characterized by different microscopic and spectroscopic techniques. The PB@n-PANI modified GPE exhibited three well-separated oxidation peaks at potentials 0.24, 0.36 and 0.74 V for HQ, CC and RC, respectively (Fig. 1). The analytical performance of the PB@n-PANI/GPE has been studied for simultaneous determination of HQ, CC and RS in different real sample matrices with satisfactory recoveries. Furthermore, different electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry have been used to perform electrochemical surface characterization of the modified GPE. The results from CV and ESI were used to evaluate the charge transfer properties of the PB@n-PANI/GPE and the results from chronoamperometric studies were used to calculate the diffusion coefficients of the DHB isomers. In addition, active surface area of the modified GPE and the standard heterogenous rate constant for the DHB isomers have also been calculated. Overall, we have demonstrated that the presence of PB and n-PANI enhances the redox-active surface area and plays a synergistic role in improving the electrocatalytic activity of the PB@n-PANI/GPE. Therefore, PB@n-PANI/GPE is a promising analytical platform for simultaneous detection of DHB isomers.

One-Stage Plasma-Assisted Electrochemical Synthesis of Cobalt-Containing Catalysts for Oxygen Reduction

t—The potentialities of single-stage plasma-assisted electrochemical synthesis of few-layer graphene structures with high electrocatalytic characteristics toward the oxygen reduction reaction are demonstrated.

Electrocatalytic Oxidation of Sulfadiazine with Ni-Doped Sb-SnO2 Ceramic Ring Particle Electrode

The excessive use and abuse of antibiotics has brought about serious threats to water environmental safety and human health. It is necessary to develop efficient, cheap, and environmentally friendly treatment technologies for antibiotics. In this work, a Ni-doped Sb-SnO2 microporous ceramic ring particle electrode was prepared by the dipping method and characterized by scanning electron microscopy, energy dispersion spectroscopy, and X-ray diffraction. The electrocatalytic oxidation ability and kinetic characteristics of sulfadiazine (SDZ) were studied using the prepared electrode, and the degradation pathways of SDZ were analyzed preliminarily. The results showed that Ni and Sb-SnO2 crystals were loaded on the particle electrode surface, which is beneficial for electron transfer and SDZ adsorption and improvement of electrocatalytic oxidation efficiency. Under the conditions of 0.02 mol·L-1 NaCl solution (pH 8), 15 mA·cm-2 of current density, and 15 g particle electrode, 50 mg·L-1 SDZ could be completely removed on the three-dimensional electrode within 15 min. The removal efficiency of TOC in the reaction solution reached 80.8% for 3 h degradation and was 17.6% higher than that with two-dimensional electrode. The kinetic process of the electrocatalytic oxidation could be well described by the first-order reaction kinetic model, and the rate constant was 0.329 min-1. The degradation products of SDZ were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the possible pathways of electrocatalytic degradation mainly include the fractures of S-N bond on sulfamido and C-N bond on pyrimidine ring, desulfonation, deamination, and·OH oxidation.

Surface engineering of CeO2–TiO2 composite electrode for enhanced electron transport characteristics and alkaline hydrogen evolution reaction

Herein, we report the fine tuning of electrocatalytic characteristics of CeO2–TiO2 composite by surface engineering to reduce overpotential and to improve exchange current density for enhanced alkaline hydrogen evolution reaction (HER). The enhanced electrocatalytic activity of the surface engineered CeO2–TiO2 composite through Ni and P decoration is attributed to the improved electron transport ability. The surface roughness characteristics and surface composition of electroactive species are tuned to generate high electronic conductivity on the surface engineered composite electrode surface. The developed hard electrode with leptokurtic surface (Sku > 3) exhibited a high average roughness value (Sa) of 3 μm due to incorporation of the mesoporous catalyst material into it. Tuning of a compact and continuous electrode surface with critical composition of elements Ni (52 at.%), P (20 at.%), Ce (9 at.%) and Ti (8 at.%) furnishes the high conductivity (contact potential difference = 0.83 V) to the electrode. The developed electrode with surface engineered CeO2–TiO2 catalyst exhibited a low overpotential of −111 mV (at a high current density of 250 mA cm−2) and high exchange current density (1.6 × 10−1 mA cm−2) with low charge transfer resistance (615 Ω cm2). High electrocatalytic activity and stability of the surface engineered CeO2–TiO2 catalyst electrode during alkaline (32 w/v.% NaOH) HER ensure its promising performance and applicability for long term HER.

Boron-Induced Electronic-Structure Reformation of CoP Nanoparticles Drives Enhanced pH-Universal Hydrogen Evolution.

Even though transition-metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)-modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B-CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm-2 ). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons' delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.

Boron‐Induced Electronic‐Structure Reformation of CoP Nanoparticles Drives Enhanced pH‐Universal Hydrogen Evolution

AbstractEven though transition‐metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)‐modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B‐CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm−2). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.

Tuning of the electrocatalytic characteristics of PANI/Fe2O3 composite coating for alkaline hydrogen evolution reaction.

The paper reports a simple and cost-effective strategy for the development of a stable and reproducible PANI/Fe2O3 composite coating as an efficient electrode for the electrocatalytic alkaline hydrogen evolution reaction (HER). The surface characteristics of the developed PANI/Fe2O3 composite coatings are tuned to achieve high hardness (510 HVN), thickness (26 μm), porosity, and surface roughness (Sa = 3.760 μm). The PANI/Fe2O3 composite coating with tuned surface characteristics (PANI/Fe2O3-2GL) facilitates the effective conduction of electrons from a highly conducting polymer to a metal. This increases the electron density on the coating surface and enhances the active surface area, which effectively enhances the hydrogen adsorption efficiency on the coating surface to improve HER activity. The composite coating exhibits enhanced HER activity with low overpotential (110 mV) and high exchange current density (95.32 mA cm-2). The mechanism of HER on the coating surface follows the Volmer-Heyrovsky reaction with the Heyrovsky step as the rate-determining step. The stability of the composite coating under aggressive reaction conditions even after long-term HER confirms its competency with commercial electrocatalysts.

Efficient electrocatalyst of α-Fe2O3 nanorings for oxygen evolution reaction in acidic conditions.

Large-scale application of sustainable energy devices urgently requires cost-effective electrocatalysts to overcome the sluggish kinetics related to the oxygen evolution reaction (OER) under acidic conditions. Here, we first report the highly efficient electrocatalytic characteristics of α-Fe2O3 nanorings (NRs), which exhibits prominent OER electrocatalytic activity with lower overpotential of 1.43 V at 10 mA cm−2 and great stability in 1 M HCl, surpassing the start-of-the art Ir/C electrocatalyst. The significantly optimized OER activity of the α-Fe2O3 NRs mainly attributes to the synergistic effect of the excellent electrical conductivity and a large effective active surface because of their unique nanoring structure, disordered surface, and the dynamic stability of α-Fe2O3 NRs in acidic conditions.

OBTAINING PARTIALLY UNZIPPED CARBON NANOTUBES FOR OXYGEN ELECTRODES

Various methods for unzipping carbon nanotubes are described, which differ only in the method of acting on multi-walled carbon nanotubes which leads to obtain a partial unzipped carbon nanotubes or the creation of a defective hybrid structure in carbon nanotubes.
 By electrochemical anodic oxidation in 80 % sulfuric acid of multi-walled carbon nanotubes synthesized partially unzipped nanotubes and shows the results of the study. Using the methods of X-ray phase analysis, electron microscopy, and Raman spectra, it has been established that, as a result of electrochemical anodic oxidation, partially unzipped multi-walled carbon nanotubes are obtained. Two-layer oxygen electrodes were made, where synthesized materials were used as an active layer. Studies of the electrocatalytic characteristics of oxygen electrodes from partially unzipped multi-walled carbon nanotubes were carried out in a mock up of fuel cell with alkaline electrolyte. It is established that the degree of unzipping of multi-walled carbon nanotubes depends on the time of electrochemical oxidation. It has been suggested that it is possible to control the process of synthesis of partially unzipped nanotubes. It has been established that one of the methods for estimating the degree of unzipping of multi-walled carbon nanotubes can be studies the electrochemical characteristics of oxygen electrodes based on these materials.
 Electrochemical investigation has established that the obtained samples of partially unzipped multi-walled carbon nanotubes are promising materials as catalysts carrier for oxygen electrodes of fuel cells. The developed method synthesis of partially unzipped multi-walled carbon nanotubes allows obtaining electrode materials for chemical current sources. Oxygen electrodes, based on such electrochemically produced materials, were stable for six months at a discharge current density of 200 mA/cm2. Partially unzipped multi-walled carbon nanotubes are promising catalyst carrier for electrodes of chemical current sources, as well as a material for hybrid nanocomposites with predetermined characteristics.

Synthesis of mesoporous nickel ferrite nanoparticles by use of citrate framework methodology and application for electrooxidation of glucose in alkaline media

Electrooxidation of glucose in alkaline media is a critical issue as a clean source for Fuel cell application. The using of noble metals as anodes obstructs the economic cost of the glucose fuel cells (GFCS). That is why the trend is towards the recent doped metal oxides designs as low-cost anodes electrocatalysts. Here, Nickel ferrite (NiFe2O4) nanoparticles (NFNPs) were simply prepared by the formation of citrate framework followed by combustion and calcination as a promising anode for GFCS at high pH. The as-designed NFNPs were investigated in terms of FE-SEM, TEM, EDX, and XRD analyses. The crystallinity study confirms the formation of NiFe2O4 cubic spinel with a crystallite size of around 13.7 nm. The surface morphology has a sponge-like structure with an irregular shape of pores. The diameters of sponge are varying, and the average is around ~ 572 nm. The successful formation of a porous network can be related to the releasing of considerable amounts of gaseous products during the combustion process at 180 °C and calcination process at 400 °C. The synthesized NFNPs showed enhanced electrocatalytic characteristics at different glucose contents up to 60.0 mM. Besides the high produced current, the enhanced stability and charge transfer were observed for the application of NFNPs in GEO.

Effect of K2Cr2O7 on preparation and properties of Ti/Sn–Sb–RuOx/α-PbO2 for zinc electrowinning

In this study, a Ti/Sn–Sb–RuOx/α-PbO2 electrode was prepared by continuous extrusion coating technique. The surface microstructure of α-PbO2 coating was examined by scanning electron microscopy (SEM). The electrocatalytic characteristics of the electrode were explored by anodic polarization curves, linear sweep voltammetry curve, electrochemical impedance spectroscopy (EIS). It was found that the addition of potassium dichromate (K2Cr2O7) to the alkaline lead plating solution can significantly inhibit the cathode deposition of lead, which can stabilize the lead ions in the plating solution, prevent the solution from decomposing red Pb3O4, and increase α-PbO2 deposition rate; when the amount of K2Cr2O7 added is 2%, the prepared Ti/Sn–Sb–RuOx/α-PbO2 electrode has the best performance, and the oxygen evolution potential of the electrode is 1.5962 V (500 A m−2), the charge transfer resistance Rt is 28.81 Ω · cm2.

Temperature-dependent (20–55 °C) electrocatalytic characteristics during ethanol/propionate degradation by methanogenic communities grown on conductive carbon fibers

Conductive materials have been incorporated in anaerobic bioreactors to stimulate direct interspecies electron transfer (DIET), a recently discovered microbial electron-sharing network. Previous studies emphasized the significance of electrocatalytic features associated with DIET, while research gaps are remaining in the understanding of how different operating temperatures and substrate variation will affect those electrochemical characteristics. Consequently, this study examined various electrochemical features, including biomass conductivity, pilA gene, heme-binding proteins, and electron transfers rates (kapp) for methanogenic biomass from conductive carbon fibers amended anaerobic bioreactors operated under different temperatures (20, 37, and 55 °C) with substrate variation (ethanol/propionate). Our results demonstrated a distinct temperature-dependent correlation between biomass conductivities, pilA gene, and heme-binding proteins, suggesting operating temperature would influence the relative contributions of various DIET routes (via pili, redox proteins, and conductive materials). When fed with ethanol, the estimated kapp was the highest at 37 °C (0.0033 s−1 vs 1.1 d−1), followed by 20 °C (0.0018 s−1 vs. 0.74 d−1), and 55 °C (0.0012 s−1 vs. 0.29 d−1), which were positively correlated with the estimated methanogenesis rates. While methanogenesis performance was independent of electron transfer rates (0.0026–0.0032 s−1) during operation with propionate; only carbon fibers amended bioreactor operated at 37 °C showed stable performance in response to substrate variation. Thus, it appeared that bioreactors operated under different temperatures might face a different level of instability caused by substrate variation. Overall, our results linked electrocatalytic features of biomass with temperature and substrate variation, suggesting the importance of temperature-dependent optimization of DIET for improving anaerobic digestion of complex organic feedstock.

An efficient and stable photoelectrochemical system with 9% solar-to-hydrogen conversion efficiency via InGaP/GaAs double junction

Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications. Here, we present a simple and efficient strategy for III-V-based photoelectrodes that functionally and spatially decouples the light harvesting component of the device from the electrolysis part that eliminates parasitic light absorption, reduces the cost, and enhances the stability without any compromise in efficiency. The monolithically integrated PEC cell was fabricated by an epitaxial lift-off and transfer of inversely grown InGaP/GaAs to a robust Ni-substrate and the resultant photoanode exhibits an STH efficiency of ~9% with stability ~150 h. Moreover, with the ability to access both sides of the device, we constructed a fully-integrated, unassisted-wireless “artificial leaf” system with an STH efficiency of ~6%. The excellent efficiency and stability achieved herein are attributed to the light harvesting/catalysis decoupling scheme, which concurrently improves the optical, electrical, and electrocatalytic characteristics.

Preparation and Characterization of Bhant Leaves‐derived Nitrogen‐doped Carbon and its Use as an Electrocatalyst for Detecting Ketoconazole

AbstractIn this study, the electrocatalytic characteristics of nitrogen‐doped carbon (NDC) prepared from Clerodendrum Infortunatum L leaves on a glassy carbon electrode (GCE) surface was evaluated with regards to its ability to detect the electroactive drug ketoconazole (KCZ). The NDC was prepared by carrying out a simple pyrolysis of dry powder of the leaves at 850 °C. The prepared NDC was characterized using field‐emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and Brunauer‐Emmett‐Teller analysis, and was then used as an electrode material. The performance of the electrochemical KCZ sensor with the NDC‐modified glassy carbon electrode (NDC/GCE) was found to be optimal when using PBS buffer at pH 3 and a concentration of 0.1 mg/ml of NDC in the conjugate with Nafion polymer. Under these conditions, the NDC/GCE displayed a KCZ detection limit of 3 μM and a linear dependence of its response on KCZ concentration over a wide range of KCZ concentrations from 47 μM to 752 μM (R2=0.9742). These results confirmed the potential of NDC as an electrocatalyst.

Mixed Copper/Copper-Oxide Anchored Mesoporous Fullerene Nanohybrids as Superior Electrocatalysts toward Oxygen Reduction Reaction.

Developing a highly active, stable, and efficient non-noble metal-free functional electrocatalyst to supplant the benchmark Pt/C-based catalysts in practical fuel cell applications remains a stupendous challenge. A rational strategy is developed to directly anchor highly active and dispersed copper (Cu) nanospecies on mesoporous fullerenes (referred to as Cu-MFC60 ) toward enhancing oxygen reduction reaction (ORR) electrocatalysis. The preparation of Cu-MFC60 involves i) the synthesis of ordered MFC60 via the prevalent nanohard templating technique and ii) the postfunctionalization of MFC60 with finely distributed Cu nanospecies through incipient wet impregnation. The concurrence of Cu and cuprous oxide nanoparticles in the as-developed Cu-MFC60 samples through relevant material characterizations is affirmed. The optimized ORR catalyst, Cu(15%)-MFC60 , exhibits superior electrocatalytic ORR characteristics with an onset potential of 0.860 vs reversible hydrogen electrode, diffusion-limiting current density (-5.183 mA cm-2 ), improved stability, and tolerance to methanol crossover along with a high selectivity (four-electron transfer). This enhanced ORR performance can be attributed to the rapid mass transfer and abundant active sites owing to the synergistic coupling effects arising from the mixed copper nanospecies and the fullerene framework.

Mn-doped Co3O4 nanoarrays as a promising electrocatalyst for oxygen evolution reaction

Microstructures and electrocatalytic characteristics of a series of MnxCo3−xO4 nanostructures for oxygen evolution reaction were investigated by adjusting hydrothermal reaction time, temperature and the molar ratio of Mn2+/Co2+, followed by an alkali treatment at room temperature. The results indicate that the synthesis process is optimal when hydrothermal reaction time, temperature and the molar ratio of Mn2+/Co2+ are 10 h, 100 °C and 1:3, respectively. Under this condition, MnxCo3−xO4 possesses an optimal electrocatalytic performance for OER. Moreover, after treated in the mixed alkali solution of 1 M NaBH4 and 3 M NaOH, the catalytic performance of MnxCo3−xO4 for OER has been enhanced furtherly. The unique architecture and its corresponding morphology after alkalization treatment, such as highly exposed active sites and high surface roughness, are mainly responsible for its excellent electrocatalytic performance for the OER process.

Efficient nitrogen-doped porous carbon/carbon nanotube-supported Co3O4/Co catalysts for oxygen reduction reactions in alkaline media

In this study, Co3O4/Co nanoparticles are synthesized within nitrogen-doped porous carbon/carbon nanotube matrix (Co3O4/Co@NC/CNT) by using ZIF-67 metal-organic frameworks. In comparison with commercial Pt/C catalysts, the composite exhibits better electrocatalytic characteristics for oxygen reduction reactions in alkaline media, such as onset potential, half-wave potential, current density, cycle stability, and methanol tolerance. For instance, onset potential and half-wave potential are positively shifted by 67 mV and 25 mV, respectively. Structural and composition analysis demonstrate that enhanced properties result from the formation of pyridinic nitrogen and Co-N-C active sites within carbon matrix. The findings above indicate that the Co3O4/Co@NC/CNT catalyst can replace expensive Pt/C catalyst for potential applications in fuel cells and metal-air batteries.

Electrocatalytic and Optoelectronic Characteristics of Exfoliated Two-Dimensional Titanium Nitride Ti4N3Tx mxene

A relatively new class of two-dimensional (2D) materials called MXenes have garnered tremendous interest in the field of energy storage and conversion. Thus far nearly all MXenes reported experimentally have been described as metals, with a lone report of a mixed-metal carbide phase exhibiting semiconducting character. Here, we report the optical, electrocatalytic and electrical properties of the 2D Ti4N3TxMXene (Tx= basal plane surface terminating groups) and show this material exhibits both metallic and semiconducting behavior. We provide complete structural characterization of exfoliated Ti4N3TxMXene and assign Tx= O and/or OH and find that this material is susceptible to surface oxidation. Optical experiments indicate that the exfoliated Ti4N3TxMXene forms a hybrid with a thin surface oxide layer resulting in visible light absorption at energies greater than ~2.0 eV and an excitation wavelength-dependent defect-state emission over a broad range centered at ~2.9 eV. As an electrocatalyst for the hydrogen evolution reaction, the exfoliated Ti4N3Txshows an overpotential of ~300 mV at –10 mA cm–2and a Tafel slope of ~190 mV/decade. Finally, we observe a clear semiconductor-to-metal transition at ~90 K from temperature-dependent transport measurements under 5 T magnetic field likely resulting from the thin oxide layer. These results unveil the intriguing optical, electrocatalytic, and electrical properties of this 2D Ti4N3TxMXene that expands the potential of these new 2D materials into electrocatalysis and (opto)electronic applications.

Crystalline nickel boride nanoparticle agglomerates for enhanced electrocatalytic methanol oxidation

In this paper, crystalline Ni3B nanoparticle agglomerates have been successfully prepared via dry-powder annealing of the solution-produced amorphous nickel boride. The electron microscopy (EM) images indicate that the Ni3B nanomaterial is composed of numerous nano-sized particles with a diameter ranging from 100 to 200 nm. The electrocatalytic characteristics of nickel boride in an alkaline medium were observed by cyclic voltammetry (CV) and chronoamperomerty (CA). Compared to the amorphous nickel boride/Ni foam (ANB/NF), the crystalline Ni3B/Ni foam (CNB/NF) electrode exhibits a higher catalytic performance with low initial oxidation potential of 0.35 V and a high anodic oxidation current density of 62 A g−1 at 0.55 V in a 6 M KOH solution with 0.5 M methanol. And the CNB/NF electrode shows good long-term cycling stability and the catalytic current of methanol retains 87% of the initial value after 1000 time cycles. The CNB/NF electrode should be a promising candidate for alkaline direct methanol fuel cells (DMFCs).

Enhanced Catalytic Activity Based on “Oxygen Self-Breathing” Ce-Doped Perovskite Oxygen Electrode

The rechargeable metal-air batteries have attracted extensive interests due to their high energy density and environmental friendliness. However, the poor stability, high cost of the oxygen electrodes, and especially the sluggish kinetics hinder the large-scale applications of metal-air batteries. To enhance the oxygen reaction rate, the high-efficient catalyst, which can accelerate oxygen evolution reaction (OER: 4OH-→O2+2H2O+4e-) and oxygen reduction reaction (ORR: O2+2H2O+4e-→4OH-) is urgently required. Among the oxygen electrode catalysts, perovskite oxides with the general formula ABO3-δ, in which A is rare-earth or alkaline earth element and B is transition metal, have received significant attention due to high ionic and electronic conductivity as well as the good stability. In recent years, considerable efforts have been devoted to understanding the catalytic mechanism of ABO3-δ perovskite oxides to achieve high efficient OER and ORR. It is widely accepted that the OER and ORR processes involve a sequence of intermediates (OH*, O* and OOH*) on the active atoms, which is intimately related to electronic structure (various electron and orbital distribution) and geometric structure of active atoms. The electronic structure is sensitive to the component, valence state of A and B site and particularly the concentration of oxygen vacancies. The oxygen molecules produced during OER process could fill the oxygen vacancies, which could further supply oxygen loss in ORR process. Therefore, the presence of oxygen vacancies can significantly affect the catalytic activity. Besides the electronic structure, the geometric structure of active atom can directly affect the band length and band angle of active atom-intermediates, which could modify the adsorption energy of intermediates. Therefore, the optimization of electron structure and geometric structure plays crucial role in achieving the enhanced electrocatalytic activity of perovskite oxides. Following this strategy, in this work, cerium (Ce) ions are successfully doped into LaCoO3-δ, causing the improved catalytic activity by modifying the electronic and geometric structures. The cerium oxides with co-existed +3 and +4 valence state are capable in storing and releasing oxygen (“oxygen self-breathing”) into LaCoO3-δ, which is beneficial to improve the electrocatalytic activity. The XPS analysis of Ce 3d shows the characteristic peaks due to the coexistence of Ce3+ and Ce4+ ions (Figure 1a), confirming the doping of Ce ions in LaCoO3-δ. To further verify the introduction of oxygen vacancies in LaCoO3-δ, the O 1s core-level spectrum is shown in Figure 1b. As can be seen, the peak at 528.5 eV corresponds to the lattice oxygen species (O2-). Notably, Ce-doped LaCoO3- δ(La0.9Ce0.1CoO3-δ) catalyst possesses the higher O2- percentage than that of LaCoO3-δ. The electrocatalytic characteristics of the perovskite oxides have been systematically investigated with RDE system in the O2-saturated 0.1 M KOH solution. The La0.9Ce0.1CoO3-δ shows the enhanced ORR and OER activities in comparison with LaCoO3-δ. As shown in Figure 1(c), the La0.9Ce0.1CoO3-δ shows better ORR performance with the half-wave potential (0.677V) at -3 mA cm-2 and the onset potential (0.835V) at -2 mA cm-2. Meanwhile, La0.9Ce0.1CoO3-δ catalyst also displays better OER performance (Figure 1(d)). Compared with LaCoO3-δ catalyst, the over-potential of La0.9Ce0.1CoO3-δ catalyst shifts negatively by 76.8 mV at 10 mA cm-2. In conclusion, the Ce ions have been successfully doped into LaCoO3-δ, offering large amount of lattice oxygen species in perovskite structure and thus leading to the enhanced electrocatalytic activities. Figure 1