Electrocatalytic Performances of LaNi1-xMgxO3 Perovskite Oxides as Bi-functional Catalysts for Lithium Air Batteries (original) (raw)
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ACS Applied Energy Materials, 2019
Rational design of efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is important for rechargeable zinc-air batteries. Herein, Mg doped perovskite LaNiO 3 (LNO) nanofibers (LNMO NFs) were prepared by a facile electrospinning method combined with subsequent calcination. LNMO NFs show a more positive half-wave potential of 0.69V and a lower overpotential of 0.45 V at a current density of 10 mA cm-2 than those of the pristine LNO NFs. As an air electrode for zinc-air battery, the cell with LaNi 0.85 Mg 0.15 O 3 NFs catalyst is able to deliver a high specific capacity of 809.9 mAh g-1 at a current density of 5 mA cm-2. It also shows an excellent cycling stability over 110 h at a current density of 10 mA cm −2. DFT calculation results demonstrate that the LNMO surface binds oxygen stronger than LNO, which contributes to enhanced OER activity as observed in our experiments. The results indicate that LNMO NFs is an efficient and durable bifunctional catalyst for zinc-air batteries.
ECS Electrochemistry Letters, 2015
LaNiO 3 catalyst was synthesized by RHP method and sprayed onto a GDL. Electrochemical activity for oxygen reactions of asprepared GDE was evaluated under half-cell condition in oxygen-saturated 7 M KOH electrolyte. Best performance in terms of potential difference E between ORR and OER amounted 0.688 V @ 10 mA cm −2 for 20 wt% LaNiO 3 /C HSAG compared to 1 V for 20 wt% Pt/C Vulcan. Moreover, by increasing perovskite:carbon weight ratio up to 3:2, E in oxygen decreased down to 0.57 V that is the lowest value ever reported in the literature. However, phase segregation and loss in ORR activity was observed during cycling.
In Situ Formed Layered-Layered Metal Oxide as Bifunctional Catalyst for Li-Air Batteries
The electrochemical activity of a Li-air battery cathode catalyst derived from the lithium rich layered-layered metal oxide of the formula 0.5Li 2 MnO 3 .0.5LiMn 0.5 Ni 0.35 Co 0.15 O 2 is reported. The catalyst formed in-situ by electrochemically de-lithiating this metal oxide embedded in a high surface area carbon matrix behaved as a bifunctional catalyst for O 2 reduction reaction (ORR) and O 2 evolution reaction (OER) in a non-aqueous Li-O 2 cell. Cyclic voltammetry (CV) in both half and full cells revealed enhanced OER and ORR catalytic activity by: i-) displaying a more positive potential shift during ORR, ii-) stabilizing the initial ORR product LiO 2 , and iii-) showing an additional potential step in the oxidation of the ORR products. In the CV of catalyzed cells, a reduction peak appeared before the main peroxide (O 2 2−) formation peak suggesting that the catalyst stabilizes the superoxide (O 2 −) formed prior to the formation of peroxide. Evidence for LiO 2 as the initial discharge product was obtained from both the Raman spectrum and X-ray diffraction (XRD) pattern of Li-air cell cathodes after galvanostatic discharge to 2 V. Surface features for the discharged cathodes obtained from Field Emission Scanning Electron Microscope (FESEM) unveiled dissimilar morphologies for the discharge products from catalyzed and uncatalyzed cells, originating from different nucleation mechanisms. The catalyzed cells exhibited longer cycle life than uncatalyzed cells under similar cycling conditions. Conventional lithium ion batteries with one-electron reversible transfer per metal in transition metal oxide cathodes are not capable of a 300-mile (500 km) driving range for all-electric vehicles on a single charge. Advanced batteries having at least 50 percent higher energy density than today's best Li-ion battery are needed to realize such electric vehicles. In order to overcome the constraints imposed on the reversible capacity of cathode materials by the lithium intercalation reaction, it is increasingly becoming necessary to change the electrode reaction process to one of atom displacement reaction involving multiple electron transfer per atom. In this connection recharge-able non-aqueous lithium-air (i.e. Li/O 2) batteries 1,2 have opened up new horizons to search for higher energy density batteries that could achieve the 300-mile EV driving range. Now there is consensus that the ORR mechanism in non-aqueous electrolytes is different from that observed in aqueous electrolytes relevant to H 2 /O 2 fuel cells. Generally O 2 reduction reactions (ORR) in non-aqueous electrolytes, including organic electrolytes and room temperature ionic liquids, occur in the following steps: 3–6 Step 1: O 2 + Li + + e − → LiO 2 (initial one-electron electrochem-ical reduction step which can rarely be observed) Step 2: 2LiO 2 → Li 2 O 2 + O 2 (chemical decomposition to the common discharge product) Step 3: LiO 2 + e − + Li + → Li 2 O 2 (electrochemical reduction of initial reduction product LiO 2 to the common discharge product) Step 4: Li 2 O 2 + 2e − + 2Li + → 2Li 2 O (electrochemical reduction product at low potentials possible in a potentiodynamic experiment) The oxygen evolution reaction (OER) paths do not necessarily follow the reverse of those in the ORR. The most probable OER reactions are: Step 5: LiO 2 → O 2 + Li + + e − Step 6: Li 2 O 2 → O 2 + 2Li + + 2e − Step 7: Li 2 O → 1/2O 2 + 2Li + + 2e − The LiO 2 formed in step 1 is very short-lived in most non-aqueous electrolytes due to the moderately soft basicity of O 2 − which discourages its association with the hard Lewis acid Li +. The superoxide specie in most cases decomposes readily to peroxide (O 2 2−) (step 2) which is a hard base and it readily combines with Li + to form Li 2 O 2. In high donor number (DN) electrolytes such as dimethyl sulfoxide (DMSO, DN = 29.8), the acidity of Li + ions in solution is substantially decreased by its solvation with DMSO such that (DMSO) n Li + acts as a soft acid which enables the superoxide species to become ion-paired with Li + in DMSO. In such cases, the (DMSO) n LiO 2 has a relatively longer lifetime in solution. Throughout this work, we used tetra ethylene glycol dimethyl ether (TEGDME) based electrolytes which has a low Gutmann DN (DN = 16.6) providing short life time for the superoxide initially formed in the reduction of O 2. As a result the superoxide quickly decomposes according to the reaction in step 2 in this electrolyte. The discharge product of an uncatalyzed Li-O 2 cell utilizing TEGDME/LiX where X − is CF 3 SO 3 − or PF 6 − is Li 2 O 2. 5 Several technical issues and possible solutions pertaining to the Li air batteries have been documented. 3,7–10 Among them, appropriate cathode catalysts 11–13 to enhance the ORR and OER kinet-ics and reversibility is well recognized. In this paper we show that i-) the layered-layered metal oxide of the approximate composition 0.5MnO 2 .Mn 0.5 Ni 0.35 Co 0.15 O 2 obtained by the electrochemical delithiation of 0.5Li 2 MnO 3 .0.5LiMn 0.5 Ni 0.35 Co 0.15 O 2 promotes the stabilization of the initial ORR product LiO 2 by the catalyst which in turn lowers the voltage polarization of the oxidation reaction during Li-O 2 cell charging and ii-) the stabilization of the initial ORR product LiO 2 by the catalyst also lowers the activation energy of oxygen reduction reaction (Li-O 2 cell discharge) which improves the power density of the battery. Experimental Chemical reagents.—Anhydrous grade ≥99.8% acetonitrile (CH 3 CN), purum grade ≥98.0% tetraethylene glycol dimethyl ether (TEGDME), anhydrous grade ≥99.5% 1,2-dimethoxyethane (DME), and electrochemical grade tetrabutylammonium hexafluorophosphate (TBAPF 6) were purchased from SigmaAldrich, Allentown, PA. Purolyte lithium hexafluorophosphate (LiPF 6) certified to contain less than 20.0 ppm water was purchased from Novolyte Technologies and used without further treatment. Metals basis 99.9% Li foil purchased from Alfa Aesar Company was used as anode of the Li-O 2 cells. Soon after their arrival, all these reagents were stored in an MBraun Lab-master 130 argon-filled glove box with moisture maintained below 5 ppm. Synthesis of the catalyst (0.5Li 2 MnO 3 .0.5LiMn 0.5 Ni 0.35 Co 0.15 O 2).—In a synthesis, appropriate amounts of Mn(Ac) 2 .4H 2 O (Sigma Aldrich >99%), Ni(NO 3) 2 .6H 2 O (Alfa Aesar-Puratronic)
Electrochimica Acta, 2020
Recently, many works have demonstrated that tuning the A-site deficient and excessive stoichiometry can yield the positive effects on the catalytic activity of the ABO 3 perovskite toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Whereas, the universality of the deficient or excessive effects and their resulting improving mechanisms on ABO 3 perovskite are still ambiguous and need to be clarified. In this work, the simplest Mn-based perovskite (LaMnO 3) is selected to elucidate the deficient/excessive effects and improving mechanisms on both ORR and OER. We find that A-site deficient stoichiometry is favor to the catalytic activity and stability of LaMnO 3 toward both ORR and OER, whereas A-site excessive stoichiometry is deleterious to the oxygen catalytic activity and stability of LaMnO 3. The high oxygen catalytic activity of La 0$9 MnO 3 (La90) with A-site deficiency toward ORR and OER can be related to its proper Mn cation valence, large amount of oxygen vacancies, upper shift of dband center and strong adsorption capacity to oxygenated species. The results of this work highlight the A-site deficient Mn-based perovskite as the high efficient and commercially viable bifunctional catalyst for aqueous and solid-state flexible zinc-air battery (ZAB) applications.
Scientific Reports, 2014
Most Li-O 2 batteries suffer from sluggish kinetics during oxygen evolution reactions (OERs). To overcome this drawback, we take the lesson from other catalysis researches that showed improved catalytic activities by employing metal alloy catalysts. Such research effort has led us to find Pt 3 Co nanoparticles as an effective OER catalyst in Li-O 2 batteries. The superior catalytic activity was reflected in the substantially decreased overpotentials and improved cycling/rate performance compared to those of other catalysts. Density functional theory calculations suggested that the low OER overpotentials are associated with the reduced adsorption strength of LiO 2 on the outermost Pt catalytic sites. Also, the alloy catalyst generates amorphous Li 2 O 2 conformally coated around the catalyst and thus facilitates easier decomposition and higher reversibility. This investigation conveys an important message that understanding elementary reactions and surface charge engineering of air-catalysts are one of the most effective approaches in resolving the chronic sluggish charging kinetics in Li-O 2 batteries. L i-ion batteries (LIBs) have penetrated deeply into our everyday lives. They are power sources of various mobile electronics and have also begun to support future green transportation. However, the current LIBs rely on the intercalation mechanism for reversible reactions of Li ions with active materials on both cathode and anode sides, so their practical energy densities are usually limited below 250 Wh kg 21 1,2 . This limitation imposes a significant hurdle for future LIB applications, especially all-electric vehicles (EVs) that require the battery energy density substantially larger than the current values. The energy density of the EV battery is directly related to driving distance per each charge, and its driving mileage will be inevitably assessed in comparison against those of today's combustion engine-based counterparts: ,550 km per each refuel 1-3 .
Electrocatalysis
Lanthanum-based perovskites (LaMnxCo1-xO3 (0 ≤ x ≤ 1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigate the surface property and electrocatalytic characteristics (stability and activity of catalyst) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) under alkaline medium (KOH). The structural, chemical, and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM, and XPS techniques as a function of the Mn:Co elemental ratio. The time–temperature profile during the combustion process was also monitored to study the completion of the combustion reaction and to understand its impact on the structure of the perovskites. SEM/EDX and XPS analysis confirmed the formation of the targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with...
ACS Applied Nano Materials, 2018
A nano-architectured La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 hybrid catalyst is prepared by a facile hydrothermal method. The La 2 O 2 CO 3 nano-rods are well distributed on the regular hexagonal La 0.7 Sr 0.3 MnO 3 nano-sheet. The La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 catalyst has better catalytic activity to oxygen reduction reaction than that of La 2 O 2 CO 3 or La 0.7 Sr 0.3 MnO 3. The reaction kinetics result shows that La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 sample follows a four-electron transferred process during oxygen reduction reaction. Furthermore, the stability of La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 is higher than that of Pt/C. By using La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 as the cathode catalysts for aluminum-air battery, the power densities can reach 223.8 mW cm −2. The high catalytic performance of the La 2 O 2 CO 3-La 0.7 Sr 0.3 MnO 3 can be attributed to the strong interaction between the La 2 O 2 CO 3 material and La 0.7 Sr 0.3 MnO 3 material.
Journal of the Brazilian Chemical Society
In this work, La0.6M0.4Ni0.6Cu0.4O3 (M = Ag, Ba, and Ce, denoted as LANC, LBNC, and LCNC, respectively) electrocatalysts were synthesized by the Pechini method at 1023 K for two hours in air. Rietveld refinement allowed the identification of the crystallographic phases present in all oxides. The electrocatalytic performance of these oxides towards the oxygen reduction reaction (ORR) was examined in alkaline medium by rotating disk electrode (RDE) technique and scanning electrochemical microscopy (SECM) in the redox competition mode. The results indicate that the best performance was found with the LANC electrocatalyst prepared with carbon as a conducting agent (LANC/Carbon), which showed good catalytic activity towards the ORR via a pseudo fourelectron transfer pathway. The enhanced electrocatalytic activity of LANC is probably a result of the presence of a Ag phase, which improves the synergistic effect between the perovskite and carbon added to increase the conductivity, thus lead...