skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • Enhanced Stability and Thickness‐Independent Oxygen Evolution Electrocatalysis of Heterostructured Anodes with Buried Epitaxial Bilayers
Title: Enhanced Stability and Thickness‐Independent Oxygen Evolution Electrocatalysis of Heterostructured Anodes with Buried Epitaxial Bilayers
Abstract

Achieving high oxygen evolution reaction (OER) activity while maintaining performance stability is a key challenge for designing perovskite structure oxide OER catalysts, which are often unstable in alkaline environments transforming into an amorphous phase. While the chemical and structural transformation occurring during electrolysis at the electrolyte–catalyst interface is now regarded as a crucial factor influencing OER activity, here, using La0.7Sr0.3CoO3−δ(LSCO) as an active OER catalyst, the critical influence of buried layers on the oxidation current stability in nanoscopically thin, chemically and structurally evolving, catalyst layers is revealed. The use of epitaxial thin films is demonstrated to engineer both depletion layer widths and chemical stability of the catalyst support structure resulting in heterostructured anodes that maintain facile transport kinetics across the electrolyte–anode interface for atomically thin (2–3 unit cells) LSCO catalyst layers and greatly enhanced oxidation current stability as the perovskite structure OER catalysts chemically and structurally transform. This work opens up an approach to design robust and active heterostructured anodes with dynamically evolving ultrathin OER electrocatalyst layers for future green fuel technologies such as conformal coatings of high‐density 3D anode topologies for water splitting.

  more » « less
NSF-PAR ID:
10460438
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Energy Materials
Volume:
9
Issue:
28
ISSN:
1614-6832
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , ECS Meeting Abstracts)

    Ever-increasing demands for energy, particularly being environmentally friendly have promoted the transition from fossil fuels to renewable energy.1Lithium-ion batteries (LIBs), arguably the most well-studied energy storage system, have dominated the energy market since their advent in the 1990s.2However, challenging issues regarding safety, supply of lithium, and high price of lithium resources limit the further advancement of LIBs for large-scale energy storage applications.3Therefore, attention is being concentrated on an alternative electrochemical energy storage device that features high safety, low cost, and long cycle life. Rechargeable aqueous zinc-ion batteries (ZIBs) is considered one of the most promising alternative energy storage systems due to the high theoretical energy and power densities where the multiple electrons (Zn2+) . In addition, aqueous ZIBs are safer due to non-flammable electrolyte (e.g., typically aqueous solution) and can be manufactured since they can be assembled in ambient air conditions.4As an essential component in aqueous Zn-based batteries, the Zn metal anode generally suffers from the growth of dendrites, which would affect battery performance in several ways. Second, the led by the loose structure of Zn dendrite may reduce the coulombic efficiency and shorten the battery lifespan.5

    Several approaches were suggested to improve the electrochemical stability of ZIBs, such as implementing an interfacial buffer layer that separates the active Zn from the bulk electrolyte.6However, the and thick thickness of the conventional Zn metal foils remain a critical challenge in this field, which may diminish the energy density of the battery drastically. According to a theretical calculation, the thickness of a Zn metal anode with an areal capacity of 1 mAh cm-2is about 1.7 μm. However, existing extrusion-based fabrication technologies are not capable of downscaling the thickness Zn metal foils below 20 μm.

    Herein, we demonstrate a thickness controllable coating approach to fabricate an ultrathin Zn metal anode as well as a thin dielectric oxide separator. First, a 1.7 μm Zn layer was uniformly thermally evaporated onto a Cu foil. Then, Al2O3, the separator was deposited through sputtering on the Zn layer to a thickness of 10 nm. The inert and high hardness Al2O3layer is expected to lower the polarization and restrain the growth of Zn dendrites. Atomic force microscopy was employed to evaluate the roughness of the surface of the deposited Zn and Al2O3/Zn anode structures. Long-term cycling stability was gauged under the symmetrical cells at 0.5 mA cm-2for 1 mAh cm-2. Then the fabricated Zn anode was paired with MnO2as a full cell for further electrochemical performance testing. To investigate the evolution of the interface between the Zn anode and the electrolyte, a home-developed in-situ optical observation battery cage was employed to record and compare the process of Zn deposition on the anodes of the Al2O3/Zn (demonstrated in this study) and the procured thick Zn anode. The surface morphology of the two Zn anodes after circulation was characterized and compared through scanning electron microscopy. The tunable ultrathin Zn metal anode with enhanced anode stability provides a pathway for future high-energy-density Zn-ion batteries.

    Obama, B., The irreversible momentum of clean energy.Science2017,355(6321), 126-129.

    Goodenough, J. B.; Park, K. S., The Li-ion rechargeable battery: a perspective.J Am Chem Soc2013,135(4), 1167-76.

    Li, C.; Xie, X.; Liang, S.; Zhou, J., Issues and Future Perspective on Zinc Metal Anode for Rechargeable Aqueous Zinc‐ion Batteries.Energy & Environmental Materials2020,3(2), 146-159.

    Jia, H.; Wang, Z.; Tawiah, B.; Wang, Y.; Chan, C.-Y.; Fei, B.; Pan, F., Recent advances in zinc anodes for high-performance aqueous Zn-ion batteries.Nano Energy2020,70.

    Yang, J.; Yin, B.; Sun, Y.; Pan, H.; Sun, W.; Jia, B.; Zhang, S.; Ma, T., Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives.Nanomicro Lett2022,14(1), 42.

    Yang, Q.; Li, Q.; Liu, Z.; Wang, D.; Guo, Y.; Li, X.; Tang, Y.; Li, H.; Dong, B.; Zhi, C., Dendrites in Zn-Based Batteries.Adv Mater2020,32(48), e2001854.

    Acknowledgment

    This work was partially supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 22011044) by KRISS.

    Figure 1

     

    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al ( , Small)
    Abstract

    Electrocatalytic reactions are known to take place at the catalyst/electrolyte interface. Whereas recent studies of size‐dependent activity in nanoparticles and thickness‐dependent activity of thin films imply that the sub‐surface layers of a catalyst can contribute to the catalytic activity as well, most of these studies consider actual modification of the surfaces. In this study, the role of catalytically active sub‐surface layers was investigated by employing atomic‐scale thickness control of the La0.7Sr0.3MnO3(LSMO) films and heterostructures, without altering the catalyst/electrolyte interface. The activity toward the oxygen evolution reaction (OER) shows a non‐monotonic thickness dependence in the LSMO films and a continuous screening effect in LSMO/SrRuO3heterostructures. The observation leads to the definition of an “electrochemically‐relevant depth” on the order of 10 unit cells. This study on the electrocatalytic activity of epitaxial heterostructures provides new insight in designing efficient electrocatalytic nanomaterials and core‐shell architectures.

     
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al ( , Nature Communications)
    Abstract

    Noble metals supported on reducible oxides, like CoOxand TiOx, exhibit superior activity in many chemical reactions, but the origin of the increased activity is not well understood. To answer this question we studied thin films of CoOxsupported on an Au(111) single crystal surface as a model for the CO oxidation reaction. We show that three reaction regimes exist in response to chemical and topographic restructuring of the CoOxcatalyst as a function of reactant gas phase CO/O2stoichiometry and temperature. Under oxygen-lean conditions and moderate temperatures (≤150 °C), partially oxidized films (CoOx<1) containing Co0were found to be efficient catalysts. In contrast, stoichiometric CoO films containing only Co2+form carbonates in the presence of CO that poison the reaction below 300 °C. Under oxygen-rich conditions a more oxidized catalyst phase (CoOx>1) forms containing Co3+species that are effective in a wide temperature range. Resonant photoemission spectroscopy (ResPES) revealed the unique role of Co3+sites in catalyzing the CO oxidation. Density function theory (DFT) calculations provided deeper insights into the pathway and free energy barriers for the reactions on these oxide phases. These findings in this work highlight the versatility of catalysts and their evolution to form different active phases, both topological and chemically, in response to reaction conditions exposing a new paradigm in the catalyst structure during operation.

     
    more » « less
  4. ; ; ; ; ; ; ( , Energy & Environmental Science)
    The two polymorphs of lithium cobalt oxide, LiCoO 2 , present an opportunity to contrast the structural requirements for reversible charge storage (battery function) vs. catalysis of water oxidation/oxygen evolution (OER; 2H 2 O → O 2 + 4H + + 4e − ). Previously, we reported high OER electrocatalytic activity from nanocrystals of the cubic phase vs. poor activity from the layered phase – the archetypal lithium-ion battery cathode. Here we apply transmission electron microscopy, electron diffraction, voltammetry and elemental analysis under OER electrolysis conditions to show that labile Li + ions partially deintercalate from layered LiCoO 2 , initiating structural reorganization to the cubic spinel LiCo 2 O 4 , in parallel with formation of a more active catalytic phase. Comparison of cubic LiCoO 2 (50 nm) to iridium (5 nm) nanoparticles for OER catalysis (commercial benchmark for membrane-based systems) in basic and neutral electrolyte reveals excellent performance in terms of Tafel slope (48 mV dec −1 ), overpotential ( η = ∼420 mV@10 mA cm −2 at pH = 14), faradaic yield (100%) and OER stability (no loss in 14 hours). The inherent OER activity of cubic LiCoO 2 and spinel LiCo 2 O 4 is attributed to the presence of [Co 4 O 4 ] n+ cubane structural units, which provide lower oxidation potential to Co 4+ and lower inter-cubane hole mobility. By contrast, the layered phase, which lacks cubane units, exhibits extensive intra-planar hole delocalization which entropically hinders the four electron/hole concerted OER reaction. An essential distinguishing trait of a truly relevant catalyst is efficient continuous operation in a real electrolyzer stack. Initial trials of cubic LiCoO 2 in a solid electrolyte alkaline membrane electrolyzer indicate continuous operation for 1000 hours (without failure) at current densities up to 400 mA cm −2 and overpotential lower than proven PGM (platinum group metal) catalysts. 
    more » « less
  5. ; ; ( , Materials Research Society)
    Metal-ion batteries (e.g., lithium and sodium ion batteries) are the promising power sources for portable electronics, electric vehicles, and smart grids. Recent metal-ion batteries with organic liquid electrolytes still suffer from safety issues regarding inflammability and insufficient lifetime.1 As the next generation energy storage devices, all-solid-state batteries (ASSBs) have promising potentials for the improved safety, higher energy density, and longer cycle life than conventional Li-ion batteries.2 The nonflammable solid electrolytes (SEs), where only Li ions are mobile, could prevent battery combustion and explosion since the side reactions that cause safety issues as well as degradation of the battery performance are largely suppressed. However, their practical application is hampered by the high resistance arising at the solid–solid electrode–electrolyte interface (including cathode-electrolyte interface and anode-electrolyte interface).3 Several methods have been introduced to optimize the contact capability as well as the electrochemical/chemical stability between the metal anodes (i.e.: Li and Na) and the SEs, which exhibited decent results in decreasing the charge transfer resistance and broadening the range of the stable energy window (i.e., lowing the chemical potential of metal anode below the highest occupied molecular orbital of the SEs).4 Nevertheless, mitigation for the cathode in ASSB is tardily developed because: (1) the porous structure of the cathode is hard to be infiltrated by SEs;5 (2) SEs would be oxidized and decomposed by the high valence state elements at the surface of the cathode at high state of charge.5 Herein, we demonstrate a universal cathode design strategy to achieve superior contact capability and high electrochemical/chemical stability with SEs. Stereolithography is adopted as a manufacturing technique to realize a hierarchical three-dimensional (HTD) electrode architecture with micro-size channels, which is expected to provide larger contact areas with SEs. Then, the manufactured cathode is sintered at 700 °C in a reducing atmosphere (e.g.: H2) to accomplish the carbonization of the resin, delivering sufficiently high electronic conductivity for the cathode. To avoid the direct exposure of the cathode active materials to the SEs, oxidative chemical vapor deposition technique (oCVD) is leveraged to build conformal and highly conducting poly(3,4-ethylenedioxythiophene) (PEDOT) on the surface of the HTD cathode.6 To demonstrate our design strategy, both NCM811 and Na3V2(PO4)3 is selected as active materials in the HTD cathode, then each cathode is paired with organic (polyacrylonitrile-based) and inorganic (sulfur-based) SEs assembled into two batteries (total four batteries). SEM and TEM reveal the micro-size HTD structure with built-in channels. Featured by the HTD architecture, the intrinsic kinetic and thermodynamic conditions will be enhanced by larger surface contact areas, more active sites, improved infusion and electrolyte ion accessibility, and larger volume expansion capability. Disclosed by X-ray computed tomography, the interface between cathode and SEs in the four modified samples demonstrates higher homogeneity at the interface between the cathode and SEs than that of all other pristine samples. Atomic force microscopy is employed to measure the potential image of the cross-sectional interface by the peak force tapping mode. The average potential of modified samples is lower than that of pristine samples, which confirms a weakened space charge layer by the enhanced contact capability. In addition, through Electron Energy Loss Spectroscopy coupled with Scanning Transmission Electron Microscopy, the preserved interface between HTD cathode and SE is identified; however, the decomposing of the pristine cathode is clearly observed. In addition, Finite element method simulations validate that the diffusion dynamics of lithium ions is favored by HTD structure. Such a demonstrated universal strategy provides a new guideline to engineer cathode electrolyte interface by reconstructing electrode structures that can be applicable to all solid-state batteries in a wide range of chemical conditions. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email