Research ArticleELECTROCHEMISTRY

Oxygen-deficient triple perovskites as highly active and durable bifunctional electrocatalysts for oxygen electrode reactions

See allHide authors and affiliations

Science Advances  15 Jun 2018:
Vol. 4, no. 6, eaap9360
DOI: 10.1126/sciadv.aap9360
  • Fig. 1 Characterizations of the perovskite catalysts.

    (A) XRD patterns of BSCF, NBSCF, and NBCFM with their Rietveld refinement results. a.u., arbitrary units. (B) Lattice constants of the BSCF, NBSCF, and NBCFM (left, a and b axes; right, c axis). (C) Crystal structures of BSCF, NBSCF, and NBCFM. (D) HRTEM image of NBCFM catalyst with NBED pattern. Left inset shows the NBED pattern. Right inset shows an atomic resolution image of a yellow dotted rectangular section with an observed unit cell, its lattice parameters for a and c axes, and the line profile along a and c directions. (E) EDX elemental mapping results of NBCFM. Scale bars, 100 nm.

  • Fig. 2 Electrocatalytic activities and durabilities/stabilities of the perovskite catalysts.

    (A) OER polarization curves of BSCF, NBSCF, and NBCFM with corresponding Tafel plots (inset) before (solid line) and after (dashed line) the potential cycling. (B) ORR polarization curves of BSCF, NBSCF, and NBCFM before (solid line) and after (dashed line) potential cycling. (C) Potential increase of BSCF, NBSCF, and NBCFM at 10 mA cm−2 in OER after potential cycling. (D) Potential decreases of BSCF, NBSCF, and NBCFM at −3 mA cm−2 in ORR after potential cycling. (E) OER stabilities of BSCF, NBSCF, and NBCFM measured by chronopotentiometry at 5 mA cm−2 for 10 hours. (F) ORR stabilities of BSCF, NBSCF, and NBCFM measured by chronopotentiometry at −3 mA cm−2 for 10 hours.

  • Fig. 3 Bifunctional oxygen electrode activities and durabilities of the perovskites, NBCFM/N-rGO, and precious metal catalysts.

    (A) OER/ORR polarization curves for perovskite-based catalysts and precious metal catalysts. (B) Oxygen electrode activities (EOEREORR) of perovskite-based catalysts and precious metal catalysts. (C) Comparisons of oxygen electrode activities of NBCFM/N-rGO with the previously reported bifunctional catalysts. The numbers on the x axis denote reference numbers. (D) OER potential increase and ORR potential decrease of perovskite-based catalysts and precious metal catalysts after durability tests.

  • Fig. 4 Mechanistic insight into activity trends for oxygen electrode reactions.

    (A) Computed oxygen deficiency (δ) from the oxidation states of the B site in perovskite oxide materials using the iodometric titration method. (B) O 1s XPS spectra of BSCF, NBSCF, and NBCFM. (C) Charge-transport resistance values of the BSCF, NBSCF, and NBCFM. (D) Spectral weight (WS) of charge transfer excitations from O 2p to Co 3d and Fe 3d electronic states for BSCF, NBSCF, and NBCFM. WS is obtained from the optical conductivity spectra, as shown in fig. S8. A systematic and quantitative decrease of the hybridization between the Co and O states is observed from BSCF through NBSCF to NBCFM.

  • Table 1 Crystal-structural parameters of the catalysts from Rietveld refinement and the chemical titration method.
    BSCF (single perovskite)NBSCF (double perovskite)NBCFM (triple perovskite)
    Space groupPm3¯mPmmmP4/mmm
    Phase structureCubicOrthorhombicTetragonal
    Lattice parametera (Å)3.9793.8563.871
    b (Å)3.9793.8273.871
    c (Å)3.9797.73711.676
    Unit cell volume (Å3)62.997114.174175.866
    Oxygen deficiency, δ0.2340.3790.495
  • Table 2 Detailed data of electrocatalytic activities and durabilities for the perovskite-based catalysts with noble metal catalysts.
    CatalystOERORREOEREORR (V)
    EOER at
    10 mA cm−2
    (V versus RHE)
    Tafel
    slope
    (mV decade−1)
    Potential
    increase at
    10 mA cm−2
    (mV)
    EORR at −3 mA cm−2
    (V versus RHE)
    Tafel slope
    (mV decade−1)
    jd
    (mA cm−2)
    Potential decrease
    at −3 mA cm−2 (mV)
    BSCF1.62586260.64164−4.8530.984
    NBSCF1.60484240.65387−5.1290.951
    NBCFM1.58981170.69863−5.9150.891
    NBCFM/N-rGO1.5878820.88944−6.2140.698
    Ir/C1.56170920.7920.769
    Pt/C1.6950.89440−6.3100.801

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/6/eaap9360/DC1

    fig. S1. Structural and elemental analyses of the perovskite catalysts.

    fig. S2. Nitrogen adsorption-desorption and XPS analysis of the perovskite catalysts.

    fig. S3. ORR activity of the perovskite catalysts.

    fig. S4. Structural changes of the perovskite catalysts after or during the OER.

    fig. S5. Physicochemical and electrochemical characterizations of the NBCFM/N-rGO catalyst.

    fig. S6. Long-term durability and stability of catalysts for OER and ORR.

    fig. S7. EIS analysis of the perovskite-based catalysts.

    fig. S8. Optical properties and electronic structures of the perovskite-based catalysts.

    table S1. Textural properties of the perovskite-based catalysts.

    table S2. Comparison of the OER/ORR bifunctional activity of NBCFM/N-rGO with the reported bifunctional perovskite catalysts.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Structural and elemental analyses of the perovskite catalysts.
    • fig. S2. Nitrogen adsorption-desorption and XPS analysis of the perovskite catalysts.
    • fig. S3. ORR activity of the perovskite catalysts.
    • fig. S4. Structural changes of the perovskite catalysts after or during the OER.
    • fig. S5. Physicochemical and electrochemical characterizations of the NBCFM/N-rGO catalyst.
    • fig. S6. Long-term durability and stability of catalysts for OER and ORR.
    • fig. S7. EIS analysis of the perovskite-based catalysts.
    • fig. S8. Optical properties and electronic structures of the perovskite-based catalysts.
    • table S1. Textural properties of the perovskite-based catalysts.
    • table S2. Comparison of the OER/ORR bifunctional activity of NBCFM/N-rGO with the reported bifunctional perovskite catalysts.

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article