Tuning the electrocatalytic water oxidation properties of AB2O4 spinel nanocrystals: A (Li, Mg, Zn) and B (Mn, Co) site variants of LiMn2O4

Clyde W. Cady, Graeme Gardner, Zachary O. Maron, Maria Retuerto, Yong Bok Go, Shreeda Segan, Martha Greenblatt, G Charles Dismukes

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Transition metal oxides containing cubic B4O4 subcores are noted for their catalytic activity in water oxidation (OER). We synthesized a series of ternary spinel oxides, AB2O4, derived from LiMn2O4 by either replacement at the tetrahedral A site or Co substitution at the octahedral B site and measured their electrocatalytic OER activity. Atomic emission and powder X-ray diffraction confirmed spinel structure type and purity. Weak activation of the OER occurs upon A-site substitution: Zn2+ > Mg2+ > A-vacancy > Li+ = 0. Zn and Mg substitution is accompanied by (1) B-site conversion of Mn(IV) to Mn(III), resulting in expansion and higher symmetry of the [Mn4O4]4+ core relative to LiMn2O4 (inducing greater flexibility of the core and lower reorganization barrier to distortions), and (2) the electrochemical oxidation potential for Mn(III)/IV) increases by 0.15-0.2 V, producing a stronger driving force for water oxidation. Progressive replacement of Mn(III/IV) by Co(III) at the B site (LiMn2-xCoxO4, 0 ≤ x ≤ 1.5) both symmetrizes the [Mn4-xCoxO4] core and increases the oxidation potential for Co(III/IV), resulting in the highest OER activity within the spinel structure type. These observations point to two predictors of OER catalysis: (1) Among AMn2O4 spinels, those starting with Mn(III) in the resting lattice (prior to oxidation) result in longer, weaker Mn-O bonds for this eg1 antibonding electronic configuration, yielding greater core flexibility and a higher oxidation potential to Mn(IV), and (2) a linear free energy relationship exists between the electrocatalytic rate and the binding affinity of the substrate oxygen (OH andOOH) to the B site.

Original languageEnglish
Pages (from-to)3403-3410
Number of pages8
JournalACS Catalysis
Volume5
Issue number6
DOIs
Publication statusPublished - Jun 5 2015

Fingerprint

Nanocrystals
Tuning
Oxidation
Water
Substitution reactions
Oxides
Electrochemical oxidation
X ray powder diffraction
Catalysis
Free energy
Vacancies
Transition metals
Catalyst activity
Chemical activation
spinell
lithium manganese oxide
Oxygen
Substrates

Keywords

  • cobalt oxide
  • manganese oxide
  • photosystem II
  • spinel
  • water oxidation catalyst
  • water splitting

ASJC Scopus subject areas

  • Catalysis

Cite this

Tuning the electrocatalytic water oxidation properties of AB2O4 spinel nanocrystals : A (Li, Mg, Zn) and B (Mn, Co) site variants of LiMn2O4. / Cady, Clyde W.; Gardner, Graeme; Maron, Zachary O.; Retuerto, Maria; Go, Yong Bok; Segan, Shreeda; Greenblatt, Martha; Dismukes, G Charles.

In: ACS Catalysis, Vol. 5, No. 6, 05.06.2015, p. 3403-3410.

Research output: Contribution to journalArticle

Cady, Clyde W. ; Gardner, Graeme ; Maron, Zachary O. ; Retuerto, Maria ; Go, Yong Bok ; Segan, Shreeda ; Greenblatt, Martha ; Dismukes, G Charles. / Tuning the electrocatalytic water oxidation properties of AB2O4 spinel nanocrystals : A (Li, Mg, Zn) and B (Mn, Co) site variants of LiMn2O4. In: ACS Catalysis. 2015 ; Vol. 5, No. 6. pp. 3403-3410.
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abstract = "Transition metal oxides containing cubic B4O4 subcores are noted for their catalytic activity in water oxidation (OER). We synthesized a series of ternary spinel oxides, AB2O4, derived from LiMn2O4 by either replacement at the tetrahedral A site or Co substitution at the octahedral B site and measured their electrocatalytic OER activity. Atomic emission and powder X-ray diffraction confirmed spinel structure type and purity. Weak activation of the OER occurs upon A-site substitution: Zn2+ > Mg2+ > A-vacancy > Li+ = 0. Zn and Mg substitution is accompanied by (1) B-site conversion of Mn(IV) to Mn(III), resulting in expansion and higher symmetry of the [Mn4O4]4+ core relative to LiMn2O4 (inducing greater flexibility of the core and lower reorganization barrier to distortions), and (2) the electrochemical oxidation potential for Mn(III)/IV) increases by 0.15-0.2 V, producing a stronger driving force for water oxidation. Progressive replacement of Mn(III/IV) by Co(III) at the B site (LiMn2-xCoxO4, 0 ≤ x ≤ 1.5) both symmetrizes the [Mn4-xCoxO4] core and increases the oxidation potential for Co(III/IV), resulting in the highest OER activity within the spinel structure type. These observations point to two predictors of OER catalysis: (1) Among AMn2O4 spinels, those starting with Mn(III) in the resting lattice (prior to oxidation) result in longer, weaker Mn-O bonds for this eg1 antibonding electronic configuration, yielding greater core flexibility and a higher oxidation potential to Mn(IV), and (2) a linear free energy relationship exists between the electrocatalytic rate and the binding affinity of the substrate oxygen (OH andOOH) to the B site.",
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T1 - Tuning the electrocatalytic water oxidation properties of AB2O4 spinel nanocrystals

T2 - A (Li, Mg, Zn) and B (Mn, Co) site variants of LiMn2O4

AU - Cady, Clyde W.

AU - Gardner, Graeme

AU - Maron, Zachary O.

AU - Retuerto, Maria

AU - Go, Yong Bok

AU - Segan, Shreeda

AU - Greenblatt, Martha

AU - Dismukes, G Charles

PY - 2015/6/5

Y1 - 2015/6/5

N2 - Transition metal oxides containing cubic B4O4 subcores are noted for their catalytic activity in water oxidation (OER). We synthesized a series of ternary spinel oxides, AB2O4, derived from LiMn2O4 by either replacement at the tetrahedral A site or Co substitution at the octahedral B site and measured their electrocatalytic OER activity. Atomic emission and powder X-ray diffraction confirmed spinel structure type and purity. Weak activation of the OER occurs upon A-site substitution: Zn2+ > Mg2+ > A-vacancy > Li+ = 0. Zn and Mg substitution is accompanied by (1) B-site conversion of Mn(IV) to Mn(III), resulting in expansion and higher symmetry of the [Mn4O4]4+ core relative to LiMn2O4 (inducing greater flexibility of the core and lower reorganization barrier to distortions), and (2) the electrochemical oxidation potential for Mn(III)/IV) increases by 0.15-0.2 V, producing a stronger driving force for water oxidation. Progressive replacement of Mn(III/IV) by Co(III) at the B site (LiMn2-xCoxO4, 0 ≤ x ≤ 1.5) both symmetrizes the [Mn4-xCoxO4] core and increases the oxidation potential for Co(III/IV), resulting in the highest OER activity within the spinel structure type. These observations point to two predictors of OER catalysis: (1) Among AMn2O4 spinels, those starting with Mn(III) in the resting lattice (prior to oxidation) result in longer, weaker Mn-O bonds for this eg1 antibonding electronic configuration, yielding greater core flexibility and a higher oxidation potential to Mn(IV), and (2) a linear free energy relationship exists between the electrocatalytic rate and the binding affinity of the substrate oxygen (OH andOOH) to the B site.

AB - Transition metal oxides containing cubic B4O4 subcores are noted for their catalytic activity in water oxidation (OER). We synthesized a series of ternary spinel oxides, AB2O4, derived from LiMn2O4 by either replacement at the tetrahedral A site or Co substitution at the octahedral B site and measured their electrocatalytic OER activity. Atomic emission and powder X-ray diffraction confirmed spinel structure type and purity. Weak activation of the OER occurs upon A-site substitution: Zn2+ > Mg2+ > A-vacancy > Li+ = 0. Zn and Mg substitution is accompanied by (1) B-site conversion of Mn(IV) to Mn(III), resulting in expansion and higher symmetry of the [Mn4O4]4+ core relative to LiMn2O4 (inducing greater flexibility of the core and lower reorganization barrier to distortions), and (2) the electrochemical oxidation potential for Mn(III)/IV) increases by 0.15-0.2 V, producing a stronger driving force for water oxidation. Progressive replacement of Mn(III/IV) by Co(III) at the B site (LiMn2-xCoxO4, 0 ≤ x ≤ 1.5) both symmetrizes the [Mn4-xCoxO4] core and increases the oxidation potential for Co(III/IV), resulting in the highest OER activity within the spinel structure type. These observations point to two predictors of OER catalysis: (1) Among AMn2O4 spinels, those starting with Mn(III) in the resting lattice (prior to oxidation) result in longer, weaker Mn-O bonds for this eg1 antibonding electronic configuration, yielding greater core flexibility and a higher oxidation potential to Mn(IV), and (2) a linear free energy relationship exists between the electrocatalytic rate and the binding affinity of the substrate oxygen (OH andOOH) to the B site.

KW - cobalt oxide

KW - manganese oxide

KW - photosystem II

KW - spinel

KW - water oxidation catalyst

KW - water splitting

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