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 language | English |
|---|---|
| Pages (from-to) | 3403-3410 |
| Number of pages | 8 |
| Journal | ACS Catalysis |
| Volume | 5 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - Jun 5 2015 |
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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 journal › Article
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TY - JOUR
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
UR - http://www.scopus.com/inward/record.url?scp=84930640307&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84930640307&partnerID=8YFLogxK
U2 - 10.1021/acscatal.5b00265
DO - 10.1021/acscatal.5b00265
M3 - Article
AN - SCOPUS:84930640307
VL - 5
SP - 3403
EP - 3410
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 6
ER -