Charge-transfer-energy-dependent oxygen evolution reaction mechanisms for perovskite oxides

Hong, Wonbin; Stoerzinger, Kelsey A.; Lee, Yueh‐Lin; Giordano, Livia; Grimaud, Alexis; Johnson, Alyssa M.; Hwang, Jonathan; Crumlin, Ethan J.; Yang, Wanli; Shao‐Horn, Yang

doi:10.1039/c7ee02052j

“…Thecalculated Ocharge (À1.833) for CoAl 2 O 4 also exhibits certain shift from its ionic charge (À2). The charge deviation of Co Td [7] Thes trong orbital overlap between the octahedral TM and Oe lucidates the critical role of octahedral geometry in OER. Further shifting the oxygen charge to catalytically critical octahedral site is essential in enhancing OER activity.…”

Section: Angewandte Chemiementioning

confidence: 88%

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides

Sun

¹

,

Sun

²

,

Zhou

³

et al. 2019

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Cobalt spinel oxides are ac lass of promising transition metal (TM) oxides for catalyzing oxygen evolution reaction (OER). Their catalytic activity depends on the electronic structure.I naspinel oxide lattice,e acho xygen anion is shared amongst its four nearest transition metal cations,ofwhich one is located within the tetrahedral interstices and the remaining three cations are in the octahedral interstices. This work uncovered the influence of oxygen anion charge distribution on the electronic structure of the redox-active building blockC o ÀO. The charge of oxygen anion tends to shift toward the octahedral-occupied Co instead of tetrahedraloccupied Co,w hich hence produces strong orbital interaction between octahedral Co and O. Thus,t he OER activity can be promoted by pushing more Co into the octahedral site or shifting the oxygen charge towards the redox-active metal center in CoO 6 octahedra.The clean-burning hydrogen fuel, if produced by electrochemical water splitting, would revolutionize the global energy infrastructure.T he major limitation of water splitting is the sluggish oxygen evolution reaction (OER) at the anode. [1] To date,the most efficient OER electrocatalysts are made from noble metal ruthenium or iridium. In order to meet the broader goal of sustainability,e xploring earthabundant transition metal (TM) oxide catalysts have been prioritized. [1b, 2] Better understanding of the OER reaction on TM oxides is necessary to this end. It has been found that the surface redox-active centers in TM oxides play ak ey role in oxygen electrocatalysis. [3] Thec onventional perception of oxygen evolution regards the redox-active metallic center as the active site and it is the redox ability of TM that mediates the transition of [M n+ ÀOH ad ]/[M n+1 ÀO ad ]d uring OER. [3,4] However,t he redox of late transition metal oxides (e.g., Coand Ni-based) could involve both the transition metal and oxygen ligand due to the increased orbital hybridization between TM 3d and O2 p. [2,5] Earlier reports had demonstrated that the energy in TM 3d orbital cannot be treated in isolation from O2pwhen there is significant overlap between TM 3d and O2 p. Recent studies on oxygen-deficient perovskite oxides reveal that the oxygen anion could also act as the redox partner in OER. [6] Direct evidence for lattice oxygen participated OER using in situ 18 Oi sotope labelling mass spectrometry has been given by Alexis et al. [6b] Thefact that the oxygen anion can also act as the redox-active center emphasizes the importance of considering TM À Obond as the redox-active building block. More recently,t he covalent character (covalency) of TM Bs ite ÀOb ond (TM B the TM in B site) has been proposed to be adominating factor in OER on perovskite oxides. [6b, 7] TheA -site rare-earth metals (low in electronegativity) tend to form an ionic bond with Oa nd weaken the influence of M A -O block on OER. Spinel oxides, ah uge crystal family for oxygen electrocatalysis, [2,4,8] require more complex analysis because the tetrahedral and octahe...

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“…This is because the band center determination method takes the energy states that are not involved in TM À Ob onding into consideration as well. [7] Thes trong orbital overlap between the octahedral TM and Oe lucidates the critical role of octahedral geometry in OER. ForC oAl 2 O 4 oxide, the Al charge is calculated to be + 3, which indicates that the Al is ionically bound to the O. Thet etrahedral Co,h owever, give ac harge of + 1.332, which is deviating from its ionic charge of + 2.…”

Section: Angewandte Chemiementioning

confidence: 92%

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides

Sun

¹

,

Sun

²

,

Zhou

³

et al. 2019

View full text Add to dashboard Cite

Cobalt spinel oxides are ac lass of promising transition metal (TM) oxides for catalyzing oxygen evolution reaction (OER). Their catalytic activity depends on the electronic structure.I naspinel oxide lattice,e acho xygen anion is shared amongst its four nearest transition metal cations,ofwhich one is located within the tetrahedral interstices and the remaining three cations are in the octahedral interstices. This work uncovered the influence of oxygen anion charge distribution on the electronic structure of the redox-active building blockC o ÀO. The charge of oxygen anion tends to shift toward the octahedral-occupied Co instead of tetrahedraloccupied Co,w hich hence produces strong orbital interaction between octahedral Co and O. Thus,t he OER activity can be promoted by pushing more Co into the octahedral site or shifting the oxygen charge towards the redox-active metal center in CoO 6 octahedra.The clean-burning hydrogen fuel, if produced by electrochemical water splitting, would revolutionize the global energy infrastructure.T he major limitation of water splitting is the sluggish oxygen evolution reaction (OER) at the anode. [1] To date,the most efficient OER electrocatalysts are made from noble metal ruthenium or iridium. In order to meet the broader goal of sustainability,e xploring earthabundant transition metal (TM) oxide catalysts have been prioritized. [1b, 2] Better understanding of the OER reaction on TM oxides is necessary to this end. It has been found that the surface redox-active centers in TM oxides play ak ey role in oxygen electrocatalysis. [3] Thec onventional perception of oxygen evolution regards the redox-active metallic center as the active site and it is the redox ability of TM that mediates the transition of [M n+ ÀOH ad ]/[M n+1 ÀO ad ]d uring OER. [3,4] However,t he redox of late transition metal oxides (e.g., Coand Ni-based) could involve both the transition metal and oxygen ligand due to the increased orbital hybridization between TM 3d and O2 p. [2,5] Earlier reports had demonstrated that the energy in TM 3d orbital cannot be treated in isolation from O2pwhen there is significant overlap between TM 3d and O2 p. Recent studies on oxygen-deficient perovskite oxides reveal that the oxygen anion could also act as the redox partner in OER. [6] Direct evidence for lattice oxygen participated OER using in situ 18 Oi sotope labelling mass spectrometry has been given by Alexis et al. [6b] Thefact that the oxygen anion can also act as the redox-active center emphasizes the importance of considering TM À Obond as the redox-active building block. More recently,t he covalent character (covalency) of TM Bs ite ÀOb ond (TM B the TM in B site) has been proposed to be adominating factor in OER on perovskite oxides. [6b, 7] TheA -site rare-earth metals (low in electronegativity) tend to form an ionic bond with Oa nd weaken the influence of M A -O block on OER. Spinel oxides, ah uge crystal family for oxygen electrocatalysis, [2,4,8] require more complex analysis because the tetrahedral and octahe...

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“…These results further confirm the four-electron transfer process for the OER. [21] Durability of ac atalyst is ac rucial parameter for the practical application of electrocatalysts.Along-term stability test of 1 À Hwas performed by chronopotentiometryresponse experiments.A ss hown in Figure S12, while the current density was kept at 500 mA cm À2 ,t he potential remained stable at % 1.54 Vv s. RHE for more than 120 h, endorsing good long-term robustness of the 1ÀHc atalyst. TheP XRD pattern shows that 1ÀHc hanged to amorphous NiFe-LDH after the long term OER test ( Figure S13a).…”

Section: Angewandte Chemiementioning

confidence: 99%

Advanced Bifunctional Oxygen Reduction and Evolution Electrocatalyst Derived from Surface‐Mounted Metal–Organic Frameworks

Li

¹

,

Xue

²

,

Watzele

³

et al. 2020

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Metal–organic frameworks (MOFs) and their derivatives are considered as promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are important for many energy provision technologies, such as electrolyzers, fuel cells and some types of advanced batteries. In this work, a “strain modulation” approach has been applied through the use of surface‐mounted NiFe‐MOFs in order to design an advanced bifunctional ORR/OER electrocatalyst. The material exhibits an excellent OER activity in alkaline media, reaching an industrially relevant current density of 200 mA cm−2 at an overpotential of only ≈210 mV. It demonstrates operational long‐term stability even at a high current density of 500 mA cm−2 and exhibits the so far narrowest “overpotential window” ΔEORR‐OER of 0.69 V in 0.1 m KOH with a mass loading being two orders of magnitude lower than that of benchmark electrocatalysts.

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Charge-transfer-energy-dependent oxygen evolution reaction mechanisms for perovskite oxides

Abstract: This work experimentally identifies the charge-transfer energy as a key factor governing the catalytic oxygen evolution reaction (OER) activity and mechanism across a wide range of perovskite chemistries.

Cited by 487 publications

References 60 publications

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides

Advanced Bifunctional Oxygen Reduction and Evolution Electrocatalyst Derived from Surface‐Mounted Metal–Organic Frameworks

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