Local structural changes in polyamorphous (Ni,Fe)Ox electrocatalysts suggest a dual-site oxygen evolution reaction mechanism

2021 ◽  
Author(s):  
Martin Schon ◽  
Oliver Calderon ◽  
Nick Randell ◽  
Santiago Jimenez Villegas ◽  
Katelynn M. Daly ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Structural Changes ◽  
Mixed Metal Oxides ◽  
Reaction Conditions ◽  
Nickel Iron ◽  
Alkaline Reaction ◽  
Dual Site ◽  
Economical Alternative

Amorphous nickel-iron mixed metal oxides have been shown to be extremely efficient oxygen evolution reaction (OER) electrocatalysts with good stability in alkaline reaction conditions. Thus, they offer an economical alternative...

scholarly journals Local Structural Changes in Polyamorphous (Ni,Fe)Ox Electrocatalysts Suggest a Dual-Site Oxygen Evolution Reaction Mechanism

2020 ◽  
Author(s):  
Martin Schoen ◽  
Nicholas Randell ◽  
Oliver Calderon ◽  
Santiago Jimenez Villegas ◽  
Katelynn Daly ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Synergistic Effect ◽  
Metal Oxides ◽  
Oxygen Evolution Reaction ◽  
Local Structure ◽  
Annealing Temperature ◽  
Mixed Metal Oxides ◽  
X Ray ◽  
Annealing Temperatures ◽  
Dual Site

<div>Amorphous nickel-iron mixed metal oxides have been shown to be extremely efficient oxygen evolution reaction (OER) electrocatalysts with good stability in alkaline reaction</div><div>conditions. Thus, they offer an economical alternative to expensive conventional platinum or iridium-based OER catalysts and could provide a crucial step towards a hydrogen-based energy economy. These favorable properties are presumably due to a synergistic effect between Fe and Ni. However, these synergistic effects strongly depend on the local structure of the catalyst and their origin – and its relation to the local structure – are still not fully understood. In this work we present a study of the thermal annealing induced structural evolution of amorphous (Ni,Fe)Ox thin films, and correlate this evolution to their OER catalytic capabilities. Samples are x-ray amorphous at low annealing temperatures. However, analysis of the x-ray absorption spectra reveals local structural transitions in all samples – before the onset of cystalization – providing evidence of polyamorphism. Transitions of the local Ni and Fe environments occur at distinctly different temperatures and coincide with a stepwise increase in the catalytic activation potential (OER thermodynamics) and the</div><div>Tafel slope (OER kinetics), respectively. We previously have attributed the increase in onset potential to a change in active site in NiOx at the phase transition temperature; considering that the mixed metal oxides’ onset potentials exhibit the same behavior with annealing temperature (Tanneal), we conclude that the potential-determining OER reaction step must occur at a Ni site. Similarly, the reaction kinetics change at the same annealing temperature as the local Fe environment; we thus infer that the rate-determining step occurs at a Fe site. To reconciliate these observations we put forward a dual-site OER reaction mechanism</div><div>with potential- and rate-determining steps happening at Ni and Fe sites, respectively. This synergistic effect is ultimately responsible for the superior OER performance of many (Ni,Fe)Ox catalysts. At higher annealing temperatures, the synergistic effect is suppressed, possibly by phase separation into NiOx and FeOx phases, as suggested by our XRD results.</div>

scholarly journals Local Structural Changes in Polyamorphous (Ni,Fe)Ox Electrocatalysts Suggest a Dual-Site Oxygen Evolution Reaction Mechanism

2020 ◽  
Author(s):  
Martin Schoen ◽  
Nicholas Randell ◽  
Oliver Calderon ◽  
Santiago Jimenez Villegas ◽  
Katelynn Daly ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Synergistic Effect ◽  
Metal Oxides ◽  
Oxygen Evolution Reaction ◽  
Local Structure ◽  
Annealing Temperature ◽  
Mixed Metal Oxides ◽  
X Ray ◽  
Annealing Temperatures ◽  
Dual Site

<div>Amorphous nickel-iron mixed metal oxides have been shown to be extremely efficient oxygen evolution reaction (OER) electrocatalysts with good stability in alkaline reaction</div><div>conditions. Thus, they offer an economical alternative to expensive conventional platinum or iridium-based OER catalysts and could provide a crucial step towards a hydrogen-based energy economy. These favorable properties are presumably due to a synergistic effect between Fe and Ni. However, these synergistic effects strongly depend on the local structure of the catalyst and their origin – and its relation to the local structure – are still not fully understood. In this work we present a study of the thermal annealing induced structural evolution of amorphous (Ni,Fe)Ox thin films, and correlate this evolution to their OER catalytic capabilities. Samples are x-ray amorphous at low annealing temperatures. However, analysis of the x-ray absorption spectra reveals local structural transitions in all samples – before the onset of cystalization – providing evidence of polyamorphism. Transitions of the local Ni and Fe environments occur at distinctly different temperatures and coincide with a stepwise increase in the catalytic activation potential (OER thermodynamics) and the</div><div>Tafel slope (OER kinetics), respectively. We previously have attributed the increase in onset potential to a change in active site in NiOx at the phase transition temperature; considering that the mixed metal oxides’ onset potentials exhibit the same behavior with annealing temperature (Tanneal), we conclude that the potential-determining OER reaction step must occur at a Ni site. Similarly, the reaction kinetics change at the same annealing temperature as the local Fe environment; we thus infer that the rate-determining step occurs at a Fe site. To reconciliate these observations we put forward a dual-site OER reaction mechanism</div><div>with potential- and rate-determining steps happening at Ni and Fe sites, respectively. This synergistic effect is ultimately responsible for the superior OER performance of many (Ni,Fe)Ox catalysts. At higher annealing temperatures, the synergistic effect is suppressed, possibly by phase separation into NiOx and FeOx phases, as suggested by our XRD results.</div>

scholarly journals Postsynthetic treatment of nickel–iron layered double hydroxides for the optimum catalysis of the oxygen evolution reaction

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Daire Tyndall ◽  
Sonia Jaskaniec ◽  
Brian Shortall ◽  
Ahin Roy ◽  
Lee Gannon ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Size Control ◽  
Operating Conditions ◽  
Nickel Iron ◽  
Treatment Techniques ◽  
Site Density ◽  
Synthetic Approaches ◽  
Double Hydroxide ◽  
Double Hydroxides

AbstractNickel–iron-layered double hydroxide (NiFe LDH) platelets with high morphological regularity and submicrometre lateral dimensions were synthesized using a homogeneous precipitation technique for highly efficient catalysis of the oxygen evolution reaction (OER). Considering edge sites are the point of activity, efforts were made to control platelet size within the synthesized dispersions. The goal is to controllably isolate and characterize size-reduced NiFe LDH particles. Synthetic approaches for size control of NiFe LDH platelets have not been transferable based on published work with other LDH materials and for that reason, we instead use postsynthetic treatment techniques to improve edge-site density. In the end, size-reduced NiFe LDH/single-wall carbon nanotube (SWCNT) composites allowed to further reduce the OER overpotential to 237 ± 7 mV (<L> = 0.16 ± 0.01 μm, 20 wt% SWCNT), which is one of the best values reported to date. This approach as well improved the long-term activity of the catalyst in operating conditions.

scholarly journals Recent advances in understanding oxygen evolution reaction mechanisms over iridium oxide

2021 ◽  
Author(s):  
Takahiro Naito ◽  
Tatsuya Shinagawa ◽  
Takeshi Nishimoto ◽  
Kazuhiro Takanabe
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Reaction Mechanisms ◽  
State Of The Art ◽  
Iridium Oxide ◽  
The State ◽  
Computational Studies ◽  
Recent Advances ◽  
Iridium Oxides

Recent spectroscopic and computational studies concerning the oxygen evolution reaction over iridium oxides are reviewed to provide the state-of-the-art understanding of its reaction mechanism.

Insight into sulfur and iron effect of binary nickel-iron sulfide on oxygen evolution reaction

Nano Research ◽  
2021 ◽  
Author(s):  
Qikang Wu ◽  
Songrui Wang ◽  
Jiahui Guo ◽  
Xueqing Feng ◽  
Han Li ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Iron Sulfide ◽  
Nickel Iron ◽  
Insight Into

scholarly journals The oxygen evolution reaction mechanism at Ir Ru1−O2 powders produced by hydrolysis synthesis

2018 ◽  
Vol 819 ◽  
pp. 547-561 ◽  
Author(s):  
Anita Hamar Reksten ◽  
Heidi Thuv ◽  
Frode Seland ◽  
Svein Sunde
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction

Electrocatalytic Oxidative Upgrading of Biomass Platform Chemicals: From the Aspect of Reaction Mechanism

2021 ◽  
Author(s):  
Hua Zhou ◽  
Zhenhua Li ◽  
Lina Ma ◽  
Haohong Duan
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Oxidation Reactions ◽  
Platform Chemicals ◽  
Wide Range

Oxidation reactions provide a wide range of important chemicals in industry; however, most of them are produced from fossil feedstocks. As a candidate of oxygen evolution reaction (OER), the electrooxidation...

Cost‐effective and Efficient Catalyst of Bimetallic Nickel Iron Selenide toward Oxygen Evolution Reaction

ChemCatChem ◽  
2020 ◽  
Vol 12 (17) ◽  
pp. 4416-4421
Author(s):  
Pengkun Wei ◽  
Zewei Hao ◽  
Hongzhi Kang ◽  
Yang ◽  
Donggang Guo ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Cost Effective ◽  
Efficient Catalyst ◽  
Nickel Iron ◽  
Iron Selenide

scholarly journals Comparison of two water oxidation electrocatalysts by copper or zinc supermolecule complexes based on porphyrin ligand

RSC Advances ◽  
2018 ◽  
Vol 8 (70) ◽  
pp. 40054-40059 ◽  
Author(s):  
Zhaodi Huang ◽  
Meixi Zhang ◽  
Huan Lin ◽  
Shuo Ding ◽  
Bin Dong ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Water Oxidation ◽  
Porphyrin Ligand

Two supermolecule complexes based on porphyrin ligand have been synthesized. The oxygen evolution reaction properties and proposed reaction mechanism of the complexes were studied.

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