A Chemical Evolution‐Like Method to Synthesize a Water‐Oxidizing Catalyst

Moghaddam, Navid Jameei; Feizi, Hadi; Mohammadi, Mohammad Reza; Bagheri, Robabeh; Chernev, Petko; Song, Zhenlun; Dau, Holger; Najafpour, Mohammad Mahdi

doi:10.1002/celc.202101105

Cited by 2 publications

(3 citation statements)

References 52 publications

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“…It is suggested that the Ni coordination compound species form aggregations of molecular species before the decomposition and then decompose to Ni (hydr)oxide. Different methods have been reported for synthesizing OER catalysts, − and the decomposition of metal coordination compounds is also a promising method for this purpose.…”

Section: Results and Discussionmentioning

confidence: 99%

Water Oxidation in the Presence of a Nickel Coordination Compound: Decomposition Products, Fe Impurity in the Electrolyte, and a Candidate as a Catalyst

et al. 2022

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Sustainable energy sources require a large-scale storage system. Water electrolysis toward hydrogen formation is a remarkable method for energy storage. However, oxygen-evolution reaction (OER) through water-oxidation reaction is a bottleneck in water-splitting systems. Different Ni-based molecular structures have been claimed to be OER catalysts. However, the impact of Ni (hydr)oxides formed by the degradation of Ni-based molecular structures on OER is a challenging issue. The effect of electrolyte impurity on OER in the presence of metal coordination compounds is rarely investigated. In this study, five important questions are considered regarding OER in the presence of a Ni coordination compound: (i) In which potential does the coordination compound start to be decomposed? (ii) After how many CVs does the decomposition occur? (iii) What is the effect of Fe impurity on OER in the presence of the Ni coordination compound? (iv) What is the product of the decomposition of the Ni coordination compound? (v) What is the true catalyst for OER in the presence of the Ni coordination compound? The roles of both the Fe impurity in the electrolyte and the Ni (hydr)oxide formed in the presence of a Ni coordination compound are investigated. The experiments showed that in the presence of the Ni coordination compound, Ni (hydr)oxide and Fe impurity in KOH formed a Ni–Fe oxide-based catalyst during OER, which is an efficient catalyst for OER. Fe impurity is a key contributor to observing OER in the presence of this Ni coordination compound.

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Section: Results and Discussionmentioning

confidence: 99%

Water Oxidation in the Presence of a Nickel Coordination Compound: Decomposition Products, Fe Impurity in the Electrolyte, and a Candidate as a Catalyst

et al. 2022

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“…Some research groups investigated the effects of other ions on layered Mn oxide to investigate its structure or catalytic activity. − These effects include inducing Mn(III), modifying the chemical and electronical properties of layered Mn oxide, enhancing charge mobility, and tuning the electronic structure. − …”

Section: Introductionmentioning

confidence: 99%

“…Different synthesis methods were used, and it was confirmed that various ions could increase the WOR. − …”

Section: Introductionmentioning

confidence: 99%

Effect of Different Metal Ions between Nanolayers of Manganese Oxide for Water Oxidation Reaction under Acidic Conditions

et al. 2023

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A new approach is used to synthesize various metal ions [Mg(II), Ca(II), Ba(II), Al(III), Zn(II), Cd(II), Mn(II), Fe(III), Co(III), Ni(II), and Cu(II)] between layers of Mn oxide in a pre-synthesized framework of layered Mn−K oxide. These Mn oxides were heated at 60−600 °C, and their electrochemistry and water oxidation reaction (WOR) were investigated at pH = 1. Using this strategy, the framework of the structure of catalysts is the same, and all are synthesized in a layered Mn oxide containing K(I) framework. Thus, comparing different ions in the same framework is easier. After calcination at 300−600 °C, X-ray absorption spectroscopy shows a layered structure with no change in bulk, but XRD shows that a few conversions regarding layered Mn oxide → α-MnO 2 → α-Mn 2 O 3 occur. Indeed, after calcination at 300−600 °C, the formed layered Mn oxide converts into a better WOR catalyst. After calcination at ≥300 °C, small amounts of α-MnO 2 /α-Mn 2 O 3 are formed in the structure, which could be important for WOR. At 600 °C, trace amounts of crystalline α-Mn 2 O 3 are usually formed in the presence of redox-inert ions, which is not an efficient catalyst for WOR. In the presence of redox-active ions, the formation of metal oxides such as Fe, Co, Ni, and Ni oxides is possible at 600 °C. These metal oxides are usually catalysts for WOR. An open structure of layered Mn oxide could increase the WOR activity of these redox-active ions. Thus, Mn ions may not be active sites for WOR and could be a substrate for these redox-active ions. Among the redox-inert ions between the layers of Mn oxides, the presence of Ca(II) at 500 °C results in a significant increase in WOR. Interestingly, a Ca/Mn cluster is present in the biological WOR catalyst.

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A Chemical Evolution‐Like Method to Synthesize a Water‐Oxidizing Catalyst

Cited by 2 publications

References 52 publications

Water Oxidation in the Presence of a Nickel Coordination Compound: Decomposition Products, Fe Impurity in the Electrolyte, and a Candidate as a Catalyst

Water Oxidation in the Presence of a Nickel Coordination Compound: Decomposition Products, Fe Impurity in the Electrolyte, and a Candidate as a Catalyst

Effect of Different Metal Ions between Nanolayers of Manganese Oxide for Water Oxidation Reaction under Acidic Conditions

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