Recent advances in water-splitting electrocatalysts based on manganese oxide

Kumbhar, Vijay S.; Lee, Hyeonkwon; Lee, Jae-Young; Lee, Ki-Young

doi:10.1016/j.crcon.2019.11.003

Cited by 34 publications

(11 citation statements)

References 143 publications

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“…Furthermore, photosystem II has an active site consisting of CaMn 4 O 5 , which makes manganese oxides scientifically interesting as biomimetic catalysts [1][2][3][4][5][6]. In the past years, the attention was mainly focused on simple manganese oxides [3][4][5][6][7][8][9][10][11][12][13], such as Mn 3 O 4 , Mn 2 O 3 , MnO 2 and variants with non-binding, redox-inactive cations, e.g. δ-AMnO 2 (A is group I/II cation) [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Reversible and irreversible processes during cyclic voltammetry of an electrodeposited manganese oxide as catalyst for the oxygen evolution reaction

Villalobos

Golnak

et al. 2020

J. Phys. Energy

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Manganese oxides have received much attention over the years among the wide range of electrocatalysts for the oxygen evolution reaction (OER) due to their low toxicity, high abundance and rich redox chemistry. While many previous studies focused on the activity of these materials, a better understanding of the material transformations relating to activation or degradation is highly desirable, both from a scientific perspective and for applications. We electrodeposited Na-containing MnO x without long-range order from an alkaline solution to investigate these aspects by cyclic voltammetry (CV), scanning electron microscopy (SEM) and X-ray absorption spectroscopy (XAS) at the Mn-K and Mn-L edges. The pristine film was assigned to a layered edge-sharing Mn 3+/4+ oxide with Mn-O bond lengths of mainly 1.87 Å and some at 2.30 Å as well as Mn-Mn bond lengths of 2.87 Å based on fits to the extended X-ray fine structure (EXAFS). The decrease of the currents at voltages before the onset of the OER followed power laws with three different exponents depending on the number of cycles and the Tafel slope decreases from 186±48 to 114±18 mV dec-1 after 100 cycles, which we interpret in the context of surface coverage with unreacted intermediates. Post-mortem microscopy and bulk spectroscopy at the Mn-K edge showed no change of the microstructure, bulk local structure or bulk Mn valence. Yet, the surface region of MnO x oxidized toward Mn 4+ , which explains the reduction of the currents in agreement with literature. Surprisingly, we find that MnO x reactivates after 30 minutes at open-circuit (OC), where the currents and also the Tafel slope increase. Reactivation processes during OC are crucial because OC is unavoidable when coupling the electrocatalysts to intermittent power sources such as solar energy for sustainable energy production.

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Section: Introductionmentioning

confidence: 99%

Reversible and irreversible processes during cyclic voltammetry of an electrodeposited manganese oxide as catalyst for the oxygen evolution reaction

Villalobos

Golnak

et al. 2020

J. Phys. Energy

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“…In the search for NPM OER electrocatalysts, researchers have focused on a range of abundant and cheap oxides, such as nickel, iron, manganese and cobalt. [9][10][11][12][13][14][15] The OER is generally catalysed by a metal oxide rather than a pure metal, with the mechanism different for oxides with different surface morphologies. It has been reported that the OER activity of metal oxides follows the trend of NiO x > CoO x > FeO x > MnO x , 16,17 with Ni based oxides reported to exhibit the most promising OER catalysis owing to their high intrinsic activity; 18,19 In exemplifying the case of a metal surface versus a metal oxide, Babar et al 17 explored a thermally oxidized porous NiO supported on nickel foam (NF) in 1.0 M KOH towards the OER.…”

Section: Introductionmentioning

confidence: 99%

Facile synthesis of Ni/NiO nanocomposites: the effect of Ni content in NiO upon the oxygen evolution reaction within alkaline media

et al. 2021

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“…First reports on this material date back to 1977, when the first electrochemical depositions of this material were reported . Since then, many follow-up studies on this oxide have been carried out to understand what defines the catalytic activity of MnO x . − For an overview of the recent state of the art in MnO x OER catalysts and the current state of understanding, the reader is referred to two recent reviews. , One important factor that determines the catalytic activity is the chemical structure of manganese-based catalysts. One generally needs to “activate” MnO x and other transition-metal oxide OER catalysts by several anodic potential sweeps.…”

Section: Introductionmentioning

confidence: 99%

“…9−14 For an overview of the recent state of the art in MnO x OER catalysts and the current state of understanding, the reader is referred to two recent reviews. 15,16 One important factor that determines the catalytic activity is the chemical structure of manganese-based catalysts. One generally needs to "activate" MnO x and other transition-metal oxide OER catalysts by several anodic potential sweeps.…”

Section: ■ Introductionmentioning

confidence: 99%

On the Origin of the OER Activity of Ultrathin Manganese Oxide Films

Plate

Höhn

Bloeck

et al. 2021

ACS Appl. Mater. Interfaces

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There is an urgent need for cheap, stable, and abundant catalyst materials for photoelectrochemical water splitting. Manganese oxide is an interesting candidate as an oxygen evolution reaction (OER) catalyst, but the minimum thickness above which MnO x thin films become OER-active has not yet been established. In this work, ultrathin (<10 nm) manganese oxide films are grown on silicon by atomic layer deposition to study the origin of OER activity under alkaline conditions. We found that MnO x films thinner than 1.5 nm are not OER-active. X-ray photoelectron spectroscopy shows that this is due to electrostatic catalyst–support interactions that prevent the electrochemical oxidation of the manganese ions close to the interface with the support, while in thicker films, MnIII and MnIV oxide layers appear as OER-active catalysts after oxidation and electrochemical treatment. From our investigations, it can be concluded that one MnIII,IV–O monolayer is sufficient to establish oxygen evolution under alkaline conditions. The results of this study provide important new design criteria for ultrathin manganese oxide oxygen evolution catalysts.

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Recent advances in water-splitting electrocatalysts based on manganese oxide

Cited by 34 publications

References 143 publications

Reversible and irreversible processes during cyclic voltammetry of an electrodeposited manganese oxide as catalyst for the oxygen evolution reaction

Reversible and irreversible processes during cyclic voltammetry of an electrodeposited manganese oxide as catalyst for the oxygen evolution reaction

Facile synthesis of Ni/NiO nanocomposites: the effect of Ni content in NiO upon the oxygen evolution reaction within alkaline media

On the Origin of the OER Activity of Ultrathin Manganese Oxide Films

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