Activating Mn Sites by Ni Replacement in α-MnO2

Sami Alharbi; Mohammed  Alkhalifah; Benjamin Howchen; Athi N. A. Rahmah; Veronica Celorrio Remartinez; David J Fermin

doi:10.1021/acsmaterialsau.3c00051

Activating Mn Sites by Ni Replacement in α-MnO2

Sami Alharbi, Mohammed Alkhalifah, Benjamin Howchen, Athi N. A. Rahmah, Veronica Celorrio Remartinez, David J Fermin

Research output: Contribution to journal › Article (Academic Journal) › peer-review

2 Citations (Scopus)

Abstract

Transition metal oxides are characterized by an acute structure and composition dependent electrocatalytic activity towards the oxygen evolution (OER) and oxygen reduction (ORR) reactions. For instance, Mn containing oxides are among the most active ORR catalysts, while Ni based compounds tend to show high activity towards the OER in alkaline solutions. In this study, we show that incorporation of Ni into α-MnO2, by adding Ni precursor into the Mn-containing hydrothermal solution, can generate distinctive sites with different electronic configuration and contrasting electrocatalytic activity. The structure and composition of the Ni modified Hollandite α-MnO2 phase were investigated by X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma – optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS). Our analysis suggests that Mn replacement by Ni into the α-MnO2 lattice (site A) occurs up to approximately 5 % of the total Mn content, while further increasing Ni content promotes the nucleation of separate Ni phases (site B). XAS and XRD shows that the introduction of sites A and B have negligible effect on the overall Mn oxidation state and bonding characteristics, while very subtle changes in the XPS spectra appears to suggest changes in the electronic configuration upon Ni incorporation into the α-MnO2 lattice. On the other hand, changes in the electronic structure promoted by site A have a significant impact in the pseudocapacitive responses obtained by cyclic voltammetry in KOH solution at pH 14, revealing the appearance of Mn 3d orbitals at the energy (potential) range relevant to the ORR. The evolution of Mn 3d upon Ni replacement significantly increases the catalytic activity of α-MnO2 towards the ORR. Interestingly, the formation of segregated Ni phases (site B) leads to a decrease in the ORR activity, while increasing OER rate.

Original language	English
Pages (from-to)	74–81
Number of pages	8
Journal	ACS Materials Au
Volume	2024, 4
Issue number	1
Early online date	20 Nov 2023
DOIs	https://doi.org/10.1021/acsmaterialsau.3c00051
Publication status	Published - 10 Jan 2024

Bibliographical note

Funding Information:
S.M.A. acknowledges the financial support from the Saudi Arabian Cultural Bureau to the UK and Qassim University. M.A.A. is also grateful for the support by the Saudi Ministry of Education and the King Faisal University. D.J.F. is thankful for the support by the Engineering and Physical Sciences Research Council through the grant EP/W032996/1. The authors are grateful to the Diamond Light Source for access to the B18 beamline (BAG April 2021).

Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.

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DIMENSIONALLY STABLE ELECTRODES FOR SUPERCRITICAL WATER ELECTROLYSIS (SuperH2)
Fermin, D. J. (Principal Investigator)
1/07/22 → 31/12/23
Project: Research

Cite this

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title = "Activating Mn Sites by Ni Replacement in α-MnO2",

abstract = "Transition metal oxides are characterized by an acute structure and composition dependent electrocatalytic activity towards the oxygen evolution (OER) and oxygen reduction (ORR) reactions. For instance, Mn containing oxides are among the most active ORR catalysts, while Ni based compounds tend to show high activity towards the OER in alkaline solutions. In this study, we show that incorporation of Ni into α-MnO2, by adding Ni precursor into the Mn-containing hydrothermal solution, can generate distinctive sites with different electronic configuration and contrasting electrocatalytic activity. The structure and composition of the Ni modified Hollandite α-MnO2 phase were investigated by X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma – optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS). Our analysis suggests that Mn replacement by Ni into the α-MnO2 lattice (site A) occurs up to approximately 5 % of the total Mn content, while further increasing Ni content promotes the nucleation of separate Ni phases (site B). XAS and XRD shows that the introduction of sites A and B have negligible effect on the overall Mn oxidation state and bonding characteristics, while very subtle changes in the XPS spectra appears to suggest changes in the electronic configuration upon Ni incorporation into the α-MnO2 lattice. On the other hand, changes in the electronic structure promoted by site A have a significant impact in the pseudocapacitive responses obtained by cyclic voltammetry in KOH solution at pH 14, revealing the appearance of Mn 3d orbitals at the energy (potential) range relevant to the ORR. The evolution of Mn 3d upon Ni replacement significantly increases the catalytic activity of α-MnO2 towards the ORR. Interestingly, the formation of segregated Ni phases (site B) leads to a decrease in the ORR activity, while increasing OER rate. ",

author = "Sami Alharbi and Mohammed Alkhalifah and Benjamin Howchen and Rahmah, {Athi N. A.} and {Celorrio Remartinez}, Veronica and Fermin, {David J}",

note = "Funding Information: S.M.A. acknowledges the financial support from the Saudi Arabian Cultural Bureau to the UK and Qassim University. M.A.A. is also grateful for the support by the Saudi Ministry of Education and the King Faisal University. D.J.F. is thankful for the support by the Engineering and Physical Sciences Research Council through the grant EP/W032996/1. The authors are grateful to the Diamond Light Source for access to the B18 beamline (BAG April 2021). Publisher Copyright: {\textcopyright} 2023 The Authors. Published by American Chemical Society.",

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doi = "10.1021/acsmaterialsau.3c00051",

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T1 - Activating Mn Sites by Ni Replacement in α-MnO2

AU - Alharbi, Sami

AU - Alkhalifah, Mohammed

AU - Howchen, Benjamin

AU - Rahmah, Athi N. A.

AU - Celorrio Remartinez, Veronica

AU - Fermin, David J

N1 - Funding Information: S.M.A. acknowledges the financial support from the Saudi Arabian Cultural Bureau to the UK and Qassim University. M.A.A. is also grateful for the support by the Saudi Ministry of Education and the King Faisal University. D.J.F. is thankful for the support by the Engineering and Physical Sciences Research Council through the grant EP/W032996/1. The authors are grateful to the Diamond Light Source for access to the B18 beamline (BAG April 2021). Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.

PY - 2024/1/10

Y1 - 2024/1/10

N2 - Transition metal oxides are characterized by an acute structure and composition dependent electrocatalytic activity towards the oxygen evolution (OER) and oxygen reduction (ORR) reactions. For instance, Mn containing oxides are among the most active ORR catalysts, while Ni based compounds tend to show high activity towards the OER in alkaline solutions. In this study, we show that incorporation of Ni into α-MnO2, by adding Ni precursor into the Mn-containing hydrothermal solution, can generate distinctive sites with different electronic configuration and contrasting electrocatalytic activity. The structure and composition of the Ni modified Hollandite α-MnO2 phase were investigated by X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma – optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS). Our analysis suggests that Mn replacement by Ni into the α-MnO2 lattice (site A) occurs up to approximately 5 % of the total Mn content, while further increasing Ni content promotes the nucleation of separate Ni phases (site B). XAS and XRD shows that the introduction of sites A and B have negligible effect on the overall Mn oxidation state and bonding characteristics, while very subtle changes in the XPS spectra appears to suggest changes in the electronic configuration upon Ni incorporation into the α-MnO2 lattice. On the other hand, changes in the electronic structure promoted by site A have a significant impact in the pseudocapacitive responses obtained by cyclic voltammetry in KOH solution at pH 14, revealing the appearance of Mn 3d orbitals at the energy (potential) range relevant to the ORR. The evolution of Mn 3d upon Ni replacement significantly increases the catalytic activity of α-MnO2 towards the ORR. Interestingly, the formation of segregated Ni phases (site B) leads to a decrease in the ORR activity, while increasing OER rate.

AB - Transition metal oxides are characterized by an acute structure and composition dependent electrocatalytic activity towards the oxygen evolution (OER) and oxygen reduction (ORR) reactions. For instance, Mn containing oxides are among the most active ORR catalysts, while Ni based compounds tend to show high activity towards the OER in alkaline solutions. In this study, we show that incorporation of Ni into α-MnO2, by adding Ni precursor into the Mn-containing hydrothermal solution, can generate distinctive sites with different electronic configuration and contrasting electrocatalytic activity. The structure and composition of the Ni modified Hollandite α-MnO2 phase were investigated by X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma – optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS). Our analysis suggests that Mn replacement by Ni into the α-MnO2 lattice (site A) occurs up to approximately 5 % of the total Mn content, while further increasing Ni content promotes the nucleation of separate Ni phases (site B). XAS and XRD shows that the introduction of sites A and B have negligible effect on the overall Mn oxidation state and bonding characteristics, while very subtle changes in the XPS spectra appears to suggest changes in the electronic configuration upon Ni incorporation into the α-MnO2 lattice. On the other hand, changes in the electronic structure promoted by site A have a significant impact in the pseudocapacitive responses obtained by cyclic voltammetry in KOH solution at pH 14, revealing the appearance of Mn 3d orbitals at the energy (potential) range relevant to the ORR. The evolution of Mn 3d upon Ni replacement significantly increases the catalytic activity of α-MnO2 towards the ORR. Interestingly, the formation of segregated Ni phases (site B) leads to a decrease in the ORR activity, while increasing OER rate.

U2 - 10.1021/acsmaterialsau.3c00051

DO - 10.1021/acsmaterialsau.3c00051

M3 - Article (Academic Journal)

C2 - 38221925

SN - 2694-2461

VL - 2024, 4

SP - 74

EP - 81

JO - ACS Materials Au

JF - ACS Materials Au

IS - 1

ER -

Activating Mn Sites by Ni Replacement in α-MnO2

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