Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Michaela Burke Stevens; Melissa E. Kreider; Anjli M. Patel; Zhenbin Wang; Yunzhi Liu; Brenna M. Gibbons; Michael J. Statt; Anton V. Ievlev; Robert Sinclair; Apurva Mehta; Ryan C. Davis; Jens K. Nørskov; Alessandro Gallo; Laurie A. King; Thomas F. Jaramillo

doi:10.1021/acsaem.0c02423

Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Michaela Burke Stevens, Melissa E. Kreider, Anjli M. Patel, Zhenbin Wang, Yunzhi Liu, Brenna M. Gibbons, Michael J. Statt, Anton V. Ievlev, Robert Sinclair, Apurva Mehta, Ryan C. Davis, Jens K. Nørskov, Alessandro Gallo, Laurie A. King, Thomas F. Jaramillo

Functional Atomic Force Microscopy Group

Research output: Contribution to journal › Article › peer-review

19 Scopus citations

Abstract

Rigorous in situ studies of electrocatalysts are required to enable the design of higher performing materials. Nonplatinum group metals for oxygen reduction reaction (ORR) catalysis containing light elements such as O, N, and C are known to be susceptible to both ex situ and in situ oxidation, leading to challenges associated with ex situ characterization methods. We have previously shown that the bulk O content plays an important role in the activity and selectivity of Mo-N catalysts, but further understanding of the role of composition and morphological changes at the surface is needed. Here, we report the measurement of in situ surface changes to a molybdenum nitride (MoN) thin film under ORR conditions using grazing incidence X-ray absorption and reflectivity. We show that the half-wave potential of MoN can be improved by ∼90 mV by potential conditioning up to 0.8 V versus RHE. Utilizing electrochemical analysis, dissolution monitoring, and surface-sensitive X-ray techniques, we show that under moderate polarization (0.3-0.7 V vs RHE) there is local ligand distortion, O incorporation, and amorphization of the MoN surface, without changes in roughness. Furthermore, with a controlled potential hold procedure, we show that the surface changes concurrent with potential conditioning are stable under ORR relevant potentials. Conversely, at higher potentials (≥0.8 V vs RHE), the film incorporates O, dissolves, and roughens, suggesting that in this higher potential regime, the performance enhancements are due to increased access to active sites. Density functional theory calculations and Pourbaix analysis provide insights into film stability and O incorporation as a function of potential. These findings coupled with in situ electrochemical surface-sensitive X-ray techniques demonstrate an approach to studying nontraditional surfaces in which we can leverage our understanding of surface dynamics to improve performance with the rational, in situ tuning of active sites.

Original language	English
Pages (from-to)	12433-12446
Number of pages	14
Journal	ACS Applied Energy Materials
Volume	3
Issue number	12
DOIs	https://doi.org/10.1021/acsaem.0c02423
State	Published - Dec 28 2020

Funding

This work was supported by the Toyota Research Institute. Author A.M.P. thanks the National Science Foundation Graduate Research Fellowship Program (NSF GRFP). Author M.J.S. gratefully acknowledges the funding by Villum Fonden, part of the Villum Center for the Science of Sustainable Fuels and Chemicals (V-SUSTAIN grant 9455). Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) and the Stanford Nanofabrication Facility (SNF), supported by the National Science Foundation under Award ECCS-1542152. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. DOE, Office of BES under Contract no. DE-AC02-76SF00515. Part of this research (ToF-SIMS characterization) was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility, using instrumentation within ORNL’s Materials Characterization Core provided by UT-Battelle, LLC under Contract no. DE-AC05-00OR22725 with the U.S. DOE. The authors thank Guanchao Li in the Stanford Environmental Measurements Facility for the acquisition of ICP-OES data. Authors M.E.K. and M.B.S. would like to thank Alan Landers for insightful discussions. The authors thank Melissa Wette, Drew Higgins, and Anders Pederson for their work in developing the GI-cell through a collaboration between Stanford University, the Joint Center for Artificial Photosynthesis, and SSRL.

Funders	Funder number
Office of BES	DE-AC02-76SF00515
U.S. DOE
Villum Center for the Science of Sustainable Fuels and Chemicals	9455
National Science Foundation
Office of Science	DE-AC05-00OR22725
Villum Fonden
Toyota Research Institute
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung	ECCS-1542152

Keywords

electrocatalysis
grazing incidence X-ray absorption spectroscopy
in situ
molybdenum nitride
oxygen reduction
surface oxidation

Access to Document

10.1021/acsaem.0c02423

Cite this

Stevens, M. B., Kreider, M. E., Patel, A. M., Wang, Z., Liu, Y., Gibbons, B. M., Statt, M. J., Ievlev, A. V., Sinclair, R., Mehta, A., Davis, R. C., Nørskov, J. K., Gallo, A., King, L. A., & Jaramillo, T. F. (2020). Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction. ACS Applied Energy Materials, 3(12), 12433-12446. https://doi.org/10.1021/acsaem.0c02423

@article{ef1a581f0dff4f8dbeb5461714b4ea50,

title = "Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction",

abstract = "Rigorous in situ studies of electrocatalysts are required to enable the design of higher performing materials. Nonplatinum group metals for oxygen reduction reaction (ORR) catalysis containing light elements such as O, N, and C are known to be susceptible to both ex situ and in situ oxidation, leading to challenges associated with ex situ characterization methods. We have previously shown that the bulk O content plays an important role in the activity and selectivity of Mo-N catalysts, but further understanding of the role of composition and morphological changes at the surface is needed. Here, we report the measurement of in situ surface changes to a molybdenum nitride (MoN) thin film under ORR conditions using grazing incidence X-ray absorption and reflectivity. We show that the half-wave potential of MoN can be improved by ∼90 mV by potential conditioning up to 0.8 V versus RHE. Utilizing electrochemical analysis, dissolution monitoring, and surface-sensitive X-ray techniques, we show that under moderate polarization (0.3-0.7 V vs RHE) there is local ligand distortion, O incorporation, and amorphization of the MoN surface, without changes in roughness. Furthermore, with a controlled potential hold procedure, we show that the surface changes concurrent with potential conditioning are stable under ORR relevant potentials. Conversely, at higher potentials (≥0.8 V vs RHE), the film incorporates O, dissolves, and roughens, suggesting that in this higher potential regime, the performance enhancements are due to increased access to active sites. Density functional theory calculations and Pourbaix analysis provide insights into film stability and O incorporation as a function of potential. These findings coupled with in situ electrochemical surface-sensitive X-ray techniques demonstrate an approach to studying nontraditional surfaces in which we can leverage our understanding of surface dynamics to improve performance with the rational, in situ tuning of active sites.",

keywords = "electrocatalysis, grazing incidence X-ray absorption spectroscopy, in situ, molybdenum nitride, oxygen reduction, surface oxidation",

author = "Stevens, {Michaela Burke} and Kreider, {Melissa E.} and Patel, {Anjli M.} and Zhenbin Wang and Yunzhi Liu and Gibbons, {Brenna M.} and Statt, {Michael J.} and Ievlev, {Anton V.} and Robert Sinclair and Apurva Mehta and Davis, {Ryan C.} and N{\o}rskov, {Jens K.} and Alessandro Gallo and King, {Laurie A.} and Jaramillo, {Thomas F.}",

note = "Publisher Copyright: {\textcopyright} ",

year = "2020",

month = dec,

day = "28",

doi = "10.1021/acsaem.0c02423",

language = "English",

volume = "3",

pages = "12433--12446",

journal = "ACS Applied Energy Materials",

issn = "2574-0962",

publisher = "American Chemical Society",

number = "12",

}

Stevens, MB, Kreider, ME, Patel, AM, Wang, Z, Liu, Y, Gibbons, BM, Statt, MJ, Ievlev, AV, Sinclair, R, Mehta, A, Davis, RC, Nørskov, JK, Gallo, A, King, LA & Jaramillo, TF 2020, 'Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction', ACS Applied Energy Materials, vol. 3, no. 12, pp. 12433-12446. https://doi.org/10.1021/acsaem.0c02423

TY - JOUR

T1 - Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

AU - Stevens, Michaela Burke

AU - Kreider, Melissa E.

AU - Patel, Anjli M.

AU - Wang, Zhenbin

AU - Liu, Yunzhi

AU - Gibbons, Brenna M.

AU - Statt, Michael J.

AU - Ievlev, Anton V.

AU - Sinclair, Robert

AU - Mehta, Apurva

AU - Davis, Ryan C.

AU - Nørskov, Jens K.

AU - Gallo, Alessandro

AU - King, Laurie A.

AU - Jaramillo, Thomas F.

PY - 2020/12/28

Y1 - 2020/12/28

N2 - Rigorous in situ studies of electrocatalysts are required to enable the design of higher performing materials. Nonplatinum group metals for oxygen reduction reaction (ORR) catalysis containing light elements such as O, N, and C are known to be susceptible to both ex situ and in situ oxidation, leading to challenges associated with ex situ characterization methods. We have previously shown that the bulk O content plays an important role in the activity and selectivity of Mo-N catalysts, but further understanding of the role of composition and morphological changes at the surface is needed. Here, we report the measurement of in situ surface changes to a molybdenum nitride (MoN) thin film under ORR conditions using grazing incidence X-ray absorption and reflectivity. We show that the half-wave potential of MoN can be improved by ∼90 mV by potential conditioning up to 0.8 V versus RHE. Utilizing electrochemical analysis, dissolution monitoring, and surface-sensitive X-ray techniques, we show that under moderate polarization (0.3-0.7 V vs RHE) there is local ligand distortion, O incorporation, and amorphization of the MoN surface, without changes in roughness. Furthermore, with a controlled potential hold procedure, we show that the surface changes concurrent with potential conditioning are stable under ORR relevant potentials. Conversely, at higher potentials (≥0.8 V vs RHE), the film incorporates O, dissolves, and roughens, suggesting that in this higher potential regime, the performance enhancements are due to increased access to active sites. Density functional theory calculations and Pourbaix analysis provide insights into film stability and O incorporation as a function of potential. These findings coupled with in situ electrochemical surface-sensitive X-ray techniques demonstrate an approach to studying nontraditional surfaces in which we can leverage our understanding of surface dynamics to improve performance with the rational, in situ tuning of active sites.

AB - Rigorous in situ studies of electrocatalysts are required to enable the design of higher performing materials. Nonplatinum group metals for oxygen reduction reaction (ORR) catalysis containing light elements such as O, N, and C are known to be susceptible to both ex situ and in situ oxidation, leading to challenges associated with ex situ characterization methods. We have previously shown that the bulk O content plays an important role in the activity and selectivity of Mo-N catalysts, but further understanding of the role of composition and morphological changes at the surface is needed. Here, we report the measurement of in situ surface changes to a molybdenum nitride (MoN) thin film under ORR conditions using grazing incidence X-ray absorption and reflectivity. We show that the half-wave potential of MoN can be improved by ∼90 mV by potential conditioning up to 0.8 V versus RHE. Utilizing electrochemical analysis, dissolution monitoring, and surface-sensitive X-ray techniques, we show that under moderate polarization (0.3-0.7 V vs RHE) there is local ligand distortion, O incorporation, and amorphization of the MoN surface, without changes in roughness. Furthermore, with a controlled potential hold procedure, we show that the surface changes concurrent with potential conditioning are stable under ORR relevant potentials. Conversely, at higher potentials (≥0.8 V vs RHE), the film incorporates O, dissolves, and roughens, suggesting that in this higher potential regime, the performance enhancements are due to increased access to active sites. Density functional theory calculations and Pourbaix analysis provide insights into film stability and O incorporation as a function of potential. These findings coupled with in situ electrochemical surface-sensitive X-ray techniques demonstrate an approach to studying nontraditional surfaces in which we can leverage our understanding of surface dynamics to improve performance with the rational, in situ tuning of active sites.

KW - electrocatalysis

KW - grazing incidence X-ray absorption spectroscopy

KW - in situ

KW - molybdenum nitride

KW - oxygen reduction

KW - surface oxidation

UR - http://www.scopus.com/inward/record.url?scp=85098962476&partnerID=8YFLogxK

U2 - 10.1021/acsaem.0c02423

DO - 10.1021/acsaem.0c02423

M3 - Article

AN - SCOPUS:85098962476

SN - 2574-0962

VL - 3

SP - 12433

EP - 12446

JO - ACS Applied Energy Materials

JF - ACS Applied Energy Materials

IS - 12

ER -

Identifying and Tuning the in Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this