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Title: In situ investigation on ultrafast oxygen evolution reactions of water splitting in proton exchange membrane electrolyzer cells

Abstract

We present that the oxygen evolution reaction (OER) is a half reaction in electrochemical devices, including low-temperature water electrolysis, which is considered as one of the most promising methods to generate hydrogen/oxygen for the storage of energy. It is affected by many factors, and its mechanism is still not completely understood. A proton exchange membrane electrolyzer cell (PEMEC) with optical access to the surface of anode catalyst layer (CL) coupled with a distinguished high-speed and micro-scale visualization system (HMVS) was developed to in situ investigate OERs. It was revealed in real time that OERs only occur on the anode CL adjacent to liquid/gas diffusion layer (LGDL). The CL electrical conductivity plays a crucial role in OERs on CLs. The large in-plane electrical resistance of CLs becomes a threshold of OERs over the entire CL, and causes a lot of catalyst waste in the middle of LGDL pores. Moreover, the oxygen bubble nucleation, growth, and detachment and the effect of current density on those processes were also characterized. Here, this study proposes a new approach for better understanding the mechanisms of OERs and optimizing the design and fabrication of membrane electrode assemblies.

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1];  [1];  [2];  [3];  [4];  [5];  [5]; ORCiD logo [6]; ORCiD logo [1]
  1. Univ. of Tennessee, Knoxville, Tullahoma, TN (United States). Department of Mechanical, Aerospace & Biomedical Engineering, UT Space Institute
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences and Center for Nanophase Materials Science Divisions
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Sciences Division
  5. National Renewable Energy Lab. (NREL), Golden, CO (United States). Materials and Chemical Science and Technolog
  6. National Renewable Energy Lab. (NREL), Golden, CO (United States). Mechanical and Thermal Engineering Sciences
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1393373
Report Number(s):
NREL/JA-5900-70048
Journal ID: ISSN 2050-7488; JMCAET
Grant/Contract Number:
AC36-08GO28308; FE0011585
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Materials Chemistry. A
Additional Journal Information:
Journal Volume: 5; Journal Issue: 35; Journal ID: ISSN 2050-7488
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; electrochemical devices; energy storage

Citation Formats

Mo, Jingke, Kang, Zhenye, Yang, Gaoqiang, Li, Yifan, Retterer, Scott T., Cullen, David A., Toops, Todd J., Bender, Guido, Pivovar, Bryan S., Green Jr, Johney B., and Zhang, Feng-Yuan. In situ investigation on ultrafast oxygen evolution reactions of water splitting in proton exchange membrane electrolyzer cells. United States: N. p., 2017. Web. doi:10.1039/C7TA05681H.
Mo, Jingke, Kang, Zhenye, Yang, Gaoqiang, Li, Yifan, Retterer, Scott T., Cullen, David A., Toops, Todd J., Bender, Guido, Pivovar, Bryan S., Green Jr, Johney B., & Zhang, Feng-Yuan. In situ investigation on ultrafast oxygen evolution reactions of water splitting in proton exchange membrane electrolyzer cells. United States. doi:10.1039/C7TA05681H.
Mo, Jingke, Kang, Zhenye, Yang, Gaoqiang, Li, Yifan, Retterer, Scott T., Cullen, David A., Toops, Todd J., Bender, Guido, Pivovar, Bryan S., Green Jr, Johney B., and Zhang, Feng-Yuan. Fri . "In situ investigation on ultrafast oxygen evolution reactions of water splitting in proton exchange membrane electrolyzer cells". United States. doi:10.1039/C7TA05681H.
@article{osti_1393373,
title = {In situ investigation on ultrafast oxygen evolution reactions of water splitting in proton exchange membrane electrolyzer cells},
author = {Mo, Jingke and Kang, Zhenye and Yang, Gaoqiang and Li, Yifan and Retterer, Scott T. and Cullen, David A. and Toops, Todd J. and Bender, Guido and Pivovar, Bryan S. and Green Jr, Johney B. and Zhang, Feng-Yuan},
abstractNote = {We present that the oxygen evolution reaction (OER) is a half reaction in electrochemical devices, including low-temperature water electrolysis, which is considered as one of the most promising methods to generate hydrogen/oxygen for the storage of energy. It is affected by many factors, and its mechanism is still not completely understood. A proton exchange membrane electrolyzer cell (PEMEC) with optical access to the surface of anode catalyst layer (CL) coupled with a distinguished high-speed and micro-scale visualization system (HMVS) was developed to in situ investigate OERs. It was revealed in real time that OERs only occur on the anode CL adjacent to liquid/gas diffusion layer (LGDL). The CL electrical conductivity plays a crucial role in OERs on CLs. The large in-plane electrical resistance of CLs becomes a threshold of OERs over the entire CL, and causes a lot of catalyst waste in the middle of LGDL pores. Moreover, the oxygen bubble nucleation, growth, and detachment and the effect of current density on those processes were also characterized. Here, this study proposes a new approach for better understanding the mechanisms of OERs and optimizing the design and fabrication of membrane electrode assemblies.},
doi = {10.1039/C7TA05681H},
journal = {Journal of Materials Chemistry. A},
number = 35,
volume = 5,
place = {United States},
year = {Fri Aug 25 00:00:00 EDT 2017},
month = {Fri Aug 25 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • Visualization investigation the oxygen bubble evolution and dynamics reveals the real phenomena inside an operating proton exchange membrane electrolyzer cell.
  • Proton exchange membrane electrolyzer cells (PEMECs) have received great attention for hydrogen/oxygen production due to their high efficiencies even at low-temperature operation. Because of the high cost of noble platinum-group metal (PGM) catalysts (Ir, Ru, Pt, etc.) that are widely used in water splitting, a PEMEC with low catalyst loadings and high catalyst utilizations is strongly desired for its wide commercialization. In this study, the ultrafast and multiscale hydrogen evolution reaction (HER) phenomena in an operating PEMEC is in-situ observed for the first time. The visualization results reveal that the HER and hydrogen bubble nucleation mainly occur on catalyst layersmore » at the rim of the pores of the thin/tunable liquid/gas diffusion layers (TT-LGDLs). This indicates that the catalyst material of the conventional catalyst-coated membrane (CCM) that is located in the middle area of the LGDL pore is underutilized/inactive. Based on this discovery, a novel thin and tunable gas diffusion electrode (GDE) with a Pt catalyst thickness of 15 nm and a total thickness of about 25 um has been proposed and developed by taking advantage of advanced micro/nano manufacturing. The novel thin GDEs are comprehensively characterized both ex-situ and in-situ, and exhibit excellent PEMEC performance. More importantly, they achieve catalyst mass activity of up to 58 times higher than conventional CCM at 1.6 V under the operating conditions of 80 degrees C and 1 atm. This study demonstrates a promising concept for PEMEC electrode development, and provides a direction of future catalyst designs and fabrications for electrochemical devices.« less
  • Proton exchange membrane electrolyzer cells (PEMECs) have received great attention for hydrogen/oxygen production due to their high efficiencies even at low-temperature operation. Because of the high cost of noble platinum-group metal (PGM) catalysts (Ir, Ru, Pt, etc.) that are widely used in water splitting, a PEMEC with low catalyst loadings and high catalyst utilizations is strongly desired for its wide commercialization. In this study, the ultrafast and multiscale hydrogen evolution reaction (HER) phenomena in an operating PEMEC is in-situ observed for the first time. The visualization results reveal that the HER and hydrogen bubble nucleation mainly occur on catalyst layersmore » at the rim of the pores of the thin/tunable liquid/gas diffusion layers (TT-LGDLs). This indicates that the catalyst material of the conventional catalyst-coated membrane (CCM) that is located in the middle area of the LGDL pore is underutilized/inactive. Based on this discovery, a novel thin and tunable gas diffusion electrode (GDE) with a Pt catalyst thickness of 15 nm and a total thickness of about 25 um has been proposed and developed by taking advantage of advanced micro/nano manufacturing. The novel thin GDEs are comprehensively characterized both ex-situ and in-situ, and exhibit excellent PEMEC performance. More importantly, they achieve catalyst mass activity of up to 58 times higher than conventional CCM at 1.6 V under the operating conditions of 80 degrees C and 1 atm. This study demonstrates a promising concept for PEMEC electrode development, and provides a direction of future catalyst designs and fabrications for electrochemical devices.« less
  • The lack of a fundamental understanding of the corrosion mechanisms in the electrochemical environments of proton exchange membrane (PEM) electrolyzer and/or fuel cells (ECs/FCs) has seriously hindered the improvement of performance and efficiency of PEM ECs/FCs. In this study, a stainless steel mesh was purposely used as an anode gas diffusion layer that was intentionally operated with high positive potentials under harsh oxidative environments in a PEMEC to study the corrosion mechanism of metal migration. A significant amount of iron and nickel cations were determined to transport through the anode catalyst layer, the PEM and the cathode catalyst layer duringmore » the PEMEC operation. The formation/deposition of iron oxide and nickel oxide on the carbon paper gas diffusion layer at the cathode side is first revealed by both scanning electron microscope and X-ray diffraction. The results indicate the corrosion elements of iron and nickel are transported from anode to cathode through the catalyst-coated membrane, and deposited on carbon fibers as oxides. This phenomenon could also open a new corrosion-based processing approach to potentially fabricate multifunctional oxide structures on carbon fiber devices. This study has demonstrated a new accelerated test method for investigating the corrosion and durability of metallic materials as well.« less