Special Issue "Catalysts for Polymer Membrane Fuel Cells"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Electrocatalysis".

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editors

Guest Editor
Prof. Dr. William Mustain

Department of Chemical Engineering, University of South Carolina, Swearingen Engineering Center, Columbia SC 29208, USA
Website | E-Mail
Interests: electrochemical energy conversion and storage
Guest Editor
Dr. Bryan Pivovar

National Renewable Energy Laboratory, Golden, CO, USA
Website | E-Mail
Interests: novel extended surface electrocatalysts and alkaline membrane fuel cells

Special Issue Information

Dear Colleagues,

Polymer membrane fuel cells are at an exciting time in their development. State-of-the-art proton exchange membrane fuel cells (PEMFCs) have high activity, stable Pt-based catalysts that have been integrated into cells, and stacks that can operate over many thousands of hours—providing clean power for a myriad of applications and PEMFCs have seen near-exponential growth in their commercial application over the last decade. However, for many applications (e.g., automotive) the overall cost remains above government and industrial targets. 

Two approaches with the potential to revolutionize the fuel cell market and allow for cost to be substantively decreased are: 1) Platinum group metal (PGM) free catalysts. PGM-free catalysts present a new learning curve from a catalysis perspective because of the uncertainty in the nature of the active site, generally low active site density and often low turnover frequencies. This leads to high catalyst loadings and thick catalyst layers, which can impart mass transport limitations into the system. 2) Rethink the chemistry of the system. Anion exchange membrane fuel cells (AEMFCs) have been rapidly increasing in popularly. It is thought that AEMFCs will allow for lower cost catalysts, bipolar plates and balance-of-plant than PEMFCs.  However, from a catalysis perspective, AEMFCs suffer from sluggish kinetics at the anode and the cathode, and the choices for catalysts outside of the PGM family are limited. 

This Special Issue will focus on experimental and theoretical investigations into new catalysts for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in PEMFCs and AEMFCs with a particular interest in the realization of Pt-free and PGM-free materials. Both fundamental and applied studies (focusing on investigating catalysts in realistic environments and improving stability) are of interest. Additionally relevant are reports that detail new methodologies for in situ and operando catalyst characterization. The hope is to compile a set of manuscripts that inform the field of the state-of-the-art in catalysis 

Prof. Dr. William Mustain
Dr. Bryan Pivovar
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Electrocatalysts
  • Activity
  • Stability
  • Platinum Group Metal Free
  • Platinum Free
  • Oxygen Reduction
  • Hydrogen Oxidation
  • Proton Exchange Membrane Fuel Cell
  • Anion Exchange Membrane Fuel Cell
  • Reversible or Unitized Regenerative Fuel Cell

Published Papers (8 papers)

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Research

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Open AccessArticle The Challenge of Achieving a High Density of Fe-Based Active Sites in a Highly Graphitic Carbon Matrix
Catalysts 2019, 9(2), 144; https://doi.org/10.3390/catal9020144
Received: 11 December 2018 / Revised: 10 January 2019 / Accepted: 11 January 2019 / Published: 2 February 2019
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Abstract
As one of the most promising platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR), Fe–N–C catalysts with a high density of FeNx moieties integrated in a highly graphitic carbon matrix with a proper porous structure have attracted extensive attention to [...] Read more.
As one of the most promising platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR), Fe–N–C catalysts with a high density of FeNx moieties integrated in a highly graphitic carbon matrix with a proper porous structure have attracted extensive attention to combine the high activity, high stability and high accessibility of active sites. Herein, we investigated a ZnCl2/NaCl eutectic salts-assisted ionothermal carbonization method (ICM) to synthesize Fe–N–C catalysts with tailored porous structure, high specific surface area and a high degree of graphitization. However, it was found to be challenging to anchor a high density of FeNx sites onto highly graphitized carbon. Iron precursors with preexisting Fe–N coordination were required to form FeNx sites in the nitrogen-doped carbon with a high degree of graphitization, while individual Fe and N precursors led to a Fe–N–C catalyst with poor-ORR activity. This provides valuable insights into the synthesis-structure relationship. Moreover, the FeNx moieties were identified as the major active sites in acidic conditions, while both FeNx sites and Fe2O3 were found to be active in alkaline medium. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessArticle Oxygen Reduction Reaction Electrocatalysis in Alkaline Electrolyte on Glassy-Carbon-Supported Nanostructured Pr6O11 Thin-Films
Catalysts 2018, 8(10), 461; https://doi.org/10.3390/catal8100461
Received: 18 September 2018 / Revised: 10 October 2018 / Accepted: 12 October 2018 / Published: 17 October 2018
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Abstract
In this work, hierarchical nanostructured Pr6O11 thin-films of brain-like morphology were successfully prepared by electrostatic spray deposition (ESD) on glassy-carbon substrates. These surfaces were used as working electrodes in the rotating disk electrode (RDE) setup and characterized in alkaline electrolyte [...] Read more.
In this work, hierarchical nanostructured Pr6O11 thin-films of brain-like morphology were successfully prepared by electrostatic spray deposition (ESD) on glassy-carbon substrates. These surfaces were used as working electrodes in the rotating disk electrode (RDE) setup and characterized in alkaline electrolyte (0.1 M NaOH at 25 ± 2 °C) for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR) for their potential application in alkaline electrolyzers or in alkaline fuel cells. The electrochemical performances of these electrodes were investigated as a function of their crystallized state (amorphous versus crystalline). Although none of the materials display spectacular HER and OER activity, the results show interesting performances of the crystallized sample towards the ORR with regards to this class of non-Pt group metal (non-PGM) electrocatalysts, the activity being, however, still far from a benchmark Pt/C electrocatalyst. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessArticle Hydrogen Oxidation on Ni-Based Electrocatalysts: The Effect of Metal Doping
Catalysts 2018, 8(10), 454; https://doi.org/10.3390/catal8100454
Received: 27 September 2018 / Revised: 9 October 2018 / Accepted: 11 October 2018 / Published: 15 October 2018
Cited by 3 | PDF Full-text (2060 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Carbon supported nanoparticles of monometallic Ni catalyst and binary Ni-Transition Metal (Ni-TM/C) electrocatalytic composites were synthesized via the chemical reduction method, where TM stands for the doping elements Fe, Co, and Cu. The chemical composition, structure and morphology of the Ni-TM/C materials were [...] Read more.
Carbon supported nanoparticles of monometallic Ni catalyst and binary Ni-Transition Metal (Ni-TM/C) electrocatalytic composites were synthesized via the chemical reduction method, where TM stands for the doping elements Fe, Co, and Cu. The chemical composition, structure and morphology of the Ni-TM/C materials were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical properties towards hydrogen oxidation reaction in alkaline medium were studied using the rotating disc electrode and cycling voltammetry methods. A significant role of the TM dopants in the promotion of the hydrogen electrooxidation kinetics of the binary Ni-TM/C materials was revealed. A record-high in exchange current density value of 0.060 mA cm2Ni was measured for Ni3Fe1/C, whereas the monometallic Ni/C counterpart has only shown 0.039 mA cm2Ni. In order to predict the feasibility of the electrocatalysts for hydrogen chemisorption, density functional theory was applied to calculate the hydrogen binding energy and hydroxide binding energy values for bare Ni and Ni3TM1. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessArticle Experimental Study on the Effect of Hydrogen Sulfide on High-Temperature Proton Exchange Membrane Fuel Cells by Using Electrochemical Impedance Spectroscopy
Catalysts 2018, 8(10), 441; https://doi.org/10.3390/catal8100441
Received: 9 September 2018 / Revised: 28 September 2018 / Accepted: 8 October 2018 / Published: 9 October 2018
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Abstract
When the fuel supplied to a high-temperature proton exchange membrane fuel cell (HT-PEMFC) is produced by hydrocarbon formation, hydrogen sulfide (H2S) may appear, resulting in decreased cell performance and durability. To study the effects of H2S on the performance [...] Read more.
When the fuel supplied to a high-temperature proton exchange membrane fuel cell (HT-PEMFC) is produced by hydrocarbon formation, hydrogen sulfide (H2S) may appear, resulting in decreased cell performance and durability. To study the effects of H2S on the performance and durability of the HT-PEMFC, a series of experiments was conducted. In the first step, the effects of polyvinylidene fluoride (PVDF) and platinum loading on cell performance were investigated and discussed under pure hydrogen operation conditions. Optimal PVDF and platinum compositions in the catalyst layer are suggested. Then, the effect of H2S on membrane electrode assembly (MEA) performance with various platinum loadings was investigated by supplying hydrogen containing 5.2 ppm of H2S to the anode of the MEA. An electrochemical impedance spectroscope was employed to measure the impedance of the MEAs under various operating conditions. Finally, degradation of the MEA when supplied with hydrogen containing 5.2 ppm of H2S was analyzed and discussed. The results suggest that the performance of an MEA with 0.7 mg Pt cm−2 and 10% PVDF can be recovered by supplying pure hydrogen. The rate of voltage decrease is around 300 μV h−1 in the presence of H2S. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessFeature PaperArticle Optimization and Tunability of 2D Graphene and 1D Carbon Nanotube Electrocatalysts Structure for PEM Fuel Cells
Catalysts 2018, 8(9), 377; https://doi.org/10.3390/catal8090377
Received: 3 August 2018 / Revised: 21 August 2018 / Accepted: 25 August 2018 / Published: 5 September 2018
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Abstract
In this work, N-doped Multi-Walled Carbon Nanotubes (MWCNTs) and Few Graphene Layers (FGLs) have been functionalized with platinum nanoparticles using two methods starting with hexachloroplatinic acid as precursor: (i) ethylene glycol (EG) reduction and (ii) impregnation followed by reduction in hydrogen atmosphere. Morphological [...] Read more.
In this work, N-doped Multi-Walled Carbon Nanotubes (MWCNTs) and Few Graphene Layers (FGLs) have been functionalized with platinum nanoparticles using two methods starting with hexachloroplatinic acid as precursor: (i) ethylene glycol (EG) reduction and (ii) impregnation followed by reduction in hydrogen atmosphere. Morphological scanning transmission electron microscopy (STEM) analyses showed a homogenous dispersion of metal particles with narrow-size distribution onto both carbon supports (Pt/C loadings between 30 wt % and 40 wt %). Electrocatalytic properties of the as-synthetized catalysts toward the Oxygen Reduction Reaction (ORR) was evaluated in aqueous electrolyte using a three electrodes electrochemical cell by cyclic voltammetry (CV) in rotating disk electrode (RDE). It is shown that a mixture of Pt supported on MWCNT and FGLs allows to enhance both the electrochemical surface area and the activity of the catalyst layer. Ageing tests performed on that optimized active layer showed higher stability than conventional Pt/C. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessArticle Assessing the Potential of Co-Pt Bronze for Electrocatalysis in Acidic Media
Catalysts 2018, 8(7), 258; https://doi.org/10.3390/catal8070258
Received: 6 June 2018 / Revised: 20 June 2018 / Accepted: 21 June 2018 / Published: 25 June 2018
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Abstract
An electron-conducting mixed oxide, Co-Pt bronze was synthesized and examined as a candidate for a highly durable electrocatalyst for both the polymer electrolyte fuel cells and electrolyzers. The motivation of this study comes from the fact that this material has not been studied [...] Read more.
An electron-conducting mixed oxide, Co-Pt bronze was synthesized and examined as a candidate for a highly durable electrocatalyst for both the polymer electrolyte fuel cells and electrolyzers. The motivation of this study comes from the fact that this material has not been studied as an electrocatalyst in acidic media, although past studies showed a high electronic conductivity and a high corrosion resistance. Co-Pt bronze without metallic Pt was obtained by solid-state synthesis and hot aqua regia rinsing. The OER activity was found to be among the highest as a material without Ir and Ru in acidic media, and it showed extremely high electrochemical stability in the OER potential range. Its oxygen reduction reaction (ORR) was obtained after potential cycles down to the hydrogen region, which formed a thin Pt metallic layer over the oxide. While its specific activity was not more than that of pure platinum nanoparticles, its durability against the potential cycles was much higher. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Open AccessArticle MgO-Templated Mesoporous Carbon as a Catalyst Support for Polymer Electrolyte Fuel Cells
Catalysts 2018, 8(6), 230; https://doi.org/10.3390/catal8060230
Received: 5 April 2018 / Revised: 28 May 2018 / Accepted: 29 May 2018 / Published: 1 June 2018
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Abstract
An MgO-templated mesoporous carbon, CNovel®, was employed as a catalyst support for the cathode of polymer electrolyte fuel cells (PEFCs) after modifying its dimensional, crystalline, surface and porous structures and the electrochemical oxygen reduction reaction (ORR) activities were examined by the [...] Read more.
An MgO-templated mesoporous carbon, CNovel®, was employed as a catalyst support for the cathode of polymer electrolyte fuel cells (PEFCs) after modifying its dimensional, crystalline, surface and porous structures and the electrochemical oxygen reduction reaction (ORR) activities were examined by the thin-film rotating disk electrode (RDE) method and as well as the membrane electrode assembly (MEA) method. Although the catalytic activity of Pt on CNovel® was comparable with that on a non-porous carbon, Vulcan®, in the RDE configuration without Nafion®, Pt/CNovel showed a considerably higher activity than Pt/Vulcan in the MEA condition with Nafion®. The mechanism inducing this difference was discussed from the results of electrochemical surface area and sulfonic coverage measurements which suggested that Pt particles on inside pores of CNovel® are not covered with Nafion® ionomer while protons can still reach those Pt particles through water network. The MEA performance in the middle and high current-density regions was drastically improved by heat-treatment in air, which modified the pore structure to through-pored ones. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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Review

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Open AccessReview Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers
Catalysts 2018, 8(12), 657; https://doi.org/10.3390/catal8120657
Received: 31 October 2018 / Revised: 30 November 2018 / Accepted: 1 December 2018 / Published: 13 December 2018
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Abstract
In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis [...] Read more.
In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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