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Electrocatalysts for Fuel Cells and Hydrogen Production

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A5: Hydrogen Energy".

Deadline for manuscript submissions: closed (20 June 2021) | Viewed by 43081

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Special Issue Editors

Dr. Francesco Vizza

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Guest Editor

Institute of Chemistry of Organometallic Compounds (ICCOM), Italian National Research Council (CNR), Rome, Italy
Interests: hydrogen; fuel cells; organometallics; catalysis; electrocatalysis
Special Issues, Collections and Topics in MDPI journals

Dr. Hamish Andrew Miller

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Guest Editor

Institute of Chemistry of Organometallic Compounds (ICCOM), Italian National Research Council (CNR), Rome, Italy
Interests: fuel cells; energy; hydrogen; catalysis; electrocatalysis
Special Issues, Collections and Topics in MDPI journals

Dr. Marco Bellini

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Guest Editor

Institute of Chemistry of Organometallic Compounds (ICCOM), Italian National Research Council (CNR), Rome, Italy
Interests: fuel cells; energy; hydrogen; catalysis; electrocatalysis

Special Issue Information

Dear Colleagues,

The development of an alternative sustainable energy economy is now unavoidable as the progressive and rapid depletion of the world’s reserves of fossil fuels combined with increasing energy demands start to take its toll on our planet. The combined effects of pollution and climate change caused by global warming exacerbate these issues. The result is an urgent need to develop a future world economy based on carbon-free and renewable resources. In this context, hydrogen (H₂), thanks to its high specific energy density and clean combustion to water, is a high-quality energy carrier and an ideal candidate to replace fossil fuels. To favor the worldwide utilization of hydrogen energy, the development of low-cost and sustainable energy conversion technologies, in particular electrolyzers and fuel cells, is required. Currently, low efficiency and high investment costs limit the diffusion of these electrochemical technologies. The search for sustainable, stable, and active electrocatalysts play a key role in reaching the performance required for these devices and thus facilitating their large-scale deployment.

Research work submitted to this Special Issue should be centered on providing key insights in achieving highly active, stable, and sustainable electrocatalysts for fuel cells and electrolytic hydrogen production. Such understanding will provide stimulus and boost future research to bring a hydrogen-based energy economy closer to realization. We, therefore, invite papers on innovative technical developments (new materials), reviews, studies on performance and stability, and papers from different disciplines, which are relevant to electrocatalysis for fuel cells and hydrogen production.

Dr. Francesco Vizza
Dr. Hamish Andrew Miller
Dr. Marco Bellini
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

fuel cells
hydrogen production
renewable energy
electrocatalysis
oxygen reduction and evolution
hydrogen oxidation and evolution
alcohol and small molecule electro-oxidation
noble metals
non-noble metals
acidic
neutral or alkaline media

Published Papers (13 papers)

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Research

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12 pages, 1922 KiB

Open AccessArticle

Integration of Portable Sedimentary Microbial Fuel Cells in Autonomous Underwater Vehicles

by Giulia Massaglia, Adriano Sacco, Alain Favetto, Luciano Scaltrito, Sergio Ferrero, Roberto Mo, Candido F. Pirri and Marzia Quaglio

Energies 2021, 14(15), 4551; https://doi.org/10.3390/en14154551 - 28 Jul 2021

Cited by 6 | Viewed by 1777

Abstract

In the present work, sedimentary microbial fuel cells (s-MFC) have been proposed as effective tools to power remote sensors in different aquatic environments, thanks to their ability to produce renewable and sustainable energy continuously and autonomously. The present work proposes the optimization of cylindrical sedimentary microbial fuel cells (s-MFC) as a compact and cost-effective system suitable to be integrated as a payload in an Autonomous Underwater Vehicle (AUV). To this purpose, a new AUV payload, named MFC-payload, is designed to host the cylindrical s-MFC and a data acquisition system to collect and store information on the voltage produced by the cell. Its overall performance was evaluated during two field measurement campaigns carried out in the Mediterranean Sea. This investigation demonstrates the power production by s-MFC during operation of the AUV in seawater and analyzes the actual influence of environmental conditions on the output power. This study demonstrates that energy production by s-MFCs integrated in AUV systems is decoupled by the navigation of the autonomous vehicle itself, showing the effectiveness of the application of MFC-based technology as a power payload for environmental analysis. All these latter results demonstrate and confirm the ability of the devices to continuously produce electricity during different AUV operation modes (i.e., depth and speed), while changing environmental conditions (i.e., pressure, temperature and oxygen content) demonstrate that cylindrical s-MFC devices are robust system that can be successfully used in underwater applications. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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15 pages, 4267 KiB

Open AccessArticle

Photoelectrochemical Hydrogen Production by Screen-Printed Copper Oxide Electrodes

by Angela Gondolini, Nicola Sangiorgi, Alex Sangiorgi and Alessandra Sanson

Energies 2021, 14(10), 2942; https://doi.org/10.3390/en14102942 - 19 May 2021

Cited by 7 | Viewed by 1955

Abstract

In this work, copper oxides-based photocathodes for photoelectrochemical cells (PEC) were produced for the first time by screen printing. A total 7 × 10⁻³ g/m² glycerine trioleate was found as optimum deflocculant amount to assure stable and homogeneous inks, based on CuO nano-powder. The inks were formulated considering different binder amounts and deposited producing films with homogenous thickness, microstructure, and roughness. The as-produced films were thermally treated to obtain Cu₂O- and Cu₂O/CuO-based electrodes. The increased porosity obtained by adding higher amounts of binder in the ink positively affected the electron transfer from the surface of the electrode to the electrolyte, thus increasing the corresponding photocurrent values. Moreover, the Cu₂O/CuO system showed a higher charge carrier and photocurrent density than the Cu₂O-based one. The mixed Cu₂O/CuO films allowed the most significant hydrogen production, especially in slightly acid reaction conditions. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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18 pages, 1266 KiB

Open AccessArticle

The Effect of Fuel Cell and Battery Size on Efficiency and Cell Lifetime for an L7e Fuel Cell Hybrid Vehicle

by Tom Fletcher and Kambiz Ebrahimi

Energies 2020, 13(22), 5889; https://doi.org/10.3390/en13225889 - 11 Nov 2020

Cited by 23 | Viewed by 4534

Abstract

The size of the fuel cell and battery of a Fuel Cell Hybrid Electric Vehicle (FCHEV) will heavily affect the overall performance of the vehicle, its fuel economy, driveability, and the rates of fuel cell degradation observed. An undersized fuel cell may experience accelerated ageing of the fuel cell membrane and catalyst due to excessive heat and transient loading. This work describes a multi-objective design exploration exercise of fuel cell size and battery capacity comparing hydrogen fuel consumption, fuel cell lifetime, vehicle mass and running cost. For each system design considered, an individually optimised Energy Management Strategy (EMS) has been generated using Stochastic Dynamic Programming (SDP) in order to prevent bias to the results due to the control strategy. It has been found that the objectives of fuel efficiency, lifetime and running cost are largely complimentary, but degradation and running costs are much more sensitive to design changes than fuel efficiency and therefore should be included in any optimisation. Additionally, due to the expense of the fuel cell, combined with the dominating effect of start/stop cycling degradation, the optimal design from an overall running cost perspective is slightly downsized from one which is optimised purely for high efficiency. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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13 pages, 6808 KiB

Open AccessArticle

Optimisation Study of Co Deposition on Chars from MAP of Waste Tyres as Green Electrodes in ORR for Alkaline Fuel Cells

by Maurizio Passaponti, Leonardo Lari, Marco Bonechi, Francesca Bruni, Walter Giurlani, Gabriele Sciortino, Luca Rosi, Lorenzo Fabbri, Martina Vizza, Vlado K. Lazarov, Claudio Fontanesi and Massimo Innocenti

Energies 2020, 13(21), 5646; https://doi.org/10.3390/en13215646 - 28 Oct 2020

Cited by 14 | Viewed by 2186

Abstract

Oxygen Reduction Reaction (ORR) catalysts, from waste automobile tyres obtained from Microwave assisted pyrolysis (MAP), were enriched with Co and Cu using the simple treatments sonochemical and electrochemical deposition. Catalytic activity was evaluated through onset potential and number of exchanged electrons measurements. Electrochemical data demonstrate an improvement in catalytic activity of the electrochemical modified char with Co. Char electrodes enriched with Co show a maximum positive shift of 40 mV with respect to raw char electrodes with a number of exchanged electrons per O₂ molecule close to 4 (as for Pt) for the best sample. This corresponds to a reduction of the production of unwanted oxygen peroxide from 23% for raw char to 1%. Sample structure evolution before and after electrochemical deposition and electro-catalysis was investigated by scanning transmission electron microscopy and XPS. Such electrochemical treatments open new possibilities of refining waste chars and finding an economic alternative to noble metals-based catalysts for alkaline fuel cells. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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18 pages, 24247 KiB

Open AccessArticle

Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

by Matteo Savastano, Maurizio Passaponti, Walter Giurlani, Leonardo Lari, Antonio Bianchi and Massimo Innocenti

Energies 2020, 13(21), 5539; https://doi.org/10.3390/en13215539 - 22 Oct 2020

Cited by 9 | Viewed by 1801

Abstract

Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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14 pages, 6656 KiB

Open AccessArticle

Thin Solid Film Electrolyte and Its Impact on Electrode Polarization in Solid Oxide Fuel Cells Studied by Three-Dimensional Microstructure-Scale Numerical Simulation

by Tomasz A. Prokop, Grzegorz Brus, Shinji Kimijima and Janusz S. Szmyd

Energies 2020, 13(19), 5127; https://doi.org/10.3390/en13195127 - 01 Oct 2020

Cited by 5 | Viewed by 1603

Abstract

In this work, a three-dimensional microstructure-scale model of a Solid Oxide Fuel Cell’s Positive-Electrolyte-Negative assembly is applied for the purpose of investigating the impact of decreasing the electrolyte thickness on the magnitude, and the composition of electrochemical losses generated within the cell. Focused-Ion-Beam Scanning Electron Microscopy reconstructions are used to construct a computational domain, in which charge transport equations are solved. Butler–Volmer model is used to compute local reaction rates, and empirical relationships are used to obtain local conductivities. The results point towards three-dimensional nature of transport phenomena in thin electrolytes, and electrode-electrolyte interfaces. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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16 pages, 1231 KiB

Open AccessArticle

Multiscale Modeling for Reversible Solid Oxide Cell Operation

by Fiammetta Rita Bianchi, Arianna Baldinelli, Linda Barelli, Giovanni Cinti, Emilio Audasso and Barbara Bosio

Energies 2020, 13(19), 5058; https://doi.org/10.3390/en13195058 - 25 Sep 2020

Cited by 18 | Viewed by 3482

Abstract

Solid Oxide Cells (SOCs) can work efficiently in reversible operation, allowing the energy storage as hydrogen in power to gas application and providing requested electricity in gas to power application. They can easily switch from fuel cell to electrolyzer mode in order to guarantee the production of electricity, heat or directly hydrogen as fuel depending on energy demand and utilization. The proposed modeling is able to calculate effectively SOC performance in both operating modes, basing on the same electrochemical equations and system parameters, just setting the current density direction. The identified kinetic core is implemented in different simulation tools as a function of the scale under study. When the analysis mainly focuses on the kinetics affecting the global performance of small-sized single cells, a 0D code written in Fortran and then executed in Aspen Plus is used. When larger-scale single or stacked cells are considered and local maps of the main physicochemical properties on the cell plane are of interest, a detailed in-home 2D Fortran code is carried out. The presented modeling is validated on experimental data collected on laboratory SOCs of different scales and electrode materials, showing a good agreement between calculated and measured values and so confirming its applicability for multiscale approach studies. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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14 pages, 9124 KiB

Open AccessArticle

Mayenite Electrides and Their Doped Forms for Oxygen Reduction Reaction in Solid Oxide Fuel Cells

by Navaratnarajah Kuganathan, Ruslan V. Vovk and Alexander Chroneos

Energies 2020, 13(18), 4978; https://doi.org/10.3390/en13184978 - 22 Sep 2020

Viewed by 2280

Abstract

The oxygen reduction reaction is an important reaction at the cathode in solid oxide fuel cells. Materials that exhibit high chemical and mechanical stability, high ionic and electronic conductivity, and are non-toxic are of great interest as cathodes for the reduction of oxygen. Here, we use density functional theory simulations to examine the efficacy of 12CaO·7Al₂O₃ and 12SrO·7Al₂O₃ electrides and their doped forms for the conversion of O₂ gas to form O²⁻ in their nanocages via encapsulation. Calculations show that encapsulation is exoergic in the un-doped electrides, and the formation of O²⁻ is confirmed by the charge analysis. A stronger encapsulation is noted for C12A7 electride than the S12A7 electride. The C12A7 electride doped with B or Ga also exhibits exoergic encapsulation, but its encapsulation energy is slightly lower than that calculated for the un-doped C12A7 electride. There is an enhancement in the encapsulation for the S12A7 electride doped with B compared to its un-doped form. Doping of Ga in S12A7 electride exhibits only a very small change in the encapsulation with respect to its un-doped form. The present results can be of interest in the design of cathode material for solid oxide fuel cells. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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14 pages, 1690 KiB

Open AccessArticle

Faraday’s Efficiency Modeling of a Proton Exchange Membrane Electrolyzer Based on Experimental Data

by Burin Yodwong, Damien Guilbert, Matheepot Phattanasak, Wattana Kaewmanee, Melika Hinaje and Gianpaolo Vitale

Energies 2020, 13(18), 4792; https://doi.org/10.3390/en13184792 - 14 Sep 2020

Cited by 36 | Viewed by 7276

Abstract

In electrolyzers, Faraday’s efficiency is a relevant parameter to assess the amount of hydrogen generated according to the input energy and energy efficiency. Faraday’s efficiency expresses the faradaic losses due to the gas crossover current. The thickness of the membrane and operating conditions (i.e., temperature, gas pressure) may affect the Faraday’s efficiency. The developed models in the literature are mainly focused on alkaline electrolyzers and based on the current and temperature change. However, the modeling of the effect of gas pressure on Faraday’s efficiency remains a major concern. In proton exchange membrane (PEM) electrolyzers, the thickness of the used membranes is very thin, enabling decreasing ohmic losses and the membrane to operate at high pressure because of its high mechanical resistance. Nowadays, high-pressure hydrogen production is mandatory to make its storage easier and to avoid the use of an external compressor. However, when increasing the hydrogen pressure, the hydrogen crossover currents rise, particularly at low current densities. Therefore, faradaic losses due to the hydrogen crossover increase. In this article, experiments are performed on a commercial PEM electrolyzer to investigate Faraday’s efficiency based on the current and hydrogen pressure change. The obtained results have allowed modeling the effects of Faraday’s efficiency by a simple empirical model valid for the studied PEM electrolyzer stack. The comparison between the experiments and the model shows very good accuracy in replicating Faraday’s efficiency. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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17 pages, 3156 KiB

Open AccessArticle

High Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) Activity Rh_xS_y Catalyst Synthesized with Na₂S for Hydrogen-Bromine Fuel Cell

by Yuanchao Li and Trung Van Nguyen

Energies 2020, 13(15), 3971; https://doi.org/10.3390/en13153971 - 02 Aug 2020

Cited by 2 | Viewed by 2669

Abstract

A Rh_xS_y/C catalyst with high mass-specific electrochemical surface area (ECSA/mass), high hydrogen oxidation reaction (HOR)/hydrogen evolution reaction (HER) activity, and high Nafion^® ionomer-affinity was synthesized and evaluated. A new sulfur source, Na₂S instead of (NH₄)₂S₂O₃, was applied to prepare the rhodium sulfide precursor Rh₂S₃ that resulted in a Rh_xS_y catalyst with higher HOR/HER catalytic activity after thermal treatment. The higher activity was attributed to the higher quantity formation of the more active phase Rh₃S_4, in addition to the other active Rh₁₇S₁₅ phase, in the Rh_xS_y catalyst. Using this new sulfur source, carbon substrate functionalization, and the mass-transfer-controlled nanoparticle growth process, the average particle size of this catalyst was reduced from 13.5 nm to 3.2 nm, and its ECSA/mass was increased from 9.3 m²/g-Rh to 43.0 m²/g-Rh. Finally, by applying the Baeyer–Villiger and ester hydrolysis process to convert the Nafion^® ionomer-unfriendly ketone group on the carbon support surface to the Nafion ionomer-friendly carboxylic group, which increases the Nafion^® affinity of this catalyst, its use in the hydrogen electrode of an H₂-Br₂ fuel cell resulted in a performance that is 2.5× higher than that of the fuel cell with a commercial Rh_xS_y catalyst. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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15 pages, 1498 KiB

Open AccessArticle

CO₂ Electrochemical Reduction by Exohedral N-Pyridine Decorated Metal-Free Carbon Nanotubes

by Giulia Tuci, Jonathan Filippi, Andrea Rossin, Lapo Luconi, Cuong Pham-Huu, Dmitry Yakhvarov, Francesco Vizza and Giuliano Giambastiani

Energies 2020, 13(11), 2703; https://doi.org/10.3390/en13112703 - 28 May 2020

Cited by 9 | Viewed by 2988

Abstract

Electrochemical CO₂ reduction reaction (CO₂RR) to fuels and chemicals represents nowadays one of the most challenging solutions for renewable energy storage and utilization. Among the possible reaction pathways, CO₂-to-CO conversion is the first (2e⁻) reduction step towards the production of a key-feedstock that holds great relevance for chemical industry. In this report we describe the electrocatalytic CO₂-to-CO reduction by a series of tailored N-decorated carbon nanotubes to be employed as chemoselective metal-free electrocatalysts. The choice of an exohedral functionalization tool for the introduction of defined N-groups at the outer surface of carbon nanomaterials warrants a unique control on N-configuration and electronic charge density distribution at the dangling heterocycles. A comparative electrochemical screening of variably N-substituted carbon nanomaterials in CO₂RR together with an analysis of the electronic charge density distribution at each heterocycle have suggested the existence of a coherent descriptor for the catalyst’s CO faradaic efficiency (FE_CO). Evidence allows to infer that N-configuration (N-pyridinic vs. N-pyrrolic) of exohedral dopants and electronic charge density distribution at the N-neighboring carbon atoms of each heterocycle are directly engaged in the activation and stabilization of CO₂ and its reduction intermediates. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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21 pages, 5132 KiB

Open AccessArticle

Platinum and Platinum Group Metal-Free Catalysts for Anion Exchange Membrane Fuel Cells

by Van Men Truong, Julian Richard Tolchard, Jørgen Svendby, Maidhily Manikandan, Hamish A. Miller, Svein Sunde, Hsiharng Yang, Dario R. Dekel and Alejandro Oyarce Barnett

Energies 2020, 13(3), 582; https://doi.org/10.3390/en13030582 - 27 Jan 2020

Cited by 53 | Viewed by 5133

Abstract

The development of active hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts for use in anion exchange membrane fuel cells (AEMFCs), which are free from platinum group metals (PGMs), is expected to bring this technology one step closer to commercial applications. This paper reports our recent progress developing HOR Pt-free and PGM-free catalysts (Pd/CeO₂ and NiCo/C, respectively), and ORR PGM-free Co₃O₄ for AEMFCs. The catalysts were prepared by different synthesis techniques and characterized by both physical-chemical and electrochemical methods. A hydrothermally synthesized Co₃O₄ + C composite ORR catalyst used in combination with Pt/C as HOR catalyst shows good H₂/O₂ AEMFC performance (peak power density of ~388 mW cm⁻²), while the same catalyst coupled with our flame spray pyrolysis synthesised Pd/CeO₂ anode catalysts reaches peak power densities of ~309 mW cm⁻². Changing the anode to nanostructured NiCo/C catalyst, the performance is significantly reduced. This study confirms previous conclusions, that is indeed possible to develop high performing AEMFCs free from Pt; however, the challenge to achieve completely PGM-free AEMFCs still remains. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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Review

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17 pages, 3558 KiB

Open AccessReview

Iron Phthalocyanine/Graphene Composites as Promising Electrocatalysts for the Oxygen Reduction Reaction

by Jong S. Park and Dong Wook Chang

Energies 2020, 13(16), 4073; https://doi.org/10.3390/en13164073 - 06 Aug 2020

Cited by 16 | Viewed by 4062

Abstract

Recently, the development of non-precious electrocatalysts for the oxygen reduction reaction (ORR) has become important in replacing currently employed platinum (Pt)-based catalysts. Although Pt-based catalysts exhibit satisfactory ORR performances, their high price, easy methanol/CO₂ poisoning, and poor long-term stability significantly hamper the forward movement of fuel cell technology. Among the various candidates, graphene-supported iron phthalocyanine (FePc) composites have attracted great attention because of their unique advantages, including low cost, good dimensional stability, high durability, and tunable catalytic activity. In the composite catalyst, FePc molecules are immobilized on graphene via noncovalent or covalent interactions. In addition, two-dimensional graphene substrates can improve not only the electrical conductivity of the composite, but also the dispersion of FePc molecules, triggering a significant improvement in the catalytic properties of the composite catalyst. Herein, we summarize the recent advances in FePc/graphene composite catalysts used for the ORR. Moreover, we discuss the challenges and future perspectives of this promising field. Full article

(This article belongs to the Special Issue Electrocatalysts for Fuel Cells and Hydrogen Production)

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