Fuel Cells and Hydrogen

From Fundamentals to Applied Research

Viktor Hacker, Shigenori Mitsushima

• Publisher: Elsevier
• Year: 2018
• Print ISBN: 9780128114599
• eBook ISBN: 9780128115374
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria chimica e biochimica

Fuel Cells and Hydrogen: From Fundamentals to Applied Research provides an overview of the basic principles of fuel cell and hydrogen technology, which subsequently allows the reader to delve more deeply into applied research. In addition to covering the basic principles of fuel cells and hydrogen technologies, the book examines the principles and methods to develop and test fuel cells, the evaluation of the performance and lifetime of fuel cells and the concepts of hydrogen production.Fuel Cells and Hydrogen: From Fundamentals to Applied Research acts as an invaluable reference book for fuel cell developers and students, researchers in industry entering the area of fuel cells and lecturers teaching fuel cells and hydrogen technology.- Includes laboratory methods for fuel cell characterization and manufacture- Outlines approaches in modelling components, cells and stacks- Covers practical and theoretical methods for hydrogen production and storage

Chapter 1

Introduction

Shigenori Mitsushima^⁎; Bernhard Gollas^†; Viktor Hacker^{‡ ⁎} Yokohama National University, Graduate School of Engineering Science, Institute of Advanced Sciences, Yokohama, Japan
^† Graz University of Technology, Institute for Chemistry and Technology of Materials, Graz, Austria
^‡ Graz University of Technology, Institute of Chemical Engineering and Environmental Technology, Graz, Austria

Abstract

This chapter provides a comprehensive introduction to the topic of electrochemical systems and fuel cells. The chapter covers the basic principles of the different types of fuel cells and compares them with other electrochemical systems, such as batteries and capacitors.

A major part of this chapter deals with the theoretical and practical efficiencies of fuel cells, considering the different applications such as combined heat and power systems for residential houses or mobile applications.

Keywords

Electrochemical systems; Fuel cells; Energy conversion efficiency

Chapter Outline

• 1.1 Electrochemical Systems and Fuel Cells
• 1.2 Types of Fuel Cells and Their Applications
• 1.3 Thermodynamics
  • 1.3.1 Energy Conversion Efficiency of Fuel Cells
  • 1.3.2 Electrochemical and Thermal Energy Conversion Efficiency
  • 1.3.3 Ideal Reversible Fuel Cell Efficiencies
• 1.4 Recapitulation
• 1.5 Comprehension Questions and Exercises
• References

1.1 Electrochemical Systems and Fuel Cells

Electricity is undoubtedly the most versatile energy carrier. Electrochemical systems, such as fuel cells, have a simple structure, and take fuel as an input and produce electrical energy as the output. Fuel cells consist of two electrodes, an electrolyte, a separator, and an external electrical circuit. Each component of the electrochemical system fulfills specific tasks. The electrodes are electronically conductive and have a large electroactive surface area. The electrolyte is an electrical insulator, but has high ionic conductivity. Such ions are typically positively (cation) or negatively (anion) charged atoms, or molecules, that represent the mobile species in electrochemical reactions.

Although the set-up of such an electrochemical system looks rather simple, the electrochemical reactions at the interface between the electrodes and the electrolyte are often complex.

One of the two electrodes is called an “anode.” The anode is the negative electrode of the system, where the reactant (fuel) is oxidized. During the electrochemical reaction, electrons are released from the reactant and are utilized in an external load. The oxidized (anode) reactant, i.e. cations, are transported away from the anode through the electrolyte to the second electrode called “cathode” due to the potential gradient (migration) and the concentration gradient (diffusion). The cathode is the positive electrode in the electrochemical system, where the oxidant is reduced. The electrons required for this reduction are supplied from the external circuit and originate from the charge separation at the anode. During its reduction at the cathode the oxidant reacts with the cations from the anode and forms the respective product. The separator ensures separation of the anode and cathode reactants to avoid direct chemical reaction and further prevent a direct electronic contact between the anode and cathode.

Typically, hydrogen is the anode reactant, or fuel; whereas oxygen is the cathode reactant or oxidant. The corresponding product of the reaction of hydrogen and oxygen is water. In order to enable an electrochemical reaction, the electrolyte must be ionically conductive. In Fig. 1.1, a schematic drawing of a hydrogen-oxygen electrochemical system with a proton conductive electrolyte is shown. Such a system is generally known as a fuel cell – more specifically as an acidic fuel cell, because acids are typically used as proton conductive electrolytes.

Fig. 1.1 Schematic drawing of a fuel cell with proton conductive electrolyte.

Electrochemical and total reactions are as follows:

$\text{Anode}:{\mathrm{H}}_2\to 2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}$

(1.1)

$\text{Cathode}:2{\mathrm{H}}^{+}+\frac{1}{2}{\mathrm{O}}^2+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2\mathrm{O}$

(1.2)

$\text{Total}:{\mathrm{H}}_2+\frac{1}{2}{\mathrm{O}}_2\to {\mathrm{H}}_2\mathrm{O}$

(1.3)

Hydrogen (H₂) is supplied to the fuel cell, where it is oxidized, forming cations (H₃O⁺, hydrated proton...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Nomenclature
• Chapter 1: Introduction
• Chapter 2: Irreversible Losses in Fuel Cells
• Chapter 3: Modeling of Polymer Electrolyte Fuel Cells
• Chapter 4: Polymer Electrolyte Fuel Cells
• Chapter 5: Other Polymer Electrolyte Fuel Cells
• Chapter 6: Preparation of MEA
• Chapter 7: Degradation Mechanisms and Their Lifetime
• Chapter 8: Characterization Methods for Components and Materials
• Chapter 9: Electrochemical Measurement Methods and Characterization on the Cell Level
• Chapter 10: Hydrogen Production
• Chapter 11: Role of Hydrogen Energy Carriers
• Chapter 12: Environmental Impact Factors Associated with Hydrogen Energy
• Index