ABSTRACT
Cell (PEMFC) ....................................................118 9.2.6.5 Phosphoric Acid Fuel Cell (PAFC) ....................119 9.2.6.6 Direct Methanol Fuel Cell (DMFC) ...................119 9.3 Hydrogen Storage Technology ..................................................... 120 9.3.1 Introduction to the Problem ............................................. 120
9.3.2 Safety of Hydrogen .......................................................... 121 9.4 Hydrogen Storage of Carbon Nanofibers .................................... 122 9.5 Different Applications of CNFs in Fuel Cells .............................. 130 9.5.1 The Carbon Nanofiber Hydrogen Fuel Tank .................... 130 9.5.2 Carbon Nanofibers for Electrode and Catalyst
Support in Fuel Cells ........................................................ 132 9.6 Carbon Nanofibers in Direct Methanol Fuel Cells ...................... 134 9.6.1 Introduction to Direct Methanol Fuel Cells ..................... 134 9.6.2 Commonly Used Catalyst Carbon Supports .................... 136 9.6.3 CNT and CNF-Based Catalyst Supports .......................... 137 9.6.3.1 Significance of CNTs and CNFs ....................... 137 9.6.3.2 Carbon Nanotubes (CNTs) ................................ 138 9.6.3.3 Carbon Nanofibers (CNFs) ............................... 140 9.6.4 Challenges to Nanocatalysts in DMFCs .......................... 141 9.6.4.1 Control of Particle Size ..................................... 141 9.6.4.2 Distribution of Catalyst Nanoparticles .............. 142 9.6.4.3 Fabrication of DMFC Electrode ........................ 142 9.7 Conclusions and Prospects ........................................................... 143 Appendix ............................................................................................... 144 A. Diagram of fuel cells invention history ......................................... 144 B. (a) Schematic representation of the structure of a
carbon nanofiber; (b) enlarged section .......................................... 145 C. Schematic operation of (a) Solid Oxide fuel cells (SOFC)
and (b) Proton Exchange Membrane fuel cells (PEM) ................. 145 D. Useful Fuel Cell Equations ............................................................ 146 D1. Equations of Oxygen and Air Usage .................................. 146 D2. Equations of Air Exit Flow Rate ........................................ 148 D3. Equations of Hydrogen Usage ............................................ 148 D4. Equations of Water Production ........................................... 150 D5. Equations of Heat Produced ............................................... 151 Keywords .............................................................................................. 151 References ............................................................................................. 152
9.1 INTRODUCTION TO HYDROGEN STORAGE AND FUEL CELL SYSTEMS
Fuel cells are an electrochemical energy conversion technology to directly convert the chemical energy of fuels, such as hydrogen, methanol and natural gas, to electrical energy, which was invented by Sir William Grove [1]. They inherently have a significantly higher efficiency than that of conventional energy conversion technologies, such as an internal combustion engine (ICE). Fuel cells are considered to be the most efficient and least polluting power-creating technology and are a potential and practical candidate to moderate the fast increase in power requirements and to minimize the impact of the increased power consumption on the environment.
