ABSTRACT
From an automotive manufacturer point of view, proton exchange membrane fuel cells (PEMFCs) have evolved, over the past couple of decades, from a laboratory experiment to one of the most probable successors to the internal combustion engine. High efficiency, modularity, and local zero emission of green house gases are only some of the advantages of this technology. On the downside, cost, durability targets, and the deployment of a hydrogen distribution infrastructure remain challenges to be addressed in order for the fuel cell electric vehicle to make it into mass production. This chapter first reviews PEMFC developments and achievements in the automotive industry in general and at PSA Peugeot Citroën in particular, over the past decades. Through two very different examples, namely the design of next generations bipolar plates and fuel cell state of
health monitoring for control purposes, it then highlights the need for thorough physical understanding of phenomena governing fuel cell performance. 1.1 A Brief History of PEMFC for the
The first fuel cell, or “gas battery” as it was labeled at the time, is due to William Grove and dates back from 1843. It was then largely considered as an interesting experiment without much potential for practical use. Indeed, it took a little over a century before it was first tested in a vehicle. 1.1.1 Early Prototypes: 1960-000
Fuel cells first came out of the laboratory to power a vehicle in October 1959. The experimental tractor by Allis-Chalmers featured a 1008-cell alkaline fuel cell stack, fed by propane, which supplied power to a 20 horsepower DC motor. Following this early prototype, the first significant attempt to use a hydrogen fuel cell for vehicle traction, dates back from 1966 and is due to General Motors. The converted GMC Handivan then called the Electrovan, packed a 32 kW alkaline fuel cell, with a peak power of 160 kW. Weighing 3.2 metric tons, the original six-seater was left with only the front seats once 32 fuel cell modules, 170 m of piping and 2 cryogenic tanks were fitted in. It had, nevertheless, a top speed of 110 km/h and a range of 240 km. Fuel cells for road transportation were then forgotten for over 20 years due to high costs and security concerns. However successful they were in space, alkaline fuel cell were indeed less suited for automotive transportation, mainly due to the use of a liquid and highly corrosive electrolyte, and high sensitivity to CO2poisoning. This technology, thus, never was a serious contender to the internal combustion engine. During the same period, two major technological break throughs paved the way toward modern PEMFC. In 1955, General Electric chemist Willard Grubb developed a first sulfonated polystyrene ion-exchange membrane. This solid acid polymer, which serves as the electrolyte in PEMFC, combines a unique set of physical and chemical properties within a few tens of microns. It ensures proton
conductivity between anode and cathode while providing electrical insulation. Protons are able to cross the membrane only if attached to water molecules, as shown by the basic schematic of Fig. 1.1. Hydrogen
Figure 1.1 Basic description of proton conduction within a polymer membrane. Three years after Grubb’s invention, co-worker Leonard Niedrach devised a way of depositing platinum onto this membrane.1 It, thus, became possible to easily create a large number of electrocatalytic sites at the boundary between active layers and membrane: the so called “triple contact points”. At these locations, gas molecules, proton-conducting membrane, electron conducting GDL and catalyst come into contact as shown in Fig. 1.2. Thanks to both these inventions, which would be constantly improved over the next decades, mass production of large active area power dense MEA could be envisioned. Further major milestones on the road to the first PEMFC-powered car include • the invention of Nafion in the late 1960s by Walther Grot of DuPont, boosting performance and durability, • the development of a thin-film electrode production process using catalyst nanoparticles at the Los Alamos National
Laboratory in the mid 1980s, which reduced the amount of Platinum needed by a factor of more than 20,
• the development of efficient designs by Geoffrey Ballard and his team in the late 1980s, which led to power outputs of several tens of kilowatts from stacks that would soon fit into buses and then cars.
