The first to discover the principle of fuel cells was the Englishman Sir William Grove (1811~1896), a lawyer and amateur science enthusiast. In an accidental electrolysis experiment in 1839 [Fig. 1(a)], it was observed that when two electrodes in an electrolyzer were connected together [Fig. 1(b)], a current flowed in the opposite direction, consuming both hydrogen and oxygen. . He called the device a “gas battery.” The gas cell consisted of a hydrogen-oxygen test tube with a Pt electrode immersed in dilute sulfuric acid. The device produced about 1V.
The first practical fuel cell was developed by chemical engineer Francis Bacon at the University of Cambridge in England in 1950, an alkaline fuel cell. In the 1960s, the American IFC (International Fuel Cell) company built a fuel cell device for the Apollo moon landing spacecraft to provide electricity and drinking water for astronauts. The fuel cell can continuously provide 1.5kW of electricity. Its reliability is quite high, it has worked for more than 10,000 hours, and has completed 18 missions without any problems. With the development of fuel cells today, the technology has made great progress. (click here to open for more battery knowledge)
- Classification of fuel cells
Fuel cells can be divided into many types. According to different reaction temperatures, they can be divided into three types: low temperature, medium temperature and high temperature. According to different electrolyte types, they can be divided into alkaline fuel cells (AFC), proton exchange membrane fuel cells (PEMFC), phosphates Fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), their structures, properties and application directions are shown in Table 1.
①Alkaline fuel cell (AFC) has an operating temperature of about 80°C and has been widely used on spacecraft and submarines, and is also being tested on some minivans.
②The working temperature of solid polymer fuel cell (SPFC, also known as proton exchange membrane fuel cell PEMFC) is 60~130℃. The proton exchange membrane used is a solid polymer material with excellent proton (hydrogen ion) Conductivity. Now the most commonly used product is DuPont’s Nafion. Nafion was originally used in the chlor-alkali industry and was later used in proton exchange membrane fuel cells.
The catalyst is mainly Pt, and a Pt/Ru alloy catalyst must be used when the reformed gas is used as the fuel. Due to the high price of these catalysts, in order to save costs, these catalysts are now mostly coated on special activated carbon, and the by-product is called Pt/C or Pt-Ru/C. This electrolyte membrane is extremely thin, so it has higher power/ The weight-to-weight ratio, combined with low operating temperatures and short start-up times, make this fuel cell suitable for transportation vehicles. Such fuel cells have great potential for cost reduction and can be expected to be commercialized within 5 to 10 years.
③ Phosphate fuel cell (PAFC), the energy conversion efficiency is approximately 40%, and the working temperature is about 200 ℃. They are suitable for commercial and light industrial use. Systems of 200 kW are currently commercially available, and pilot plants of 1.3 MW in Italy and 11 MW in Japan have been established, but their cost is still high (about 2500 EUR/kW).
④ Molten Carbonate Fuel Cell (MCFC), with an efficiency of approximately 55%, the operating temperature is around 650 ℃, and it can provide heat and electricity at the same time. There are still some technical issues that have not been resolved, such as corrosion and reliability. It may take 5-10 years before commercialization. A 2MW system has been established and is undergoing verification tests, but reliability is still an issue.
⑤Solid oxide fuel cell (SOFC), the efficiency is relatively high, and the working temperature is between 700 and 1000 °C. A 100kW plant has been established in the Netherlands. Raw materials and costs still need to be studied. It is expected to be commercialized in about 10 years. Proton exchange membrane fuel cell (PEMFC) has the characteristics of low operating temperature, high power density, fast start-up, long service life and simple structure, so it has developed rapidly. It is predicted that the proton exchange membrane fuel cell (PEMFC) may be the earliest commercialized fuel cell after the phosphate fuel cell (PAFC).
Read more: A 100-year review of automotive development