How a fuel cell differs from a battery
A battery stores its chemicals inside and runs down as they are used. A fuel cell is supplied with fuel, usually hydrogen, and an oxidizer, usually oxygen from the air, and keeps producing electricity as long as both keep flowing in. Rather than burning hydrogen, it combines it with oxygen electrochemically, making electricity, heat and water.
Water splitting and Grove
The idea builds on an observation made right after the voltaic pile appeared in 1800: William Nicholson and Anthony Carlisle used current to split water into hydrogen and oxygen. A natural question was whether the process could run in reverse.
In 1839 the Welsh scientist and lawyer William Grove built what he called a gas voltaic battery. It used platinum electrodes dipped in dilute sulfuric acid, with one end exposed to hydrogen and the other to oxygen, and it produced a small current. Grove later linked several cells in series. The German chemist Christian Friedrich Schönbein was investigating the same effect at nearly the same time, and the two exchanged letters about it. Credit for the principle is usually given to Grove, with Schönbein recognized as a contemporary.
These cells produced very little power, and platinum was costly. Gas batteries were a scientific curiosity.
A name and a long wait
In 1889, Ludwig Mond and Charles Langer built a gas battery meant to run on coal-derived gas, and they are generally credited with introducing the term fuel cell. They struggled with poor output and electrode problems. Around the same time, the steam engine and then the internal combustion engine were improving fast, and for general power, burning fuel was simply cheaper and more reliable than any cell.
Bacon and the alkaline cell
Progress picked up in the twentieth century. The British engineer Francis Thomas Bacon began working on hydrogen-oxygen cells in the 1930s, replacing acid with an alkaline potassium hydroxide electrolyte and using porous nickel electrodes instead of platinum. After wartime interruptions, he developed larger units, and in 1959 a roughly five-kilowatt cell stack was demonstrated powering equipment such as a welding machine. Exact figures vary by account, so treat details as approximate.
Spacecraft use
Fuel cells found their first major use where weight mattered and cost mattered less. NASA’s Gemini spacecraft, beginning in the mid-1960s, used fuel cells with solid polymer membranes developed by General Electric. The Apollo missions used alkaline fuel cells, whose design drew on Bacon’s work, and they supplied both electricity and drinking water for crews. On longer flights, they were lighter than batteries of equal capacity would have been.
Other kinds of fuel cell
Researchers developed several types. Phosphoric acid cells became early stationary power units. Molten carbonate and solid oxide cells operate at high temperatures and can use fuels beyond hydrogen. Proton exchange membrane cells, the type descended from the Gemini design, run at lower temperatures and later became the leading candidate for vehicles.
Hydrogen as a fuel
Hydrogen is attractive because its use produces only water at the point of use, but it is not an energy source in itself, since it has to be produced first. Most hydrogen today is made from natural gas, a process that emits carbon dioxide. It can also be made by electrolysis using electricity from wind turbines or solar panels, which is more expensive. Storing it also takes pressurized tanks, cryogenic liquid or chemical carriers, because it is very light. The same element is needed to make synthetic fertilizer, which is why large-scale hydrogen production already exists for industry.
Where things stand
Demonstration fuel cell cars and buses have been built since the 1990s, and fuel cells have been used for backup power and forklifts. But infrastructure, cost and competition from batteries have kept adoption limited, and experts disagree about how large a role hydrogen will have in the future. The history suggests that the technology works well in specific niches, and whether it spreads further depends on economics as much as engineering.