Given the recent focus on fuel cells, the assumption might be that they are a recent technology. But, in fact, efforts to develop an efficient fuel cell go back to the mid-nineteenth century (see Fuel Cell Origins: 1840-1890). During the 1880s, Edison, who was always on the lookout for new and efficient ways to produce electricity, became one in a long line of inventors to contribute to the development of fuel-cell technology.
Unlike primary and secondary batteries, in which the electrodes themselves are consumed in chemical reactions, a fuel cell operates by the replenishment of an oxidizable fuel, such as hydrogen or carbon, to produce free electrons. In the case of carbon, this could be done directly by the reaction of coal with other substances, such as nitrates, or by the creation of an ionized gas.
In 1882, Edison first began working on a system to convert coal directly into electricity. His first patent application for this process Edison and Early Fuel Cell Technology (U.S. Patent 460,122) was filed in May of that year. In this design, Edison sought to generate a current by efficiently oxidizing a carbon electrode by means of an active oxidizing agent, such as a fusible metal, in a heated iron vessel. Over the next two years, Edison focused on what was in essence early fuel-cell technology. His research led him to predict in an 1885 essay reprinted in the Scientific American that a "marvelous revolution" from the cheap electricity produced by the direct conversion of coal into electricity was in the offing.
Edison filed two additional applications for direct conversion employing fuel cells in 1883. The first, in September (U.S. Pat. 435,688), covered a process for producing an ionized gas from either a metal or carbon in reaction with an oxidizable substance. He employed a vacuum chamber to maintain the gas in a rarefied state and to prevent reaction with atmospheric oxygen. The second application, filed in November (U.S. Pat. 490,953), described an improvement over his 1882 design.
Edison's most intensive experimental work on fuel cells occurred in the summer of 1884. He experimented with using a finely divided metal and a peroxide (usually manganese) in a solution of sulphuric acid to catalyze the oxidation of the carbon. By the end of that summer, he had "obtained a very strong current" using anthracite coal, and he planned to show his system at the Philadelphia Electrical Exhibition in the fall. This system, however, proved to be too dangerous after "all the windows were blown out of his laboratory." In an interview he gave about this time, Edison gave himself “five years to work at it, and shall think myself lucky if I succeed in that time." Although Edison conducted periodic experiments over the next few years, he had largely abandoned these experiments by early 1888.