This letter, from the archives of the Ri, details the world's first fuel cell. William Robert Grove successfully converted chemical energy stored in the bonds of hydrogen into electrical energy.
Though it would take over a century for his work to lead to a commecially viable fuel cell, this was a pivotal moment in the history of science.
The full letter transcript
William Robert Grove to Faraday 22 October 1842
My dear Sir I have just completed a curious voltaic pile which I think you would like to see, it is composed of alternate tubes of oxygen & hydrogen through each of which passes platina foil so as to dip into separate vessels of water acidulated with sulphuric acid the liquid just touching the extremities of the foil as in the rough figure below.
The platina is platinized so as to expose by capillary attraction a greater surface of liquid to the gas, with 60 of these altenations I get an unpleasant shock & decompose not only iodide of potassium but water so plainly that a continuous stream of fine bubbles ascends from each electrode. Thus water is decomposed by its composition - no oxidable metal is employed. I have reserved the tubes & tried all the counter experiments bur the phenomena are too marked I think to render any mistakes possible. Mr Gassiot was with me today & saw the experiments. Can you spare me an hour next week on Tuesday if it suits you or any day except Wednesday at any hour from 11 to 3 - at the Laboratory or the London Institution. l cannot but regard the experiment as an important one both as to the chemical & other theories of the pile & as to the catalytic effect of the combination of the gases by platina.
I remain my dear Sir
yours very sincerely