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NCERT tells you that a hydrogen-oxygen fuel cell powered the Apollo space programme. The idea is far older. In 1842 a Welsh barrister named William Grove ran water-splitting in reverse and got electricity out of hydrogen and oxygen. This post covers who he was, what his paper actually reports, a worked example built on his own observation, common mistakes, and what you can take from his way of working.
Who was William Grove?
The Dictionary of Welsh Biography gives his birth as 11 July 1811 in Swansea. He graduated from Brasenose College, Oxford, in 1832, was called to the Bar in 1835 and joined the Royal Institution the same year. He held the chair of experimental philosophy at the London Institution from 1840 to 1847, received the Royal Society's medal in 1847, served as a judge from 1871 to 1887 and was knighted in 1872. He died in London on 1 August 1896. The Royal Society's record shows his election as a Fellow on 26 November 1840.
APS News notes that he is also known for the Grove cell, a strong zinc-platinum battery that early telegraph lines relied on, and that science historians generally treat his gas battery as the first true fuel cell.
How did the idea start?
In February 1839 Grove published On voltaic series and the combination of gases by platinum in the Philosophical Magazine. Looking back in his 1842 paper, he says a galvanometer was "permanently deflected" when connected to two strips of platinum covered by tubes of oxygen and hydrogen. He had ended that note with a hope: "I hope, by repeating this experiment in series, to effect decomposition of water by means of its composition."
He admits he thought it unlikely. Three years later he tried it.
What did the 1842 gas battery do?
His paper On a Gaseous Voltaic Battery, dated December 1842, describes 50 pairs of tubes, one of oxygen and one of hydrogen in each pair, each holding a strip of platinised platinum foil about a quarter of an inch wide, dipping into dilute sulphuric acid. He reported that:
a shock could be felt by five people joining hands;
a bright spark, visible in daylight, jumped between charcoal points;
potassium iodide, hydrochloric acid and acidified water were decomposed, and 26 pairs were the fewest that would split water;
with air in every tube nothing happened, and swapping the gases reversed the current.
He also spotted the main engineering problem. The reaction could only happen at the line where liquid, gas and platinum met. That is why he used platinised foil, which spreads the liquid in a thin film over a larger surface. Modern cells solve the same problem: NCERT's cell bubbles the gases through porous carbon electrodes with finely divided platinum or palladium as catalysts.
Worked example: why hydrogen disappeared twice as fast
Grove's assistant noticed that "the hydrogen was absorbed twice as fast as the oxygen". You can predict that.
In acid, the half-reactions are:
Anode: H₂ → 2H⁺ + 2e⁻
Cathode: O₂ + 4H⁺ + 4e⁻ → 2H₂O
Overall: 2H₂ + O₂ → 2H₂O
For every 4 electrons, 2 mol of H₂ and 1 mol of O₂ are used. At the same temperature and pressure, equal moles of gas take equal volumes, so the volume ratio is 2 : 1.
Now put numbers on it. Sample numbers: one cell gives 10 mA for 1 hour.
Q = It = 0.010 × 3,600 = 36 C.
Moles of electrons = 36 / 96,485 = 3.73 × 10⁻⁴ mol.
H₂ = 3.73 × 10⁻⁴ / 2 = 1.87 × 10⁻⁴ mol. O₂ = 3.73 × 10⁻⁴ / 4 = 9.33 × 10⁻⁵ mol.
Taking 22.7 L/mol at 273.15 K and 1 bar, that is about 4.2 mL of hydrogen and 2.1 mL of oxygen.
Grove expected the same bookkeeping in reverse: the gas made at the electrodes of the water he split should equal the gas used up in his battery.
What mistakes do students make with fuel cells?
Using n = 2 for oxygen. Each O₂ takes 4 electrons; each H₂ gives 2.
Mixing acid and alkaline equations. Grove's cell was acidic. NCERT's cell uses concentrated NaOH, so its half-reactions have OH⁻, though the overall reaction is the same.
Using molar volume without stating conditions. Say which value you use and why.
Calling the fuel cell a battery that stores charge. It runs only while fuel is supplied.
The JEE (Main) 2026 syllabus lists fuel cells in its electrochemistry unit, and the reactions are in NCERT Class 12 Chemistry Unit 2. Check your own year's syllabus. For the efficiency calculation using ΔG = −nFE, see our batteries and fuel cells guide.
If the link between charge and moles still feels loose, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer.
What can a student take from Grove's way of working?
Write your hopes down, then go back. His 1839 note told him what to try in 1842.
Run the boring controls. Air in every tube, swapped gases, nitrogen with hydrogen: each one ruled out a false explanation.
Ask what the theory really says. Of the contact theory of the battery he asked: "Where is the contact in this experiment, if not everywhere?" He used the result to argue the current came from chemistry.
Next step: work out the volume of oxygen used when the same cell gives 50 mA for 30 minutes.
