Two electrode plates sit in a water-based electrolyte. Applying a voltage above roughly 1.23 V (the thermodynamic minimum for splitting water) drives current through the ions dissolved in the electrolyte: at the cathode, water molecules gain electrons and hydrogen gas nucleates as bubbles; at the anode, water loses electrons and oxygen gas forms, at half the rate. Ion concentration sets how much current the electrolyte can carry, and temperature speeds up both ion mobility and molecular jitter.
current density ∝ conc · exp(k·(V − 1.23V)) · (1 + 0.02·(T−25))
gas rate ∝ current density (Faraday's law)
cell efficiency = 1.48V / V_applied (thermoneutral / applied)
- Applied voltage — pushes current across the cell; higher voltage makes gas faster but wastes more energy as heat above the 1.23 V minimum.
- Electrolyte concentration — how many ions carry charge between the plates; a weak electrolyte limits current no matter the voltage.
- Temperature — warmer electrolyte has faster, more mobile ions and molecules, nudging current and gas rate up.
- Ion field — toggle the visible drift of charged particles moving under the applied field.
Real-world relevance: this electrode-scale view is what happens inside every real PEM or alkaline electrolyzer used to produce green hydrogen — the same cell run in reverse, with hydrogen and oxygen recombining across a membrane, is a hydrogen fuel cell.