MOXIE: Mars Oxygen ISRU Electrolysis

Electrolysis Stack

Cell voltage 1.30 V

Stack size (cells) 10

CO₂ inlet flow 4.0 slm

Stack temperature 800 °C

Live Readouts

Warming up stack…

O₂ output

0.0 g/hr

Stack current

0.0 A

Power draw

0.0 W

CO₂ conversion

0.0 %

How it works

MOXIE (Mars Oxygen ISRU Experiment, flown on Perseverance) proved that CO₂ from the Martian atmosphere (95.3% CO₂ at ~0.6 kPa) can be split into breathable/propellant O₂ using solid-oxide electrolysis, a technology this simulator models directly:

Cathode:  2 CO2 + 4 e-  →  2 CO + 2 O2-
Anode:    2 O2-         →  O2 + 4 e-
Net:      2 CO2         →  2 CO + O2

Each electrolysis cell needs a driving voltage above the Nernst potential V_N (≈1.0 V for this reaction at ~800 °C). The excess drives current through the cell's area-specific resistance (ASR), which falls as the ceramic electrolyte gets hotter:

ASR(T) ≈ ASR0 · exp[Ea/R · (1/T − 1/T0)]
I = n_cells · (V − V_N) / ASR(T)     (Ohmic model)

Faraday's law then converts stack current directly into oxygen mass flow — 4 electrons move per O₂ molecule produced:

ṁ(O2) = η_F · I · M_O2 / (4 · F) × 3600   [g/hr]
F = 96 485 C/mol,  M_O2 = 32 g/mol

Cell voltage — raise it past V_N to push more current (and more O₂), at the cost of more power and lower Faradaic efficiency η_F as side reactions grow.
Stack size — cells in series add their voltage requirement but each contributes O₂; MOXIE flew a 10-cell stack.
CO₂ inlet flow — caps the reaction: production can never exceed the CO₂ actually being fed in, so a small stack starved of CO₂ tops out early (shown as conversion approaching 100%).
Temperature — higher T lowers ASR (more current per volt) but real MOXIE ran ~750–800 °C to protect the ceramic membrane; efficiency in this model also drifts with T.

The 3D view shows orange CO₂ molecules flowing into the stack and cyan O₂ molecules flowing out, at a rate scaled to the live current — a stalled/underpowered stack visibly stops producing.

CO₂ inlet O₂ outlet CO byproduct

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