Auxiliary Electrolysis Cell
Small-Scale PEM Electrolysis Cell for Local O2/H2
The auxiliary electrolysis cell is a 15 kg proton-exchange membrane unit that provides localized, on-demand oxygen and hydrogen for habitat life-support backup and gas reserve replenishment. Operating at 500 W, the device uses a Nafion 117 membrane with a platinum cathode and iridium oxide anode to generate 0.5 kg of oxygen and 0.06 kg of hydrogen per day at 1 to 5 bar. Its low power requirement supports intermittent operation during power-constrained lunar night cycles, delivering oxygen directly to life-support architecture independently of main fuel-cell reactant storage across a 50,000-hour mean time between failures.
Small-scale PEM electrolyzer providing on-demand O2 (and H2) for local non-RFC needs (life support backup, gas reserve refill).
Purpose
Small-scale PEM electrolyzer providing on-demand O2 (and H2) for local non-RFC needs (life support backup, gas reserve refill).
Context
Child of L2-WTR-ELEC in L1-WTR water processing chain
Principles
- ▸PEM electrolyzer chemistry (see L3-ESS-FC-ELEC for details)
- ▸Smaller scale (~500 W) vs L3-ESS-FC-ELEC (~15 kW)
- ▸Lower-pressure output (1-5 bar) for direct life-support use
- ▸Modular cell stack replaceable via L1-MNT
- ▸Pt cathode catalyst with reduced Ir anode for lifetime
Typical implementations
- ▸NASA OGS (Oxygen Generation System) on ISS
- ▸Industrial PEM electrolyzers (Proton OnSite/Nel Hydrogen)
- ▸Submarine OBOGS small-scale electrolyzers (heritage)
Lunar considerations
- ▸Backup O2 source independent of L2-ESS-FC reactant tanks
- ▸Lower power consumption suits intermittent operation
- ▸Output piped to L1-WMS gas storage and/or L1-HAB ATMO
Specifications
Functional
| primary function | Small-scale PEM electrolyzer providing on-demand O2 (and H2) for local non-RFC needs (life support backup, gas reserve refill). |
| o2 production kg per day | 0.5 |
| h2 production kg per day | 0.06 |
Physical
| mass kg | 15 |
| materials | Nafion 117 PEM, Pt cathode, Ir oxide anode, Ti BPP |
| vacuum compatibility | True |
Operational
| power consumption w | 500 |
| thermal range c | -40, 70 |
| lifetime years | 15 |
| mtbf hours | 50000 |
Interfaces
Provides
- O2 to atmosphere/storage
- H2 to reactant inventory
Requires
- DI water input
- Electrolysis power (~500 W)
Cite this entry
Lunar Ark Codex. "Auxiliary Electrolysis Cell" (L3-WTR-ELEC-CELL). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-WTR-ELEC-CELL
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.