Electrolysis in space environments presents unique challenges due to the absence of gravity, which affects fluid dynamics, gas separation, and thermal management. Adapting this technology for zero-gravity conditions is critical for sustained human presence in space, particularly for oxygen generation and hydrogen production in lunar and Martian missions. Key focus areas include bubble management, electrolyte containment, and electrode design, all of which must be re-engineered to function effectively in microgravity.

Bubble management is a primary concern in space-based electrolysis. On Earth, buoyancy forces naturally separate gas bubbles from the electrolyte, but in microgravity, bubbles remain suspended, accumulating at electrode surfaces and reducing efficiency. The International Space Station (ISS) has conducted experiments demonstrating that bubble coalescence can lead to large gas pockets, obstructing ion transport and increasing ohmic resistance. To mitigate this, researchers have explored pulsed voltage application, which periodically disrupts bubble adhesion. Another approach involves structured electrodes with microchannels or porous materials to guide bubble movement. For instance, experiments with mesh electrodes showed improved gas release by leveraging surface tension effects. Future systems may incorporate centrifugal forces in rotating electrolysis cells to simulate gravity-induced bubble separation, particularly for lunar and Mars missions where partial gravity exists.

Electrolyte containment is another critical challenge. In microgravity, liquids do not settle at the bottom of a container, leading to unpredictable fluid behavior. Traditional electrolysis cells rely on gravity to maintain electrolyte contact with electrodes, but in space, capillary forces and wetting properties dominate. The ISS has tested membrane-based electrolysis cells, where ion-exchange membranes confine the electrolyte while allowing gas diffusion. These membranes prevent electrolyte drift and ensure consistent electrode wetting. Additionally, hydrophobic coatings on gas diffusion layers help direct gas bubbles away from the electrolyte. For long-duration missions, passive systems are preferred to minimize moving parts. Electrolyte circulation via electroosmotic pumps or capillary-driven flows has been explored to maintain homogeneity without mechanical agitation.

Electrode design must also adapt to zero-gravity conditions. Conventional flat-plate electrodes suffer from reduced active surface area due to bubble coverage. Three-dimensional electrodes, such as felts or foams, increase surface area and improve gas evacuation. The ISS experiments with nickel-based porous electrodes demonstrated higher efficiency compared to planar designs. Another innovation involves electrocatalysts with hydrophobic and hydrophilic regions to direct bubbles toward collection zones. For lunar and Martian applications, electrode materials must withstand dust contamination and temperature fluctuations. Platinum-group metals remain effective but are costly; alternatives like nickel-iron alloys are being tested for durability in extraterrestrial conditions.

Thermal management is intrinsically linked to electrolysis performance in space. Without convection, heat accumulates unevenly, potentially damaging components. ISS experiments revealed that localized hot spots form near electrodes, necessitating active cooling or advanced heat-spreading materials. Future systems may integrate phase-change materials or heat pipes to dissipate thermal energy efficiently.

Future lunar and Mars missions will require scalable electrolysis systems for in-situ resource utilization (ISRU). On the Moon, water ice electrolysis could provide oxygen and hydrogen for life support and propulsion. Mars missions face additional challenges due to lower gravity and dust storms, which may clog electrolysis systems. Modular designs with redundant components will be essential for reliability.

Lessons from ISS experiments highlight the need for robust, maintenance-free systems. For example, the Oxygen Generation Assembly (OGA) on the ISS uses a solid polymer electrolyte, reducing reliance on free liquid electrolytes. Future advancements may focus on self-cleaning electrodes and automated bubble removal mechanisms.

In summary, space-based electrolysis demands rethinking traditional approaches. Bubble management requires active or passive separation techniques, electrolyte containment relies on membranes and capillary forces, and electrode design must maximize surface area while facilitating gas removal. Thermal regulation and material durability are equally critical for long-term operation. As humanity ventures beyond Earth, adapting electrolysis for zero-gravity environments will be pivotal for sustainable exploration.