Reaction interface engineering enables gravity-independent electrolysis.

Abstract

Electrochemical gas evolution reactions are essential for oxygen and fuel production in space in situ resource utilization (ISRU), yet their performance is fundamentally limited by gravity-dependent bubble removal. Under reduced-gravity conditions, suppressed buoyancy results in prolonged bubble residence, increased electrode coverage, and unstable electrochemical performance. Here, we demonstrate an alternative strategy that eliminates the dependence of electrolysis on gravity by fundamentally separating the gas and liquid phases. Direct visualization of gas diffusion electrodes reveals that maintaining a stable liquid-gas interface is highly sensitive to pressure fluctuations and surface wettability, making complete suppression of bubble evolution difficult through conventional electrode engineering alone. Guided by these observations, a dual-membrane single-electrolyte (DMSE) electrolyzer is investigated, in which a shared central electrolyte supplies the ionic pathway for two membrane electrode assemblies (MEAs), while gaseous products are generated directly into separate gas channels without entering the liquid electrolyte. Compared with a conventional water electrolyzer, the DMSE architecture completely eliminates bubble-induced voltage fluctuations and significantly improves electrochemical stability. Frequency-domain and statistical analyses confirm the absence of bubble-induced transients during operation. Although the present DMSE electrolyzer requires approximately 500 mV higher working potential than the conventional configuration at -100 mA cm-2, electrochemical analysis shows that this additional overpotential arises predominantly from incomplete electrode utilization (more than 100 times less electrochemical active area) rather than the DMSE cell architecture itself, indicating substantial scope for further performance optimization. The proposed DMSE demonstrates a feasible approach toward gravity-independent electrolysis. Further optimization of ionic transport in the catalyst layer is expected to improve its performance and facilitate its application in future ISRU systems.

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