Low-temperature CO₂ electrolysis explored for long-term Mars resource self-sufficiency
image: It presents a cyclical and integrated approach that connects four key pillars: low-temperature technology, experimental validation, computer simulations, and commercial viability. Each pillar contributes to the development and deployment of ECO2R technologies, providing a feasible alternative for ISRU in outer space.
Credit: Paulina Govea-Alvarez, Zhiyuan Chen, Deepak Pant, Kevin M. Van Geem, Yi Ouyang
A review published in Engineering outlines the technical framework and extraterrestrial application prospects of electrochemical CO₂ reduction (ECO2R), positioning low-temperature electrolysis as a viable supplementary in-situ resource utilization (ISRU) pathway for upcoming Mars missions, while benchmarking its performance against established high-temperature electrolysis systems.
The paper, authored by a cross-institutional research team from Ghent University and Flemish Institute for Technological Research, systematically compares mainstream CO₂ electrolysis technologies, including solid-oxide electrolyzer cells (SOECs), proton-exchange membrane fuel cells, anion-exchange membrane fuel cells, and molten-salt fuel cells. Unlike SOECs operating at 600 to 1000 °C, ECO2R runs within a mild temperature window of 25–80 °C, matching competitive Faradaic efficiency metrics while demonstrating improved long-term material stability and broader product diversity beyond carbon monoxide and oxygen generated by solid-oxide electrolysis. The analysis highlights gas diffusion electrodes (GDEs) as a core structural component mitigating CO₂ mass transport limits, forming a gas–liquid–solid three-phase boundary that facilitates sustained high current densities required for scaled operation. The review details how catalyst material selection dictates reaction selectivity: Silver and gold catalysts favor CO production; tin, indium, and lead primarily yield formate; and copper enables C–C coupling to generate multi-carbon fuels and oxygenates, though copper catalysts carry inherent selectivity trade-offs requiring further optimization.
The work integrates computational fluid dynamics (CFD) and machine learning as complementary tools to streamline ECO2R development, establishing a bidirectional feedback loop between numerical simulation and physical experimentation. Multiphase flow, interphase mass transfer, porous electrode, and surface reaction models jointly resolve complex transport phenomena inside GDE reactors, while machine learning accelerates catalyst screening by processing material geometric, electronic, and configurational datasets to predict reaction performance. These modeling approaches address experimental barriers unique to space environments, such as altered bubble detachment behavior under microgravity and low Martian atmospheric pressure, which lowers molar CO₂ concentration despite the planet’s 96% CO₂ atmospheric composition.
The review contrasts ECO2R with NASA’s MOXIE, a SOEC-based ISRU device trialed on Mars’ Perseverance rover. MOXIE relies on 800 °C operation with ceramic components, suffering from thermal cycling-induced material degradation and high preheating energy consumption, while low-temperature ECO2R avoids intensive thermal management and polymer-based cell construction supports lighter, compact hardware suited for autonomous deep-space deployment. The paper frames a phased Mars ISRU roadmap integrating ECO2R alongside reverse water–gas shift and water electrolysis, covering near-term atmospheric CO₂ capture, mid-term combined fuel and oxygen co-production, and far-term closed-loop self-sustaining habitat systems independent of Earth resupply.
Distinct design criteria separate terrestrial and space-facing ECO2R hardware: Earth systems prioritize cost and scalability, while space electrolyzers must tolerate cosmic radiation, extreme thermal swings, vacuum, and microgravity, with closed-loop water recovery and capillary-assisted phase separation replacing gravity-driven product separation. The review notes remaining technical gaps, including electrolyte freezing risks under Martian frigid conditions and CO₂ crossover across anion-exchange membranes, and calls for integrated research spanning catalyst engineering, reactor architecture, and multiphysics modeling to advance ECO2R to higher technology readiness levels for crewed Mars expeditions.
The paper “Integrating Electrochemical CO2 Reduction Technology for Smart, Sustainable, and Stable in-Situ Resource Utilization for Outer-Space Applications,” is authored by Paulina Govea-Alvarez, Zhiyuan Chen, Deepak Pant, Kevin M. Van Geem, Yi Ouyang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.12.010. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.