Fuel cell (FC) and electrolyser (EC) systems are a vital and space proven technology supporting the upcoming expansion of human presence into the solar system. In particular, unitized regenerative FCs pose an elegant energy storage solution. They are a robust power system benefiting from the high energy density of hydrogen while they can also be operated in reverse to electrolyse water potentially derived from in situ resource utilization (ISRU) processes creating fuel on demand. While these properties are very promising, the technology needs to be adapted in order to endure harmful constituents in ISRU derived resources. For example, in the case of lunar ISRU, large amounts of H2S, NH3, SO2 and CH3OH were spectroscopically detected alongside water in an ejecta plume originating from an impact into a permanently shadowed crater. All these chemicals are well-known catalyst poisons causing a premature system degradation and failure. Notably H2S and SO2 are problematic, since conventional FCs require essentially sulphur-free feed gases with a sulphur compound limit of only a few ppb. On earth, these impurities are removed by complex, energy intensive purification methods before the fuel is in a usable condition, yet in the extreme environment of a lunar outpost less complex and costly solutions will be essential. The objective of this project on ISRU-proof unitized regenerative fuel cells is to study and improve the FC/EC resistance against ISRU-derived catalyst poisons. The output from this study will provide the exploration community with fundamental insight into the interaction between ISRU process output and FC/EC stack technology. Such a comprehensive understanding is critical in successfully developing robust energy systems for lunar but also Martian exploration. This project is a collaboration between the ICTM and the Institute of Chemical Engineering and Environmental Technology and carried out in the context of an ESA Contract under a programme of and funded by the European Space Agency.