Investigation of non-precious metal cathode catalysts for direct borohydride fuel cells

Borohydride crossover in anion exchange membrane (AEM) based direct borohydride fuel cells (DBFCs) impairs their performance and induces cathode catalyst poisoning. This study evaluates three non-precious metal catalysts, namely LaMn_0.5Co_0.5O₃ (LMCO) perovskite, MnCo₂O₄ (MCS) spinel, and Fe-N-C, for their application as cathode catalysts in DBFCs. The rotating disk electrode (RDE) testing shows significant borohydride tolerance of MCS. Moreover, MCS has exhibited exceptional stability in accelerated durability tests (ADTs), with a minimal reduction of 10 mV in half-wave potential. DFT calculations further reveal that these catalysts predominantly adsorb over , unlike commercial Pt/C which preferentially adsorbs . In DBFCs, MCS can deliver a peak power density of 1.5 W cm^-2, and a 3% voltage loss after a 5 hours durability test. In contrast, LMCO and Fe-N-C have exhibited significantly lower peak power density and stability. The analysis of the TEM, XRD, and XPS results before and after the single-cell stability tests suggests that the diminished stability of LMCO and Fe-N-C catalysts is due to catalyst detachment from carbon supports, resulting from the nanoparticle aggregation during the high-temperature preparation process. Such findings suggest that MCS can effectively mitigate the fuel crossover challenge inherent in DBFCs, thus enhancing its viability for practical application.