Ce (III)-terephthalic acid metal-organic frameworks as highly efficient ·OH radical scavengers for fuel cells and investigation of its antioxidation mechanism

Herein, in order to relieve the chemical degradation of perfluorosulfonic acid (PFSA) membranes without decreasing their proton conductivity, Ce (III)-terephthalic acid metal-organic frameworks (Ce-TPA MOFs) with efficient ·OH radical scavenging efficiency are designed via coordinating the organic antioxidant ligand (TPA) with inorganic radical scavenger (Ce ions). Ce-TPA MOFs with a different weight ratio of 0.5, 1.0, or 2.0% was introduced in PFSA matrix to produce composite membranes. On the one hand, the hydrophilic groups of Ce-TPA MOFs caused better water absorption, which promoted the proton conduction to some extent. Also, the presence of the redox Ce3+/Ce4+ couple, oxygen vacancy, and TPA molecules in Ce-TPA MOFs scavenging ·OH radical together via synergy effect. The optimum peak power density of the PFSA/Ce-TPA1.0 composite membrane at 75 °C under 80% relative humidity was 1086 mW/cm that of pristine PFSA membrane was only 1032 mW/cm. Furthermore, PFSA/Ce-TPA1.0 composite membrane experienced the decay of only 0.31 mV/h during 96 h operation under the same conditions, whereas that of pristine PFSA membrane was 2.20 mV/h. Thus, the PFSA/Ce-TPA membrane was a potential candidate for proton exchange membrane fuel cells.