Two-Dimensional Layer {P 4 Mo 6 } Clusters Constructed with N-Ligands for Bifunctional Properties of Proton Conduction and Supercapacitors

Proton exchange membrane fuel cells (PEMFCs) are developing into very meaningful clean energy to fundamentally address environmental pollution. Among which the most studied Nafion series membranes are limited under large-scale use, and some strong oxidizing groups such as hydrogen peroxide will attack the structure of Nafion, shortening the lifespan of PEMFCs. Therefore, it is crucial to develop a proton-conductive material with strong stability and broad application. In this study, a novel hourglass-type P 4 Mo 6 -based POMOFs denoted as (H 2 timb) 2 [Mn 3 (H 3 P 4 Mo 6 O 31 ) 2 ]·4H 2 O was synthesized using 1,3,5-tri(1 H -imidazole-1-yl)benzene (timb) as a ligand. It was found that CUST-577 exhibited an excellent proton conductivity of 8.9 × 10 –3 S cm –1 at 80 °C and 98% RH (relative humidity), proving that CUST-577 was conducted by protons. In addition, CUST-577 also had a greater H 2 O 2 decomposition ability, thereby improving the longevity of fuel cells. In a three-electrode system, CUST-577 displayed a specific capacitance (Cs) value of 308 F g –1 at a current density of 0.15 A g –1, with a capacitance retention of 88.3% after 2000 cycles. Since the proton-conductive electrolyte can deliver protons for the redox reaction of various pseudocapacitor (PC) electrode materials, CUST-577 may be a promising polyacid-based proton conductor material and PC electrode material.