Molybdenum-functionalized metal-organic framework crystals interconnected by carbon nanotubes as negative electrodes for supercapacitors

As the pseudocapacitive material operated in the negative potential window in an aqueous electrolyte, the molybdenum-functionalized MOF-808-CNT nanocomposite can obviously outperform both the molybdenum-functionalized MOF-808 and molybdenum-functionalized CNT. Crystals of a water-stable Zr-based metal-organic framework (MOF), MOF-808, are directly grown on the surface of carboxylic acid-functionalized carbon nanotubes (CNT) to synthesize the nanocomposites with tunable MOF-to-CNT ratios. The crystallinity, morphology, porosity, and electrical conductivity of all nanocomposites are characterized. To install the electrochemically active sites within the highly porous MOF framework, the obtained MOF-808-CNT nanocomposites are further subjected to the functionalization of spatially dispersed Mo(VI) sites by a self-limiting process followed by the electrochemical reduction to generate the molybdenum nanoparticles confined within the MOF pore. Thin films of these Mo-functionalized materials are served as the pseudocapacitive materials in aqueous electrolytes and operated in a negative potential window. By utilizing the electrochemically active molybdenum confined within the highly porous MOF and the electronic conduction between MOF crystals facilitated by CNT, the optimal Mo-functionalized nanocomposite can significantly outperform both the Mo-functionalized MOF and Mo-functionalized CNT.

Automated summary

By growing water-stable MOF-808 crystals directly on the surface of CNT and further functionalizing with confined molybdenum nanoparticles, the MOF-808-CNT nanocomposite shows excellent pseudocapacitive performance in a negative potential window.