Nanocrystals of a zirconium-based metal-organic framework (MOF), UiO-66, are grown on the surface of the carboxylic acid-functionalized multi-walled carbon nanotubes (CNT) at room temperature to synthesize the UiO-66-CNT nanocomposites with tunable MOF-to-CNT ratios. The porosity, crystallinity, morphology, and electrical conductivity of the nanocomposite are characterized. Spatially dispersed iridium sites are thereafter installed on the defect sites presented within the entire UiO-66 crystals in these nanocomposites by a self-limiting solution-phase approach. The resulting Ir-functionalized UiO-66, CNT, and UiO-66-CNT nanocomposites are served as the electrocatalysts for water oxidation in acidic aqueous solutions. By utilizing the redox-hopping pathways to transport electrons within the Ir-functionalized MOF crystals as well as the electronic conduction between MOF crystals provided by CNT, the nanocomposite with the optimal MOF-to-CNT ratio can outperform both the Ir-functionalized UiO-66 and CNT. Electrochemical impedance spectroscopy (EIS) is utilized to probe the reaction kinetics occurring on the decorated iridium sites and the transporting behaviors of electrons/ions within these catalytic thin films. For the first time, the electrocatalytic kinetics and the transporting limitations within the MOF-based thin film can be decoupled with the help of EIS technique. Post-electrocatalysis characterizations of the nanocomposite after water oxidation are also performed.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry