Development of the processing step from MOF to supported catalyst by electrospinning

In order to increase the flexibility of renewable energies and improve their integration into existing energy grids, efficient intermediate storage is necessary. High-purity hydrogen produced in a water electrolysis cell is a suitable energy carrier. However, the use of some electrolyzers is associated with high costs due to the required use of precious metals as catalysts, while others have disadvantages in terms of load modulation. In this sense anion exchange membrane water electrolysis (AEMWE) arises as an attractive alternative technology that combines convenient features of other type of electrolyzers. Nevertheless, there is a necessity in improvement regarding the performance of AEMWE. The oxygen evolution reaction (OER) in the anode, is the major source of energy loss and therefore, there is potential to optimize OER catalysts. In this work, supported catalysts for the OER were developed using Metal-Organic Frameworks (MOF74) dopped with Ni and/or Co and fibers obtained from an electrospinning process, as supporting material. The MOFs were pyrolyzed to obtain a carbon scaffold with finely dispersed transition metals, as well as the polymer fibers, which structure the catalyst, allowing to tune conductivity and mass transport. Two different routes for combining the MOFs with the fibers were studied. In order to investigate the electrospinning process, polymer concentration, solvent, applied voltage and polymer were varied. The improved parameters were selected and Polyacrylonitrile (PAN) fibers were successfully electrospun and pyrolyzed. The MOFs were characterized physically, chemically and electrochemically. Pure Ni-MOF74 showed increasing current along the Cyclic Voltammetry cycles, reaching a mass-specific current of 732 mA mg -1 after 50 cycles. A supported catalyst was obtained after impregnation of the Ni-MOF74 over the pyrolyzed fibers and characterized. The combined catalyst showed a similar behavior compared with the pure Ni-MOF74.