Porous NiFe-oxide Nanocubes, Derived from Metal-organic Framework, as a Bifunctional Electrocatalyst for Overall Water Splitting

Kumar, Ashwani (2017) Porous NiFe-oxide Nanocubes, Derived from Metal-organic Framework, as a Bifunctional Electrocatalyst for Overall Water Splitting. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Ashwani Kumar (12MS063)) MS_-_THESIS_ASHWANI_KUMAR_12MS063.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Electrochemical water splitting provides a facile way for high-purity hydrogen production, but the commercialization of the system is hindered due to high cost of the noble metal electrocatalysts such as IrO2 and Pt for oxygen evolution reaction and hydrogen evolution reaction (OER & HER), respectively. Designing of a bifunctional noble metal free electrocatalyst for overall water splitting is therefore necessary to reduce cost of the system. In this respect, earth-abundant Ni-Fe based catalyst are very attractive towards water splitting in alkaline medium due to high corrosion-resistant nature, lower overpotential requirement and long term stability in comparison to pristine Ni-O and Fe-O. The tunability of an electrocatalyst in terms of its porosity and morphology is essential to enhance the activity of the catalyst. Herein we derived a highly porous NiFe-oxide nanocube system as a bifunctional electrocatalyst from NiFe-PBA MOF which outperforms NiFe nanoparticles and requires very low overpotential for both OER and HER. They demonstrate an overpotential of 271 and 197 mV for electrochemical OER and HER, respectively in 1M KOH at 10 mA/cm² on carbon fiber paper (CFP) (2.2 mg/cm²) which is much better than the NiFe-oxide nanoparticles with the same composition. The latter requires 339 and 347 mV for achieving current density of 10 mA/cm² for OER and HER, respectively. The electrolyzer constructed using NiFe-oxide nanocubes in a two electrode configuration delivers a current density of 10 mA/cm² at 1.67 V, which is impressive. The better catalytic activity of the nanocubes are observed because of its uniform morphology and high porosity which exposes maximum number of active sites. The cubes edges also play a significant role in the enhanced activity of the catalyst.

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