Diffusion driven nanostructuring of metal–organic frameworks (MOFs) for graphene hydrogel based tunable heterostructures: highly active electrocatalysts for efficient water oxidation†
Abstract
Exposing the surface states of metal–organic frameworks (MOFs) by tuning the shape and size of their nanostructures is expected to enhance their functionalities in practical applications. Herein, a highly scalable ‘hydrogel–organic interfacial diffusion’ driven approach is utilized for direct growth of metal–organic framework (MOF) nanocrystals over a porous graphene hydrogel framework with fine structural control. Molecular dynamics (MD) simulation of this heterostructure reveals that, two-stage diffusion (hydrogel–organic interfacial and intra-hydrogel) control of organic ligand molecules and their interaction with the graphene surface play key roles in tunable MOF–hydrogel formation. The resulting tri-metallic MOF–hydrogel-hybrid derived porous aerogel exhibits state-of-the-art oxygen evolution reaction (OER) performance metrics with excellent operational stability in alkaline medium. The overpotential required to achieve a current density of 10 mA cm−2 is as low as 255 mV and a small Tafel slope of 44.3 mV dec−1 signifies a very high rate of oxygen evolution reaction. The hydrogel–organic interfacial principle of this material could be applied to produce versatile graphene–MOF heterostructures as well as other diverse functional graphene-gel-nanohybrids (e.g. metal nanoparticles, conducting polymers) with intriguing application prospects.
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