Amorphous Metal-Organic Framework-Dominated Nanocomposites with Both Compositional and Structural Heterogeneity for Oxygen Evolution.

Amorphous metal-organic frameworks (aMOFs) are an emerging family of attractive materials with great application potential, however aMOFs are usually prepared under harsh conditions and aMOFs with complex compositions and structures are rarely reported. In this work, an aMOF-dominated nanocomposite (aMOF-NC) with both structural and compositional complexity has been synthesized using a facile approach. A ligand-competition amorphization mechanism is proposed based on experimental and density functional theory calculation results. The aMOF-NC possesses a core-shell nanorod@nanosheet architecture, including a Fe-rich Fe-Co-aMOF core and a Co-rich Fe-Co-aMOF shell in the core-shell structured nanorod, and amorphous Co(OH)2 nanosheets as the outer layer. Benefiting from the structural and compositional heterogeneity, the aMOF-NC demonstrates an excellent oxygen evolution reaction activity with a low overpotential of 249 mV at 10.0 mA cm-2 and Tafel slope of 39.5 mV dec-1 .