Double-Shelled Open Hollow Metal-Organic Frameworks for Efficient Aqueous Zn-Ion Batteries.

Multi-shelled hollow metal-organic frameworks (MH-MOFs) are highly promising as electrode materials due to their impressive surface area and efficient mass transfer capabilities. However, the fabrication of MH-MOFs has remained a formidable challenge. In this study, two types of double-shelled open hollow Prussian blue analogues, one with divalent iron (DHPBA-Fe(II)) and the other with trivalent iron (DHPBA-Fe(III)), through an innovative inner-outer growth strategy are successfully developed. The growth mechanism is found to involve lattice matching growth and ligand exchange processes. Subsequently, DHPBA-Fe(II) and DHPBA-Fe(III) are employed as cathodes in aqueous Zn-ion batteries. Significantly, DHPBA-Fe(II) demonstrated exceptional performance, exhibiting a capacity of 92.5 mAh g-1 at 1 A g-1, and maintaining remarkable stability over an astounding 10 000 cycles. This research is poised to catalyze further exploration into the fabrication techniques of MH-MOFs and offer fresh insights into the intricate interplay between electronic structure and battery performance.

Metal-organic frameworks-derived oxalate ligand modified NiCo hydroxides for enhanced electrochemical glycerol oxidation reaction.

Glycerol oxidation reaction can be substituted for oxygen evolution reaction for more efficient hydrogen production due to its lower thermodynamic potential. Herein, a series of NiCo hydroxide nanosheets containing abundant Ni3+ species and surface ligands were synthesized by in-situ structural transformation of bimetallic organic frameworks in alkaline media for efficient glycerol oxidation reaction. It is found that the incorporation of Co ions increases the content of the Ni3+ species, and that the Ni/Co ratio of 1.0 lead to the optimal catalytic performance. The oxalate-modified nickel-cobalt hydroxide with the optimized Ni/Co ratio can deliver a current density of 10 mA cm-2 at 1.26 V vs. RHE (reversible hydrogen electrode), and reaches its maximum selectivity and Faradaic efficiency at 1.30 V vs. RHE. A high selectivity of 82.9% and a Faradaic efficiency of 91.0% are achieved. The high catalytic activity can be mainly attributed to the abundant Ni3+ species and surface carboxyl groups.