Rationally tuning the d-band center of the open active sites in 2D Ni-based MOFs to enhance the performance of Li-O2 batteries

The rational design of electron structures in open active sites of metal-organic frameworks (MOFs) was a highly effective strategy for enhancing electrocatalytic activity. In this study, we constructed a heterostructure comprising functionalized carbon nanotubes (CNTs) coupled with ultrathin two dimensional Ni-BDC-MOF nanosheet (denoted as 2D Ni-MOF-CNTs). This configuration facilitated the redistribution of electron density between the CNTs and the 2D Ni-MOF. The CNTs served as a rapid electron conduction pathway, significantly improving electron transport across the 2D Ni-MOF plane. Furthermore, the open Ni sites exhibited elevated oxidation states and a lower d-band center, which enhanced the adsorption of the oxygen-containing intermediates. This optimization led to a facilitated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Li-O2 battery incorporating the 2D Ni-MOF-CNTs heterostructure demonstrated superior electrochemical performance, including enhanced reaction kinetics, reduced overpotential, improved rate performance and a high specific capacity. Notably, the battery exhibited exceptional long-term durability, sustaining ~ 850 cycles at 500 mA g-1. This work provides a novel perspective on the design of open active sites in MOF-based materials for advanced, long-lasting battery system.