Multi-functional carbon nanotube encapsulated by covalent organic frameworks for lithium-sulfur chemistry and photothermal electrocatalysis.

It is significant to tailor multifunctional electrode materials for storing sustainable energy in lithium-sulfur (Li-S) batteries and converting intermittent solar energy into H, facilitated by electricity. In this context, COF-1@CNT obtained through interfacial interaction fulfilled both requisites via post-functionalization. Upon integrating COF-1@CNT with S as the cathode for Li-S batteries, the system exhibited an initial discharge capacity of 1360 mAh g. Subsequently, it maintained a sustained actual capacity even after undergoing 200 charge-discharge cycles at 0.5C. The performance improvement was attributed to the optimized conductivity due to the addition of carbon nanotubes (CNTs). Furthermore, the synergistic interaction between the nitrogen of COF-1 and lithium mitigated the shuttle effect in Li-S batteries. In the modified three-electrode electrolytic cell system, COF-1@CNT-Ru produced by COF-1@CNT with RuCl showed better electrochemical reactivity for photothermal-assisted hydrogen evolution reaction (HER). This effect was demonstrated by reducing the overpotential to 140 mV relative to the no-photothermal condition (180 mV) at a current density of 10 mA cm. This study marked the first simultaneous application of covalent organic frameworks (COFs) based materials in Li-S batteries and photothermal-assisted electrocatalysts. The modified electrocatalytic system held promise as a novel avenue for exploring solar thermal energy utilization.