Phenolic hydroxyl-functionalized covalent organic frameworks for efficient hydrogen evolution in alkaline media

Abstract

Developing economical and highly active metal-free electrocatalysts for the hydrogen evolution reaction (HER) is crucial for advancing sustainable hydrogen energy through water electrolysis. Although alkaline water electrolysis holds great potential as a scalable technology, the process is hindered by two major challenges: the sluggish water dissociation step and the limited intrinsic activity of metal-free catalysts. Here, we report TFPheMePh, a nitrogen-containing, hydroxyl-functionalized covalent organic framework (COF) synthesized via polycondensation, yielding a crystalline, porous material with a high BET surface area of 1309 m 2  g -1 . To maximise catalyst utilisation and facilitate efficient electron transport, the synthesized COF was drop-casted onto a three-dimensional dynamic hydrogen bubble template copper foam (DHBT-Cuf). Its interconnected porous architecture provides a highly conductive scaffold, enhanced electrolyte accessibility, and abundant exposed active sites, thereby facilitating water activation and HER. The resulting COF/DHBT-Cuf electrode delivers efficient HER activity in 1 M KOH, achieving an overpotential of 285 mV at 10 mA cm -2 with a Tafel slope of 263 mV dec −1 . This performance arises from the synergy of nitrogen-rich active sites, phenolic groups, the electron-donating inductive effect of methyl substituents, a high-surface-area microporous channel network, and an extended π-conjugated backbone, collectively promoting charge transport, reactant accessibility, and catalytic kinetics. This work highlights the potential of the rational design of COFs integrated with three-dimensional conductive architectures as efficient metal-free electrocatalysts for alkaline HER and provides valuable insights into the development of advanced organic framework-based catalysts for sustainable green hydrogen production.