In situ construction of carboxyl-based hydrophilic COFs for efficient electrocatalytic alkaline hydrogen evolution

In the context of the global energy transition, the key challenge of electrocatalytic hydrogen production technology is to develop high-performance and low-cost catalysts to achieve efficient HER. In this study, we created a metal-free, in situ carboxylic acid COF named JLNU-314, using 4,4''-diformyl-[1,1′:4′,1''-terphenyl]-2′,5′-dicarboxylic acid (TP-COOH) as the building block through a solvothermal process. JLNU-314 exhibits high crystallinity, robust chemical stability, and superior hydrophilicity. JLNU-314 exhibits a low overpotential of 166 mV at a current density of 10 mA cm −2 in alkaline electrolytes, outperforming the performance of JLNU-315, which does not possess carboxyl groups. Theoretical calculations reveal that the carboxyl group (─COOH) maintains COF's planar structure, enhances hydrophilicity, and offers hydrogen bonding sites. As a polar functional group, it creates a directional electric field, accelerating charge separation and migration, optimizing alkaline HER performance. This represents the first in situ carboxylic acid-based COF electrocatalytic system for HER. It provides a new idea for the development of electrocatalysts in the future.