Surface-Modified Covalent Organic Polymer for Metal-Free Electrocatalytic Hydrogen Evolution Reaction

Rapid global warming forced people to replace conventional energy sources with green renewable solar and wind energies. Consequently, renewable energy production and storage technologies have recently received significant attention of several industries for day-to-day applications. Hydrogen production through metal-free electrocatalyst water splitting is crucial for obtaining sustainable and clean fuel. In the present study, we report a Schiff-base-type reaction between 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (TPM) and 1,3,5-tris(4-formylphenyl)benzene (TFPB) under solvothermal conditions that produced a porous covalent organic polymer (TFPB-PAM). Excellent hydrogen evolution reaction (HER) activity is observed in our recently developed metal-free TFPB-PAM electrocatalyst, which shows a current density (η10) of 10 mA cm–2 at a moderately low overpotential of 185 mV and also shows a low Tafel slope of 68.5 mV decade–1. The crucial role of branched the polyphenylene moiety of TFPB-PAM in hydrogen evolution reaction (HER) activity has been elucidated by an experimental study along with quantum chemical calculations. The faradic efficiency (98%) and durability (retained 86% of initial current density after 3000 cycles) of the TFPB-PAM catalyst display excellent HER activities. Our findings will pave a route to develop the next-generation metal-free porous organic polymer for the HER.