3D honeycomb porous sulfonated covalent organic polymer (PCOP) synthesized on carbon fabric at refrigerated temperature: supercapacitor and metal-free proton relay for water oxidation in alkaline and neutral media†

Abstract

The sluggish rate of proton transfers during proton-coupled electron transfer is one of the challenges in designing a holistic blueprint for complete biomimicry. Here, we present a one-pot, facile method for the refrigerated synthesis of two different covalent organic polymers by the separate copolymerization of diphenylamine-4-sulfonic acid and diphenylamine with para-aminophenol. Substituting diphenylamine with its porous sulfonate analog (PCOP) significantly alters the structural design and proton shuttling characteristics, resulting in remarkable efficiency in the uncommon non-concentrated proton-coupled electron transfer (n-PCET) during OER in both alkaline and neutral media. The functionalized carbon fabric (FCF)/PCOP requires an overpotential of 234 mV at 10 mA cm⁻², comparable to metal-based electrocatalysts. A striking semi-reflective boundary condition in the Nyquist plot in acidic media introduces a net capacitive behavior upon protonation of –SO₃⁻, revealing an ideal capacitor, which has been targeted in the design of a supercapacitor in 0.1 M H₂SO₄ with capacitance C_sp = 670.79 F g⁻¹, retaining 89.52% even after 12 000 charge–discharge cycles. Further experimental evidence was obtained by D/H isotope studies, proton inventory, pH dependence analysis, PCOP-water ATR spectroscopy and Gerischer impedance spectroscopy. The results of the DFT studies were used to further explore the structural engineering driven by water clusters and SDS molecules during the cooled synthesis of the COP.