Electrocatalysis of Poly-Neutral Red for Hydrogen Evolution Reaction in Acidic Media

Metal -free hydrogen -bonding conductive polymer catalysts (HCPCs) are emerging alternatives to platinum -group -metals (PGMs) for electrocatalytic hydrogen evolution reaction (HER). In this study, electrodes coated with poly -neutral red (PNR) films were fabricated by oxidative chemical vapor deposition (oCVD) and electropolymerization deposition (EPD) to study their activities as HER-electrocatalysts in acidic media. PNR (EPD) exhibited a superior performance, i.e., an overpotential of 194 mV (at 10 mA cm-2) owing to a high exchange current density of 0.711 mA cm-2. The activity is substantiated by spectroelectrochemical measurements and time -dependent density functional theory (TDDFT) calculation unveiling a doubly reduced and doubly protonated PNRH2 as the reaction intermediate for the evolution of H2. It resulted in a first -order kinetic constant of k = 9.98 x 10-4s-1 to indicate a slow dissociation of PNRH2 to release H2. Large Tafel slope of 176 mV dec-1 also limits the electrocatalytic activity of PNR.