The effect of copolymerization on the electrocatalytic hydrogen evolution properties of polyaniline in acidic medium

In this work, we explore the electrochemical hydrogen evolution reaction (HER) properties of polyaniline homopolymer and copolymers synthesized via the chemical polymerization route. The as-prepared polyaniline (PANI) homopolymer, poly (aniline-co-3-aminobenzoic acid) (P(ANI-co-ABA), poly (aniline-co-triphenylaniline) (P(ANI-co-TPA) and poly (aniline-co-3-nitroaniline) (P(ANI-co-3NI) were characterized and interrogated using several analytical techniques. The FTIR and XRD analyses revealed similar resemblance between PANI homopolymer and copolymers, suggesting that the polymer backbone were not disrupted during copolymerization. Furthermore, the reduction in optical band gap for P(ANI-co-3NI) means that the said copolymer exhibits higher electrical conductivity, which is of great importance for HER applications. In contrast, the HER performance of the as-prepared polymers was evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). The highly conductive P(ANI-co-3NI) exhibited superior HER performance with higher surface coverage, electrochemical surface area and faster kinetics as compared to other as-prepared polymers. Moreover, P(ANI-co-3NI) copolymer possessed a Tafel slope of 47.9 mV.dec−1, 318 mV overpotential at a current density of 1.0 mA.cm−2 and turnover frequency (TOF) of 3 mmol H2.s−1 which are noticeable higher HER performance than that of PANI homopolymer (Tafel slope of 64.6 mV.dec−1 and TOF of 0.25 mmol H2.s−1). The P(ANI-co-3NI) copolymer showed a good long term chronoamperometric stability. This study provides an efficient route for the development of metal-free electrocatalyst with excellent HER performance.