Self-standing polyaniline membrane containing quaternary ammonium groups loaded with hollow spherical NiCo2O4 electrocatalyst for alkaline water electrolyser

Abstract

Bi-functional electrocatalysts are expected to improve the efficiency of overall water splitting in alkaline media by the simultaneous oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). We prepared a free-standing, anion-conducting and stable polyaniline (PAni) membrane, where the central secondary and two terminal tertiary amine groups act as gel inhibitors. The prepared alkaline membranes were used as substrates for loading an electrocatalyst and fabricating the membrane electrode assembly (MEA). Nickel cobaltite (NiCo₂O₄) is generally considered a promising candidate for the OER, but has morphology-dependent bi-functional catalytic activity for overall water splitting that prompted us to develop the hollow spherical-structured NiCo₂O₄ for simultaneous OER and HER in alkaline media. The reported electrocatalyst achieved 10 mA cm⁻² current density at 1.63 V for the OER, and 0.24 V for the HER. The fabricated MEA showed better overall water splitting performance for the PAni-1.03 membrane in comparison with commercially available membranes, and good durability for alkaline water electrolysis at 50 °C under an applied current density of 200 mA cm⁻². Further, the proposed highly conducting and stable alkaline membrane electrolyser may be a turning point for efficient water splitting in alkaline media for O₂/H₂ evolution.