Binary metallic sponges as an efficient electrocatalyst for alkaline water electrolysis

Abstract

Binary metallic sponges comprising of nickel–cobalt (NiCo) hydroxide/oxide composites are prepared using a simple pyrolysis method by employing cyanocobalamin as a new sacrificial template. Subsequently these highly porous materials are demonstrated as an efficient electrocatalyst for oxygen evolution reaction (OER) under alkaline conditions. Structure, morphology and porosity of these materials are controlled through thermal oxidation between 200 and 600 °C and the resultant materials are designated as NiCo-200, NiCo-400 and NiCo-600 respectively. Among the different materials studied in this work, NiCo-200 exhibits better electrocatalytic behaviour for OER with a lower overpotential of 420 mV for obtaining a current density of 10 mA/cm2 along with a turnover frequency value of 0.0234 s−1. The observed higher electrocatalytic activity is attributed to the presence of hydrophilic surface, enriched pores and crystalline nature of NiCo-200. Further the stability studies carried out under alkaline medium at a fixed current density of 20 mA/cm2 showed that both NiCo-200 and NiCo-600 displayed a good stability and retain OER characteristics for a longer duration. Finally our results clearly show that the binary metallic hydroxide/oxide sponges could potentially act as a new class of electrocatalyst in energy conversion devices mainly for alkaline water electrolysis. Highly porous, binary Ni–Co metallic hydroxide/oxide sponges are prepared through a novel route using cyanocobalamin as a sacrificial bio-source. Structure, morphology and porosity of these metallic sponges are controlled by temperature. Further these cost-effective materials are explored as electrocatalysts for oxygen evolution reaction associated with alkaline water electrolysis.