Aqueous alkaline pH stable halide ((PEA)2CoCl4) perovskite for oxygen reaction electrocatalysis

Abstract

Despite gaining significant importance as an exciting class of materials, the extremely low stability of metal halide perovskites (MHPs) in aqueous medium impedes their potential application beyond photovoltaics and photocatalysis. Herein, the stability of cobalt-based halide perovskite (PEA)₂CoCl₄ (PEA = phenylethylammonium) in an aqueous alkaline pH electrolyte has been enhanced by employing a hydrophobic organic cation as the A-site and further wrapping it with electronic conductive N-doped reduced graphene oxide (NrGO). The increased stability allows the developed perovskite composite to be applied to electrocatalysis, such as the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The effective surface passivation of (PEA)₂CoCl₄ results in controlled exposure of aqueous electrolytes to the active sites of perovskite during catalysis. (PEA)₂CoCl₄ coated with NrGO (NPCo) shows an ORR onset potential of 0.94 V at 0.1 mA cm⁻² and an overpotential of 353 mV at 10 mA cm⁻² towards the OER as compared to the state-of-the-art (Pt/C) (1.00 V) and RuO₂ (346 mV) catalysts. Furthermore, the NPCo catalyst is used in rechargeable Zn–air batteries and shows a specific capacity of 760 mA h g⁻¹ with a peak power density of 116 mW cm⁻². The developed NPCo electrode materials are utilized to demonstrate flexible electronics. Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations clarify the active role of NrGO coating in preventing the perovskite structure from flooding with water molecules and facilitating electrocatalysis.