Efficient electrocatalytic oxidation of water: minimization of catalyst loading by an electrostatic assembly of hydrous iridium oxide colloids

Abstract

Exploiting an effective catalyst has been an essential and significant task in the development of electrochemical water oxidation. A highly electrocatalytic iridium oxide colloidal electrode, prepared by the electrostatic assembly fashion, is reported herein. Poly(allylamine hydrochloride) (PAH) was utilized to facilitate the formation of stable PAH/iridium oxide colloid clusters, resulting in a high catalytic utility (turnover efficiency of 6.36 ± 0.25 s⁻¹ at low overpotential, η = 0.28 V) towards the oxygen evolution reaction (OER), with the smallest Ir loading (Γ_cov = 2.3 × 10⁻⁹ mol cm⁻²) of any yet reported. A variety of examinations and approaches were conducted to gain better understanding of such electrostatically assembled architecture and to identify hexahydroxyiridate(IV), [Ir(OH)₆]²⁻, as the key active catalytic species.