Amorphous multinary phyllosilicate catalysts for electrochemical water oxidation

Abstract

© The Royal Society of Chemistry 2019.The practical realization of a water-splitting system necessitates the development of high-performance oxygen evolution reaction (OER) catalysts. Despite tremendous research efforts aimed at identifying earth-abundant 3d transition-metal-based catalysts, their insufficient catalytic efficiencies continue to jeopardize their real-world application. Herein, we introduce amorphous cobalt-iron phyllosilicates (ACFPs) as highly efficient OER catalysts. The ACFPs were designed by tailoring the metal chemistry of the phyllosilicate framework which consists of laminations of silicate (SiO4) layers and layered Co-Fe (oxy)hydroxide motifs, and prepared using a facile room-temperature precipitation method. It is demonstrated that the OER properties/mechanisms are sensitively affected by the Co/Fe ratio, with an exceptionally low overpotential (η ∼ 329 mV for a current density of 10 mA cm-2) delivered at the optimized composition of 40 at% Fe. This catalytic efficiency is greater than that of the structurally analogous Co-Fe (oxy)hydroxide as well as those of pure Co or Fe phyllosilicate, suggesting the beneficial role of the phyllosilicate framework along with the synergistic interplay of Co and Fe ions in the framework. Density functional theory calculations revealed that the introduction of Fe at the surface of Co phyllosilicate perturbs the local structural environment of oxygen sites, providing additional active sites. This work proposes a valid strategy for the design of high-performance catalysts by chemically tuning both the redox-active and redox-inert elements concomitantly in novel multinary phyllosilicate-based OER catalysts