Multi-Element Doping Boosts a Layered Metal Oxide Electrode for Superior Water Oxidation

Abstract

More than precisely controlling the active species to optimize the binding with reaction intermediates, applying lab-designed electrocatalysts for practical water electrolysis requires overcoming limitations of mass and electron transports, which are however difficult to achieve by a single strategy. Here, based on a category of layered cobalt oxides (ACoO2, A = alkali metal), we report a multi-element doping method to favor the in-situ reconstruction of more-active species during water oxidation, boost the electronic conductivities, and extend the potential range of kinetic currents. Specifically, various doping elements including both cationic and anionic ones were screened experimentally for ACoO2 and the composition of LiCo1-x-y-zNixFeyPdzO2 was identified with the optimal catalytic properties. Compared with common cobalt oxides and (oxy)hydroxides, LiCo1-x-y-zNixFeyPdzO2 regulated the in-situ catalyst reconstruction during both room- and high-temperature water oxidation, and boosted electronic conductivity by 2-4 orders of magnitudes. Consequently, LiCo1-x-y-zNixFeyPdzO2 outperformed RuO2, Co3O4, α- and β-Co(OH)2 by delivering an anion exchange membrane water electrolysis current density of 1 A cm-2 at about 1.75 V, and showed little degradation during the 500-hour stability test. This work represents a step forward in rationally boosting the catalytic properties of anode materials for practical membrane water electrolysis.