Anion-rich Ir-doped CoO_x for boosting oxygen evolution reaction in water electrolysis

Abstract

Owing to the sluggish kinetics of oxygen evolution reaction (OER) in electrochemical water electrolysis process, efficient and durable OER electrocatalysts are crucially needed. However, it is a great challenge to improve the comprehensive performance of OER electrocatalysts by utilizing various synergistic methodologies. To solve these issues, herein, Ir-doped Co-based compounds with regulated anions were synthesized using a coprecipitation method as the electrodes for boosting the OERs. Doping with Ir atoms modified the coordination environments and electronic structures of the CoO_x-CO₃^2- lattice, and the generated Co³⁺ species promoted the generation of active species for the OER. It is worthwhile noting that a hybrid crystalline/amorphous IrCoO_x-CO₃^2- compound was obtained with an Ir content of 10.09 wt.% and a large amount of Co³⁺, and demonstrated excellent electrocatalytic OER performance. The overpotential required for the developed IrCoO_x-CO₃^2- to achieve 10 mA cm^-2 was as low as 207 mV with a very low Tafel slope of 61.7 mV dec^-1, which is better than the commercial IrO₂. Furthermore, anions created in the IrCoO_x significantly promoted the OER, and their effects were decreased in the order of CO₃^2- > PO₄^3- > OH^-. This work clarifies the synergistic mechanism of cations and anions on the electrocatalytic OER performance of Co-based compounds, providing new insights for designs of high-performance OER electrocatalysts for water electrolysis.

Keywords

Oxygen evolution reaction / Co-based compounds / Ir atoms / crystalline/amorphous structures / high-valence Co⁴⁺

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