Optimal Geometrical Configuration of Metal Cations in Single Spinel CoxRh3-XO4 Nanoparticles to Promote Oxygen Evolution Reaction

Abstract

Hydrogen (H2), which is widely considered as an ideal energy carrier to alternate traditional fossil fuels, can be produced by water electrolysis. Water electrolysis is a simple and promising technology due to its eco-friendly advantages. However, an anodic oxygen evolution reaction (OER) in water splitting devices provokes significant energy loss owing to its sluggish reaction kinetics. Therefore, designing advanced OER electrocatalysts is a very popular topic, among which spinel oxides have been widely studied for OER.Hence, in this work, we construct single spinel of various Co x Rh3-x O4 with 0.95 ≤ x ≤ 2.05 nanoparticles (NPs) as an outstanding OER electrocatalysts in alkaline condition. First, rhodium hydroxide and cobalt hydroxide were precipitated through acid-base reaction between dilute 0.1M NaOH and metal precursors solutions, then purified metal hydroxides was synthesized into Co x Rh3-x O4 NPs via thermal annealing process. The morphology of Co x Rh3-x O4 NPs was measured by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The physical properties of Co x Rh3-x O4 NPs were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity and stability of Co x Rh3-x O4 NPs are studied toward OER in Ar-saturated 1 M NaOH aqueous solution with rotating disk electrode (RDE) voltammetry. Electrochemical impedance spectroscopy (EIS) was carried out to further investigate the electrochemical behaviors of the Co x Rh3-x O4 NPs. Conclusively, we have identified which atomic ratio and configuration of Co and Rh cations can produce optimal synergistic effect toward OER. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2020R1A2B5B01001984).