Investigation of Oxygen Evolution Reaction by Spinel Materials

Electrochemically catalyzed water splitting reaction is a promising green energy source. The water splitting commonly involves two reactions, including Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). However, the OER is more sluggish than HER because four electrons are involved in OER. Recently, many researches are working on spinel materials for OER because of the both high reactivity and good long-term stability. Nevertheless, the mechanism of spinel materials toward catalyzing OER is still unclear. Consequently, more studies are essential to figure out what the metal ion actually act in spinel catalyst. In this work, we synthesized a series of spinel materials (AB2O4, A = Co, Zn; B = Co, Cr) via a co-precipitation method in order to find out which part of spinel can electrochemically catalyze OER. X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscope (SEM), transmission Electron Microscopy (TEM) and Current-Voltage characterization were carried out to realize the mechanism behind the reaction. Finally, we proposed that both sites in spinel can’t catalyze OER directly. However, the Co2+ ion in spinel can transform into Co(O)OH which is a good catalyst for OER.