Syntheses, characterization and oxygen evolution reaction (OER) electrocatalytic properties of M(II) based bromo-salophen complexes

Abstract

• Ni(II) and Cu(II) bromosalophen complexes synthesized and characterized. • Both complexes were decomposed to obtain corresponding oxides. • Decomposed products were analysed by SEM and PXRD. • Complexes as well as decomposed products were used as electrocatalysts in OER. Efficient oxygen evolution reaction catalyst can be prepared via controlled decomposition method, and there is still minimal mechanistic understanding of such method. Here, we introduce a 3-Bromo-salophen ligated nickel(II) and copper(II) complexes as a precursor to obtain a Ni and Cu-based oxygen evolution reaction electrocatalyst via the controlled decomposed method. In our case, the unique O,N chelation mode of the 3-Bromo-salophen ligand (bis[2-bromosalicylydene]-1,2-iminophenylenediamine) was used to synthesize M(II) complexes. By regulating the decomposition conditions, we successfully obtained varied structures. The designing of a nonprecious, highly efficient and long-lasting oxygen evolution reaction electrocatalyst for electrochemical water splitting is a current emergency for reducing energy demand in the future. In this study, we found cost-effective decomposed products of NiO and CuO which are prepared by a simple one-step chemical precipitate method at high temperature (500 °C). The chemical composition, structure and morphology of the decomposed products NiO and CuO were confirmed by PXRD, FTIR and SEM spectroscopy. The decomposed products were loaded onto a glassy carbon electrode by a drop-casting method. For the oxygen evolution reaction, the complexes as well as their decomposed products, NiO and CuO achieve an ultralow over-potential exhibit onset lower potential 1.5 V in 0.1 M KOH solution. Ni(II) and Cu(II) bromosalophen complexes synthesized and decomposed and complexes as well as the decomposed products used as electrocatalysts for OER.