IrO2/Co3O4 supported mesoporous SBA-16: An efficient electro-catalyst for oxygen evolution reaction

Abstract

A non-conducting mesoporous silica support (SBA-16) with active supported electroactive iridium and cobalt was synthesized by a simple hydrothermal and impregnation method. The synthesized catalysts were represented as 5% IrO2/SBA-16, 10% IrO2/SBA-16, and 5% Co3O4 / 10% IrO2, respectively. All catalysts were characterized by XRD, BET-Surface area, XPS, EDAX, and HR-TEM techniques to study their structural, morphological, chemical and micro structural properties. Small-angle XRD confirmed the mesoporous nature of the material formation, showing major faces at (100), (110), (200), and (220). High-angle XRD confirmed the formation of Co3O4 and IrO2 phase on the catalyst surface. Nitrogen sorption isotherm showed a ordered material with surface areas of the decreasing order of 5% IrO2/SBA-16, 10% IrO2/SBA-16, and 5% Co3O4/10% IrO2/SBA-16, respectively. EDAX analysis confirmed the presence of Ir and Co levels in the bimetallic catalysts. The oxidation state of Ir +4 and Co3+ were confirmed by XPS analysis. HR-TEM images showed that this material was highly porous and contained active metal particles dispersed throughout the surface. These metal particles play an important role in decreasing lower overpotential and current densities. In particular, the 5% Co3O4 /10% IrO2/SBA-16 showed a lower overpotential of 380 mV at a current density of 10 mA. Compared to the activities of all the catalysts, 5% Co3O4 /10% IrO2/SBA-16 showed higher activity due to the broad distribution of active sites with frequent electron transfers. Furthermore, during chronopotentiometry testing, a stable potential was maintained for over 12 hours at a constant current density of 10 mA.