Transition Metal Exchanged β Zeolites: CoM/β (M = Zn, Ce, and Cu) as Oxygen Electrode in Alkaline Media

Abstract

The zeolite structure, with its precisely distinct pores, settled cages, and adsorption sites, enables the formation and stabilization of isolated metal centers. These well-defined structures make metal-loaded zeolites promising catalysts. Three different β zeolites were synthesized by an aqueous ion-exchange procedure, firstly with cobalt (Co), and secondly with zinc (Zn), cerium (Ce), and copper (Cu), to make three bimetallic CoZn/β, CoCe/β, and CoCu/β zeolites, respectively. X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and low-temperature nitrogen adsorption analysis revealed the structural, morphological, and surface properties of the studied materials, while optical properties were investigated by UV-Vis diffuse reflectance spectroscopy. The lowest onset potential of 1.67 V was obtained for both CoZn/β and CoCe/β, while the somewhat positive value of 1.70 V was observed for CoCu/β. CoZn/β exhibited the lowest value of Tafel slope of 89 mV dec^−1, while slightly higher values of 109 and 113 mV dec⁻¹ were calculated for CoCe/β and CoCu/β during ORR, respectively. CoZn/β showed four-electron pathways of ORR, CoCu/β showed a mixed ORR mechanism, while CoCe/β offered two-electron pathways of ORR. All presented results established that CoZn/β had the highest OER/ORR activity, followed by CoCu/β, while CoCe/β had the lowest activity detected.