Synthesis and characterization of new nanocomposite based on di-substituted Keggin-type phosphotungstate@ceramic as a new and high-performance nanocatalyst for O2 evolution from water oxidation reaction

Abstract

In this research, a new nanocomposite was synthesized via the sol-gel method by covalent immobilizing of di-substituted Keggin-type heteropolyanion containing cobalt (PW10Co2) on the surface of manganese oxide (MnO2) ceramic. The desired nanocomposite (PW10Co2@MnO2) was used as an effective heterogeneous catalyst in the water oxidation reaction for oxygen evolution. The PW10Co2@MnO2 nanocatalyst was identified through Fourier transform infrared (FT-IR), ultraviolet–visible (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) methods in detail. After confirming the preparation of the PW10Co2@MnO2, its catalytic activity in the water splitting reaction was assessed in the presence of cerium (Ⅳ) ammonium nitrate (CAN) as an efficient oxidant at different pH (pH = 7 and 9). The PW10Co2@MnO2 nanocatalyst demonstrated turnover number (TON), turnover frequency (TOF), and O2 evolution of 520.12 mmolO2molCo.s, 178 mmolO2molCo, and 0.003 mgO2L.S, respectively, which are the highest values at pH = 9 in the water oxidation process. Moreover, the effect of CAN concentration, pH, and the amount of KOH was assessed on the catalytic activity, and a plausible reaction mechanism was proposed. In the present study, the PW10Co2@MnO2 nanocatalyst provides valuable insights into the design of other catalysts for the water oxidation reaction and beyond.