NiCo2O4 spinel for efficient toluene oxidation: The effect of crystal plane and solvent

Spinel oxides, e.g., NiCo2O4, is a promising catalyst for the catalytic oxidation of toluene. Understanding and designing versatile NiCo2O4 spinel is important for low-temperature toluene oxidation. Here, we investigated the surface-characteristic-dependent degradation activity of NiCo2O4 crystals through experiment and characterization. NiCo2O4 nanosheet using ethanol as solvent (named E-NiCo2O4) exposing {110} crystal planes exhibited the lowest temperature toluene oxidation. The T99 of toluene conversion was 256 degrees C, which is much lower than that of NiCo2O4 nanosheet using ethylene glycol as solvent (named EG-NiCo2O4), NiCo2O4 octahedron (named O-NiCo2O4) and NiCo2O4 truncated octahedron (named TO-NiCo2O4). Characterization using various techniques such as XRD, TEM, BET, XPS, H-2-TPR and CO2-TPD showed that Co3+ and surface adsorbed oxygen (Osur) enriched surface, excellent redox properties and effective diffusion of the reaction product reasonably explain the enhancement in catalytic activity over the E-NiCo2O4. The research reveals that the effect of specific crystal planes and solvent was the key factor to govern the activity of low-temperature toluene oxidation. (C) 2020 Elsevier Ltd. All rights reserved.