Morphology engineering of Co3O4 spinel for efficient oxidation of lean methane at low temperature

Abstract

Nowadays, the development of high-performance non-noble metal catalysts is an important research direction for controlling methane emissions from liquefied natural gas (LNG)-powered vehicles and vessels, and Co3O4 spinel has attracted great attention. In this work, Co3O4 catalysts with different morphologies (flower, sheet, particle, and cube) were synthesized by hydrothermal method and their catalytic performance was evaluated. The results showed that the flower-like Co3O4 (Co3O4-F) catalyst exhibited the highest activity in the lean methane oxidation with the T90 (temperature at the methane conversion of 90%) of 365 °C. Compared to other catalysts, Co3O4-F contained an amount of Co3+ sites and the weakest Co3+-O bond, which facilitated the extraction of active lattice oxygen and the initial oxidation of methane to intermediate products (formate and -COO-) on the catalyst surface. Meanwhile, the abundant oxygen vacancies on the surface of the Co3O4 catalyst could efficient activate O2 to form active oxygen species, which promoted the oxidation of intermediate products to CO2 and H2O. The methane oxidation over the Co3O4-F was confirmed to conform with Mars-van Krevelen mechanism. This work provides a facile way to enhance the methane oxidation activity of Co3O4 catalysts by modulating the morphology.