In Situ Growth of Rich-Oxygen-Vacancy Mno2 on Nickel Foam for Enhancing Low-Temperature Methane Oxidation

Abstract

Methane (CH4) catalytic oxidation has been recognized to be a promising strategy. A major challenge in this field lies in the fabrication of monolithic catalysts that demonstrate superior performance at reduced operating temperatures, which is essential for practical industrial implementation. This study presents a novel approach for synthesizing monolithic MnO2-Ov/NF catalysts through the in situ development of K2NiFe(CN)6 (NiFePBA, a metal-organic framework template) on nickel foam (NF), subsequently undergoing a redox-etching treatment. The synthesized MnO2-Ov-0.01/NF catalyst exhibits exceptional catalytic efficiency at low temperatures, achieving 90% CH4 conversion (T90) at 325 °C. Detailed characterization indicates that the NiFePBA template serves dual functions: it enables the high-density in situ growth of MnO2 on the NF while simultaneously promoting the generation of supplementary oxygen vacancies. These structural defects obviously enhance the oxygen activation potential of MnO2, consequently boosting the catalytic performance of the MnO2-Ov-0.01/NF in low-temperature CH4 oxidation. Through operando DRIFTS-MS analysis, it was observed that terminal-type oxygen species (M=O) preferentially adsorb CH4 molecules, leading to its oxidation to CO2 and H2O at lower temperatures. With the increasing temperature, bridge-type oxygen species (M−O−M) become more reactive with CH4. Notably, key intermediates such as monodentate carbonates, which are crucial for forming reactive oxygen species onto catalyst surface, are readily decomposed under lower temperatures. Moreover, such results offer valuable perspectives for designing and optimizing monolithic catalysts for low-temperature CH4 oxidation applications.

Keywords: Monolithic catalysts, Catalytic oxidation, CH4 oxidation, Surface oxygen, Operando DRIFTS-MS