MnO₂-decorated N-doped carbon nanotube with boosted activity for low-temperature oxidation of formaldehyde

Low-temperature oxidative degradation of formaldehyde (HCHO) using non-noble metal catalysts is challenging. Herein, novel manganese dioxide (MnO₂)/N-doped carbon nanotubes (NCNT) composites were prepared with varying MnO₂ content. The surface properties and morphologies were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM). Comparing with MnO₂/carbon nanotubes (CNTs) catalyst, the 40% MnO₂/NCNT exhibited much better activity and selectivity for HCHO oxidation, mineralizing 95% of HCHO (at 100 ppm) into CO₂ at 30 °C at a gas hourly space velocity (GHSV) of 30,000 mL h^-1  g^-1. Density functional theory (DFT) calculation was used to analyze the difference in the catalytic activity of MnO₂ with CNTs and NCNT carrier. It was confirmed that the oxygen on NCNT was more active than CNTs, which facilitated the regeneration of MnO₂. This resulted in remarkably boosted activity for HCHO oxidation. The present work thus exploited an inexpensive approach to enhance the catalytic activity of transition metal oxides via depositing them on a suitable support.