Tuning the nitrogen contents in carbon matrix encapsulating Co nanoparticles for promoting formaldehyde removal through Mott-Schottky effect

The increment of N dopants in carbon matrix can effectively enrich the electron density of N-doped carbon encapsulating metal nanoparticles (NPs) via Mott-Schottky effect, thereby favoring the activation of molecular O₂ with abundant free electrons on carbon surface. Herein, given the essential role of oxygen activation in formaldehyde (HCHO) oxidation, Co NPs-embedded nitrogen-doped carbon and carbon nanotubes (Co/NCNT) with controllable N contents (2.30 ~ 4.38 wt%) were prepared and utilized for catalytic oxidation of HCHO at room temperature. Electron transfer from the Co core to the N-doped carbon layer was modulated by the tailorable concentrations of N dopant through the Mott-Schottky effect at their interface, being validated by X-ray and ultraviolet photoelectron spectroscopy, as well as CO₂ temperature-programmed desorption experiment. The catalytic activity increased gradually with the elevation of nitrogen content, achieving a HCHO removal efficiency of approximately 80% over Co/NCNT-5 with the maximum nitrogen content. Combined with the comprehensive characterizations, the mechanism underlying the catalytic activity improvement in HCHO oxidation induced by the Mott-Schottky effect was proposed. This work provides a new insight into optimizing the non-noble metal catalysts for HCHO oxidation at room temperature.