Cobalt nanoparticles encapsulated in porous nitrogen-doped carbon: Oxygen activation and efficient catalytic removal of formaldehyde at room temperature

The removal of carcinogenic formaldehyde (HCHO) to improve indoor air quality has attracted significant attention. Designing efficient catalysts for practical HCHO oxidation without use of noble metals remains challenging. In this study, metallic Co nanoparticles were encapsulated with porous nitrogen-doped carbon (Co@NC). This catalyst achieved HCHO elimination at room temperature for the first time. The as-prepared Co@NC catalyst exhibited superior catalytic activity (>80%) for HCHO removal compared with the oxidized one, and possessed the excellent stability. Theoretical calculations showed that the metallic Co in Co@NC is the active site for O₂ dissociation, which enhanced the catalytic activity compared to traditional transition-metal oxides, such as Co₃O₄ with the high-valence state Co³⁺ providing active sites. The formate species was the main intermediate, which was further oxidized to CO₂ as the final product. Hence, an efficient non-noble-metal catalyst for room-temperature HCHO oxidation was developed.