FeCo alloy encased in nitrogen-doped carbon for efficient formaldehyde removal: Preparation, electronic structure, and d-band center tailoring

Formaldehyde is a typical indoor air pollutant that has posed severely adverse effects on human health. Herein, a novel FeCo alloy nanoparticle-embedded nitrogen-doped carbon (FeCo@NC) was synthesized with the aim of tailoring the transition-metal d-band structure toward an improved formaldehyde oxidation activity for the first time. A unique core@shell metal–organic frameworks (MOFs) architecture with a Fe-based Prussian blue analogue core and Co-containing zeolite imidazole framework shell was firstly fabricated. Then, Fe and Co ion alloying was readily achieved owing to the inherent MOF porosity and interionic nonequilibrium diffusion occurring during pyrolysis . High-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectra confirm that small FeCo alloys in situ form in FeCo@NC, which exhibits a higher formaldehyde removal efficiency (93%) than the monometallic Fe-based catalyst and a remarkable CO 2 selectivity (85%) at room temperature. Density functional theory calculations indicate the number of electrons transferred from the metal core to the outer carbon layer is altered by alloying Fe and Co. More importantly, a downshift in the d-band center relative to the Fermi level occurs from − 0.93 to − 1.04 eV after introducing Co, which could alleviate the adsorption of reaction intermediates and greatly improve the catalytic performance.