Co-embedded sulfur vacant MoS2 monolayer as a promising catalyst for formaldehyde oxidation: a theoretical evaluation

Abstract

In this work, we theoretically evaluated the complete catalytic oxidation of formaldehyde (HCHO) catalyzed by a cobalt embedded sulfur vacant MoS₂ (CO_Sv–MoS₂) monolayer. The density functional theory calculations demonstrate that the Co atom is strongly anchored at the S vacancy site of the MoS₂ monolayer forming a single-atom catalyst without metal clustering. From the study of all possible elementary steps, we propose two possible catalytic pathways for HCHO oxidation; (1) consecutive path: HCHO dehydrogenation followed by CO oxidation with O₂, and (2) co-adsorption path: HCHO oxidation by O₂ through the Langmuir–Hinshelwood mechanism. Compared to the catalysts reported in the literature, this catalyst presents lower activation energy barriers for C–H bond cleavage. At room temperature, the consecutive path is found to be dominant, and the calculated activation free energy barrier is only 0.46 eV (44.38 kJ mol⁻¹). Our kinetic analyses show that HCHO oxidation can easily occur at room temperature with a rate of 1.12 × 10⁵ s⁻¹. Therefore, this non-noble metal single atom CO_Sv–MoS₂ catalyst demonstrates excellent activity for HCHO catalytic oxidation at low temperatures.