A theoretical study of formaldehyde adsorption and decomposition on a WC (0001) surface.

A lot of research attention has been paid to designing and exploring efficient adsorbents for HCHO adsorption and decomposition. Herein, we have demonstrated a highly active material, WC, for HCHO adsorption through first-principles calculations. Due to the exposed three-coordinated W atoms (W) of the WC (0001) surface, HCHO molecules can be settled on the WC (0001) surface through newly formed O-W and/or C-W bonds, forming different adsorption configurations. When settled on the WC (0001) surface, the molecular configuration of the HCHO molecule and the corresponding C-H and C-O bond lengths would be greatly changed. Due to the enlarged C-H and C-O bond lengths, the adsorbed HCHO molecules tend to dissociate through two possible pathways; these are the two-step C-H bond scission or the one-step C-O bond scission. The former results in two H adatoms and a CO molecule chemisorbed to the surface and the latter produces an O adatom and a CH group on the surface. Further Cl-NEB calculations demonstrate that the pre-adsorbed O atom has little influence on the first C-H bond scission and the C-O bond scission, while promoting the second C-H bond scission. Considering the dissociative products, H and CH have the potential to couple into a CH group (or even a CH molecule) and two CH groups may couple into a CH molecule. In the end, we propose that OH ions may couple with the dissociative products of HCHO, so an alkali solution could be used to post-process the WC (0001) surface to restore its surface active sites. These results demonstrated the potential of WC in HCHO sensing and abatement.