Visualizing Formation of Tungsten Carbide Model Catalyst and its Interaction with Oxygen

Construction of model metal carbide surfaces is essential for surface catalysis studies over carbide‐based catalysts. Here, well‐controlled growth of tungsten carbide (WC x ) layers on W(110) including carbon‐rich R(15×3)‐C/W(110) and carbon‐poor R(15×12)‐C/W(110) structures has been clearly demonstrated using chemical vapor deposition (CVD) on a clean W(110) surface or carbon segregation from the bulk. Low‐energy electron microscopy (LEEM) and micro‐region LEED (μ‐LEED) characterizations confirm that the R(15×12) structure forms first and then transforms to the R(15×3) structure by incorporating more carbon atoms in the CVD or surface segregation processes. Oxidation of the WC x /W(110) surfaces in O 2 atmosphere removes surface carbon atoms, driving the structural transformation from R(15×3) to R(15×12) first and then to a two‐dimensional oxide surface. Our work provides a clear guide for well‐controlled growth of model WC x catalysts and the structural transformation between them.