Enhanced Stability of PtML/MML/WC(0001) Multilayer Alloys under Electrochemical Conditions: A First Principle Study.

A platinum (Pt) monolayer catalyst could greatly reduce the use of Pt. However, the core or subsurface transition metal could easily segregate to the surface and eventually selectively dissolve in the working conditions. In this work, a type of PtML/MML/tungsten carbide (WC) multilayer structure catalyst has been designed using the density functional theory method. The results show that the stability of W-terminated core catalysts is lower than that of the corresponding C-terminated one. More importantly, the C-terminated PtML/CoML/WC alloy could also maintain a stable Pt monolayer structure in various electrolyte solutions (e.g., perchloric acid, phosphoric acid, and alkaline solutions) and via different oxygen reduction reaction (ORR) pathways, in addition to the previously well-known precious alloy elements, such as Ru, Ir, and so forth. The segregation of the M metal will be suppressed by introducing a high electronegativity nonmetal element in the core such as C through enhanced interaction between the C and M interlayers. The improved ORR activity and the stability of C-terminated PtML/Co(Ru)ML/WC(0001) multilayer structures highlight the importance of surface chemistry of the substrate in rational design Pt monolayer catalysts.