The search for stable sp2 zigzag edge graphene nanoribbon termination

The zig-zag edge of a graphene ribbon has attracted much attention, since it is predicted to support a spin-polarized edge state. However, it is difficult to produce thermodynamic conditions that favor a pure sp$^2$ termination of a graphene sheet, since the edge carbons generally prefer to bond to two hydrogen atoms, in sp$^3$ hybridization, rather than one hydrogen, as sp$^2$. We examine several candidate alternative termination groups which can modify the thermodynamics of various edge configurations to favor the sp$^2$ edge termination. Ab-initio calculations demonstrate these alternative terminations can support robust edge states across a broad range of synthetic conditions.