A novel conductive catalyst was designed based on a quasi core shell structure of N-doped graphene/cobalt sulfide. This platinum-free catalyst shows high catalytic activity and conductivity owing to close interactions between the core (cobalt sulphide) and the shell (N-doped graphene). It enables dye-sensitized solar cells (DSSCs) to obtain high energy conversion efficiency up to 10.71%, which is as far as we know the highest efficiency for DSSCs based on a platinum-free counter electrode.