Nitrogen-doped truncated carbon nanotubes inserted into nitrogen-doped graphene nanosheets with a sandwich structure: a highly efficient metal-free catalyst for the HER

A highly efficient and robust metal-free catalyst (N-TCNT@NGS), with a sandwich structure of 1D nitrogen-doped truncated carbon nanotubes inserted between 2D nitrogen-doped graphene nanosheets, was synthesized by a facile and green hydrothermal method.