Carbon nanomaterials with sp or/and sp hybridization in energy conversion and storage applications: A review

Carbonaceous nanomaterials are widely considered in energy conversion and storage applications owing to special structures and chemical-physical properties as well as available versatile dimensionality. Huge interest has been paid recently in the development of carbon allotropes with high degrees of sp hybridization as the presence of ethynyl units can considerably affect their properties. In this review, the general properties of three carbon allotropes with different hybridized carbon atoms (graphene quantum dots (GQDs), graphdiyne and carbyne) are summarized. Special focus has been given to the fabrication strategies and recent energy storage and conversion applications based on GQDs and graphdiyne including supercapacitors, lithium ion batteries and solar cells. Finally, conclusions and possible challenges are proposed. This work will shed light on the fabrication of interesting carbon nanomaterials for future energy-oriented applications.