Achieving ultrahigh energy density and excellent stability in carbon pentazole†
Abstract
Binary CN compounds received considerable interest in green energy and sustainable materials. However, the energy density and structural stability at the ambient conditions are usually mutually exclusive in high-nitrogen CN materials. In this work, CN20 is identified via ab initio evolutionary searches at 35 GPa, termed as P21c-C(N5)4, in which carbon is only 4.11% in mass fraction but can provide enough electrons to stabilize the aromatic cycle-N5− anions. The results show that P21c-C(N5)4 exhibits excellent thermodynamic and dynamic stability under the synthesis pressure, and the robust covalent structure of P21c-C(N5)4 can be maintained under ambient conditions while releasing the pressure. The electronic structures indicate that P21c-C(N5)4 possesses high chemical inertness because of its non-absorption of visible light with a well-proportioned charge distribution. In addition, the decomposition of P21c-C(N5)4 can release an energy of 6.53 kJ g−1, which, to our knowledge, is the highest recorded among room-temperature stable binary nitrogen-rich compounds. The energy released can be further improved to 11.13 kJ g−1 under an oxygen-rich environment. Moreover, the detonation pressure of P21c-C(N5)4 is up to 44.76 GPa, which is similar to that of a potential rocket propellant. In light of these hallmarks, P21c-C(N5)4 is a promising low cost and environmentally friendly high energy density material.