Ordered mesoporous borocarbonitride-reduced graphene oxide heterostructure for quasi solid-state supercapacitors and sodium-ion batteries

Abstract

Mesoporous electrochemically active materials are gaining significant attention due to their high surface area and pore volume, and tunable pore size which facilitate superior ion transfer and contribute to superior electrochemical properties. Ordered mesoporous heterostructures composed of mesoporous borocarbonitride (BCN) and reduced graphene oxide (rGO) were developed using SBA-15 which acts as the hard template. The conductivity of the prepared hybrids was fine-tuned with the simple adjustment of the rGO sheets. The optimized BCN-rGO hybrid showed an excellent surface area of 1139 m² g⁻¹ with an average pore diameter of ∼9 nm and an ordered mesoporous structure. In the hybrid, BCN is responsible for the overall charge storage, whereas the use of rGO enhances the charge transfer and electronic conductivity. Theoretical calculations confirmed that the BCN-rGO hybrid exhibited excellent conductivity and affinity for Na ions The electrochemical properties were exploited by investigating the nanohybrid in supercapacitors, wherein at a current density of 0.5 A g⁻¹, the material demonstrated an exceptional supercapacitance of 338.1 F g⁻¹. The hybrid also showed a capacity of 204.4 mAh g⁻¹ at 0.1 A g⁻¹ when utilized as anodes for sodium-ion batteries which demonstrated excellent cyclability and rate capability. Through the theoretical studies, the favorable active sites for their adsorption were identified and it was demonstrated that 24 Na⁺ ions may be accommodated in the BCN-rGO hybrid.