Band gap-Tunable Porous Borocarbonitride Nanosheets for High Energy-Density Supercapacitors

Abstract

Band gap-tunable porous borocarbonitride (BCN) nanosheets were successfully fabricated with cheap and readily available precursors by annealing and exfoliating. The band gap of the as-prepared BCN materials ranges from 5.5 to 1.0 eV; these samples exhibit beneficial structural features suitable for the application in supercapacitors. Especially, the BCN material with a band gap of 1.0 eV exhibits a great specific surface area (600.9 m g), massive active sites, and excellent conductivity (10.8 S m). In addition, this example displays great specific capacitance (464.5 F g), excellent cycle stability (98.5% performance retention after 10 000 cycles), and ultrahigh energy density (50.4 W h kg, in 1 M EtNBF electrolyte). This excellent electrochemical performance and facile effective synthesis of band gap-tunable BCN materials will provide a promising strategy for configuring nanostructured multiple compound electrodes for other energy storage and conversion devices.

High‐Energy Density Li‐Ion Capacitor with Layered SnS2/Reduced Graphene Oxide Anode and BCN Nanosheet Cathode

“…Reasons for the improved high‐rate performance were testified by the electrochemical impedance spectroscopy (EIS) on the SnS 2 /RGO, RGO, and SnS 2 electrodes. As shown in Figure S6c (Supporting Information), all the EIS plots show a characteristic semicircle in high‐frequency region and a sloping line in low‐frequency region . The charge transfer resistance (45 Ω) of SnS 2 /RGO is lower than that of the SnS 2 electrode (80 Ω) but higher than RGO (30 Ω), indicating the high conductivity and superior charge transfer afforded by the SnS 2 /RGO composite .…”

“…The SEM elemental mapping analysis further demonstrated the homogenous dispersion of C, N, and B in BCN (Figure c). This result suggests that BCN materials were successfully prepared, and the heteroatom (B and N) doped in carbon materials may enhance the pseudocapacitance contribution …”

“…Figure S10b in the Supporting Information gives the high‐resolution B 1s spectrum of BCN, which can be deconvoluted into three peaks assigned to BC (190.4 eV), BN (191.5 eV), and BO (192.4 eV) bonds (see the Supporting Information). The B‐doping of the carbon frameworks with unpaired electrons would induce surface polarization, and induce extra pseudocapacitance . For the C 1s high‐resolution spectra (Figure S10c, Supporting Information), several carbon atoms probably connected to B, O, and N heteroatoms.…”

“…Synthesis of BCN Nanosheets : The cathode material BCN was prepared by a modified solid‐phase synthesis method as described previously . Boric acid (1.0 g), urea (1.0 g) and glucose (8.0 g) were dissolved in 80 mL deionized water, followed the obtained gel was freeze‐dried.…”

“…Doping heteroatoms (e.g., nitrogen, boron, and sulfur) is an effective strategy to enhance the electrical conductivity as well as accelerate pseudocapacitive reactions. In a previous work we have fabricated a B/N codoped carbon (BCN) electrode, and a high specific capacitance (464.5 F g −1 ) was achieved . The doping of boron can decrease energy barrier for electrolyte anion diffusion, enhance the operating voltage of LICs, and finally improve the energy density .…”