RESUMEN
In this work, nitrogen (N)-doped graphene film is synthesized, as a photo-catalyst, on one side of the copper foam by chemical vapor deposition and the copper foam is directly used as an electrode after porous Pd@rGO cathode loading to the other side of the foam for the photo-assisted charging of the Li-ion oxygen battery. The amount of urea (CO(NH2)2), which is used as N atom source, is optimized to get maximum photo-anodic currents from the n-type graphene films. The optical band gap and the valance band edge potential of the optimized N-doped graphene film are determined as 2.00 eV and 3.71 VLi+/Li, respectively. X-ray photoelectron spectra provided that the atomic percent of N atoms in the graphene film is 1.34% and the graphitic, pyrrolic and pyridinic N atom percentages are 54.01%, 42.20% and 3.79%, respectively. The photo-assisted charging tests indicated that the N-doped graphene film photo-catalyst reduced the charging potential significantly even at 1000 mA g-1 (0.1 mA cm-2) current density and improved the cyclic discharge-charge performance of the Li-ion oxygen battery considerably.
RESUMEN
In this work, we aimed to synthesize an effective nanocomposite photocatalyst for the photo-assisted charging of the Li-ion oxygen battery. Initially the graphene films were synthesized by chemical vapor deposition, and subsequently, g-C3N4/graphene nanocomposites were synthesized by thermal reduction as photocatalysts. FTIR spectra analysis showed that novel C=C bonds can form between g-C3N4 and graphene films during the synthesis process. The photocurrent measurements indicated that the presence of graphene considerably contributed to the visible light utilization and photocatalytic efficiency of g-C3N4. This contribution was also revealed by the UV-vis diffuse reflectance spectra measurements, which showed that the incremental addition of the graphene reduced the optical band gap of the nanocomposite incrementally. The photocatalyst performance of the g-C3N4/graphene nanocomposite was also observed in the photo-assisted charging tests of the Li-ion oxygen battery, and the presence of 2D graphene in the structure improved the effectiveness of g-C3N4 in the reduction of the charging potential, especially at high current densities.
RESUMEN
In this work, g-C3N4/rGO nanocomposites were synthesized to use them as photocatalysts in Li-ion oxygen batteries by aiming at the reduction of the charging potential efficiently under photoassisted conditions. Fourier transform infrared (FTIR) spectra showed that novel CâC bonds formed between g-C3N4 and rGO during the decomposition of melamine and that the formation of these bonds was assumed to cause a red shift in the optical absorption band edge. The competition between the narrowing in the optical band gaps of the nanocomposites as a result of the red shift due to the presence of rGO and the degradation in the visible light utilization as a result of favorably absorbed incident light by rGO instead of g-C3N4 pointed out that the g-C3N4/3% rGO nanocomposite has the optimum light absorbance efficiency. The photoassisted charging tests indicated that the g-C3N4/3% rGO nanocomposite reduced the charging potential effectively, especially at higher current densities, and improved the cyclic discharge-charge performance of the Li-ion oxygen batteries considerably.