In situ preparation of N–ZnO/graphene nanocomposites: excellent candidate as a photocatalyst for enhanced solar hydrogen generation and high performance supercapacitor electrode

Abstract

We have demonstrated a facile in situ wet chemical method to synthesize nanostructured nitrogen doped ZnO/Graphene (N-ZnO/GR) nanocomposites for the first time. Nitrogen doped ZnO over graphene (N-ZnO/GR) was studied using various concentrations of graphene. During the synthesis of N-ZnO/GR nanocomposites, in situ formation of graphene via GO reduction and formation of 4-9 nm N-ZnO have been demonstrated. The composite N-ZnO/GR absorbs in the visible region and this property is used for the photocatalytic reaction to transform hazardous H 2 S waste into eco-friendly hydrogen using solar light. The N-ZnO/GR nanocomposite with 0.3% graphene exhibits an enhanced photocatalytic stable hydrogen production rate i.e. $5072 mmol h À1 under visible light irradiation. It is noteworthy that the N-ZnO/GR electrode exhibits a high specific capacitance of 555 F g À1 and excellent cyclic performance with nearly 96.20% capacity retention after 2000 cycles at a current density of 10 A g À1 . These results indicate great potential applications of N-ZnO/GR in developing high hydrogen production and supercapacitors with high energy and power densities. † Electronic supplementary information (ESI) available: Raman spectrum of GO, XPS of GO, FTIR of samples GO, Z1, Z3, Z4, Z5 and Z6, FESEM of GO, undoped ZnO and N-ZnO, TEM of Z3, hydrogen evolution of the recycled Z4 sample, XRD of sample (Z4) aer three cycles of the photocatalytic study, Raman spectrum of sample Z4 aer three cycles of the photocatalytic study, and XPS of sample (Z4) aer three cycles of the photocatalytic study. See

Synergistic effect of N-decorated and Mn2+ doped ZnO nanofibers with enhanced photocatalytic activity

“…3a)36. Obviously, the ZnO nanofiber sample (3.25 eV) is much higher than Mn 2+ -doped samples, but a little lower than the theoretical value (3.37 eV), which may be affected by the nanometer size effect19. And the bandgaps for Mn-ZnO nanofibers are further narrowed by an increased loading (see Table S2).…”

“…They could trap the charge carriers shallowly and efficiently to facilitate the detrapping process of charge carriers to the surface of the catalyst which accelerate the interfacial charge transfer processes17. Moreover, previous studies of N-doped TiO 2 or ZnO have shown a significant red shift in light absorption wavelength and notable improvement in photocatalytic activity141819. Here we report a significant enhancement in visible-light photocatalytic activity of ZnO by creating intentional defects in its crystal lattice via Mn 2+ -doping and N 2 atmosphere annealing.…”

N-doped ZnO–MoS2 binary heterojunctions: the dual role of 2D MoS2 in the enhancement of photostability and photocatalytic activity under visible light irradiation for tetracycline degradation

“…It is well known that PL emission intensity results from the recombination of photogenerated charge carriers in semiconductor materials. 53 Figure 12b presents the PL emission spectra measured at room temperature. The excitation wavelength was chosen to be 372 nm, as the UV-vis spectrum of ZnO NR exhibit a strong absorption peak at this wavelength (Figure 12a).…”

Carbon Nano‐Onion and Zinc Oxide Composites as an Electron Transport Layer in Inverted Organic Solar Cells

“…In the present study, we used ZnO due to its interesting physico‐chemical properties with a band gap of 3.37 eV, which is not effective for visible light‐driven photocatalysis . ZnO is characterized by a high exciton binding energy (60 meV) and piezoelectricity at room temperature .…”