Preparation of 3D urchin-like RGO/ZnO and its photocatalytic activity

Three-dimensional urchin-like RGO/ZnO was successfully prepared for the first time by using a secondary hydrothermal method. The morphologies and hexagonal wurtzite structure of the prepared RGO/ZnO were characterized by SEM, TEM, and XRD. SEM and TEM results showed that the composite possessed a micro/nano size of about 2–4 μm, which is conducive to recycling after photocatalysis. Raman and XPS tests demonstrated that GO was reduced to RGO during the secondary hydrothermal process and that planar heterojunction occurred. Further investigation of UV–Vis diffuse reflectance spectra and RhB light degradation showed that light absorption was extended to the Vis range and even the near-infrared region after ZnO compounded with RGO, rendering the composite a viable visible-light-driven photocatalyst. Among the tested materials, the composite with 1.5 wt% RGO had the strongest integrated absorbance intensity; this material increased photocatalytic efficiency by 64.57% compared with the 3D urchin-like ZnO. Overall, the 3D urchin-like RGO/ZnO composite is an ideal visible-light-driven photocatalyst. Given the high surface area, several electronic transmission channels, large spectral response range, and p-type conductivity of RGO, the 3D urchin-like RGO/ZnO composite is expected to be applied in photovoltaic and even lithium/sodium-ion batteries.