Synergistic effect between carbon nanomaterials and ZnO for photocatalytic water decontamination

• Carbon/ZnO hybrids with outstanding photoactivity toward phenol oxidation under solar light.
• Surface oxygen groups and nitrogen doping of carbon materials improve the activity of the hybrids.
• N-CNT/ZnO shows the highest photoactivity with N-CNT acting as electron scavenger.

ZnO synthesized by chemical vapor deposition (CVD) was combined with different carbon nanomaterials namely nanotubes, nanofibers, nanodiamonds, fullerene and graphene. The materials were characterized by physical adsorption of nitrogen, diffuse reflectance, UV–Vis and photoluminescence (PL) spectroscopies, transmission electron microscopy and temperature programmed desorption. The photocatalytic efficiency of the resulting carbon/ZnO composites was evaluated for phenol degradation under simulated solar light irradiation. In general, the carbon materials enhance the efficiency of ZnO, and the composite containing nitrogen-doped carbon nanotubes (N-CNT/ZnO) showed the highest photocatalytic activity. An increase of 100% in the apparent first order rate constant for phenol degradation was achieved when using N-CNT/ZnO instead of bare ZnO. PL spectra confirmed the presence of efficient electron transfer between the carbon phase and the ZnO with a maximum quenching of ZnO PL emission in the presence of N-CNT. Both ZnO and N-CNT/ZnO show high stability after four reuses.

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