CoAl2O4–g‑C3N4 Nanocomposite Photocatalysts for Powerful Visible-Light-Driven Hydrogen Production

There is no doubt that the rate of hydrogen production via the water splitting reaction is profoundly affected to a remarkable degree based on the isolation of photogenerated electrons from holes. The precipitation of any cocatalysts on the substrate surfaces (including semiconductor materials) provides significant hindrance to such reincorporation. In this regard, a graphite-like structure in the form of mesoporous g-C3N4 formed in the presence of a template of mesoporous silica has been synthesized via the known combustion method. Hence, the resulting g-C3N4 nanosheets were decorated with varying amounts of mesoporous CoAl2O4 nanoparticles (1.0–4.0%). The efficiencies of the photocatalytic H2 production by CoAl2O4-doped g-C3N4 nanocomposites were studied and compared with those of pure CoAl2O4 and g-C3N4. Visible light irradiation was carried out in the presence of glycerol as a scavenger. The results showed that the noticeable photocatalytic enhancement rate was due to the presence of CoAl2O4 nanoparticles distributed on the g-C3N4 surface. The 3.0% CoAl2O4–g-C3N4 nanocomposite had the optimum concentration. This photocatalyst showed extremely high photocatalytic activities that were up to 22 and 45 times greater than those of CoAl2O4 and g-C3N4, respectively. This photocatalyst also showed 5 times higher photocatalytic stability than that of CoAl2O4 or g-C3N4. The presence of CoAl2O4 nanoparticles as a cocatalyst increased both the efficiency and productivity of the CoAl2O4–g-C3N4 photocatalyst. This outcome was attributed to the mesostructures being efficient charge separation carriers with narrow band gaps and high surface areas, which were due to the presence of CoAl2O4.