Annealing-free synthesis of carbonaceous Nb2O5 microspheres by flame thermal method and enhanced photocatalytic activity for hydrogen evolution

Abstract An annealing-free synthesis of carbonaceous Nb2O5 photocatalyst via a one-step flame assisted pyrolysis approach was proposed for the first time. Nearly amorphous carbonaceous Nb2O5 microspheres were obtained directly through the facile and waste-free method. The presence of carbonate species was confirmed by means of EDS, XPS, BET and TEM. Both FT-IR and Raman analysis further revealed the existence form of carbon residuals for the resulted sample. UV–vis diffuse reflectance spectra showed the strong absorption of visible light and narrowed band gap for the carbon modified Nb2O5. On account of the vital role that carbon played in efficient electron-hole separation and light absorption, the hydrogen generation rate was 2.7 times that of the annealed and commercial Nb2O5 samples. Further calcination can foster the crystallinity and expand specific surface area but lower the photocatalytic performance of as-prepared Nb2O5 because of the elimination of carbon species. This work provides a new strategy for the preparation of carbonaceous Nb2O5 candidates with enhanced photocatalytic activity.