N-doped carbon nanotubes enhanced charge transport between Ni nanoparticles and g-C3N4 nanosheets for photocatalytic H2 generation and 4-nitrophenol removal

Carbon nanotubes with well conductivity can improve photogenerated carrier separation and transport for enhanced photocatalytic performance. In this paper, Ni nanoparticles embedded N-doped carbon nanotubes (CNTs) were decorated on superior thin g-C3N4 nanosheets as a co-catalyst via a mechano-chemical pre-reaction and thermal polymerization at high temperature. The admirable conductivity and unique one-dimensional structure of Ni-decorated CNTs (NiCNTs) generated more active sites and supplied efficient charge transfer. Abundant unpaired electron and π-conjugated structure of N-doped CNTs promoted the delocalization, retarded recombination, and stabilized charge separation. Ni nanoparticles acted as active sites to trap photogenerated electrons for photoreduction reaction. g-C3N4/NiCNTs composites with an optimized ratio revealed a hydrogen (H2) generation rate as high as 1050.4 μmol g−1 h−1, exhibiting an increase of ∼137 times compared with pure g-C3N4 without using Pt as co-catalyst. The H2 generation rate was even higher than that of g-C3N4/Pt, suggesting that NiCNTs can substitute noble metals completely. In addition, the g-C3N4/NiCNTs sample removed 4-nitrophenol (4-NP) within 10 min under visible light irradiation. The rate constant of g-C3N4/NiCNTs sample was ∼49 times of that of pristine g-C3N4. This work proposed a novel bifunctional catalyst for pollutant treatment and clean energy production.