Significantly enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS with carbon nanotubes as the electron mediators

Abstract The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts. However, it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system. In the present paper, the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators, and its photocatalytic hydrogen production performance was studied. Compared with single-phase g-C3N4, CdZnS and biphasic g-C3N4/CdZnS photocatalysts, the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced. Meanwhile, g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability. The enhanced photocatalytic hydrogen production performance of g-C3N4/CNTs/CdZnS is attributed to the fact that CNTs, as an electron mediator, can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS, which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons, increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers. This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.