Enhancing charge density and steering charge unidirectional flow in 2D non-metallic semiconductor-CNTs-metal coupled photocatalyst for solar energy conversion

[Display omitted] The photogenerated electrons with the high density can unidirectionally flow in the composite, which can effectively enhanced the photocatalytic activity of the semiconductor. •In Ag/2D-C3N4/CNTs composite, the electrons can unidirectional flow from Ag to 2D-C3N4, and then to CNTs.•The enhanced photocatalytic activity is due to the efficient unidirectional transfer of the electrons with high density and efficient separation of the e-h pairs.•By ESR analysis, the photocatalytic mechanism was researched detailed. The effective separation of the electron and hole (e-h) pairs plays a key role in enhancing the photocatalytic performance of the semiconductors. The density of electrons participating in the reduction reaction also determines photocatalytic performance. We report here a rational design of a photocatalyst assembly composed of n-type semiconducting two-dimensional g-C3N4 nanosheets (2D-C3N4), carbon nanotubes (CNTs), and plasmonic Ag nanocubes, which exhibits enhanced density of electrons and controlled unidirectional change flow to promote the photocatalytic hydrogen evolution reaction. Plasmonic Ag nanocubes inject the hot-electrons into conduction band of 2D-C3N4 to increase the density of electrons while the CNTs act as a power pump of the electrons to steer electron flow from the conduction band of 2D-C3N4 to reactants. The photocatalytic performance of Ag/2D-C3N4/CNTs assembly was dramatically enhanced for the H2 evolution from water. The enhanced photocatalytic activity is due to the efficient unidirectional transfer of the electrons with high density and efficient separation of the e-h pairs.