Double-sided assembly of 0D polydopamine on 1D hexagonal tubular carbon nitride for boosting photocatalytic Cr(VI) reduction

The low efficient transfer/separation of photogenerated carriers and the inferior interfacial attraction between Cr(VI) and carbon nitride are the dominant limiting factors in the photocatalytic Cr(VI) reduction. Herein, a metal-free 0D/1D heterostructure of polydopamine (PDA) modified hexagonal carbon nitride tubes (HCN) was constructed for improving the photoreduced efficiency of Cr(VI). In the 0D/1D heterostructure, HCN exhibited a one-dimensional hexagonal tubular structure, and the zero-dimensional PDA nanoparticles were widely distributed on the outside and inside of HCN. After verified, the introduced PDA modified on the double surfaces of HCN played multiple roles in boosting the photocatalytic Cr(VI) reduction. Firstly, the 0D/1D heterostructure was conducive to accelerating the transfer/separation and spatially separating the photogenerated carriers. Secondly, PDA could regard as an “electron acceptor”, and enhance visible light absorption. Thirdly, PDA could promote the adsorption capacity of Cr(VI) which was attributed to the plentiful amino and catechol groups in the constitutional unit of PDA, and then improve the interfacial attraction between photocatalyst and Cr(VI). As expected, the photoreduced efficiency of Cr(VI) was markedly enhanced by the 0D/1D heterostructure. The photocatalytic reaction rate constant of Cr(VI) by the optimal PDA modified HCN was about 6.6 times than HCN.