Embedding ZnCo2O4 quantum dots onto graphdiyne (g-CnH2n-2) nanosheets as a 0D/2D S-scheme heterojunction for highly efficient photocatalytic H2 evolution

Abstract

The design of environmentally friendly and cost-effective S-scheme heterojunctions with robust interfacial interactions is pivotal for enhancing photocatalytic performance and facilitating practical application. In this work, ZnCo2O4 quantum dots (QDs)/graphdiyne (ZCOG) S-scheme heterojunction was synthesized by a simple hydrothermal method. ZnCo2O4 QDs with quantum size effect were prepared by calcination, while graphdiyne (GDY) nanosheets were synthesized by reduction-elimination reaction using CuBr as catalyst. The maximum hydrogen production rate of ZCOG reaches 2472.80 μmol g-1h−1, which is 30.75 and 10.84 times higher than that of ZnCo2O4 QDs and GDY, respectively. This significantly enhanced photocatalytic activity is attributed to the strongly coupled S-scheme heterojunction between GDY and ZnCo2O4 QDs, which accelerates the photogenerated electron transfer while effectively suppressing the recombination of photogenerated carriers. In addition, the quantum size effect of the ZnCo2O4 QDs leads to an increase in the width of the electronic forbidden band, which enhances the energy of electrons (holes) in the conduction band (valence band). The S-scheme mechanism of ZCOG was revealed by in situ XPS, UPS and TRPL spectroscopy, and the reliability of the conclusions was further verified by DFT calculations. This work provides an efficient strategy for the construction of GDY-based photocatalysts with quantum size effect.