Synergetic control of specific orientation and self-distribution of photoelectrons in micro-nano ZnIn2S4/black phosphorus quantum dots (BPQDs) heterojunction to enhance photocatalytic hydrogen evolution.

Black phosphorus quantum dots (BPQDs)-based materials possess excellent photocatalytic efficiency; however, they often present a loss of photo-induced carriers and random active sites in electron transfer of heterojunctions, thus restricting the enhancement of hydrogen (H2) evolution and their potential application. In this study, a micro-nano ZnIn2S4/BPQDs (MN-ZISBP) composite is constructed to enable specific orientation and self-distribution of photoelectrons transferred from ZnIn2S4 (ZIS) to BPQDs. The relationship between photoelectron transfer and H2 evolution efficiency is investigated via experiments and density functional theory (DFT) calculations. MN-ZISBP with a nanorod-like structure presents an H2 evolution rate of 1207 μmol/g/h and is higher than that of the sheet-shaped (S-ZISBP, 1023 μmol/g/h) and flower-like composites (F-ZISBP, 744 μmol/g/h) under visible light irradiation. The MN-ZISBP composite with a lower conduction band level and larger specific surface area increases the number of active sites on BPQDs via "self-distribution" for H2 evolution. Finally, the electron transfer direction and bonding orbitals of MN-ZISBP are calculated using the work function and density of states results to verify the above conclusions. The novel construction technique and photocatalytic mechanism of MN-ZISBP reported in this study provide significant insights into the BPQDs-based photocatalysts for H2 evolution.