Black Ultrathin Single-Crystalline Flakes of CuVP 2 S 6 and CuCrP 2 S 6 for Near-Infrared-Driven Photocatalytic Hydrogen Evolution.

The development of new near-infrared-responsive photocatalysts is a fascinating and challenging approach to acquire high photocatalytic hydrogen evolution (PHE) performance. Herein, near-infrared-responsive black CuVP 2 S 6 and CuCrP 2 S 6 flakes, as well as CuInP 2 S 6 flakes, are designed and constructed for PHE. Atom-resolved scanning transmission electron microscopy images and X-ray absorption fine structure evidence the formation of ultrathin single-crystalline sheet-like structure of CuVP 2 S 6 and CuCrP 2 S 6 . The synthetic CuVP 2 S 6 and CuCrP 2 S 6 , with a narrow bandgap of ≈1.0 eV, shows the high light-absorption edge exceeding 1100 nm. Moreover, through the femtosecond-resolved transient absorption spectroscopy, CuCrP 2 S 6 displays the efficient charge transfer and long charge lifetime (18318.1 ps), which is nearly 3 and 29 times longer than that of CuVP 2 S 6 and CuInP 2 S 6 , respectively. In addition, CuCrP 2 S 6 , with the appropriate d-band and p-band, is thermodynamically favorable for the H + adsorption and H 2 desorption by contrast with CuVP 2 S 6 and CuInP 2 S 6 . As a result, CuCrP 2 S 6 exhibits high PHE rates of 9.12 and 0.66 mmol h -1 g -1 under simulated sunlight and near-infrared light irradiation, respectively, far exceeding other layered metal phospho-sulfides. This work offers a distinctive perspective for the development of new near-infrared-responsive photocatalysts.