Black Ultrathin Single‐Crystalline Flakes of CuVP2S6 and CuCrP2S6 for Near‐Infrared‐Driven Photocatalytic Hydrogen Evolution

Abstract 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.