SiP Nanosheets: A Metal-Free Two-Dimensional Photocatalyst for Visible-Light Photocatalytic H2 Production and Nitrogen Fixation.

Two-dimensional (2D) semiconductors for photocatalysis are more advantageous than the other photocatalytic materials since the 2D semiconductors generally have large specific surface area and abundant active sites. Phosphorus silicon (SiP), with an indirect bandgap in bulk and a direct bandgap in the monolayer, has recently emerged as an attractive 2D material because of its anisotropic layered structure, tunable bandgap, and high charge carrier mobility. However, the utilization of SiP as a photocatalyst for photocatalysis has been scarcely studied experimentally. Herein, we reported the synthesis of SiP nanosheets (SiP NSs) prepared from bulk SiP by an ultrasound-assisted liquid-phase exfoliation approach which can act as a metal-free, efficient, and visible-light-responsive photocatalyst for photocatalytic H2 production and nitrogen fixation. In a half-reaction system, the maximal H2 and NH3 generation rate under visible light irradiation achieves 528 and 35 µmol·h-1·g-1, respectively. Additionally, the apparent quantum yield for H2 production at 420 nm reaches 3.56%. Furthermore, a Z-scheme photocatalytic overall water-splitting system was successfully constructed by using Pt-loaded SiP NSs as the H2-evolving photocatalyst, Co3O4/BiVO4 as the O2-evolving photocatalyst, and Co(bpy)33+/2+ as an electron mediator. Notably, the highest H2 and O2 generation rate with respect to Pt/SiP NSs achieves 71 and 31 µmol·h-1·g-1, respectively. This study explores the potential application of 2D SiP as a metal-free visible-light-responsive photocatalyst for photocatalysis.