Which Is More Efficient in Promoting the Photocatalytic H2 Evolution Performance of g-C3N4: Monometallic Nanocrystal, Heterostructural Nanocrystal, or Bimetallic Nanocrystal?

Generally, an excellent cocatalyst could promote the photocatalytic hydrogen (H2) evolution performance of g-C3N4 significantly. Herein, a superior cocatalyst of gold-platinum (AuPt) nanocrystal with an ultralow content of Pt was successfully decorated on carbon self-doping g-C3N4 nanosheets (AuPt/CCN) via a facile photodeposition route. The corresponding Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN were also prepared for comparison. It is found that AuPt/CCN exhibits much superior photocatalytic H2 evolution performance (1135 μmol/h) when irradiated with a 300 W Xe lamp, up to 20, 12, 5, 2, and 1.5 times that of the pristine CCN, Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN, respectively. The quantum efficiency (QE) of AuPt/CCN at 420 nm reaches 12.5%. The experimental and density functional theory calculation results suggested that the improved AuPt performance can be mainly ascribed to the non-plasmon-related synergistic effect of Au and Pt atoms in AuPt nanocrystal: (1) the proximity and the electronegativity difference of Au and Pt atoms in AuPt accelerate the transfer and separation of charge carriers and (2) the synergistic interaction between Pt and Au atoms optimizes the Gibbs free energy (ΔGH*) of H* (atom) adsorption on AuPt, promoting the H2 generation kinetics of AuPt/CCN.