Effect of Photodeposited Noble Metal Nanoparticles on the Sacrificial-Agent-Free H₂O₂ Photosynthesis Performance of g-C₃N₄

Photodeposition of noble metal nanoparticles is one of the effective strategies to enhance the photocatalytic activity of g-C3N4, but there are few reports about its application to improve the photocatalytic production of hydrogen peroxide (H2O2) by g-C3N4. In this work, different types and surface states of noble metal (Pt, Rh, Ru, Au, and Ag) nanoparticles were loaded on the surface of g-C3N4 through photodeposition. Based on their decomposition activity to H2O2, it was found that the weak adsorption between noble metals (such as metallic Ag, metallic Au, and negatively charged Au) and H2O2 was an important factor in inhibiting H2O2 decomposition. In addition, compared with metallic Au and metallic Ag, negatively charged Au was more conducive to O2 adsorption and activation. More importantly, besides the inhibition of carrier recombination benefiting from cocatalyst loading, the surface plasmon resonance effect of Au facilitated more electrons to participate in the reduction reaction. Thereby, the g-C3N4 loaded with negatively charged Au obtained the highest H2O2 concentration (16.98 μM in the first hour) in the absence of sacrificial agents through a two-step single-electron O2 reduction reaction pathway.