Oriented p–n Heterojunction Ag₂O/Zn(O,S) Nanodiodes on Mesoporous SiO₂ for Photocatalytic Hydrogen Production

Hydrogen is a great candidate fuel to replace fossil fuels in the future since it has high energy density, zero-emission, and renewability. Here, we report our design with p-type Ag2O and n-type Zn(O,S) loaded on mesoporous silica to form SiO2/Ag2O/Zn(O,S) with the nano p–n heterojunction to improve the efficiency of photocatalytic hydrogen evolution reaction (HER). The photocatalysts were systematically characterized to identify their properties. Through the optimization of the Zn(O,S)-loaded amount and position of p-Ag2O, the highest hydrogen production rate of 9200 μmol·g–1·cat·h–1 was achieved by SiO2/Ag2O/Zn(O,S)-0.6 catalyst with corresponding apparent quantum yield of 10.3%, which was about 2.7 times higher than pure Zn(O,S). By placing n-Zn(O,S) of diodes outward was proposed for the electron-rich part to enhance the reduction reaction, while placing p-Ag2O inward for the hole-rich part to modulate the electron concentration and establish the built-in electrical nanofield. The relative mechanism for improving the efficiency of HER has been investigated in this Article.