G-CN sheet nanoarchitectonics with island-like crystalline/amorphous homojunctions towards efficient H and HO evolution.

Photocatalystic evolution of HO from water and oxygen has attracted significant attention because of environmentally friendly. The absorption in visible and hydrophilic feature of graphitic carbon nitride (g-CN) make it a good candidate. In this paper, a rapid post-treatment at high temperature was developed to obtain g-CN nanosheets with abundant crystalline/amorphous interfaces to form homojunctions, which optimized uniplanar carrier mobility dynamics. The conversion from bulk to two-dimensional g-CN resulted from the breakage of interplanar hydrogen bonds and interlayer Van der Waals force. The unique morphology not only rendered photocatalyst with larger specific surface area but also inhibited the robust volume recombination of charge carriers. The accelerated charge carriers flow at the interface, interplane and interlayer together ameliorated the separation and transfer of electrons and holes. A new-emerged n→π* transition ameliorated the poor light utilization efficiency. Beyond the increased photocatalytic H evolution property (779.2 μmol g h), optimized sample displayed a HO evolution activity as high as 4877.1 μM g h under visible light illumination, which was ∼5.8 times of that of bulk g-CN. Detailed photocatalytic mechanism investigation manifested that the two-step single-electron oxygen reduction process occupied the dominant status in HO evolution. This work proposed a novel strategy for obtaining g-CN homojunctions as a promising bi-functional metal-free catalyst to be applied in clean energy production field.