Directional surface hydroxylation on 6H-SiC induces surface electron polarization and proton activation promoting photocatalytic water splitting for hydrogen

Abstract

Photocatalytic water splitting for hydrogen production is a promising solution to converse solar energy to green fuel. A high-performance photocatalyst system always requires fast surface reaction rate and efficient charge separation. Herein, a novel strategy that photo-assisted silanizing-hydrolyzing method is used to trigger in situ surface hydroxylation selectively on Si atoms of micro-sized 6H-SiC particles. Due to this functionalization, the results show that the silanizing-hydrolyzing process occurs at the Si sites while the C is passivated, leading the Si atoms with electron deficiency property by XPS characterization. It also drives the SiC surface from native hydrophobicity to hydrophilicity, which is benefit to proton absorption and desorption of generated H2 by FT-IR and contact angle (CA) result. Furthermore, the photo-electron-chemical characterization demonstrate the charge migration and separation of SiC are promoted. The DFT calculation further indicates these surface properties changes are mainly attribute to the surface electron polarization through the hydroxylation, inducing the Si-O spatial charge separation. More importantly, the positive Si atoms exhibit an appropriate proton absorption energy, resulting in easily H2 desorption from SiC surface. The hydrogen evolution is significantly enhanced by 33 times compared to pristine SiC without any cocatalysts introduced. Our method provides an efficient route to design an environmental-friendly photocatalytic material SiC and construct highly efficient solar energy conversion systems, which can simultaneously facilitate carrier generation, transportation and surface reduction reaction rate.