Bifunctional g-C3N4 nanospheres/CdZnS QDs S-scheme photocatalyst with boosted H2 evolution and furfural synthesis mechanism

Abstract

Photocatalytic H2 evolution coupled with organic oxidation could replace the slow four-electron water oxidation and utilize charge carriers to obtain high-valued chemicals. Herein, inorganic CdZnS quantum dots (QDs) are skillfully deposited on g-C3N4 nanospheres to construct an inorganic-polymeric S-scheme heterostructure. The C3N4-CdZnS photocatalyst presents enhanced light absorption, abundant active sites, and intimate interface contact. The optimized composite exhibits an enhanced H2 evolution rate of 582.3 μmol/g/h and a furfuryl alcohol (FAL) conversion of 84.2 %. Femtosecond transient absorption (fs-TA) spectroscopy, in-situ irradiation X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and theoretical calculation (DFT) verify the S-scheme mechanism, which promotes charge separation and strengthens carrier redox ability. In-situ infrared spectra reveal that FAL is first activated to ·C5H5O2 radical by holes in CdZnS and further oxidized to furfural (FF) with dehydrogenation of its hydroxyl group. This work supplies new insight into designing efficient photocatalysts for H2 generation and organic synthesis.