Photosynthesis-Inspired Acceleration of Carrier Separation: Co–O–Ac and CH3COO– Ions Synergistically Enhanced Photocatalytic Hydrogen Evolution of Graphitic Carbon Nitride

摘要

In natural photosynthesis, photoexcited carriers are transferred to the reactive sites by a series of transport mediators, and the multistep carrier transfer facilitates charge separation, thus conferring photosynthesis high quantum efficiency. However, the present strategy for improving artificial photosynthetic efficiency is commonly anchoring an oxidation or reduction cocatalyst onto the photocatalyst to execute one-step transport of the photogenerated holes or electrons. To further accelerate the charge separation during the artificial photosynthesis, we propose a synergistic transfer of holes by a fixed oxidation cocatalyst (cobalt oxide acetate, Co–O–Ac) and freely moving hole-transfer mediators (CH_(3)COO~(–) ions), the cooperation of which leads to markedly accelerated photocatalytic reaction kinetics of the reduction side of graphitic carbon nitride (g-C_(3)N_(4)). The optimal hydrogen evolution rate is up to 3932 μmol·h~(–1)·g~(–1), 3.8 times that of the bare g-C_(3)N_(4) (1030 μmol·h~(–1)·g~(–1)). The apparent quantum efficiency is 21.61% at 420 ± 10 nm. Our findings provide a facile and effective method for accelerating the hole transfer and thus for promoting the photocatalytic reaction kinetics.