Self-Accelerating H2 Evolution Activity by In Situ Transformation on Noble-Metal-Free Photocatalyst of Covalent Organic Framework and Cu2O Composite

It is expected that the activity of photocatalysts can remain the same or decrease as little as possible in photocatalysis reaction. Herein, for the first time, a self-accelerating H-2 production activity in a noble-metal-free Cu2O/TpPa-2-COF photocatalyst is reported. It shows a beginning H-2 production rate of 4.41 mmol h(-1) g(-1) under visible light illuminance, while the activity kept increasing to 27.27 mmol h(-1) g(-1) after 25 h reaction, which is 6.2 times higher than the beginning activity and reaches a record high. It is confirmed that part of Cu2O in Cu2O/TpPa-2-COF in situ transformed to Cu-0 in photocatalytic reaction, which acting as cocatalyst promotes the separation of photogenerated charge carriers. Further density functional theory calculations demonstrate that the Schottky barrier height of Cu-Cu2O (111) interface is much smaller than that of Pt-Cu2O (111), supporting its more efficient effect than that with Pt as cocatalyst.