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

Abstract 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 H₂ production activity in a noble‐metal‐free Cu₂O/TpPa‐2‐COF photocatalyst is reported. It shows a beginning H₂ 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 Cu⁰ 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.