CdS/Pt photocatalytic activity boosted by high-energetic photons based on efficient triplet-triplet annihilation upconversion

- The TTA-UCL clusters possesses a core-shell structure which is of crucial importance for enhancing the mobility of core liquid.
- The core-shell structure provides a solid surface for coupling with CdS which absorbs the converted high energy photons from TTA-UCL.
- Pt as co-catalyst is deposited on CdS surface to facilitate the separation of photo-generated electrons and holes.
- The CdS/Pt system based on TTA-UCL has a preferable photocatalytic activity in decomposing tetracycline and photoinduced hydrogen evolution.
- This work opens a distinctive perspective for building a kind of TTA-based upconversion-photocatalysis system.

We herein report the triplet-triplet annihilation upconversion luminescence (TTA-UCL) clusters achieved by loading the platinum(II)-octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA) into silica shells. This aqueous-based system possesses a core-shell structure which is of crucial importance for enhancing the mobility of core liquid. The encapsulated clusters with efficient green-to-blue upconversion without deoxygenation are conjoined with cadmium sulfide (CdS) as the photocatalyst. Platinum (Pt) is used to improve the separation of electron−hole pairs on the photocatalytic system. Given the band gap of photocatalysts, tetracycline (TC) degradation and photoinduced hydrogen evolution are used to perform the photocatalytic activity. CdS loaded with Pt has higher Pseudo-first-order rate constant (kpfo) in decomposing tetracycline than pure CdS. Moreover, the excellent hydrogen evolution property appears when the converted high energy photons from TTA-UCL-based clusters are introduced to the photocatalytic system. The quantum efficiency of hydrogen evolution increases further after the cocatalyst Pt deposition. This work not only fabricates an encapsulated structure for TTA-UCL clusters, but also provides an effective TTA-supported upconversion-photocatalysis system.

154Schematic illustration of the photocatalysis mechanism of PtDPA@SiO2@CdS/Pt based on TTA-UCL process. The core-shell structure to encapsulate the inert organic medium containing triplet-triplet annihilation upconversion chromophores (PtOEP as the sensitizer and DPA as the emitter) in a rigid silica shell. The green excited light with lower energy photons (2.23 eV < E < 2.38 eV) can't acitve the catalyst CdS that has a band-gap width of 2.4 eV, while obtained higher energy photons (3.06 eV > E > 2.91 eV) through triplet-triplet annihilation upconversion process can sensitize effectively CdS. The sensitized CdS further makes the photogenerated electron transfer to the noble metal Pt. This upconversion-photocatalysis system opens a distinctive perspective for improving photocatalytic activity.