Solid-Solution-Like o-C₃N₄/Ag₂SO₄ Nanocomposite as a Direct Z-Scheme Photocatalytic System for Photosynthesis of Active Oxygen Species

Abstract

Efficient photosynthesis of active oxygen species (e.g., •OH, •O2 –, and H2O2) is of cardinal significance for environmental science and biochemistry. We report a system of o-C3N4/Ag2SO4 with solid-solution-like structure synthesized by coordinating the 5s orbit of Ag+ with surface 2p lone electrons of o-C3N4. The as-synthesized o-C3N4/Ag2SO4 demonstrates a unique electronic structure, as illuminated high light absorption, perfect redox potentials, large BET specific area, abundant active sites, and efficient interfacial charge transfer. Electron paramagnetic resonance spectra and Mott–Schottky measurements confirm that o-C3N4/Ag2SO4 photocatalysts demonstrate highly efficient activity for yielding •OH, •O2 –, and H2O2 species with the Z-scheme photocatalytic principle. Experimental and DFT calculation reveal that the transferred electrons on the conduction band (CB) made up of Ag 5s were favorably shifted into the valence band (VB) composed of N 2p with the formed coordination under irradiation, greatly promoting electron transportation in the Z-scheme photocatalytic system. (o-C3N4)2/(Ag2SO4)1 with the mass ratio of 2 to 1 possesses the highest photocatalytic rate of •OH (45 μmol L–1 h–1), •O2 – (87 μmol L–1 h–1), and H2O2 (480 μmol L–1 h–1). The work provides a new approach to design advanced photocatalysts to efficiently yield active oxygen species for environmental purification.

S‐Scheme Photocatalytic Systems

“…In Figure 4e, direct Z‐scheme solid solution containing g‐C 3 N 4 and Ag 2 SO 4 has been prepared for efficiently evolving reactive oxygen species. [ 17 ] Theoretical prediction confirmed that photon‐conversed electrons transferred electrons from Ag 2 SO 4 CB made up of Ag 5 s to g‐C 3 N 4 VB composed of N 2 p under irradiation, significantly boosting electron transfer in Z‐scheme photocatalytic system. In Z‐scheme photocatalytic systems, researchers consider that SC II with higher Fermi level promotes its electrons naturally flow to SC I via their interfaces until their Fermi energies with same levels.…”

TiO2/Chlorophyll S-Scheme Composite Photocatalyst with Improved Photocatalytic Bactericidal Performance

“…One of the very effective charge separation mode is the electron transfer chain that exists in natural photosynthesis, which is named as the Z-scheme. By constructing a heterojunction system, the electron–hole separation rate can be greatly improved. − With the development of the Z-scheme, Yu et al proposed the step-scheme (S-scheme) heterojunction system concept in 2019 . In S-scheme heterojunctions, after two semiconductors contact, electron transfer from the conduction band (CB) of semiconductor II (SC II) to semiconductor I (SC I) bends the band edge of SC II upward and leads to the downwardness of the band edge of SC I (Figure ).…”

A Z‐Scheme Polyimide/AgBr@Ag Aerogel with Excellent Photocatalytic Performance for the Degradation of Oxytetracycline

“…OH/H 2 O, so PI alone cannot oxidize H 2 O to . OH . Therefore, a Z‐scheme photocatalytic principle is proposed.…”