Insights into Molten Salts Induced Structural Defects in Graphitic Carbon Nitrides for Piezo‐Photocatalysis with Multiple H₂O₂ Production Channels

Abstract

Elucidating the impact of heteroatoms in graphitic carbon nitrides (g‐C3N4) is of utmost importance to rationalize materials. Hence, in this study, oxygen‐doped g‐C3N4 containing trace amounts of halogen in the structures for piezo‐photosynthesis of hydrogen peroxides (H2O2) is fabricated. The findings reveal that oxygen atoms may be inserted into g‐C3N4 in‐plane structures, while halogen atoms tend to become intercalated between g‐C3N4 layers. Furthermore, the presence of ammonium molten salts (NH4X) during the synthesis alters the concentration of mono and cluster vacancies of carbon and nitrogen in the materials, certifying by positron annihilation spectroscopy (PAS). These defective contributions will be meaningfully accelerate catalytic performance by providing trapping states. Additionally, the decomposition of generated H2O2 can produce highly oxidative hydroxyl radicals, inducing degradations on the catalyst's structures and unexpectedly decreasing catalytic outcomes. From the mechanistic view, different reduction and oxidation channels will be play a pivotal role in generating H2O2. Moreover, the influence of ultrasound and light is also carefully investigated in the work to gain more insights into how the catalysts are triggered to improve catalytic performance. Thus, this study highlights the importance of carefully characterizing structures of g‐C3N4 to precisely understand the catalytic properties, benefiting catalytic design and development.

Simultaneously Utilizing Excited Holes and Electrons for Piezoelectric-Enhanced Photoproduction of H2O2 from S-Scheme 2D S-Doped VOx/g-C3N4 Nanostructures

“…Further radical trapping experiments were conducted to study the roles of radicals in generating H 2 O 2 and verify the S-scheme charge transfer in the composites. Notably, 1 mM silver nitrate (AgNO 3 ), 5 mM l -tryptophan ( l -tryp), 5 mM para -benzoquinone ( p -BQ), and 5 mM ethylenediaminetetraacetic acid disodium salt (EDTA.2Na) were added to the solution to scavenge excited electrons (e – ), 1 O 2 , superoxide ( − O 2 · ), and excited holes (h + ), respectively . The catalytic performance in Figure e exhibits the strong dependence of H 2 O 2 on the formation of oxygenic radicals, indicating that the catalytic mechanism entails radical pathways from the reduction and oxidation of oxygen species.…”

“…• ), and excited holes (h + ), respectively. 56 The catalytic performance in Figure 5e exhibits the strong dependence of H 2 O 2 on the formation of oxygenic radicals, indicating that the catalytic mechanism entails radical pathways from the reduction and oxidation of oxygen species. There is no doubt that AgNO 3 will compete with O 2 to consume excited electrons, and the production of H 2 O 2 was limited due to the unavailability of electrons to reduce oxygen.…”

Promoting Proton Donation through Hydrogen Bond Breaking on Carbon Nitride for Enhanced H2O2 Photosynthesis

“…In addition, sacrificial agents are required for most reported catalysts . Two-electron oxygen reduction reaction (ORR) and two-electron water oxidation reaction (WOR) represent two promising pathways for achieving photocatalytic H 2 O 2 production. − Among these pathways, the two-electron ORR has mainly been investigated for H 2 O 2 production due to its superior thermodynamic favorability compared to the two-electron WOR. The ORR process can be classified into direct one-step two-electron reduction (eq ) and indirect two-step single-electron reduction (eqs and ).…”