Direct Attack and Indirect Transfer Mechanisms Dominated by Reactive Oxygen Species for Photocatalytic H₂O₂ Production on g-C₃N₄ Possessing Nitrogen Vacancies

Abstract

It is widely accepted that photogenerated holes are the only driving force for oxidizing an electron donor to form H+ during photocatalytic H2O2 production (PHP). Here, we use nitrogen deficiency carbon nitride as a model catalyst and propose several different reaction mechanisms of PHP based on the comprehensive analysis of experiment and simulation results. Nitrogen vacancies can serve as a center for oxidation, reduction, and charge recombination, promoting the generation of h+, •O2 –, and 1O2, respectively, and thus induce H2O2 generation through five different pathways. In particular, the 1O2 anchored on the catalyst surface can realize the indirect oxidation of isopropanol with the assistance of surrounding water molecules and produce H2O2 with the lowest barrier. This work proves that H2O2 can be generated through multiple pathways and highlights the main roles of 1O2, which are ignored by previous studies.

Acetylene/Vinylene‐Bridged π‐Conjugated Covalent Triazine Polymers for Photocatalytic Aerobic Oxidation Reactions under Visible Light Irradiation

“…Based on the band positions of CTP samples determined by UV/Vis DRS and Mott‐Schottky curves, the LUMO level possesses enough potential to reduce O 2 to O 2 .− ( E red =−0.33 V vs. NHE) [67] . Under the action of photogenerated electrons, the adsorbed O 2 on the catalyst surface is thus rapidly converted into ROS O 2 .− , whereas the photogenerated holes can participate in the oxidization of the sulfides or amines into cationic radicals; besides, the generation process of O 2 .− is followed by the spontaneous oxidation with remaining holes to 1 O 2 on the catalyst surface [68–70] . Two oxidation processes, during which ROS O 2 .− reacts with cationic radicals of sulfides to produce dipolar peroxysulfoxide intermediate and 1 O 2 reacts with sulfides to generate diradical peroxysulfoxide intermediate, simultaneously occur and then give the sulfoxide products.…”

“…[67] Under the action of photogenerated electrons, the adsorbed O 2 on the catalyst surface is thus rapidly converted into ROS O 2 *À , whereas the photogenerated holes can participate in the oxidization of the sulfides or amines into cationic radicals; besides, the generation process of O 2 *À is followed by the spontaneous oxidation with remaining holes to 1 O 2 on the catalyst surface. [68][69][70] Two oxidation processes, during which ROS O 2 *À reacts with cationic radicals of sulfides to produce dipolar peroxysulfoxide intermediate and 1 O 2 reacts with sulfides to generate diradical peroxysulfoxide intermediate, simultaneously occur and then give the sulfoxide products. In the case of the oxidative coupling of amines, the ROS O 2 *À and 1 O 2 reacted with the formed cationic of amines with the generation of hydroperoxy intermediate and subsequently generate the imines products.…”

Reduced graphene oxide-modified Z-scheme g-C3N4/CdS photocatalyst with a staggered structure for the enhanced photoreduction of CO2

“…This is because CN and CdS have sufficiently negative CB that can produce ˙O 2 − (O 2 /˙O 2 − , −0.33 V), and the composite CS-65 retains more photogenerated electrons for the reduction reaction. 60 Thus, while the transport rate is enhanced by rGO, the photogenerated electrons effectively participate in the photocatalytic CO 2 reduction.…”

A potential link between the structure of iron catalysts and Fenton-like performance: from fundamental understanding to engineering design

“…59 In order to make the simulation consistent with the experimental solution environment, self-consistent reaction elds with the solvent model density (SMD) model are suggested to be employed. 60,61…”