A Minireview: The Mechanism of H₂O₂ Photoproduction by Graphitic Carbon Nitride

Abstract

Hydrogen peroxide (H2O2) is extensively used in production and life, functioning as an ecofriendly oxidant. However, the dominant method currently employed, the anthraquinone method, is not conducive to sustainable development. Recently, photocatalytic H2O2 synthesis has garnered significant attention as an environment‐friendly approach. Graphitic carbon nitride (g‐C3N4), a new type of photocatalyst, shows great potential for generating H2O2 due to its excellent stability, high photocatalytic activity, selectivity, easy adjustability, and low cost. However, the research on the mechanism of H2O2 photoproduction has not been fully understood, which limits its development and practical application. Herein, the recent progress on modified g‐C3N4 is summarized and the effect of modification methods on the photocatalytic activity and H2O2 generation process is discussed. The challenges and perspectives of g‐C3N4 toward H2O2 photoproduction are proposed.

MXene Schottky Functionalized Z-scheme Ternary Heterostructure for Enhanced Photocatalytic H2O2 Production and H2 Evolution

“…Up to now, various diversities of photocatalysts have been used for H 2 O 2 photoproduction and H 2 evolution, such as metal oxides, metal sulfides, layered double hydroxides, metal organic frameworks, and organic polymers. − Among these, graphitic carbon nitride (g-C 3 N 4 ) is considered as a superexcellent photocatalyst and is widely used in photoproduction of H 2 O 2 as it can selectively reduce O 2 to H 2 O 2 via 1,4-endoperoxide formation and also has the ability to reduce H 2 O for H 2 evolution. − Nevertheless, bulk g-C 3 N 4 suffers from fast charge recombination and harvests lower solar radiation, impeding its efficiency toward photocatalysis. − Apart from many modification strategies, morphology modification to form nanosheets and intrinsic doping with a nonmetallic heteroatom have been adopted widely and were reported for various photocatalytic reactions. − In this regard, O-doped tube-shaped g-C 3 N 4 was reported by Fu et al for better CO 2 photoreduction activity . Yu et al studied photocatalytic H 2 O 2 production by P-modified porous g-C 3 N 4 .…”

H2O2 Photosynthesis from H2O and O2 under Weak Light by Carbon Nitrides with the Piezoelectric Effect

“…Artificial photocatalysis offers a potential way to drive chemical conversions under very mild conditions. − Recently, engineering polymeric carbon nitride (pCN)-based photocatalysts has become a promising strategy for overall H 2 O 2 production by using water and oxygen as raw materials without any sacrificial agents. − It involves a 2e – oxygen reduction reaction (ORR, eq ) and a 2e – or 4e – water oxidation reaction (WOR, eqs –) . On the one hand, although favorable in thermodynamics, the 4e – WOR (+1.23 V vs NHE, eq ) exhibits sluggish kinetics, compared to the 2e – WOR at higher oxidation potential (+1.76 V vs NHE, eq ; +2.73 V vs NHE, eq ).…”

Recent advancements in graphitic carbon nitride based direct Z- and S-scheme heterostructures for photocatalytic H2O2 production

“…This attention can be attributed to its advantageous electronic band structure, exceptional physicochemical stability, facile synthesis methods, cost-effectiveness, and high resistance to photocorrosion. 66–72 Additionally, the specific alignment of its conduction and valence bands favours oxygen (O 2 ) reduction while concurrently limiting the undesired oxidative breakdown of H 2 O 2 , which gives it an edge over oxide-based alternatives. 73 This benefit is further amplified by its high selectivity in generating H 2 O 2 through a mechanism involving the formation of superoxide radicals (˙O 2 − ) and subsequent 1,4-endoperoxide intermediates on its melem units.…”