Recent Strategies for Hydrogen Peroxide Production by Metal-Free Carbon Nitride Photocatalysts

Abstract

Hydrogen peroxide (H2O2) is a chemical which has gained wide importance in several industrial and research fields. Its mass production is mostly performed by the anthraquinone (AQ) oxidation reaction, leading to high energy consumption and significant generation of wastes. Other methods of synthesis found in the literature include the direct synthesis from oxygen and hydrogen. However, this H2O2 production process is prone to explosion hazard or undesirable by‑product generation. With the growing demand of H2O2, the development of cleaner and economically viable processes has been under intense investigation. Heterogeneous photocatalysis for H2O2 production has appeared as a promising alternative since it requires only an optical semiconductor, water, oxygen, and ideally solar light irradiation. Moreover, employing a metal-free semiconductor minimizes possible toxicity consequences and reinforces the sustainability of the process. The most studied metal‑free catalyst employed for H2O2 production is polymeric carbon nitride (CN). Several chemical and physical modifications over CN have been investigated together with the assessment of different sacrificial agents and light sources. This review shows the recent developments on CN materials design for enhancing the synthesis of H2O2, along with the proposed mechanisms of H2O2 production. Finally, the direct in situ generation of H2O2, when dealing with the photocatalytic synthesis of added-value organic compounds and water treatment, is discussed.

Electrochemical and Photoelectrochemical Water Oxidation for Hydrogen Peroxide Production

“…It has been widely used for pulp and textile bleaching, as a first‐aid disinfectant, in advanced oxidation processes (AOPs) for wastewater treatment, hydrometallurgy, and the electronics industry [8] . In addition to being a valuable and clean oxidizing reagent for environmental remediation, [9] H 2 O 2 could also serve as a liquid fuel in a fuel cell alternative to H 2 and O 2 . The energy density of H 2 O 2 (2.1 MJ kg −1 for 60 % aqueous H 2 O 2 ) is comparable to that of H 2 (3.5 MJ kg −1 for compressed H 2 ) [10–14] .…”

Graphitic carbon nitride photocatalysis: the hydroperoxyl radical role revealed by kinetic modelling

“…photogenerated electrons; [75][76][77] or (iv) H 2 O 2 is being transformed into water after the removal of the primary proton donor. 17,50,53 In the presence of these different theories, it is also necessary to establish the correct reaction path that occurs to explain these results, as well as correlate with what was observed during PhOH degradation with the generation of H 2 O 2 , along with the impact of DO concentration.…”

“…[11][12][13][14][15] In addition, GCN has attracted significant attention as a non-metallic material for eco-friendly H 2 O 2 production. [16][17][18][19] For this, heterogeneous photocatalysis takes the benefit of generating reactive oxygen species (ROS), such as the case of oxy-radicals (hydroxyl -HO˙, superoxide -O 2 ˙−, among others). These radicals can be generated by oxidation reactions in the valence band (VB) and by reduction reactions in the conduction band (CB).…”

Hydrogen Peroxide Versus Hydrogen Generation at Bipolar Pd/Au Nano-catalysts Grown into an Intrinsically Microporous Polyamine (PIM-EA-TB)

“…New types of sustainable single-atom catalysts for the conversion of oxygen into hydrogen peroxide are under development [29]. Although photolytic processes are successfully employed to drive the reduction of O 2 to H 2 O 2 [30], there are also some successful dark chemical processes based on ambient oxygen and chemical reducing agents such as glucose [31] or formic acid [32].…”