S-Scheme Heterostructured CdS/g-C₃N₄ Nanocatalysts for Piezo-Photocatalytic Synthesis of H₂O₂

Abstract

Sustainability in catalysis is increasingly becoming the primary target in academic and industrial studies. Regarding the material perspective, designing heterojunction nanocatalysts to produce small molecules, such as hydrogen peroxide (H 2 O 2 ), has been an attractive research theme in recent decades. Nonetheless, most reported materials suffer from a complicated synthetic process with various steps and using unbenign solvents, hindering practical applications on an industrial scale. This study proposed a facile one-step way to fabricate heterostructured CdS/g-C 3 N 4 nanocatalysts to produce H 2 O 2 from water and oxygen under light and ultrasound irradiation. The results showed that the formation of H 2 O 2 mainly relies on oxygen radical species. Oxygen is initially converted into superoxide via excited electrons from CdS, followed by the formation of singlet oxygen from the oxidation process in g-C 3 N 4 sites. Interestingly, the formation of H 2 O 2 in an inert atmosphere is associated with the in situ evolution of oxygen from water oxidation due to the suitable electronic band position of g-C 3 N 4 to drive multioxidation reactions. Charge transfer characterizations illustrate the S-scheme mechanism in the catalytic process, giving a better understanding of the charge transportation phenomenon, thus providing a critical pathway in designing and developing heterojunction materials for catalysis with easier catalyst preparation and operation processes. KEYWORDS: g-C 3 N 4 , CdS, solid-state synthesis, S-scheme heterojunctions, H 2 O 2 , piezo-photocatalysis

Recent Advancement in Piezopolarization Induced Photocatalytic H2O2 Production: Fundamentals, Theoretical Insights, and Future Endeavors

“…However, the charge recombination largely reduces the overall H 2 O 2 production. Additionally, O 2 adsorption and successive activation are also crucial during the reduction/oxidation process. , Besides, the band edge potential and O 2 reduction path of the catalytic reaction play important roles in improving photocatalytic H 2 O 2 production. , Moreover, by designing piezoactive photocatalytic systems, the above-discussed drawbacks can be addressed, and significant enhancement in H 2 O 2 evolution can be achieved. On the basis of present research advancement, the H 2 O 2 formation route can be classified into the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR), as discussed below and illustrated in Figure .…”

“…Additionally, O 2 adsorption and successive activation are also crucial during the reduction/oxidation process. 13,17 Besides, the band edge potential and O 2 reduction path of the catalytic reaction play important roles in improving photocatalytic H 2 O 2 production. 13,65 Moreover, by designing piezoactive photocatalytic systems, the above-discussed drawbacks can be addressed, and significant enhancement in H 2 O 2 evolution can be achieved.…”

“…Both pathways involve a protoncoupled electron transfer process where the source of the proton can be either H 2 O or the used organic electron donor. 17,66 Apart from this, the four-electron competitive ORR process (O 2 + 4e − + 4h + → 2H 2 O, 1.23 V vs NHE) resulting in water decreases the overall H 2 O 2 yield. Adding more, the indirect superoxide radical route (involving multiple unpredictable reactions) requires a higher negative potential (−0.33 V vs NHE) than the direct pathway (0.68 V vs NHE), which again lowers the H 2 O 2 concentration and selectivity.…”

“…11,13 Nowadays piezo-assisted photocatalysis has emerged as a revolutionary strategy and gathered global attention toward O 2 reduction to H 2 O 2 under ambient conditions. 17 experimental and theoretical investigations to achieve improved efficiency and address the essential needs for commercialization. This review can be a diary note for researchers working on this specific field.…”

“…In this context, several modification techniques were developed and adopted, including doping, defect engineering, cocatalyst loading, forming heterojunction, etc., but the process has yet to get industrial status. , Nowadays piezo-assisted photocatalysis has emerged as a revolutionary strategy and gathered global attention toward O 2 reduction to H 2 O 2 under ambient conditions . However, this area of research is still in the preliminary phase and has a long way to go with intensive experimental and theoretical investigations to achieve improved efficiency and address the essential needs for commercialization.…”