Bridging Gaps in the Synthesis of g-CN/WO<sub>3–<i>x</i></sub> for Photocatalytic H<sub>2</sub>O<sub>2</sub> Generation: Insights into S-Scheme Heterojunction and Plasmon-Induced Hot Electrons
Aleyna Basak, Melek Sermin Özer, Zafer Eroğlu, Kang Sun, Önder Metin
Abstract
This study presents a systematic design for fabricating g-CN/WO 3– x S-scheme heterojunctions with plasmonic features (localized surface plasmon resonance (LSPR) and hot electrons) to achieve superb photocatalytic H 2 O 2 production activity. To optimize the synthesis, a rational approach is employed to how synthesis parameters influence the emergence of LSPR and hot electrons in WO 3– x and their effect on the heterojunction’s performance. As a result of such a comprehensive strategy, the developed synthesis methodology effectively bridges gaps in the literature, addressing underexplored strategies for improving photocatalytic efficiency for the controlled synthesis of the g-CN/WO 3– x heterojunction. The plasmonic characteristics attributed to oxygen deficiency in WO 3 (WO 3– x ) and g-CN/WO 3– x and interactions of g-CN and WO 3– x at the atomic level are further corroborated through a comprehensive analysis employing X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (ssNMR), and electron paramagnetic resonance (EPR). Thanks to the presence of WO 3– x, the light-harvesting ability of g-CN/WO 3– x heterojunctions spans from the visible to near-infrared region. Moreover, the generation of hot electrons on the surface of WO 3– x mitigates electron–hole recombination in the binary heterojunction. Consequently, the g-CN/WO 3– x S-scheme heterojunctions synthesized with the optimal recipe provided a superior photocatalytic H 2 O 2 generation rate of 1349.70 μmol·L –1 in 10% (v/v) aqueous methanol solution within 90 min, which is 2.36 and 7.17 times greater than that of pristine g-CN and WO 3– x, respectively, superior to other similar photocatalysts tested in photocatalytic H 2 O 2 production. The superb photocatalytic activity of the g-CN/WO 3– x heterojunction is attributed to the synergistic effects aroused in the S-scheme heterojunction, promoting efficient charge separation with enhanced redox potentials and plasmon-induced hot electrons that both accelerate reactions through the photothermal effect and serve as additional reducing species. This research broadens the perspective toward constructing nonmetallic plasmonic S-scheme heterojunctions for fields utilizing LSPR phenomena, such as photocatalysis, photonics, and biomedicine.