On-site H2O2 production with amphiphilic g-C3N4 as photocatalyst in a combined photocatalysis–extraction–separation process

Zhang, Hao; Liu, Meng; Zhang, Xingyang; Yuan, Biao; Wu, Pan; Liu, Changjun; Jiang, Wei

doi:10.1016/j.cej.2022.135664

Cited by 27 publications

(11 citation statements)

References 33 publications

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“…17,18 The observed effects might be negligible in very dilute solutions of benzyl alcohol, but they might represent a dominant mechanism under solvent-free (only benzyl alcohol) or biphasic (e.g., equivolumetric benzyl alcohol/water mixtures) conditions. [38][39][40][41][42][43] Two further points are noteworthy with respect to the visible light activity. Firstly, the designation of a 420 nm cut-off filter implies, per definitionem, that the transmittance at 420 nm is 50%, i.e., there can be a small portion of higher energy light still transmitted when using these filters.…”

Section: Does Benzaldehyde Once Formed Undergo Further Transformation...mentioning

confidence: 97%

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Krivtsov

Vazirani²,

Mitoraj³

et al. 2022

Preprint

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Selective photooxidation of aromatic alcohols to corresponding aldehydes is a widely used model reaction for evaluation of performance of heterogeneous photocatalysts. A chief example is the photocatalytic production of hydrogen peroxide via reduction of dioxygen with concomitant photooxidation of benzyl alcohol to benzaldehyde. Although it has long been known that photoexcitation of benzaldehyde under UV light yields reactive benzaldehyde radicals capable of oxidizing substrates such as benzyl alcohol, it was assumed that such autocatalytic processes cannot be initiated under visible light irradiation. Herein we demonstrate the ability of benzaldehyde to promote auto-photocatalytic oxidation of benzyl alcohol and produce large quantities of H2O2 in solvent-free (no water) or biphasic (with water) systems even under nominally solar-simulated visible light (>420 nm cutoff filter) irradiation. While these results open up broader prospects for the use of benzaldehyde in visible light-driven photocatalysis as exemplified by the ability of benzaldehyde to photocatalyze H2O2 production even in the presence of alternative electron donors (e.g., ethanol), they also shed some critical light on the plethora of research reports on photocatalytic H2O2 production in which benzyl alcohol was employed as electron donor. Since the autocatalytic pathway based on the photocatalytic activity of benzaldehyde formed during photocatalysis under such conditions cannot be neglected, the interpretations of photocatalytic performance are likely contentious and distorted in such reports. We conclude that the use of benzyl alcohol as a model electron donor in photocatalytic studies should be definitely discouraged, and highlight the importance of carrying out simple check protocols for excluding similar issues when using alternative substrates.

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Section: Does Benzaldehyde Once Formed Undergo Further Transformation...mentioning

confidence: 97%

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Krivtsov

Vazirani²,

Mitoraj³

et al. 2022

Preprint

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Section: Resultsmentioning

confidence: 99%

“…The presence of the sacrificial agent during the photocatalytic process is essential to allow for sufficient H + , these latter originated from the oxidation of the parent molecule in contact with negatively charged moieties in the photocatalyst materials (Figure 10). 61,121 The improved light absorption proved to be beneficial for the photocatalytic reactions, but it was not the only factor at play, since the absorption decreases following the order CN-P > CN-G > CN-A (Figure 6a), which is inversely correlated with the photoactivity. As discussed above, the alteration in the band positions was fundamental to obtain the best functionality of CN.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Boosting Carbon Nitride Photoactivity by Metal-Free Functionalization for Selective H₂O₂ Synthesis under Visible Light

Torres‐Pinto

Boumeriame

Silva

et al. 2023

ACS Sustainable Chem. Eng.

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Carbon nitride (CN) is a polymer-based material thoroughly studied for different photocatalytic applications due to its optical, electronic, and chemical properties. Its main limitation is fast electron/hole recombination. To overcome this drawback, several functionalization methods have been applied using organic solvents and severe operating conditions. In the present work, a thermally exfoliated CN was functionalized for the first time via a hydrothermal route using glucose (G), perylene (P), and anthraquinone (A) by implementing water as solvent at a mild temperature (120 °C). The materials were tested for the photocatalytic production of hydrogen peroxide (H 2 O 2 ) in aqueous solutions saturated with dissolved oxygen and in the presence of a sacrificial agent (isopropyl alcohol). Improved evolution rates of H 2 O 2 were confirmed from 9.7 mmol g −1 h −1 for the unmodified CN material, up to 11.1, 14.2, and 25.0 mmol g −1 h −1 for the functionalized photocatalysts CN-G, CN-P, and CN-A, respectively. The surface chemistry studied by XPS, EDX, and FTIR revealed the specific functionalities allowing for improved energy transfer, faster redox reactions, and enhanced photoactivation. The optical and electrochemical characterizations corroborate the photocatalytic results since photoluminescence was severely quenched after functionalization, and the electronic properties were enhanced, both indicating reduced recombination of charge carriers. The band structure was also investigated, proving that the generation of H 2 O 2 was thermodynamically favored for the functionalized materials, while H 2 O 2 decomposition was suppressed.

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“…78 Furthermore, extracting H 2 O 2 from organic extractants necessitates an energy-intensive distillation process, and H 2 O 2 decomposes easily in this process because of high temperatures. 154 Zhang et al developed a facile photosynthesis–extraction–separation process for on-site PHP water contamination. 154 Unlike traditional aqueous phase synthesis, hydrogen peroxide is synthesized via photocatalysis in a hydrophobic organic phase and then separated from organics via water extraction.…”

Section: On-site Php For Water Remediationmentioning

confidence: 99%

“…154 Zhang et al developed a facile photosynthesis–extraction–separation process for on-site PHP water contamination. 154 Unlike traditional aqueous phase synthesis, hydrogen peroxide is synthesized via photocatalysis in a hydrophobic organic phase and then separated from organics via water extraction. Concurrently, an aqueous hydrogen peroxide solution is generated, which can be used directly for on-site water treatment.…”

Section: On-site Php For Water Remediationmentioning

confidence: 99%

Photosynthesis of hydrogen peroxide in water: a promising on-site strategy for water remediation

Chu

Wang

Deng

et al. 2022

Environ. Sci.: Water Res. Technol.

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On-site H2O2 production with amphiphilic g-C3N4 as photocatalyst in a combined photocatalysis–extraction–separation process

Cited by 27 publications

References 33 publications

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Boosting Carbon Nitride Photoactivity by Metal-Free Functionalization for Selective H₂O₂ Synthesis under Visible Light

Photosynthesis of hydrogen peroxide in water: a promising on-site strategy for water remediation

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On-site H2O2 production with amphiphilic g-C3N4 as photocatalyst in a combined photocatalysis–extraction–separation process

Cited by 27 publications

References 33 publications

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Boosting Carbon Nitride Photoactivity by Metal-Free Functionalization for Selective H2O2 Synthesis under Visible Light

Photosynthesis of hydrogen peroxide in water: a promising on-site strategy for water remediation

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Boosting Carbon Nitride Photoactivity by Metal-Free Functionalization for Selective H₂O₂ Synthesis under Visible Light