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    Öğe
    Enhanced Photocatalytic Hydrogen Evolution by Star-Shaped Viologen-Sensitized TiO2 Nanoparticles
    (American Chemical Society, 2023) Turgut, Kubra; Altınışık, Sinem; Yanalak, Gizem; Koyuncu, Sermet; Hatay Patir, Imren
    Viologens are well-suited for serving as electron-transfer mediators in redox systems due to their low reduction potential and ability to form stable radical cations. Because of this feature, viologens can play a key role in modifying semiconductors toward enhanced photocatalytic performance. Herein, a series of hybrid photocatalysts composed of TiO2 nanoparticles and star-shaped viologen derivatives with different alkyl chains [TPCBP-X_TiO2; X: ethyl (E), butyl (B), hexyl (H) and octyl (O)] were prepared for the photocatalytic hydrogen evolution from water under visible-light irradiation. The TPCBP-X molecules not only provide photosensitization of TiO2 nanoparticles in the visible-light region but also act as an efficient electron-transfer mediator for the transfer of photoinduced electrons to TiO2 and Pt. Among these photocatalysts, TPCBP-E_TiO2 exhibited a 1.013 mmol g(-1) h(-1) H-2 evolution rate with an apparent quantum yield (AQY) of 20.15% (470 nm), which dramatically improved hydrogen evolution activity among the other structures [TPCBP-X_TiO2 (X; B, H, O)] due to the more porous and uniform surface, resulting in its low barrier effect for electron transfer. In addition, in the presence of a Pt cocatalyst, TPCBP-E_TiO2 yielded a H-2 evolution rate of 17.7 mmol g(-1), which is about 2.2 times higher than that of pure TPCBP-E_TiO2 (8.1 mmol g(-1)) after 8 h of visible-light illumination.
  • [ X ]
    Öğe
    Hydrophilic porous organic polymers with fluorene-viologen units for enhanced photocatalytic hydrogen production
    (Elsevier, 2025) Altinisik, Sinem; Yildiz, Gizem; Turgut, Kubra; Yayla, Cansu; Patir, Imren Hatay; Koyuncu, Sermet
    The rising energy demand and environmental concerns have intensified the search for clean energy solutions. Photocatalytic water splitting offers a promising route, yet efficiency remains limited by the need for advanced photocatalysts with enhanced light absorption, charge separation, and water interaction. Porous organic polymers (POPs) are emerging as efficient materials for solar energy conversion due to their ordered conjugated structures. This study explores the impact of a ketone moiety on the hydrophilicity and photocatalytic hydrogen evolution efficiency of fluorene-bridged bicarbazole-viologen-based POPs (POP-MB-TP(DCzFO) and POP-MB-TP (DCzF)). Our results show that POP-MB-TP(DCzF) achieves a hydrogen evolution rate of 3.37 mmol g- 1 h- 1, nearly twice that of POP-MB-TP(DCzFO) (1.72 mmol g- 1 h- 1). This improvement highlights the role of hydrophilicity in charge transport and catalytic efficiency, providing insights for designing highly efficient organic photocatalysts for sustainable hydrogen production.