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    Identification of active sites and their redox strength to select products from photocatalysis in aqueous solutions
    (2026-04-01)
    Nguyen, Van Can
    ;
    Ardchon, Chatiya
    ;
    Wongpromrat, Patthranit
    ;
    Lee, Yuh Lang
    ;
    Teng, Hsisheng
    Solar-driven photocatalytic H<inf>2</inf> evolution from aqueous solutions is promising for sustainable energy production, but it typically requires sacrificial electron donors to expedite the evolution. The fate and reaction pathways of these donors, especially their selective oxidation driven by active sites with distinct redox strengths, are rarely studied. The present study demonstrates that the reforming of sacrificial methanol in photocatalytic H<inf>2</inf> evolution can be directed toward selective production of value-added C<inf>2</inf> chemicals by tuning the redox properties of co-catalyst-derived active sites. Model catalysts, potassium poly(heptazine imide) (KPHI) decorated with Pt and CoP co-catalysts, i.e., Pt@KPHI and CoP@KPHI, are used to elucidate the reaction pathways, where acetate and ethylene glycol are the predominant liquid-phase products, respectively, alongside the gaseous H<inf>2</inf> evolution. In the Pt@KPHI system, Pt serves as a strong electron trap to effectively reduce water into H<inf>2</inf> and methanol into <sup>•</sup>CH<inf>3</inf> and induces hole-driven deep oxidation of methanol into <sup>•</sup>CO<inf>2</inf><sup>−</sup> on KPHI. The C−C coupling of <sup>•</sup>CH<inf>3</inf> and <sup>•</sup>CO<inf>2</inf><sup>−</sup> radicals selectively forms acetate. In the CoP@KPHI system, CoP served as a mild hole trap to proceed with methanol dehydrogenation into <sup>•</sup>CH<inf>2</inf>OH radicals and then ethylene glycol, while mild reduction takes place over KPHI to produce H<inf>2</inf>, presenting parallel redox reactions without any interaction. Our work illustrates how co-catalyst-induced active sites govern charge transfer and interaction between the redox reactions, thus selectively producing valuable chemicals from H<inf>2</inf>-evolution photocatalysis.
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    Magnetic and ultrasonic integrated photocatalytic hydrogen evolution effects with Nanosize CoOCu2OZnO and TiO2 decorated on reduced graphene oxide
    (2023-12-01)
    Areerob, Yonrapach
    ;
    Meng, Zeda
    ;
    Ullah, Kefayat
    ;
    Wijaya, Karna
    ;
    Otgonbayar, Zambaga
    In this study, metal oxide composite (CoOCu<inf>2</inf>OZnO) and TiO<inf>2</inf> on graphene oxide composite (CCZ−G−T) were synthesized to improve visible light-driven H<inf>2</inf> evolution through the addition of a cation scavenger, ultrasonic effect, and magnetic field effect. The synthesized nanocomposites were characterized through structural, surface, and electrochemical analyses with band structure. The photocatalyst showed hydrogen production of 792 μmol·g<sup>−1</sup> for 4 hours. Moreover, this CCZ−G−T photocatalyst exhibits relatively high photocatalytic activity at (530−810) μmol·g<sup>−1</sup> when using a scavenger, 1,190 μmol·g<sup>−1</sup> when using a magnetic field of 0.14 T, and 1,230 μmol·g<sup>−1</sup> when using ultrasonic waves. The CCZ−G−T composite exhibited 630 μmol·g<sup>−1</sup> under a magnetic field condition of 0.14 T for 1 hour, which was significantly higher than the hydrogen production rate of 510 μmol·g<sup>−1</sup> under ultrasonic conditions. The current study provides new insights into the magnetic field effect on the hydrogen evolution reaction (HER) of graphene-based photocatalysts.
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    A Novel Synthesis of Rod-Shape BaNiSn-Graphene Decorated TiO2 Composite as a Ternary Photocatalyst to Improve Visible-Light Driven H2 Evolution with Lactic Acid and TEA
    (2023-03-01)
    Areerob, Yonrapach
    ;
    Rafat, Md Nazmodduha
    ;
    Ullah, Kefayat
    ;
    Oh, Won Chun
    A novel rod-shape BaNiSn-Graphene oxide decorated TiO<inf>2</inf> composite (BaNiSn-GT) has been synthesized using a simple ultrasonic method to enhance the visible-light-driven H<inf>2</inf> evolution with cationic scavengers. The unique structure between the interfaces of BaNiSn-Graphene and TiO<inf>2</inf> provides graphene oxide of contact and excellent electron transfer for H<inf>2</inf> evolution activity. The BaNiSn-GT ternary photocatalyst exhibits relatively high photocatalytic activity with a hydrogen evolution rate of 1012 μmol/g during 4 h. On the other hand, BaNiSn-GT composite exhibited significantly higher hydrogen evolution rates of 870 μmol/g with TEA scavenger and 730 μmol/g with LA scavenger during 1 h, respectively. Moreover, the higher photocurrent density of BaNiSn-GT is correlated with electron–hole recombination, providing evidence for its inhibition, which leads to a longer lifetime of carriers produced by photoelectrons. The mechanism of the photocatalytic H<inf>2</inf> evolution of BaNiSn-GT based on a full physicochemical characterization was proposed. This study provides new insight into the efficient hydrogen-evolution of graphene-based photocatalysts.