Monday, March 20 2023 Sign In   |    Register

News Quick Search



Front Page
Power News
Today's News
Yesterday's News
Week of Mar 20
Week of Mar 13
Week of Mar 06
Week of Feb 27
Week of Feb 20
By Topic
By News Partner
Gas News
News Customization


Pro Plus(+)

Add on products to your professional subscription.
  • Energy Archive News

    Home > News > Power News > News Article

    Share by Email E-mail Printer Friendly Print

    A dual-purpose photocatalytic reaction for hydrogen evolution and simultaneous organic pollutant degradation

    January 20, 2023 - India Engineering News


      January 20 -- Photocatalysis is a green and sustainable technology that has received extensive attention because of its ability to utilize solar energy to address the energy crisis and environmental pollution. Water pollution is mainly caused by contaminants consisting of heavy metal ions and organic pollutants. Among these, organic pollutants possess high toxicity, carcinogenicity, and refractory degradation, posing a serious threat to human health.

      In recent years, the photocatalytic decomposition of organic pollutants has been considered a promising water treatment technology. Comparably, hydrogen production through photocatalytic water splitting has shown to be an efficient approach for transforming solar energy into hydrogen energy.

      Nevertheless, most current research in the field of photocatalysis has either focused on the purification of wastewater or on the production of hydrogen. However, oxidative degradation and proton reduction reactions may be more valuable as photocatalytic processes for wastewater purification and energy recovery.

      Dual-functional photocatalytic processes may be effective in persistently improving the efficiency of light quantum utilization, such as photocatalytic H2 evolution reactions (HER) for simultaneous organic molecule degradation, which is expected to achieve H2 evolution from organic wastewater.

      During this process, the photogenerated reactive oxygen species (ROS) decompose organics into less harmful small molecules, and photo-electrons convert hydrogen protons or water molecules into H2. Although a variety of materials (e.g., MOFs, metal oxides, metal sulfides, and carbon-based composites) have been increasingly employed for dual-purpose photocatalytic technology, dual-functional photocatalytic performance is considered relatively unsatisfactory at present due to the intrinsic defects of the photocatalysts and corresponding insufficient research on the mechanism.

      Therefore, it is worth emphasizing that the designs and development of photocatalysts with dual-purpose activity and efficient light quantum utilization are valuable for promising practical applications.

      Among the various semiconductors used for photocatalyst fabrication, metal sulfide has shown to be an extremely promising candidate for photocatalytic H2 production or pollutant degradation. ZnIn2S4 is a ternary chalcogenide (AB2X4) with low toxicity, a suitable band-gap (2.1–2.4 eV), and relatively high chemical stability. However, pristine ZnIn2S4 has shown limited photo-reactivity due to its higher HER overpotential and fast electron-hole recombination.

      In recent years, MoS2 has been widely used in photocatalytic organic compound degradation and hydrogen evolution due to its many advantages such as environmental friendliness, large surface area, excellent stability, and easy preparation. Previous studies have suggested that MoS2 is a more effective H2-evolution cocatalyst than many noble metals, due to its number of unsaturated S atom active sites on its exposed edges.

      Recently, some scholars have reported that oxygen-doped MoS2 can significantly enhance photocatalytic activity and provide more surface activity reaction sites. Therefore, oxygen-doped MoS2 may be a good choice for fabricating high-performance photocatalytic materials.

      Previously, MoS2-ZnIn2S4 composites was mainly considered for either photocatalytic HER or organic degradation. The research on dual-purpose photocatalytic characteristics and influencing factors of MoS2/ZnIn2S4 composites was limited in recent years. However, the principal issue of dual-functional systems, including thermodynamic and kinetic aspects, should be examined in more detail to further clarify the inherent mechanism of dual-functional photocatalysis.

      In this work, the researchers from University of Jinan designed a novel urchin-like oxygen-doped MoS2/ZnIn2S4 (OMS/ZIS) composite through the in-situ growth of ZnIn2S4 nanosheets on the surfaces of oxygen-doped MoS2 (OMS) nanospheres. Then, a dual-functional photocatalysis system based on the OMS/ZIS composite for simultaneous photocatalytic H2 production and organic degradation was successfully constructed.

      The expected dual-purpose performance was investigated using resorcinol, tetracycline, bisphenol A, and natural organic matter (NOM) as the matrix, to elucidate the mutual coupling effect of the designed photocatalytic oxidation-reduction reactions. The primary mechanism of this dual-purpose system was also discussed to clarify in detail the principal issue and internal relation. The results of this study may provide inspiration for the rational design of highly efficient, dual-functional photocatalysts in the future.

      This study entitled "Highly effective visible-photocatalytic hydrogen evolution and simultaneous organic pollutant degradation over an urchin-like oxygen-doped MoS2/ZnIn2S4 composite" is published online in Frontiers of Environmental Science & Engineering in 2022.

      In this work, an urchin-like oxygen-doped MoS2/ZnIn2S4 (OMS/ZIS) composite was fabricated for the first time using a simple solvothermal method. The unique microstructure with abundant active sites and fast charge transfer channels further shortened the charge migration distance and compressed carrier recombination.

      The obtained composite exhibited an efficient H2 evolution reaction rate of 12.8 mmol/g/h under visible light, which was nearly times higher than pristine ZnIn2S4, and the apparent quantum efficiency was 14.9% (420 nm).

      The results of the simultaneous photocatalytic H2 evolution and organic pollutant decomposition test were satisfactory, resulting in decomposition efficiencies of resorcinol, tetracycline, and bisphenol A that reached 41.5%, 63.5%, and 53.0% after 4 h, respectively, and the highest H2 evolution rate was 672.7 µmol/g/h for bisphenol A.

      Furthermore, natural organic matter (NOM) abundantly found in actual water was adopted as an electron donor for H production under simulated sunlight irradiation, indicating the promising practicability of simultaneous hydrogen evolution and NOM decomposition. Moreover, the mechanisms of the dual-purpose photocatalytic reactions, as well as the synergistic effect between the molecular structures of the organic pollutants and the corresponding adsorption behavior on the photocatalyst surface were illustrated in detail.

      In this study, an urchin-like OMS/ZIS composite with a considerably higher and stable photocatalytic H2 evolution activity was assembled for the first time using a simple solvothermal method. The highest efficiency was obtained over 10-OMS/ZIS with an HER rate of 12.8 mmol/g/h under visible light conditions.

      The excellent photocatalytic H2 evolution activity was ascribed to the unique microstructure, which contained abundant active sites and fast charge transfer channels and shortened the charge migration distance and compressed the carrier recombination. This resulted in a reduction in the charge transfer resistance and lower overpotential of HER. Furthermore, the results of photocatalytic H2 evolution over different organic molecules illustrated the outstanding photocatalytic dual-purpose performance, in which HER was driven by the photo-induced electrons and the organics were mainly decomposed by the holes through direct oxidation.

      The distinct HER rate differences using different organic molecules as electron donors were likely due to the synergistic effect between the organic molecule structure and corresponding adsorption on the photocatalyst surface. This study may provide new insights into the design of high-activity dual-functional photocatalysts for environmental and energy applications.


    Other Articles - Utility Business / General


       Home  -  Feedback  -  Contact Us  -  Safe Sender  -  About Energy Central   
    Copyright © 1996-2023 by CyberTech, Inc. All rights reserved.
    Energy Central® and Energy Central Professional® are registered trademarks of CyberTech, Incorporated. Data and information is provided for informational purposes only, and is not intended for trading purposes. CyberTech does not warrant that the information or services of Energy Central will meet any specific requirements; nor will it be error free or uninterrupted; nor shall CyberTech be liable for any indirect, incidental or consequential damages (including lost data, information or profits) sustained or incurred in connection with the use of, operation of, or inability to use Energy Central. Other terms of use may apply. Membership information is confidential and subject to our privacy agreement.