Self‐sustaining photocatalytic NO3−reduction systems could become ideal NO3−removal methods. Developing an efficient, highly active photocatalyst is the key to the photocatalytic reduction of NO3−. In this work, we present the synthesis of Ni2P‐modified Ta3N5(Ni2P/Ta3N5), TaON (Ni2P/TaON), and TiO2(Ni2P/TiO2). Starting with a 2 mM (28 g/mL NO3−−N) aqueous solution of NO3−, as made Ni2P/Ta3N5and Ni2P/TaON display as high as 79% and 61% NO3−conversion under 419 nm light within 12 h, which correspond to reaction rates per gram of 196 μmol g−1 h−1and 153 μmol g−1 h−1, respectively, and apparent quantum yields of 3–4%. Compared to 24% NO3−conversion in Ni2P/TiO2, Ni2P/Ta3N5and Ni2P/TaON exhibit higher activities due to the visible light active semiconductor (SC) substrates Ta3N5and TaON. We also discuss two possible electron migration pathways in Ni2P/semiconductor heterostructures. Our experimental results suggest one dominant electron migration pathway in these materials, namely: Photo‐generated electrons migrate from the semiconductor to co‐catalyst Ni2P, and upshift its Fermi level. The higher Fermi level provides greater driving force and allows NO3−reduction to occur on the Ni2P surface.
Graphitic carbon nitride (g‐C3N4) has gained great interest as a visible‐light‐activated photocatalyst. As an emerging nanomaterial for environmental applications, its competitive performance and environmentally responsible synthesis are critical to its success. A powerful tool for informing material development with reduced environmental impacts is life cycle assessment (LCA). In this study, LCA is used to evaluate the environmental impacts of g‐C3N4nanosheet produced via eight existing synthesis routes. The results reveal electricity as the main contributor to the cumulative impacts of all eight g‐C3N4syntheses. There are opportunities to reduce energy demand, and consequently the synthesis impacts, by revising synthesis procedures (i.e., removing or reducing time of use of a piece of equipment), optimizing the calcination step (i.e., faster heating rate, lower heating time, lower temperature), and moving to cleaner electricity sources. Further, benchmarking the environmental impacts of g‐C3N4nanosheets to a well‐established metal‐based photocatalyst, titanium dioxide nanoparticles (nano‐TiO2), reveals mixed comparative results. The synthesis method substantially influences the comparative impacts. Considering use‐phase benefits of activating g‐C3N4with visible wavelength light emitting diodes compared to ultraviolet (UV) wavelengths for nano‐TiO2results in a 52% energy demand reduction (in kWh). Performance of g‐C3N4compared to a high‐energy disinfection approach (i.e., conventional UV) reveals an inability to meet drinking water disinfection standards for viral load reduction (4‐log reduction) with any mass of g‐C3N4, given its high embodied resource footprint. This work establishes a foundation to inform and direct g‐C3N4nanosheets toward improved sustainable development.
more » « less- NSF-PAR ID:
- 10407182
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Industrial Ecology
- Volume:
- 27
- Issue:
- 3
- ISSN:
- 1088-1980
- Page Range / eLocation ID:
- p. 1008-1020
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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