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Open AccessArticle

Mesoporous Tungsten Trioxide Photoanodes Modified with Nitrogen-Doped Carbon Quantum Dots for Enhanced Oxygen Evolution Photo-Reaction

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Electrochemical Sciences Research Chair (ESRC), Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
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Department of Astronomy and Physics, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
*
Author to whom correspondence should be addressed.
Nanomaterials 2019, 9(10), 1502; https://doi.org/10.3390/nano9101502
Received: 29 September 2019 / Revised: 17 October 2019 / Accepted: 18 October 2019 / Published: 22 October 2019
(This article belongs to the Special Issue Nanostructured Catalysts for Sustainable Applications)
Nanostructured photoanodes are attractive materials for hydrogen production via water photo-electrolysis process. This study focused on the incorporation of carbon quantum dots doped with nitrogen as a photosensitizer into mesoporous tungsten trioxide photoanodes (N-CQD/meso-WO3) using a surfactant self-assembly template approach. The crystal structure, composition, and morphology of pure and N-CQD- modified mesoporous WO3 photoanodes were investigated using scanning electron and transmission microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Due to their high surface area, enhanced optical absorption, and charge-carrier separation and transfer, the resulting N-CQD/meso-WO3 photoanodes exhibited a significantly enhanced photocurrent density of 1.45 mA cm−2 at 1.23 V vs. RHE under AM 1.5 G illumination in 0.5 M Na2SO4 without any co-catalysts or sacrificial reagent, which was about 2.23 times greater than its corresponding pure meso-WO3. Moreover, the oxygen evolution onset potential of the N-CQD/meso-WO3 photoanodes exhibited a negative shift of 95 mV, signifying that both the charge-carrier separation and transfer processes were promoted. View Full-Text
Keywords: mesoporous; tungsten; trioxide; carbon; quantum; dots; photo-electrochemical; water splitting mesoporous; tungsten; trioxide; carbon; quantum; dots; photo-electrochemical; water splitting
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Amer, M.S.; Arunachalam, P.; Al-Mayouf, A.M.; Prasad, S.; Alshalwi, M.N.; Ghanem, M.A. Mesoporous Tungsten Trioxide Photoanodes Modified with Nitrogen-Doped Carbon Quantum Dots for Enhanced Oxygen Evolution Photo-Reaction. Nanomaterials 2019, 9, 1502.

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    Link: https://zenodo.org/deposit/3464406
    Description: Figure S1: FTIR spectra of CQDs and N-CQDs samples, Figure S2: (a) XPS survey spectra for the CQDs, N-CQD-7 and N-CQD-20 samples. The only elements identified were carbon, nitrogen, and oxygen. (c) C 1s, (d) N 1s and (E) O 1s high resolution XPS spectra for N-CQD-7 sample, Figure S3: EDX spectra of N-CQDs samples, (a) N-CQD-3, (b) N-CQD-5, (c) N-CQD-7, and (d) N-CQD-20, Figure S4: (a) UV-Vis absorption spectra for the CQDs and N-CQDs samples. Inserts show digital photos of aqueous N-CQD-7 (left) and their bright blue PL (right) under UV, (b,c,d) PL spectra for the N-CQD-7, N-CQD-13, and N-CQD-20. The excitation wavelength was increased from 340 to 540 nm in 20 nm increments. (e) External quantum yields for the N-CQDs samples under 360 nm excitation, calibrated against quinine sulfate, Figure S5: steps for the synthesis of meso-WO3 and modification with CQDs, Figure S6: Thickness of meso-WO3 and modification with CQDs as measured by a profilometer, Table S1: a comparison the photocurrent density of WO3 based composite materials.
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