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

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.