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Nitrogen-Doped Carbon Dots/TiO2 Nanoparticle Composites for Photoelectrochemical Water Oxidation
journal contribution
posted on 2020-03-27, 18:03 authored by Hui Luo, Stoichko Dimitrov, Matyas Daboczi, Ji-Seon Kim, Qian Guo, Yuanxing Fang, Marc-Antoine Stoeckel, Paolo Samorì, Oliver Fenwick, Ana Belen Jorge Sobrido, Xinchen Wang, Maria-Magdalena TitiriciCarbon
dots on photoactive semiconductor nanomaterials have represented
an effective strategy for enhancing their photoelectrochemical (PEC)
activity. By carefully designing and manipulating a carbon dot/support
composite, a high photocurrent could be obtained. Currently, there
is not much fundamental understanding of how the interaction between
such materials can facilitate the reaction process. This hinders the
wide applicability of PEC devices. To address this need of improving
the fundamental understanding of the carbon dots/semiconductor nanocomposite,
we have taken the TiO2 case as a model semiconductor system
with nitrogen-doped carbon dots (NCDs). We present here with in-depth
investigation of the structural hybridization and energy transitions
in the NCDs/TiO2 photoelectrode via high-resolution scanning
transmission microscopy (HR-STEM), electron energy loss spectroscopy
(EELS), UV–vis absorption, electrochemical impedance spectroscopy
(EIS), Mott–Schottky (M–S), time-correlated single-photon
counting (TCSPC), and ultraviolet photoelectron spectroscopy (UPS),
which shed some light on the charge-transfer process at the carbon
dots and TiO2 interface. We show that N doping in carbon
dots can effectively prolong the carrier lifetime, and the hybridization
of NCDs and TiO2 is able not only to extend TiO2 light response into the visible range but also to form a heterojunction
at the NCDs/TiO2 interface with a properly aligned band
structure that allows a spatial separation of the charges. This work
is arguably the first to report the direct probing of the band positions
of the carbon dot–TiO2 nanoparticle composite in
a PEC system for understanding the energy-transfer mechanism, demonstrating
the favorable role of NCDs in the photocurrent response of TiO2 for the water oxidation process. This study reveals the importance
of combining structural, photophysical, and electrochemical experiments
to develop a comprehensive understanding of the nanoscale charge-transfer
processes between the carbon dots and their catalyst supports.
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Keywords
electrochemical impedance spectroscopyTCSPCPhotoelectrochemical Water Oxidation Carbon dotsEELSTiO 2 casescanning transmission microscopymodel semiconductor systemunderstandingnanoscale charge-transfer processesUPSwater oxidation processUVcarbon dotsPECTiO 2 light responsephotoactive semiconductor nanomaterialsEISTiO 2HR-STEMTiO 2 interfacenitrogen-doped carbon dotsNCD
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