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Nitrogen-doped carbon dots/TiO2 nanoparticle composites for photoelectrochemical water oxidation

DOI: 10.1021/acsanm.9b02412 DOI Help

Authors: Hui Luo (Queen Mary University of London; Imperial College London) , Stoichko D. Dimitrov (Swansea University; Queen Mary University of London) , Matyas Daboczi (Imperial College London) , Ji-seon Kim (Imperial College London) , Qian Guo (Queen Mary University of London) , Yuanxing Fang (Fuzhou University) , Marc-antoine Stoeckel (Université de Strasbourg, CNRS) , Paolo Samorì (Université de Strasbourg, CNRS) , Oliver Fenwick (Queen Mary University of London) , Ana Belen Jorge Sobrido (Queen Mary University of London) , Xinchen Wang (Fuzhou University) , Maria-magdalena Titirici (Queen Mary University of London; Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Nano Materials

State: Published (Approved)
Published: March 2020
Diamond Proposal Number(s): 22447

Abstract: Carbon dots on photoactive semiconductor nanomaterials have represented an effective strategy for enhancing their photoelectrochemical (PEC) activity. By carefully designing and manipulating carbon dots/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 in PEC devices. To address this need of improving the fundamental understanding of 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 ultra-violet 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 hybridisation of NCDs and TiO2 is able not only to extend TiO2 light response into the visible range but also to form heterojunction at the NCDs/TiO2 interface with 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 carbon dots-TiO2 nanoparticle composite in a PEC system for understanding the energy transfer mechanism, demonstrating the favourable role of NCDs in the photocurrent response of TiO2 for water oxidation process. This study reveals the importance of combining structural, photophysical and electrochemical experiments to develop a comprehensive understanding of the charge injection/electronic communication between the carbon dots and their current collectors or catalyst supports.

Journal Keywords: Carbon dots; Photoelectrocatalysis; Heterojunction; Charge transfer; Band structure

Subject Areas: Materials, Chemistry, Energy

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E01-JEM ARM 200CF