Electronic Structure and Interface Energetics of CuBi2O4Photoelectrodes

Freddy E. Oropeza (Corresponding author), Nelson Y. Dzade, Amalia Pons-Martí, Zhenni Yang, Kelvin H.L. Zhang, Nora H. De Leeuw, Emiel J.M. Hensen, Jan P. Hofmann (Corresponding author)

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

49 Citaten (Scopus)

Samenvatting

CuBi2O4 exhibits significant potential for the photoelectrochemical (PEC) conversion of solar energy into chemical fuels, owing to its extended visible-light absorption and positive flat band potential vs the reversible hydrogen electrode. A detailed understanding of the fundamental electronic structure and its correlation with PEC activity is of significant importance to address limiting factors, such as poor charge carrier mobility and stability under PEC conditions. In this study, the electronic structure of CuBi2O4 has been studied by a combination of hard X-ray photoemission spectroscopy, resonant photoemission spectroscopy, and X-ray absorption spectroscopy (XAS) and compared with density functional theory (DFT) calculations. The photoemission study indicates that there is a strong Bi 6s-O 2p hybrid electronic state at 2.3 eV below the Fermi level, whereas the valence band maximum (VBM) has a predominant Cu 3d-O 2p hybrid character. XAS at the O K-edge supported by DFT calculations provides a good description of the conduction band, indicating that the conduction band minimum is composed of unoccupied Cu 3d-O 2p states. The combined experimental and theoretical results suggest that the low charge carrier mobility for CuBi2O4 derives from an intrinsic charge localization at the VBM. Also, the low-energy visible-light absorption in CuBi2O4 may result from a direct but forbidden Cu d-d electronic transition, leading to a low absorption coefficient. Additionally, the ionization potential of CuBi2O4 is higher than that of the related binary oxide CuO or that of NiO, which is commonly used as a hole transport/extraction layer in photoelectrodes. This work provides a solid electronic basis for topical materials science approaches to increase the charge transport and improve the photoelectrochemical properties of CuBi2O4-based photoelectrodes.

Originele taal-2Engels
Pagina's (van-tot)22416-22425
Aantal pagina's10
TijdschriftJournal of Physical Chemistry C
Volume124
Nummer van het tijdschrift41
DOI's
StatusGepubliceerd - 15 okt. 2020

Financiering

This work was supported by The Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), an NWO Gravitation program funded by the Ministry of Education, Culture and Science of the government of The Netherlands. K.H.L.Z. is grateful for funding support by the National Science Foundation of China (NSFC) (reference number: 21872116). The synchrotron data shown here were collected during beamtimes SI19191-1 (Diamond) and 20170915 (LNLS). We thank Dr. Tien-Lin Lee and Dr. Pardeep Kumar Thakur (I09 at Diamond), and Dr. Julio Criginski Cezar (PGM at LNLS) for their technical assistance during synchrotron data collection. N.Y.D. and N.H.d.L. thank the Engineering and Physical Sciences Research Council for funding (grants EP/S001395/1 and EP/K009567/2). The calculations were performed using the computational facilities of the Advanced Research Computing @ Cardiff (ARCCA) Division, Cardiff University, and we also acknowledge the use of HPC Wales, Supercomputing Wales, and associated support services in the completion of this work.

FinanciersFinanciernummer
MCEC
Netherlands Center for Multiscale Catalytic Energy Conversion
Engineering and Physical Sciences Research CouncilEP/S001395/1, EP/K009567/2
National Natural Science Foundation of China21872116
Ministerie van OCW
Nederlandse Organisatie voor Wetenschappelijk Onderzoek

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