WO₃/BiVO₄: impact of charge separation at the timescale of water oxidation

Journal article

Oxygen vacancies are ubiquitous in metal oxides and critical to performance, yet the impact of these states upon charge carrier dynamics important for photoelectrochemical and photocatalytic applications remains contentious and poorly understood. A key challenge is the unambiguous identification of spectroscopic fingerprints which can be used to track their function. Herein, we employ five complementary techniques to modulate the electronic occupancy of states associated with oxygen vacancies in situ in BiVO4 photoanodes, allowing us to identify a spectral signature for the ionization of these states. We obtain an activation energy of ∼0.2 eV for this ionization process, with thermally activated electron detrapping from these states determining the kinetics of electron extraction, consistent with improved photoelectrochemical performance at higher temperatures. Bulk, un-ionized states, however, function as deep hole traps, with such trapped holes energetically unable to drive water oxidation. These observations help address recent controversies in the literature regarding oxygen vacancy function, providing new insights into their impact upon photoelectrochemical performance

Authors: Selim, S; Francàs, L; García-Tecedor, M; Corby, S; Blackman, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry
• Journal: Chemical Science
• Volume: 10
• Issue: 9
• Pages: 2643-2652
• Publication date: 2019-01-16
• DOI: 10.1039/c8sc04679d
• EISSN: 2041-6539
• ISSN: 2041-6520
• Language: English
• Keywords: Quantum mechanics; Nanotechnology; Charge (physics); Optoelectronics; Analytical Chemistry (journal); Physics; Charge carrier; Chemical physics; Environmental chemistry; Materials science; Chemistry