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submitted on 19.10.2017 and posted on 20.10.2017by Chang-Ming Jiang, Gideon Segev, Lucas H. Hess, Guiji Liu, Gregory Zaborski, Francesca M. Toma, Jason K. Cooper, Ian D. Sharp
photoelectrochemical (PEC) functionalities are systematically analyzed on a
series of copper vanadate photoanodes with different Cu:V elemental ratios.
Homogeneous, highly continuous, and phase-pure thin films of β-Cu2V2O7,
Cu11V6O26 and Cu5V2O10
are grown via reactive co-sputtering deposition and then evaluated for their
performances in light-driven oxygen evolution reaction (OER). Despite all four
compounds have similar 1.8 – 2.0 eV bandgaps, Cu-rich phases are found to
exhibit shorted absorption length in addition to higher charge separation
efficiencies at the semiconductor/electrolyte junction. In the presence of
sacrificial hole acceptor, the superior bulk properties of Cu5V2O10
photoanode translate to the most cathodic (0.67 V vs. RHE) onset potential and
a 206 μA/cm2 photocurrent density that is four times higher than β-Cu2V2O7
at 1.23 V. vs. RHE. Nevertheless, the sluggish OER kinetics competes with
carrier recombination through Cu-associated surface states, and transient photocurrent
spectroscopy quantitatively reveals the deterioration of surface catalytic
activity with increasing Cu:V elemental ratio. This comprehensive analysis of
PEC characteristics – light absorption, carrier separation, and heterogeneous
charge transfer – not only gives insights into functional roles of individual
elements in ternary metal oxide photoanodes, but also provides strategies for
rational discovery, design, and engineering of new photoelectrode materials for
solar fuel production.