posted on 2016-04-22, 00:00authored byPengtao Xu, Tyler J. Milstein, Thomas E. Mallouk
Exfoliated
nanosheets derived from Dion–Jacobson phase layer perovskites
(TBAxH1–xA2B3O10, A = Sr, Ca, B = Nb,
Ta) were grown layer-by-layer on fluorine-doped tin oxide and gold
electrode surfaces. Electrochemical impedance spectra (EIS) of the
five-layer nanosheet films in contact with aqueous electrolyte solutions
were analyzed by the Mott–Schottky method to obtain flat-band
potentials (VFB) of the oxide semiconductors
as a function of pH. Despite capacitive contributions from the electrode–solution
interface, reliable values could be obtained from capacitance measurements
over a limited potential range near VFB. The measured values of VFB shifted
−59 mV/pH over the pH range of 4–8 and were in close
agreement with the empirical correlation between conduction band-edge
potentials and optical band gaps proposed by Matsumoto (J. Solid State Chem.1996, 126 (2), 227–234). Density functional
theory calculations showed that A-site substitution influenced band
energies by modulating the strength of A–O bonding, and that
subsitution of Ta for Nb on B-sites resulted in a negative shift of
the conduction band-edge potential.