Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is © the Owner Societies 2014
Carrier dynamics of a visible-light-responsive Ta3N5 photoanode for water oxidation Ahmed Ziani,a Ela Nurlaela,a Dattatray S. Dhawale,a Diego Alves Silva,a Erkki Alarousu,b Omar F. Mohammed,b and Kazuhiro Takanabea* a
Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), b Solar and Photovoltaic Engineering Research Center (SPERC) King Abdullah University of Science and Technology (KAUST) Thuwal, 23955-6900 (Saudi Arabia) * E-mail:
[email protected] http://catec.kaust.edu.sa
Fig. S1. Cyclic voltammogram of a) 160 nm, b) 370 nm, c) 470 nm, and d) 6 x 160 nm Ta3N5 films at different scan rates. The experiments were conducted under bubbling Ar using a 0.5 M NaOH solution (pH 13.5) as the electrolyte, a Pt wire as the counter electrode, and Ag/AgCl as the reference electrode.
Fig. S2. Plot showing the linear relationship between the capacitive current and the scan rate for all of the films.
Table S1. Relative electrochemical active surface areas of Ta3N5 films (using 160 nm film as the baseline) Film thickness (nm)
Capacitance (µF cm-2)
160
10.3
320
8.6
470
18.3
6 × 160
94.6
Fig. S3. Mott-Schottky plots at different frequencies taken at two different potential range for a) 160, b) 320, c) 470, and d) 6 × 160 nm Ta3N5 film. The experiments were conducted under bubbling Ar using a 0.5 M NaOH solution (pH 13.5) as the electrolyte, a Pt wire as the counter electrode, and Ag/AgCl as the reference electrode.
Table S2. Potentials at x-intercept and donor density for Ta3N5 films with different thickness calculated from Mott-Schottky plots.
160
Intercept potential from potential range of 1.21.0 V vs. RHE (V vs. RHE) 0.9
4 × 1020
Intercept potential from potential range of 0.6-0.1 V vs. RHE (V vs. RHE) −0.1
320
0.9
5 × 1020
−0.05
6 × 1021
470
0.85
4 × 1020
−0.1
4 × 1022
6 × 160
1.1
2 × 1021
−0.15
2 × 1024
Film thickness (nm)
Donor density (cm−3)
Donor density (cm−3) 5 × 1021
Fig. S4. Nyquist plots of a) 160 nm and c) 370 nm and Bode plots of b) 160 nm and d) 370 nm Ta3N5 films obtained from “staircase” potential electrochemical impedance spectra used to calculate the Mott-Schottky plots of the samples. The amplitude of the perturbation signal was 5 mV (0.5 M NaOH, pH 13.5).
Fig. S5. Nyquist plots of a) 470 nm and c) 6 × 160 nm and Bode plots of b) 470 nm and d) 6 × 160 nm Ta3N5 films obtained from “staircase” potential electrochemical impedance spectra used to calculate the Mott-Schottky plots of the samples. The amplitude of the perturbation signal was 5 mV (0.5 M NaOH, pH 13.5).
Fig. S6. Linear sweep voltammogram (anodic direction) of 160 nm Ta3N5 film with and without Co cocatalyst under AM 1.5 G solar light irradiation in a 0.1 M Na2SO4 electrolyte solution (pH 13 adjusted by adding NaOH) at 10 mV sec−1.
Fig. S7. Linear sweep voltammogram of 160 nm Ta3N5 film on a Pt (200 nm) grown on silicon (100) substrate under AM 1.5 solar light irradiation in a 0.1 M Na2SO4 electrolyte solution.
