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*

aDivision of Physical Sciences and Engineering, KAUST Catalysis Center (KCC),

bSolar and Photovoltaic Engineering Research Center (SPERC) King Abdullah University of Science and Technology (KAUST)

Thuwal, 23955-6900 (Saudi Arabia) *E-mail: kazuhiro.takanabe@kaust.edu.sa

http://catec.kaust.edu.sa

Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics.This journal is © the Owner Societies 2014

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.

Film thickness

(nm)

Intercept potential from

potential range of 1.2-

1.0 V vs. RHE (V vs. RHE)

Donor density (cm−3)

Intercept potential from potential range of 0.6-0.1 V vs.

RHE (V vs. RHE)

Donor density (cm−3)

160 0.9 4 × 1020 −0.1 5 × 1021

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

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.