S1

Tungsten-Based Porous Thin-Films for

Electrocatalytic Hydrogen Generation—Electronic

Supplementary Information

Huilong Fei,†,# Yang Yang,†

,‡,# Xiujun Fan,‡ Gunuk Wang,† Gedeng Ruan† and James M.

Tour†,‡,¶,*

†Department of Chemistry, ‡Richard E. Smalley Institute for Nanoscale Science and

Technology, ¶Department of Materials Science and NanoEngineering, Rice University,

6100 Main Street, Houston, Texas 77005, USA

#These authors contributed equally to this work.

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2015

S2

Figure S1. SEM images of (a-b) PWO, (c-d) PWS, (e-f) PWC at lower magnifications,

suggesting the uniform porous structures of these films across the treated areas.

S3

Figure S2. TEM images of PWS at (a) low and (b) high magnifications.

a b

Figure S3. (a) TEM image of PWC, showing that the PWC are composed of

interconnected nanoparticles. (b) Enlarged view of the squared area in (a), which shows

the carbon layers surrounding the WC nanoparticles.

S4

a b

38 36 34 32 30 28

Inte

nsity (

a.u

.)

Binding energy (eV)

W 4f7/2

W 4f5/2

PWC-700

PWC-600

PWC-500

38 36 34 32 30

W 4f7/2

In

tensity (

a.u

.) PWS-450

PWS-400

PWS-350

Binding energy (eV)

W 4f5/2

Figure S4. XPS spectra of W 4f for (a) PWS and (b) PWC synthesized at different

temperatures. The PWC-500 shows broadened peaks and have higher binding energy

compared to PWC-600 and PWC-700, suggesting that the conversion from oxide to

carbide at 500 °C is incomplete.

168 166 164 162 160 158

S 2p3/2

Inte

nsity (

a.u

.)

PWS-450

PWS-400

PWS-350

Binding energy (eV)

S 2p1/2

Figure S5. XPS spectra of S 2p for PWS-350, PWS-400 and PWS-450.

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288 286 284 282 280

In

ten

sity (

a.u

.)

Binding energy (eV)

PWC-700

PWC-600

PWC-500

C 1s

Figure S6. XPS spectra of C 1s for PWC-500, PWC-600 and PWC-700.

250 300 350 400 450 500

A1

gE

1

2g

Inte

nsity (

a.u

.)

Raman shift (cm-1

)

PWS-450

PWS-400

PWS-350

Figure S7. Raman spectra for PWS-350, PWS-400 and PWS-450, all of which show the

characteristic E1

2g and A1

g vibration modes.

S6

1000 1200 1400 1600 1800 2000

Inte

nsity (

a.u

.)

Raman shift (cm-1)

G bandD band

PWC-700

PWC-600

PWC-500

Figure S8. Raman spectra for PWC-500, PWC-600 and PWC-700, all of which show the

characteristic D band and G band of carbon with larger peak intensity at higher synthesis

temperature.

1000 1200 1400 1600 1800 2000

G band

Inte

nsity (

a.u

.)

Raman shift (cm-1)

D band

300 360 420 480

A1

g

Inte

nsity (

a.u

.)

Raman shift (cm-1)

E1

2g

a b

Figure S9. Raman spectra of the (a) NPWS and (b) NPWC

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a b

Figure S10. SEM images of the (a) NPWS and (b) NPWC.

-0.3 -0.2 -0.1 0.0 0.1-25

-20

-15

-10

-5

0

j (m

A c

m-2)

E (V vs RHE)

PWC-500

PWC-600

PWC-700

a b

-0.3 -0.2 -0.1 0.0 0.1

-20

-16

-12

-8

-4

0

j (m

A c

m-2)

E (V vs RHE)

PWS-350

PWS-400

PWS-450

Figure S11. LSV polarization curves of (a) PWS and (b) PWC samples synthesized at

different temperatures.

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a b

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

0.16

0.18

0.20

0.22

67 mV decade-1

88 mV decade-1

(

E v

s R

HE

)

log (-j [mA cm-2])

PWS-300

PWS-350

PWS-400

84 mV decade-1

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

0.17

0.18

0.19

0.20

0.21

0.22

0.23

0.24

69 mV decade-1

67 mV decade-1

log (-j [mA cm-2])

(

E v

s R

HE

)

PWC-500

PWC-600

PWC-700

70 mV decade-1

Figure S12. Tafel plots of (a) PWS and (b) PWC samples synthesized at different

temperatures.

Figure S13. Morphologic characterization of the porous thin films after stability tests.

SEM images of the (a) initial PWS and (b) PWC after stability tests.

Table S1. Comparison of the HER activities of reported electrocatalysts.

Catalyst

Mass

loading

(μg cm-2

)

Onset

overpotential

(mV)

Tafel

slope

(mV

Overpotential

for 10 mA cm-2

(mV)a

Reference

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decade-1

)

Porous WS2 thin

film ~ 80 ~ 100 67 265

This

work

Porous WC thin

film ~ 160 ~ 120 67 274

This

work

WS2 nanosheets 285 ~ 60 72 ~ 156 1

WS2/rGO sheets 400 150 – 200 58 ~ 275 2

1T-WS2

nanosheets NG ~ 100 60 ~ 250 3

1T-WS2

nanosheets

(WS2 prepared

by CVD

method)

~ 1000 ~ 75 70 ~ 142 4

Ultrathin WS2

nanoflakes 350 ~ 100 48 ~ 180 5

Nano-sized WC

on carbon black ~ 740 ~ 165

b NG ~ 255 6

a Most of the values are estimations on the basis of polarization curves.

b The value is

determined at current density of 1 mA cm-2

.

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