Templated electrochemical fabrication of hollow. molybdenum sulfide micro and nanostructures. with catalytic properties for hydrogen production

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1 Supporting Information Templated electrochemical fabrication of hollow molybdenum sulfide micro and nanostructures with catalytic properties for hydrogen production Adriano Ambrosi, Martin Pumera* Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore , Singapore. Fax: (65) , 1

2 -.2V V Deposition in EG.2V.4V 1 μa.6v.8v Potential (V) Figure S1. Cyclic voltammograms recorded during electrodeposition in ethylene glycol (EG) of 5 mm (NH 4 ) 2 MoS 4 in the presence of.1 M KCl and.6 M NH 4 Cl as electrolytes. A fixed number of cyclic voltammetric scans (2) was imposed, but varying the anodic potential limit between -.2 V (top) and.8 V (bottom). 2

3 Current density (ma cm ) Current density (ma cm ) A Optimizaziondeposition range in H 2 O (2 scans) 1scan 1min -.2V 5scan 5min -4 V -4 1scan -4 1min.2V 2scan 2min 3scan.4V 4scan 3min -8.6V scan 4min.8V D Optimizazion deposition range in EG (2 scans) B E Optimization No. scans in H 2 O (.2->-1.3V) Optimization No. scans in EG (.4->-1V) -.2V 1scan 1min -4 V -4 5scan -4 5min 1scan.2V 2scan 1min.4Vb 3scan 2min -8.6Vb -8 4scan -8 3min.8Vb 5scan 4min C F Optimization deposition time in H 2 O (at -1.2 V) Optimization deposition time in EG (at -.9 V) Figure S2. Polarization curves recorded in.5 M H 2 SO 4 at 5 mv s -1 scan rate using GC electrodes modified with electrodeposited MoS 2 films. Electrodeposition in aqueous (NH 4 ) 2 MoS 4 (5 mm) (A, B, C) employing A) cyclic voltammetry with different anodic limits; B) varying the number of CV scans and C) using the potentiostatic method at the fixed cathodic potential of -1.2 V but varying the deposition time. Electrodeposition in ethylene glycol (D, E, F) of (NH 4 ) 2 MoS 4 (5 mm) employing D) cyclic voltammetry with different anodic limits; E) varying the number of CV scans and F) using the potentiostatic method at the fixed cathodic potential of -.9 V but varying the deposition time. 3

4 A O1s C 1s Intensity (a.u.) EG-3 min O1s Mo 3p Mo 3p C 1s Mo 3d Cl 2p S 2p Mo 3d Al 2p EG-3 scan S 2p Cl 2p Al 2p Binding energy (ev) 2 B Mo 3d S 2p Intensity (a.u.) EG-3 min EG-3 min EG-3 scan EG-3 scan Binding energy (ev) Figure S3. A) Survey XPS spectra for MoS 2 films prepared using the potentiostatic method (upper spectrum) and the cyclic voltammetry method (lower spectrum) in EG solution. B) High-resolution XPS spectra of Mo 3d (left) and S 2p (right) for the MoS 2 films prepared using the potentiostatic method (upper spectrum) and the cyclic voltammetry method (lower spectrum). 4

5 Figure S4. SEM images of MoS 2 films obtained after dissolution of PS particles (.24 µm diameter) in toluene. MoS 2 film was electrodeposited during 4 CV scans onto ITO electrode. No structure was observable due to the complete coverage of the particles by the film. 5

6 Current density (ma cm ) -4-8 H2O-3scan ED-MoS 2-1 st measurement H2O-3scannd ED-MoS 2 nd measurement Figure S5. Polarization curves recorded in.5 M H 2 SO 4 at 5 mv s -1 scan rate using GC electrodes modified with the hollow spherical structure film after dissolution of PS particles (3 um diameter). Film was deposited during 3 CV scans onto GC electrode. Catalytic performance is maintained for multiple measurements with only the inherent pre-reduction wave being eliminated. 6

7 A B C Current density (ma cm ) -15 Unstructured after -.2 V -15 Microporous after -.2 V V V V Time (h) Time (h) -15 Hollow sphere after -.2 V Time (h) Figure S6. Polarization curves recorded in.5 M H 2 SO 4 at 5 mv s -1 scan rate using GC electrodes modified with for A) the unstructured, B) microporous structured and C) hollow spherical structured film before (black) and after (blue) a potentiostatic overpotential of 2 mv (vs RHE) was applied for 12 h. Lower panels show the corresponding chronoamperograms for each film. 7

8 Figure S7. A) Homemade H-shaped cell to measure the volume of H 2 produced by electrolysis. Pt counter and Ag/AgCl reference electrodes are positioned on the right side of the cell. The GC electrode with electrodeposited (3 CV scans) MoS 2 film (unstructured) is positioned on the left compartment above the linking bridge. B) H 2 produced during electrolysis can be evaluated by the variation of the meniscus of the H 2 SO 4 electrolyte on the left compartment. After 45 sec of electrolysis applying a potential of -.2 V vs RHE about.25 ml of H 2 are produced at 25 C. C) Chronoamperogram recorded during electrolysis at potential of -.2 V in.5 M H 2 SO 4. Assuming 1% Faraday yield the electrolysis average current of.45 ma generates a theoretical.26 ml volume of H 2 from the Faraday s law. The Faraday yield of electrolysis with ED-MoS 2 films is thus close to 1 %. 8