Supporting Information Available ot Electron of Au Nanorods Activates the Electrocatalysis of ydrogen Evolution on MoS Nanosheets Yi Shi, Jiong Wang, Chen Wang, Ting-Ting Zhai, Wen-Jing Bao, Jing-Juan Xu, Xing-ua Xia*, and ong-yuan Chen State Key Laboratory of Analytical Chemistry for Life Science and Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 093, China. *To whom correspondence should be addressed. E-mail: xhxia@nju.edu.cn (X..X)
Scheme S1. The synthetic procedure of Au MoS nanosheets. Photograph S1. Dark field electrochemical apparatus.
Figure S1. (A) SEM image of bulk MoS. (B) TEM image of ce MoS. (C) Photograph of ce MoS solution after four weeks of storage under ambient temperature. (D) SEM image of Au rods. 3
Figure S. The survey scans of XPS spectra for the samples and their corresponding calculated atomic concentrations of Mo, S, and Au. 4
Figure S3. (A) Polarization curves of Au MoS with (red) and without (black) 808 nm laser irradiation. Green line represents the electrochemical behavior of Au MoS in the dark immediately after one irradiation cycle. Blue line represents the electrochemical behavior upon sudden light-off test. (B) ce MoS with and without laser irradiation during electrochemical measurements. (C) ER activity of Au MoS with different wavelength irradiation or laser intensity. (D) ER activity of Au MoS with different Au loading. 5
Figure S4. Gas chromatography (GC) measurements of various samples shown in the figure. standard: pure collected from the gas cylinder; dark: gas collected from the working electrode in the dark; 808: gas collected from the working electrode under 808 nm laser illumination. The electrolyzing was performed at 0.3 V vs RE in a solution of 0.5 M sulfuric acid. Three possible reaction steps suggested for the ER in acidic media: 13 O e catalyst catalyst O Volmer reaction (S1) 3 O e catalyst - catalyst O eyrovsky reaction (S) 3 catalyst - catalyst - catalyst Tafel reaction (S3) 6
Assessment of activation energy (E a ): Figure S5. (A) ER activity of Au MoS under 808 nm laser excitation at different temperatures. (B) ER activity of ce MoS at different temperatures. (C) Arrhenius plots: semilogarithmic dependence of current density of ce MoS at various overpotentials plotted against inverse temperature. Overpotentials are taken from 300 to 400 mv at an interval of 5 mv. (D) Activation energy at the zero overpotential obtained through trendextrapolation. Figure S5A and B are the original data directly obtained from experiments, which are used for further activation energy (E a ) calculation. The E a for ce MoS and Au MoS catalysts were calculated from the slope of the Arrhenius plot. An Arrhenius plot displays semilogarithmic 7
dependence of exchange current density plotted against inverse temperature. The Arrhenius equation given in the form: can be written equivalently as: j Ea / RT Ae (S4) Inj 1 InA (Ea / R) (S5) T where A is pre-exponential factor, E a is activation energy, R is gas constant and T is temperature (kelvin). Assessment of turnover frequency (TOF): Figure S6. (A) Process illustrating the underpotential deposition of Cu adatoms at the defects of MoS nanosheets used to calculate the number of active sites for ER. 1 (B) Cyclic voltammogram of ce MoS. Oxidation current starting from 0.75 V vs RE attributable to the 8
transitions from MoS MoO 3 and cathodic current due to the evolution of hydrogen are observed. (C) Cyclic voltammograms of ce MoS and GC in 0.1 M SO 4 in the presence of cupric sulfate (CuSO 4, mm). I A and I C peaks correspond to the stripping and bulk deposition of Cu, respectively. II A and II C broad peaks are assigned to the underpotential processes of Cu adatoms. In ref. 1, Voiry et al. have demonstrated that at a particular potential the same quantity of copper adatoms as hydrogen adatoms is deposited on the surface of the electrode at the active sites. Thus, the number of active sites can be calculated by applying underpotential deposition (UPD) of copper (schematic diagram shown in Figure S6A). From Figure S6B, we come to a conclusion that the scanning potential value in UPD experiment can only reach as high as 0.75 V, since higher potential will result in oxidation of MoS to MoO 3. It is shown that compared to glassy carbon (GC), copper ions can be electrochemically reduced on ce-mos at higher potentials (underpotential deposition, UPD) than its thermodynamic potential (Figure S6C). From the quantity of charges generated during the Cu adatoms stripping for the peak centered at 566 mv vs RE, it can be calculated that 3.98 14 mol of Cu adatoms (Q Cu /96500/) have been deposited. From this, an active site density 5.63 sites/ (n Cu /A electrode ) is obtained for hydrogen adsorption on ce MoS. Conversion of measured current to turnover (assuming 0% Faradaic efficiency): 18 1 A 1C 6.41 e 1 ( j ma / ) (3.1 00 ma 1 A 1C e ma ) per TOF at 300 mv: ce MoS : ma.17 (3.1 ) 6.77 9
Mo 1. Mo 5.63 / s 6.77 Au MoS : 16.7 ) / s (3.1 ma.33 7 Mo 4 Mo 5.63.7 16 808 nm laser excited Au MoS : 16 4.98 ) (3.1 ma.07 16 Mo 8.76 Mo 5.63 4.98 16
Table S1. ER activities of MoS based catalysts. Catalysts Onset potential/ V Tafel slope/ /mv TOF 1 mv dec 1 Ce MoS (in this work) 0.6 94 300 1. Au MoS (in this work) 0. 86 300 4 Irradiated Au MoS (in this work) 0.16 71 300 8.76 [Mo 3 S 4 ] 4+ cubanes / OPG 3 0.0 00~300 1~5 Amorphous MoS 3 4 0. 60 00 0.3 MoS Particles 5 0.16 8 N/A N/A Defect Rich MoS sheets 6 0.1 50 300 0.75 Amorphous MoS 3 CV film 7 0.16 40 0/40 0.8/ double gyroid MoS 8 0.~ 0.0 50 00 1 MoO 3 MoS nanowires 9 0.~ 0.0 50~60 7 4 Ce MoS nanosheets 0.17 54 N/A N/A MoS nanosheets 11 0. 45 N/A N/A MoS x /Graphene 1 0.11 43 N/A N/A MoS /RGO 13 0. 41 00 0.1 [Mo 3 S 13 ] clusters / OPG 0. 40 00 3 11
Figure S7. UV vis spectrum of Au rods with SPR band centered at ~650 nm. Figure S8. SPR scattering spectra of Au rods in Au/ITO and Au MoS /ITO under open circuit condition in 0.1 M KCl solution. The SPR scattering of Au rods deposited on ITO (Au/ITO) is located at ~660 nm. After MoS nanosheets are in-situ immobilized on the Au/ITO (Au MoS /ITO), the SPR scattering of Au rods shows a red-shift of ~18 nm, directly indicating that 1
hot electron is exactly transferred from Au rods to MoS nanosheets even at open circuit potential. Figure S9. The i t curves of Au/ITO and Au MoS /ITO at 0.3 V vs RE in 0.1 M KCl solution. Figure S. Polarization curves of Au MoS under 808 nm laser irradiation with EtO as hole scavenger, bulk MoS and commercial Pt/C. 13
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