CTAB-Influenced Electrochemical Dissolution of Silver Dendrites

Transcription

1 Supporting Information CTAB-Influenced Electrochemical Dissolution of Silver Dendrites Colm O Regan, 1, 2, 3 Xi Zhu, 4 Jun Zhong, 1, 2 Utkarsh Anand, 1, 2, 3, 5 Jingyu Lu, 1, 2, 3, 5 Haibin Su, 4 and 1, 2, 3, 5 Utkur Mirsaidov 1 Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, Singapore, NanoCore, National University of Singapore, 4 Engineering Drive 3, Singapore

2 Video captions Supporting Video 1: Video of silver dendrite growth and dissolution on a platinum electrode immersed in a pure aqueous 1 mm silver nitrate solution. Video shows 1 cycle of growth and dissolution at -2 V and + 2V bias voltage, respectively. Supporting Video 2: Video of silver dendrite dissolution on a platinum electrode immersed in a 1 mm silver nitrate mm CTAB solution. The video highlights the step-by-step dissolving of silver dendrites upon the application of +2 V bias to the electrode shown, along with particle formation due to Ostwald ripening. All silver metal is cleaned from solution after complete dissolution. Supporting Video 3: Video of silver dendrite dissolution from a platinum electrode immersed in a pure aqueous 1 mm silver nitrate solution. The video highlights the disconnection of the dendrites from the electrode and the incomplete dissolving of the dendrite into solution, upon the application of +2 V bias. No Ostwald ripening is observed and traces of Ag can be seen after dissolving. 2

3 Supporting figures: Figure S1. Schematic showing the chips used for assembling the electrochemical liquid-cell. The bottom chip (far left) and top chip with fabricated electrodes (second from left) were assembled on top of each other inside the TEM holder. The top chip is also fabricated with a passivation layer to isolate the electrodes. The final chip assembly consisted of the two chips sealed together to form the liquid-cell and is shown on the right. Also shown on the right is a low-magnification TEM image showing the three electrodes inside the liquid-cell. Figure S2. Additional image series showing two cycles of dendrite growth and dissolution in a pure aqueous AgNO 3 electrolyte without added CTAB. Dendrites formed on the working electrode during the application of a negative bias (t = 0 s to t = 19 s) (panels 1-3 inclusive) and dissolved back into solution when the bias was reversed (t = 20 s to t = 49 s) (panels 4 and 5). Dendrites formed again when the bias was switched back to negative (t = 49 s to t = 104 s) (panels 6-8). However, further cycles were not observed as the dendrites growing from both the working and counter electrodes made contact, causing the system to short-circuit. 3

4 Figure S3. Image series showing two cycles of growth and dissolution on the counter electrode. The solution was a pure aqueous AgNO 3 electrolyte without CTAB. Dendrites formed on the counter electrode upon the application of -2 V (panels 2-4). When the voltage was switched to +2 V, the dendrites dissolved back into solution (panels 5-7) and formed a second time when the voltage was reversed again to -2 V as shown in panels Importantly, a significant amount of Ag metal is seen in solution after the charge-discharge cycles. Figure S4. (A) TEM image showing a single branch of one Ag dendrite after growth in pure aqueous solution (no CTAB). The red circle represents the area over which the electron diffraction pattern was taken. This diffraction pattern is on the right of (A). (B) Electron diffraction pattern of a dendrite in CTAB solution. Both patterns in (A) and (B) are indexed to the face-centred-cubic silver lattice. 4

5 Figure S5. Image series didn t show any noticeable effect of the electron beam during dissolution at low flux rates. (A) Image series of dendrites on the surface of the working electrode. The bias was switched off and the electron beam was used to irradiate the sample for 120 s at an electron flux rate of less than 1 e Å -2 s -1. After 120 s, the dendrites were still intact with no visible dissolution or deformation. (B) Image series of the same dendrites showing how they dissolved upon application of a positive electrical bias (+2 V) to the working electrode. This analysis confirms the direct role of the electrical bias in dissolving the dendrites in solution and the minimal effect of the electron beam on dissolution. 5

6 Figure S6. TEM image series showing the dissolution of dendrites in aqueous AgNO 3 solution at higher magnification (and hence higher electron flux rate). No bias is applied to the electrodes, suggesting that the dissolution at these higher magnifications is due to the high flux rate of the electron beam. Figure S7. Time-series of the dendrite shown in Figure 3A in the main manuscript. The panels have been cropped to highlight the dendrite tip. The images are taken from t = 2.5 s to t = 4.8 s and show the dissolution of the dendrite, starting at the tip and proceeding down towards the electrode surface. 6

7 Figure S8. (A) Projected area plotted as a function of time for the image series shown in Figure 3A and (B) in Figure 3B in the main manuscript. The plot in Figure S7 (A) shows the area as a function of time for the image series of dendrite dissolution in an aqueous AgNO 3 solution with added CTAB surfactant (Figure 3A, main manuscript and Supporting Video 2). The curve shows a rapid drop in area from t = 0 s to t = 4 s, which corresponds to the second panel in Figure 3A, main manuscript at t = 4.0 s. Significantly, at approximately 4 s in Figure S7 (A), we saw a halt in the dissolution and a jump in area as micro-growth and particle formation occurred due to Ostwald ripening. This stage corresponds to panels 3 and 4 (Figure 3A, main manuscript) at t = 5.5 s and t = 8.4 s respectively. After this growth stage, the area decreased again as the dendrites dissolved further. The plot in S7 (B) shows the area as a function of time for the image series of dendrite dissolution in an aqueous AgNO 3 solution without added CTAB surfactant (Figure 3B, main manuscript and Supporting Video 3). The area decreased smoothly from start to finish with no jump in area or levelling off of the curve. The small oscillations in the area curve are due to the poor performance of our segmentation algorithms when processing low contrast images. Figure S9. Image series further highlighting the presence of dead silver in AgNO 3 solutions without added CTAB. Dead silver is highlighted by the red arrows in image panel-3, which show silver on the electrode surface and in solution above the electrode. The red arrow in image panel-2 highlights the dendrite dissolution beginning at the electrode surface. The dendrite dissolution does not begin at the tip, as is seen in CTAB solutions. 7