Phase evolution from rod-like ZnO to plate-like zinc hydroxysulfate during electrochemical deposition Lida Wang, Guichang Liu ∗, Longjiang Zou, Dongfeng Xue Department of Materials Science and Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, 158 Zhongshan Road, Dalian , China Advisor ： S.C.Wang Student ： Shih-Kai Shu

Outline Introduction Experimental Procedures Results and Discussion Conclusion Future work

Introduction

The effects of SO 4 2− ion concentrations on the phase evolution of electrochemical deposited films have been investigated using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results show that SO 4 2− ion concentration plays a very important role in directing the phase evolution of thick films from rod-like ZnO to plate-like zinc hydroxysulfate under fast hydroxylation. When ZnSO 4 concentrations are below 0.54mM,the oriented growth of ZnO rods tends to be enhanced with the increase of ZnSO 4 concentration. Otherwise, the vertically aligned zinc hydroxysulfate plates can be formed by the introduction of SO4 2− ions in nanocrystals.

Experimental Procedures

電解液為 27mM KNO 3 、 3mM (CH 2 ) 6 N 4 和濃度 0.3mM~3mM ZnSO 4 的 混合水溶液 將 FTO 導電玻璃 (2mm×1mm ，片電阻 15Ω/cm2) 置入電鍍液中，並使用 三電極系統進行定電壓 (-0.85V/SCE) 電化學沉積 5 小時 沉積過程中電解意溫度維持在 80°C 下，並使用稀釋硫酸溶液調整 pH 值， 維持在 的範圍 另外也討論電解液為 27mM KNO 3 、 3mM (CH 2 ) 6 N 4 和濃度 0.3mM ZnSO 4 的混合水溶液再加入濃度 3mM~24mM K 2 SO 4 ，觀察硫酸鹽對 ZnO 薄膜成長的影響 使用 SEM 、 EDX 、 XED 和 FTIR 做分析

電化學沉積氧化鋅主要分為兩部分：電化 學過程和化學過程 NO 3 − +2e + H 2 O ↔ NO 2 − +2OH − (1) Zn 2+ +2OH − ↔ Zn(OH) 2 (2) Zn(OH) 2 = ZnO + H 2 O (3)

Results and Discussion

SEM images of the as- prepared films (a–d) rod, (e) mixture of rod and plate, (f–h) plate synthesized at various ZnSO 4 concentrations. (a) 0.3mM (b) 0.36mM (c) 0.48mM (d) 0.54mM (e) 0.6mM (f) 1.2mM (g) 1.8mM (h) 3mM temperature 80 ◦ C for 5 h.

EDX spectra of marked regions (I) rod and (J) plate in film prepared at 0.6mM ZnSO 4 at the temperature 80 ◦ C for 5 h.

XRD patterns of the as-prepared films synthesized at various ZnSO 4 concentrations (a) 0.3mM, (b) 0.36mM, (c) 0.48mM, (d) 0.54mM, (e) 0.6mM at the temperature 80 ◦ C for 5 h. The standard diffraction patterns of ZnO are shown as reference. Asterisks (*) indicate the FTO substrate.

XRD patterns of the as-prepared films synthesized at various ZnSO 4 concentrations (a) 1.2mM, (b) 1.8mM, (c) 3mM, at the temperature 80 ◦ C for 5 h. The standard diffraction patterns of 6Zn(OH) 2 ZnSO 4 ·4H 2 O are shown as reference. Asterisks (*) indicate the FTO substrate.

FTIR spectra of the as-prepared films synthesized at various ZnSO 4 concentrations. (a) 0.3mM, (b) 3mM, at the temperature 80 ◦ C for 5 h.

SEM images of the as- prepared films (a) mixture of rod and plate, (b–d) plate, synthesized at various K2SO4 concentrations. (a) 3mM (b) 6mM (c) 12mM (d) 24mM at the temperature 80 ◦ C for 5 h.

XRD patterns of the as-prepared films synthesized at various K2SO4 concentrations, (a) 3mM, (b) 6mM, (c) 12mM, (d) 24mM at the temperature 80 ◦ C for 5 h. The standard diffraction patterns of ZnO and 6Zn(OH) 2 ZnSO 4 ·4H 2 O are shown as reference. Asterisks (*) indicate the FTO substrate.

Conclusion

In present work, we demonstrate that SO 4 2− ion concentration plays a very important role in controlling the phase evolution of films from ZnO rods to zinc hydroxysulfate plates under fast hydroxylation using electrochemical deposition. At lower ZnSO 4 concentrations, vertically aligned ZnO rods tend to dominate the film morphology. On the contrary, SO 4 2− ions can participate in the film growth under fast hydroxylation, thus leading to the formation of vertical aligned zinc hydroxysulfate plates. Most importantly, this work facilitates not only the researches about the nature of chemical reactions under electric field, but also the applications in optoelectronics, field effect transistor and solar cells.

Future work  Paper review