Phase evolution from rod-like ZnO to plate-like zinc hydroxysulfate during electrochemical deposition

Phase evolution from rod-like ZnO to Phase evolution from rod-like ZnO to plate-like zinc hydroxysulfate duringplate-like zinc hydroxysulfate during

electrochemical depositionelectrochemical depositionLida 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 116012, China

Advisor ： S.C.Wang Student ： Shih-Kai Shu

OutlineOutlineIntroductionExperimental ProceduresResults and DiscussionConclusionFuture work

IntroductionIntroduction

The effects of SO42− 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 SO42− 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 ZnSO4 concentrations are below 0.54mM,the oriented growth of ZnO rods tends to be enhanced with the increase of ZnSO4 concentration.

Otherwise, the vertically aligned zinc hydroxysulfate plates can be formed by the introduction of SO42− ions in nanocrystals.

Experimental ProceduresExperimental Procedures

電解液為 27mM KNO3 、 3mM (CH2)6N4和濃度 0.3mM~3mM ZnSO4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 3.0-4.0的範圍

另外也討論電解液為 27mM KNO3 、 3mM (CH2)6N4和濃度 0.3mM ZnSO4的混合水溶液再加入濃度 3mM~24mM K2SO4，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NO3

− +2e + H2O ↔ NO2− +2OH− (1)

Zn2+ +2OH−↔ Zn(OH)2 (2)Zn(OH)2 = ZnO + H2O (3)

Results and DiscussionResults and Discussion

SEM images of the as-prepared films (a–d) rod, (e) mixture of rod and plate, (f–h) plate synthesized at various ZnSO4 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 80C for 5 h.

EDX spectra of marked regions (I) rod and (J) plate in film prepared at 0.6mM ZnSO4 at the temperature 80C for 5 h.

XRD patterns of the as-prepared films synthesized at various ZnSO4 concentrations (a) 0.3mM, (b) 0.36mM, (c) 0.48mM, (d) 0.54mM, (e) 0.6mM at the temperature 80C 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 ZnSO4 concentrations (a) 1.2mM, (b) 1.8mM, (c) 3mM, at the temperature 80C for 5 h.

The standard diffraction patterns of 6Zn(OH)2 ZnSO4·4H2O are shown as reference.

Asterisks (*) indicate the FTO substrate.

FTIR spectra of the as-prepared films synthesized at various ZnSO4 concentrations.

(a) 0.3mM, (b) 3mM, at the temperature 80C 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 80C 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 80C for 5 h.

The standard diffraction patterns of ZnO and 6Zn(OH)2 ZnSO4·4H2O are shown as reference.

Asterisks (*) indicate the FTO substrate.

ConclusionConclusion

In present work, we demonstrate that SO42− 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 ZnSO4 concentrations, vertically aligned ZnO rods tend to dominate the film morphology.

On the contrary, SO42− 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 workFuture workPaper review