Optimization of 1D ZnO@TiO₂Core–Shell Nanostructures for Enhanced Photoelectrochemical Water Splitting under Solar Light Illumination

Abstract

A fast and low-cost sol-gel synthesis used to deposit a shell of TiO2 anatase onto an array of vertically aligned ZnO nanowires (NWs) is reported in this paper. The influence of the annealing atmosphere (air or N2) and of the NWs preannealing process, before TiO2 deposition, on both the physicochemical characteristics and photoelectrochemical (PEC) performance of the resulting heterostructure, was studied. The efficient application of the ZnO@TiO2 core-shells for the PEC water-splitting reaction, under simulated solar light illumination (AM 1.5G) solar light illumination in basic media, is here reported for the first time. This application has had a dual function: to enhance the photoactivity of pristine ZnO NWs and to increase the photodegradation stability, because of the protective role of the TiO2 shell. It was found that an air treatment induces a better charge separation and a lower carrier recombination, which in turn are responsible for an improvement in the PEC performance with respect to N2-treated core-shell materials. Finally, a photocurrent of 0.40 mA/cm(2) at 1.23 V versus RHE (2.2 times with respect to the pristine ZnO NWs) was obtained. This achievement can be regarded as a valuable result, considering similar nanostructured electrodes reported in the literature for this application.

Structural and electrical properties of TiO2/ZnO core–shell nanoparticles synthesized by hydrothermal method

“…TiO 2 /ZnO coreshell nanomaterial presents a high interest due to its potential applications, such as optoelectronic device [3,4], dye-sensitized solar cells (DSSCs) [5], and photocatalysis [6][7][8]. Recently, TiO 2 /ZnO core-shell nanomaterial was used for photocatalytic H 2 production through water splitting [9]. TiO 2 nanomaterial presents interest due to its potential applications in the field of photovoltaics, gas sensors, dye-sensitized solar cells (DSSCs), etc.…”

Control of charge dynamics by blending ZnO nanoparticles with poly(3-hexylthiophene) for efficient hybrid ZnO nanorods/polymer solar cells

“…Various development approaches for efficient materials and well-designed device structures have been investigated to achieve enhanced power conversion efficiency (PCE) of HPV devices [5,6]. Among the developed nanomaterials, ZnO nanorod arrays, which can be grown vertically from a substrate, have great potential for HPV applications because of their ease of synthesis [7,8] and high electron mobilities (*10 2 cm 2 V -1 s -1 ) [9] with a direct transport pathway to the electrode [10,11].…”

Visible light-driven photoelectrochemical water splitting on ZnO–TiO2 heterogeneous nanotube photoanodes

“…It also has been found that a red shift occurs, as immersion time increased, causing an increase on the amount of zinc oxide [34]. In addition, the red shift might also be due to the change in the crystal phase composition of TiO 2 [22][23][24][25][26][27][28].…”

“…As a result, it still posts a long-standing challenge to resolve these fundamental disadvantages for diverse aspects of photocatalytic applications. To solve these problems, researches have been proliferated to reinforce the photocatalytic properties by manipulating nanostructures or morphologies of TiO 2 and ZnO [14][15][16][17][18][19][20][21][22][23][24][25]. In these cases, of particular note is the coupling of TiO 2 and ZnO that has been well established to remarkably enhance the separation efficiency of photoexcited charge carriers because of the formation of heterojunction structure between them, thus boosting quantum efficiency and photostability of the hybrid photocatalyst [14].…”