Enhanced Photodegradation Activity of Hydrogen-Terminated Si Nanowires Arrays with Different-Oriented Crystal Phases

Longfei Song,Fengyun Wang,Jianjun Song,Jie Tang,Lei Liu,Linqu Luo,Shuiling Cheng,Wei Jin,Xuan Li,Hongchao Zhang

doi:10.3390/catal7120371

Abstract

Although Si nanowires (NWs) arrays are superior candidates for visible light photocatalysis, reports about the photodegradation activity of various crystal-orientated Si NWs are still insufficient. Here, light-doped hydrogen-terminated Si NWs arrays with different crystal orientations were prepared via a metal-assisted chemical etching method (MACE), which simply modulated the concentration of the oxidizer, H2O2. Their dye photodegradation activities were systematically and comprehensively investigated. When compared with Si NWs arrays with crystal orientations of (110) and (111), Si NWs arrays with (100) crystal orientation exhibit a superior photodegradation activity and stability due to the anisotropy of optical and physical properties. The n-type Si NWs arrays exhibit better photodegradation activity than the p-type Si NWs arrays of the same crystal orientation and similar length. The results provide a further understanding of the synthesis of Si NWs arrays with various orientations, and the relationships between photodegradation activity/stability and crystal orientations.

Highlights

Over the past decades, Si nanowires (NWs) have attracted tremendous interests due to their excellent optical/electrical properties, high specific area, superior chemical/physical stability, and so on [1,2,3,4,5,6,7,8]
NWs arrays, Si NWs arrays with crystal orientation (100) exhibited superior photodegradation activity and stability
To exclude the influence of different lengths, the Si NWs with various crystal orientations must mesopores, which would be uncontrollable in the experimental process [21]

Summary

Introduction

Si nanowires (NWs) have attracted tremendous interests due to their excellent optical/electrical properties, high specific area, superior chemical/physical stability, and so on [1,2,3,4,5,6,7,8]. They utilized an aluminum oxide (AAO) membrane as a mask to tune the morphology of metal catalysts, and the (110) orientated Si NWs were successfully synthesized They demonstrated a novel method to control the etching direction, the utilization of the AAO mask can restrict the productivity of Si NWs and complicate the experimental procedure [39]. The crystal orientation of the porous Si wafers or Si NWs, especially those with small diameters, is one of the most critical factors and could profoundly affect the physical or chemical properties, such as photodegradation activity [39]. For the same crystal orientation, n-type Si NWs arrays exhibited more photodegradation activity than p-type Si NWs arrays These results help to further the understanding and investigations of Si NWs for the future photocatalytic applications

Characterization of Si NWs

Photodegradation Activity of Si NWs with Various Crystal Orientations

RhB Degradation Process

Characterizations of Si NWs Arrays with Various Crystal Orientation

Conclusions