Photo-electrochemical water splitting and electrochemical performance of silicon nanowire arrays

Abstract

Silicon nanowires (SiNWs) were prepared using n-Si(100) by a simple two-step metal-assisted chemical etching (MACE) approach with different durations of 15 and 30 min. Surface morphology, structural, and optical properties of prepared SiNWs were investigated using Scanning Electron Microscope (SEM), x-ray diffraction (XRD) and UV–vis absorption, respectively. Under visible light, a photoelectrochemical cell (PEC) was used to measure the properties of a photoanode device that was fabricated based on n-SiNWs for splitting water. At 0.78 V, the SiNWs that were prepared in 30 min had a photocurrent density of 3.72 mA.cm−2 and a photoconversion efficiency (η) of 1.37%. Cyclic voltammetry (CV) measurements showed that both the n-Si(100) wafer and the n-SiNWs that were made with etching times of 15 and 30 min showed faradaic behavior with redox peaks. Electrochemical impedance spectroscopy (EIS) showed that the SiNWs photoanode prepared with 30 min of etching time had a charge transfer resistance of 3112.3. This is low enough to make it easy for charge to move across the interface. The Mott-Schottky (M-S) analysis revealed a high concentration of carriers of 4.77 × 1021 cm−3 at the working electrode/electrolyte interface,