Abstract

Photoelectrochemical (PEC) splitting of natural water was studied using silicon nanowires decorated with silver dendrites (dendritic nanostructures) as working electrode. A metal assisted wet chemical etching method has been used for the synthesis of dendritic heteronanostructures. Measured photocurrent density 1.7 mA/cm2 under white light illumination exhibits the efficient decomposition of natural water. The decomposition of water is primarily ascribed to the enhancement in the working electrode surface and water effective interface and the decrease in the recombination of light induced (photoexcited) carriers in the existence of silver dendritic nanostructures. Enhancement in photoinduced charge carriers separation caused due to the existence of Schottky barrier between the silicon and silver dendritic nanostructures. The light induced carriers (holes) in silicon are transferred to the metal (Ag) dendritic nanostructures that work as a charge basin to effectively carry out the oxidation reaction of water during PEC measurement. The solar-to-hydrogen (STH) conversion efficiency of about 4.5% was reported, indicating the efficient PEC solar water (pH 7) splitting. A cost-effective and efficient method for the PEC solar water splitting is presented in order to enhance the STH efficiency for the production of clean and renewable fuel.

Highlights

  • Water splitting is the chemical method which involves the decomposition or splitting of water molecules into hydrogen and oxygen gases [1, 2]

  • This study reports that the PEC solar water splitting using silicon silver dendrites nanostructures as working electrode can provide effective way for lower cost collection of sunlight for the renewable fuel development

  • It is noted that the calculated amount of the hydrogen gas shows nearly a linear behavior over the illumination time indicating the good constancy of the dendritic heteronanostructures as working electrodes in the water

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Summary

Introduction

Water splitting is the chemical method which involves the decomposition or splitting of water molecules into hydrogen and oxygen gases [1, 2]. The splitting of water molecules in the presence of external bias (such as sunlight) and working electrode is called as photoelectrochemical (PEC) water splitting method [1–3]. The requirement for the PEC water splitting process is that the band gap of the working electrode should be properly positioned with respect to the normal hydrogen electrode (NHE) in order to split the water under light illumination. This means that the top of the valence band must be more positive than the O2/H2O Redox potential (1.23 V) and the bottom of the conduction band must be more negative than the H+/H2 Redox potential (0 V) [1, 6, 7]

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