Photoelectrochemical behavior of Si nanostructures grown by chemical vapor deposition using waste-biomass sources

Abstract Silicon nanostructures were grown by a chemical vapor deposition (CVD) technique, using different silica masses, and their photoelectrochemical characteristics were investigated. These nanostructures were found mainly to have two kinds of structures; nanorods and nanowires. Si nanorods with an average diameter of about 250 ​± ​50 ​nm were prepared at silica mass of 15 ​mg. An increase in silica to 100 ​mg results in a high density of Si nanowires with a relatively smaller in average diameter of 30 ​± ​4 ​nm. Moreover, the band gap energies of the Si nanowires and nanorods are between 1.8 and 1.9 ​eV showing visible light absorption capability. The as-grown Si nanowires have a better photocurrent density of 0.5 ​mA ​cm-2 as compared to as-grown Si nanorods, at a potential of 0 ​V in Ag/AgCl aqueous solution. This possibly due to the extremely large surface area and large number of active sites of Si nanowires, which could result in enhancing the water splitting oxidation and reduction processes. The role of silica in the growth mechanism was also discussed.