Fabrication of silicon nanohorns via soft lithography technique for photoelectrochemical application

Water splitting for H<inf>2</inf> production by absorbing sunlight is broadly used as a common technique to counter existing energy crisis and environmental problems, caused by extreme use of fossil fuels. We report a versatile and facile method to fabricate ordered Silicon nanohorns (SiNHs) by employing prefabricated metal nano-gap template on Si. The close-packed monolayer is used to develop the nanohole template, which enables the generation of SiNHs via metal-assisted controlled chemical etching. By varying monolayer parameters and etching sequences, SiNHs with desired dimensions were obtained. Growth along the crystalline plane of the base substrate ⟨100⟩, with a consistent bent at the tip of the SiNH, has been observed. The resulting SiNHs exhibited enhanced photoelectrochemical properties, with short-circuit photocurrent density more than four times higher than that of the planer Si along with enhanced trapping of photogenerated carriers. A photocurrent density of ~4.8 mA/cm² was observed at a potential of -1 V vs. RHE. Further, the electrochemical impedance study (EIS) was carried out to understand the photoelectrochemical activity and charge transfer kinetics of the SiNHs system. These nanostructures enhance light absorption and may be one of the low-cost alternatives for optical devices, sensors, and hydrogen evolution.