Assessment and Investigation of the Pd Nanoparticles-Assisted Chemical Etching of Silicon for Ethanol Solution Electrooxidation

Abstract

The formation of porous silicon by Pd nanoparticles-assisted chemical etching of single-crystal Si with resistivity ? = 0.01 ?·cm at 25°C, 50°C and 75°C in HF/H₂O₂/H₂O solution was studied. Porous layers of silicon were studied by optical and scanning electron microscopy, and gravimetric analysis. It is shown that por-Si, formed by Pd nanoparticles-assisted chemical etching, has the property of ethanol electrooxidation. The chromatographic analysis of ethanol electrooxidation products on por-Si/Pd shows that the main products are CO₂, CH₄, H₂, CO, O₂, acetaldehyde (CHO)⁺, methanol and water vapor. The mass activity of the por-Si/Pd system was investigated by measuring the short-circuit current in ethanol solutions. The influence of the thickness of porous silicon and wafer on the mass activity and the charge measured during ethanol electrooxidation was established. Additionally, the mechanism of charge transport during ethanol electrooxidation was established. The high porosity of the sample ensures access of the reactants to the surface of por-Si/Pd and removal of the reaction products. The gradual reduction of the gas evolution rate was due to contamination of the surface with reaction products. The porous silicon thickness, porosity and solution composition are the main factors defined EEO efficiency.