Stabilization of Si Photoanodes in Aqueous Electrolytes through Surface Alkylation

Abstract

A two-step chlorination/alkylation method was used to introduce −CnH2n+1 (n = 1−6) functionality onto single-crystal, (111)-oriented, n-type Si surfaces. H-terminated Si photoanodes were unstable under illumination in contact with an aqueous 0.35 M K4Fe(CN)6−0.05 M K3Fe(CN)6 electrolyte. Such electrodes displayed low open-circuit voltages and exhibited a pronounced time-dependent deterioration in their current density vs potential characteristics due to anodic oxidation. In contrast, Si surfaces functionalized with −CH3 and −C2H5 groups displayed significant improvements in stability while displaying excellent electrochemical properties when used as photoelectrodes in the aqueous Fe(CN)63-/4- electrolyte.