Silicon nanowires fabricated by porous gold thin film assisted chemical etching and their photoelectrochemical properties

• A facile and cheap way to pattern silicon surface for wet etching.
• Nanoporous gold films for use as both masks and catalysts.
• Etched nanowire electrodes show excellent PEC performance for hydrogen evolution.

Nanoporous gold thin films fabricated by dealloying commercially available 12 kt gold leaf have been utilized as masks to catalyze the formation of silicon nanowires from p-type silicon wafers in a HF/H2O2 mixture. The resulting silicon nanowires are found to be 40–100 nm in diameter and highly porous with an average pore diameter of ca. 4 nm. These nanowires are used as photocathodes for solar hydrogen evolution, and are found to exhibit a photocurrent as high as 6.05 mA cm−2 at a potential of 0 V versus reversible hydrogen electrode (RHE), which is >30 times higher than that of the planar silicon of the same type. The electrochemical impedance spectroscopy result shows that the charge transfer resistance of the nanowire photocathodes is much smaller than that of the planar silicon, revealing a favorable charge transfer kinetics.