Primary Corrosion Processes for Polymer-Embedded Free-Standing or Substrate-Supported Silicon Microwire Arrays in Aqueous Alkaline Electrolytes.

Solar fuel devices have shown promise as a sustainable source of chemical fuels. However, long-term stability of light absorbing materials remains a substantial barrier to practical devices. Herein, multiple corrosion pathways in 1 M KOH(aq) have been defined for TiO2-protected Si microwire arrays in a polymer membrane either attached to a substrate or free-standing. Top-down corrosion was observed in both morphologies through defects in the TiO2 coating. For the substrate-based samples, bottom-up corrosion was observed through the substrate and up the adjacent wires. In the free-standing samples, uniform bottom-up corrosion was observed through the membrane with all wire material corroded within 10 days of immersion in the dark in 1 M KOH(aq).