Nanoporous black silicon photocathode for H2 production by photoelectrochemical water splitting

Nanostructured Si eliminates several critical problems with Si photocathodes and dramatically improves a photoelectrochemical (PEC) reaction important to water-splitting. Our nanostructured black Si photocathodes improve the H-2 production by providing (1) near-ideal anti-reflection that enables the absorption of most incident light and its conversion to photogenerated electrons and (2) extremely high surface area in direct contact with water that reduces the overpotential needed for the PEC hydrogen half-reaction. Application of these advances would significantly improve the solar H-2 conversion efficiency of an ideal tandem PEC system. Finally, the nanostructured Si surface facilitates bubble evolution and therefore reduces the need for surfactants in the electrolyte.