Silicon nanowire arrays were grown by vapor-liquid-solid growth from SiH4 vapor at 500 degrees C, and tested as photocathodes in [Ru (bPY)(3)](2+) (bpy = 2,2'-bipyridyl)/acetonitrile solutions. Si nanowires were grown in anodic aluminum oxide membranes by first electroplating 50 mu m long Co wires capped with 250 nm gold segments in the pores and then reacting with SiH4. The resulting Si nanowires protruded 10-15 mu m beyond the top surface of the membrane but were degeneratively doped, most likely by Al from the membrane. Nanowires grown in the same manner on Si(111)/Au substrates could be controllably doped p-type by addition of trimethylboron. These p-Si nanowire arrays gave a photovoltage of 220 mV in [Ru(bPY)(3)](2+) solution when illuminated by white light.