Nanowire structures for solar water splitting

This disclosure provides systems, methods, and apparatus related to solar water splitting. In one aspect, a structure includes a plurality of first nanowires, the plurality of first nanowires comprising an n-type semiconductor or a p-type semiconductor. The structure further includes a second nanowire, the second nanowire comprising the n-type semiconductor or the p-type semiconductor, the second nanowire being a different composition than the plurality of first nanowires. The second nanowire includes a first region and a second region, with the first region having a conductive layer disposed thereon, and each of the plurality of first nanowires being disposed on the conductive layer.