One-dimensional (1D) semiconductors such as nanorods, nanowires, and nanotubes arrays directly growing from conducting substrate demonstrate the advantageous structural merits with respect to bulk and particulate counterparts including more efficient light harvesting/scattering capabilities and unidirectional charge separation/transfer along the vectorial direction of 1D framework. We focus on the fabrication of novel 1D semiconductor-based (n or p-type) heterostructured photoelectrodes and probing their interfacial charge transfer characteristics in PEC water splitting and PEC CO2 reduction.