The present trends on water photolysis are shortly reviewed. For application in monolithically integrated structures, photoelectrocatalytically active half cell developments with p-Si are described. Using the concept of nanoemitter minority carrier harvesting, it is shown that the introduction of traces of noble metal catalysts that allow collection of light-induced carriers does not result in cost or scarcity limitations. The issue of charge transfer through an interfacial oxide and ballistic electron injection into the electrolyte vs. thermalization is discussed. The experimental data shows that the nanoemitter system can sustain the high current densities resulting from injected light-induced excess carriers from the semiconductor at low overvoltages. Limitations of planar systems with Si are discussed and possible improvements are outlined. First tests of Si rod-like microstructures are presented and the influence of localized surface plasmon excitation on light-induced H-2 evolution with p-Si is investigated. (C) 2011 Elsevier Ltd. All rights reserved.