A novel electrochemical procedure for preparation of the very stable, thin modifying layer onto the n-type Si surface was elaborated. The modification consisted of platinum or/and ruthenium ultrafine particles etched into the porous Si film. A unique sequence of modifications was applied: at first the metal particles were evenly electrodeposited onto a flat silicon surface, and in the next electrochemical step the porous structure was produced. The platinum coverage and mean particle diameter were well controlled by the electrochemical programs. All the attempts and progress in modifications were monitored by scanning electron microscope (SEM) observations. Furthermore, the materials obtained were compared with the non-porous. Pt or/and Ru modified electrodes by testing them as anodes in the photoelectrochemical (PEC) cell with organic Br-2/2Br(-) solution. In general, the porous photo-anodes gave higher output powers and the light-to-electricity conversion efficiencies. The best performance was observed for the PEC cell employing the porous anode with sequentially electrodeposited Ru and Pt particles, respectively (PS-Si/Ru/Pt).(1) This cell maintained good electrical parameter values during the 2-week tests, having a maximum output power equal to 0.23 mW/cm(2) and a cell conversion efficiency of 8.5%. The PS-Si/Pt photo-anode gained 0.21 mW/cm(2) and 7.8%, respectively. (C) 2010 Elsevier Ltd. All rights reserved.