The preparation of modified, catalytically active, functional carbon electrodes and their application to the electrochemical reduction of trinitrotoluene (TNT) is reported. Modification of the electrodes is performed with composites of nanometer-sized, mesoporous titanium dioxide, which acts as a support containing inserted/deposited nanoparticles of ruthenium, platinum, or gold. These composites are prepared by a novel sonochemical synthesis using simple and low-cost precursors. Cyclic voltammetry shows that 2,4,6-trinitrotoluene can be reduced on thus-modified carbon-paper electrodes at potentials of around -0.5 V (vs. Ag/AgCl/Cl-) in aqueous solutions. Unexpectedly, carbon-paper electrodes modified with the TiO2/nano-Pt composites demonstrate a remarkable electrochemical activity toward the reduction of trinitrotoluene. A significant finding is that the two electrode processes - the reduction of TNT and of oxygen - are quite well separated in potential on the modified carbon-paper electrodes because of selective electrochemical activity of the TiO2/nano-Pt and TiO2/nano-Au composites. TiO2/nano-Ru composites are found to be much less electrochemically active for the detection of TNT compared to the previous two. It was also established that the titanium dioxide support of TiO2/nano-Pt composites plays a specific role for facilitating the TNT- and oxygen-reduction processes.