In this investigation we studied the electrocatalytic mineralization of urea contained in alkaline aqueous medium by means of Ni(II)cyclam-modified nanoparticulate TiO₂ films (OTE/TiO₂/Ni(II)cyclam, where an optically transparent electrode OTE was utilized as electrons collector) and the simultaneous electrogeneration of H₂ through the H₂O reduction on Pt cathodes which were inserted in the same cell. Our results showed that the standard potential for the H₂ evolution (E°_H2O/H2 = -0.83V vs. NHE) was achieved on the Pt cathode when a potential of 1.0V vs. NHE was applied to the OTE/TiO₂/Ni(II)cyclam//electrolyte interface (where the urea mineralization was taking place). On the contrary, the standard potential for the H₂ evolution was achieved on the same Pt electrode when a potential of 1.2V vs. NHE was applied to the OTE/Ni(II)cyclam//electrolyte interface (in the absence of TiO₂). These interesting results demonstrated that the urea oxidation potential on Ni(II)cyclam-modified OTEs was 0.2V cathodically-shifted in the presence of nanoparticulate TiO₂.

Furthermore, H₂ was continuously evolved for 1h from Pt cathodes in three-electrodes cells where aqueous urea solutions were simultaneously electrolyzed on OTE/TiO₂/Ni(II)cyclam or OTE/Ni(II)cyclam electrodes. Interestingly, measurements of total organic carbon (TOC) which were carried out in the urea solutions with and without electrolytic treatment, revealed that the H₂ evolution proceeds on a Pt cathode when the mineralization of urea achieves efficiencies of 20.8 and 10.4% on OTE/TiO₂/Ni(II)cyclam and OTE/Ni(II)cyclam electrodes, respectively. These new results demonstrate that the OTE/TiO₂/Ni(II)cyclam electrodes represents a novel pathway to carry out the electrochemical generation of H₂ from urea as energy carrier.