Transition metal ions electroreduction

The electrochemical reaction leads to a more reduced or more oxidized state in the product than in the molten salt. Only electroreduction has so far been used to prepare compounds with tunnel structures. In such structures the tunnels contain ions, e.g., alkali-metal ions in a transition-metal oxide host lattice. Ionization of the inserted alkali-metal gives electrons to the oxide host, reducing the transition-metal cations. 

Another very interesting approach with diffusion gas electrodes modified with transition metal phthalocyanines deals with the simultaneous reduction of CO2 and NO or NOJ ions toward the production of urea or other C-N bonded compounds. The simultaneous reduction was investigated at gas diffusion electrodes with phthalocyanines containing the following metal centers Cr, Mo, Mn, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, In, Tl, Sn and Pb >. The formation of urea, CO, formic acid, and ammonia was confirmed for all the metals except for Al and Ge. The best catalyst in this case was NiPc with a maximum current efficiency of 40% at -1.5 V. Again the selectivity is dependent on the metal center and the electrochemical potential used in the experiments, but the formation of urea specifically depends on the ability of the metal center to form CO alone and ammonia alone . The mechanistic study showed that CO obtained from the electroreduction of CO2 cannot be combined with ammonia in the electrolyte to form urea and the ammonia formed in the reduction of nitrite ion... 

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