Electrochemical behavior of M_(x-1)O_x (M = Ti, Ge and Co) ultra-thin protective layers for MCFC cathode

摘要

In the world of alternative energy sources, the Molten Carbonate Fuel Cell (MCFC) is one of the promising technologies for the efficient conversion of hydrogen or hydrocarbons to power and heat. One of the main issues for optimizing this device is the control of the dissolution of the state-of-the-art porous nickel oxide cathode. A protective coating by more stable metal oxides seems to be one of the best solutions. In this paper, ultra-thin layers of TiO_2 (50 nm), Co_3O_4 (50 nm) and CeO_2 (20 nm) were deposited on porous nickel substrates, by a sequential CVD technique, known as Atomic Layer Deposition (ALD), producing high quality, homogeneous and conformal layers. The electrochemical behavior and morphological features of the three coated samples were compared in a Li_2CO_3-K_2CO_3 (62-38 mol%) eutectic melt under a standard cathode atmosphere (CO_2/air 30:70 vol%) for 230 h. Finally, the respective advantages and drawbacks of CO_3O_4, TiO_2 and CeO_2 coatings are pointed out.