Electrochemical behavior of Mx−1Ox (M = Ti, Ce and Co) ultra-thin protective layers for MCFC cathode

•ALD-processed ultrathin protective layers crystalline as-deposited.•MCFC cathode dissolution and corrosion key issue.•Three promising coating candidates compared: TiO2, CeO2 and Co3O4.•Stable single-phased or complex interfaces are produced after immersion in molten carbonates.•Lower Ni solubility is achieved for all the coatings.

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 TiO2 (50 nm), Co3O4 (50 nm) and CeO2 (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 Li2CO3–K2CO3 (62–38 mol%) eutectic melt under a standard cathode atmosphere (CO2/air 30:70 vol%) for 230 h. Finally, the respective advantages and drawbacks of Co3O4, TiO2 and CeO2 coatings are pointed out.