Analysis of the electrochemical performance of MoNi-CeO_2 cermet as anode material for solid oxide fuel cell. Part I. H_2, CH_4 and H_2/CH_4 mixtures as fuels

摘要

This paper investigates the catalytic activity and the electrochemical performance of bimetallic formulation combining Mo and Ni with CeO_2 (MoNi-Ce) in relation its potential use as anode material for SOFC. The catalytic properties were evaluated for methane partial oxidation as function of temperature and the carbon deposition on the anode surface was analysed by TG-MS. A conversion of 12.8% was reached for partial methane oxidation at 850 ℃ as well as a high coke resistance. The electrochemical performance was studied in a single cell with La_(0.58)Sr_(0.4)Fe_(0.8)Co_(0.2)O_(3-δ) (LSCF) as cathode, Lao.gSr_(0.1)-Ga_(0.8)Mg_(0.2)O_(2.85) (LSGM) as electrolyte and MoNi-Ce as anode. A thin buffer layer of La_(0.4)Ce_(0.6)O_(4-δ) (LCD) between anode and electrolyte was used to avoid possible interfacial reactions. The cell was tested in different humidified fuels (H_2, CH_4 and H_2/CH_4 mixtures) and static air at 750, 800 and 850 ℃. The electrochemical behaviour was evaluated by current-voltage curves, impedance spectroscopy and load demand. Stability tests were also performed in pure CH_4 at each studied temperature in order to assess degradation of the electrochemical cell performance. No significant performance degradation was detected in all studied fuels even pure methane, which suggests that MoNi-Ce is a suitable anode material for direct methane SOFC.