Carbon deposition occurs when carbon atoms, formed by hydrocarbon pyrolysis or CO disproportionation, deposit on the Ni catalytic surface. Carbon deposition becomes important especially when hydrocarbon fuels are used, i.e. methane, syngas. The high operating temperature of SOFC and the oxidizing environment facilitate the oxidation of Ni catalyst through reaction Ni + O2 = NiO. The oxidation reaction of Ni reduces the electrocatalytic activity and conductivity. Moreover, the density difference between Ni and NiO causes volume change on the anode surface, which could potentially lead to mechanical failure. Sulfur poisoning arises when fuel such as natural gas, gasoline, or diesel is used. Again, due to the high affinity between sulfur compounds (H2S, (CH3)2S) and the metal catalyst, even the smallest impurities of sulfur compounds in the feed stream could deactivate the Ni catalyst on the YSZ surface. Current research is focused on reducing or replacing Ni content in the anode to improve long-term performance. The modified Ni-YSZ containing other materials including CeO2, Y2O3, La2O3, MgO, TiO2, Ru, Co, etc. are invented to resist sulfur poisoning, but the improvement is limited due to the rapid initial degradation. Copper-based cerement anode is considered as a solution to carbon deposition because it is inert to carbon and stable under typical SOFC oxygen partial pressures (pO2). Cu-Co bimetallic anodes in particular show a great resistivity of carbon deposition after the exposure to pure CH4 at 800C. And Cu-CeO2-YSZ exhibits a higher electrochemical oxidation rate over Ni-YSZ when running on CO and syngas, and can achieve even higher performance using CO than H2, after adding a cobalt co-catalyst. Oxide anodes including zirconia-based fluorite and perovskites are also used to replace Ni-ceramic anodes for carbon resistance. Chromite i.e. La0.8Sr0.2Cr0.5Mn0.5O3 (LSCM) is used as anodes and exhibited comparable performance against Ni–YSZ cermet anodes. LSCM is further improved by impregnating Cu and sputtering Pt as the current collector. Electrolyte The electrolyte is a dense layer of ceramic that conducts oxygen ions. Its electronic conductivity must be kept as low as possible to prevent losses from leakage currents. The high operating temperatures of SOFCs allow the kinetics of oxygen ion transport to be sufficient for good performance. However, as the operating temperature approaches the lower limit for SOFCs at around the electrolyte begins to have large ionic transport resistances and affect the performance. Popular electrolyte materials include yttria-stabilized zirconia (YSZ) (often the 8% form 8YSZ), scandia stabilized zirconia (ScSZ)