Mechanisms of the carbon deposition at the Ni/YSZ interface: A combination study of microscopic observation and first-principles calculation

Abstract

Carbon deposition mechanisms at the Ni/YSZ interface in the CH4 environment were studied through microscale observation and density functional theory calculation. SEM and STEM observation showed that carbon deposition occurred at some Ni/YSZ interfaces but was not found at others at the early stage. The carbon deposition in the calculation was modeled by absorbing and bonding CH fragments, and the impact of vacancy configuration at the Ni/YSZ interfaces was studied using the Vienna Ab-initio Simulation Package code. Consequently, the CH–CH bonding barrier was approximately 0.6 eV in the Ni/YSZ, which is lower than the CH cleavage barrier at the last step of CH4 decomposition, indicating that CH–CH bonding occurred as the nascent carbon deposition. Some vacancy configurations made the CH fragments absorption energy more stable mainly because the CH adsorption increased the adhesion bonding force between Ni and YSZ, leading to a stable interface structure. Calculations showed the carbon growth mechanisms at the Ni/YSZ interface, illustrating why the Ni/YSZ interface had a different reactivity against carbon deposition at the atomic scales.