Role of crowded surfaces in microkinetic modelling of CO2 methanation on nickel

First-principles microkinetic modeling with realistic surface coverages provides a more accurate description of CO₂ methanation on Ni catalysts than conventional low-coverage DFT models. A dual-site model shows that H- and OH-assisted COx activation lowers barriers and that CO forms as an intermediate, reaching pseudo-steady-state before conversion to CH₄. CO₂ activation mainly occurs on terrace sites, while CO activation on B5 sites is critical for methane formation. Models using realistic coverages better match experimental turnover rates and CH₄ selectivity, highlighting the importance of crowded-surface effects in catalyst design.