First-Principles-Based Kinetic Monte Carlo Simulations of Methane Steam Reforming on Stepped Ni Surfaces

Methane Steam Reforming (MSR) is a critical process for hydrogen production in the chemical industry. Nickel-based catalysts are usually preferred for MSR due to their high activity and low cost. Several studies have shown that step edges and defects on Ni surfaces have a strong influence on the MSR kinetics. However, a detailed mechanistic-level understanding of the MSR reaction on stepped Ni surfaces has remained elusive. In this work, we have developed a DFT-parameterized Kinetic Monte Carlo (KMC) model to investigate the detailed kinetics of MSR reaction on stepped Ni surfaces (which contain step and terrace sites) and compare them systematically against the (111) facet. Comparisons of the predicted MSR turnover frequencies (TOFs) on Ni(211) and Ni(111) surfaces indicate that the TOF on Ni(211) exhibits strong temperature dependence, whereas Ni(111) is more sensitive to the partial pressure of CH4. Additionally, we found that the step sites are more active in adsorbing and dissociating water, suggesting that higher water partial pressure improves Ni(211) performance. To further understand the role of step sites, we extended our analysis by changing the density of the step sites in the KMC lattice, providing insights into the broader impact of step density on catalytic behavior. These findings contribute to a deeper understanding of the reaction mechanisms governing MSR on stepped Ni surfaces, offering valuable insights for optimizing catalyst design and improving hydrogen production efficiency.