Investigating the influence of vacancy and rhodium doping on nickel-based single-atom catalysts for methane dehydrogenation: A Brønsted–Evans–Polanyi analysis via density functional theory

This study used Density Functional Theory (DFT) to investigate how surface vacancies and Rhodium (Rh) doping affect methane dehydrogenation on Ni(111)-based surfaces. Four surface models were examined: pristine Ni(111), Rh-doped Ni(111), Ni(111) with a vacancy, and Rh-doped Ni(111) with a vacancy. The results revealed that surface vacancies significantly reduce the activation energy for CH decomposition, which promotes carbon accumulation (coke formation) at defect sites. Conversely, Rh doping increases the activation energy for the final CH dissociation step, thereby improving the surface's resistance to amorphous carbon deposition. Notably, combining Rh doping with a vacancy partially mitigates the coke-promoting effect of the defect, although its performance is still not as good as Rh-doped defect-free surfaces. Additionally, a consistent Brønsted–Evans–Polanyi (BEP) relationship was established across all surface models, enabling reliable prediction of activation barriers based on reaction enthalpies. Overall, Rh-doped, defect-free Ni(111) surfaces are identified as the best design for coke-resistant catalysts.