Novel Nickel-Based Single-Atom Alloy Catalyst for CO2 Conversion Reactions: Computational Screening and Reaction Mechanism Analysis

Catalytic conversion of CO2 to methane and syngas are two promising routes for CO2 utilization. Even though noble metals have shown high activity and stability for these reactions, cheaper nickel (Ni)-based catalysts are preferred. However, these are less active and are prone to deactivation due to carbon deposition. Boron-promoted Ni (NiB) was developed by the microstructural modification of Ni, and it showed improved stability, but with reduced activity. This is attributed to the high CO2 activation barrier. Single-atom alloys (SAA) are adequately capable of performing selective catalysis to improve the catalyst performance. In this work, using first-principles-based computational screening, a novel and thermodynamically stable NiB SAA catalyst that reduces CO2 activation barrier and improves the activity without affecting stability and selectivity of NiB is predicted. We considered 14 dopant elements that alloy with Ni (Ru, Pt, Pd, Rh, Co, Fe, Os, Ir, Re, W, Mo, Cu, Mn, and Zn) and evaluated the relative thermodynamic stability of the SAA configuration, compared to that of dimer or trimer structures. The relative stability of SAA was higher than that of the aggregates for only five metals (Pt, Pd, Rh, Cu, and Mn). We further calculated the CO2 activation barrier on these five SAAs and found that Mn-NiB SAA was the only candidate on which there is a significant reduction of the CO2 activation barrier (reduced by 56 kJ mol–1). Subsequently, we studied CO2 methanation (46 elementary reactions) and dry reforming of methane (DRM) (38 elementary reactions) reactions on Mn-NiB SAA. High CO2 adsorption energy and low CO2 and CO* activation barriers make Mn-NiB SAA a suitable catalyst for CO2 methanation. Correspondingly, the low CO2 and CH4 activation barriers make Mn-NiB SAA a perfect candidate for DRM reaction. Prominently, the high endergonicity for CH4 stepwise dehydrogenation combined with a low barrier for Boudouard reaction reduces the on-surface coke formation. Thus, we believe that Mn-NiB SAA can be a potential catalyst for CO2 methanation and DRM reactions.