Computational design and screening of Single-Atom Phthalocyanine-Coordinated transition metal catalysts for the electrochemical cyanide reduction reaction

Abstract

Catalysis facilitated by transition metals (TM), specifically when these are 4 N-coordinated and embedded within a phthalocyanine (Pc) framework, appears to have promising capabilities for the ecologically responsible generation of methane and ammonia, notably under conditions reflecting the ambient environment. The potential benefits of such applications have sparked escalating interest in studying single atom catalysts (SACs) with regard to their prospective role in the electrochemical cyanide reduction reaction (CNRR). Through the application of first-principles mechanistic investigations and electrochemical modeling, a variety of TM − Pc catalysts are examined under rigorous systematic exploration to ascertain their stability, activity and selectivity. To specifically address the scenarios, it's typically observed that the NC* model demands increased free energy inputs for CNRR, predominantly leading to the production of CH3NH2. In contrast, the analogous CN* model requires comparatively lower free energy, resulting in a more diversified mix of products, notably CH4 and NH3. Our research highlights the significant role of limiting potentials (UL) and their relationship with a particular kind of descriptor (φ) in crafting volcano plots, thereby elucidating the association between the inherent distinctive properties of various TM − Pc and their promising capabilities in CNRR activities. In a significant finding, the catalysts Sc − Pc, Ti − Pc, Cr − Pc and Fe − Pc are recognized as the most efficient electrocatalysts for CH4 and NH3 production through CNRR. This effectiveness is validated by their remarkable stability, superior reactivity, pronounced selectivity at relatively low limiting potentials (ranging from −0.05 to −0.39 V), and extraordinary Faradaic efficiencies exceeding 91.17 %.