(569eq) Exploring Dynamics in Single Atom Catalyst Research: A Comprehensive DFT-Kmc Study of Nitrogen Reduction Reaction with Focus on TM Aggregation

Transition metal (TM)-based single atom catalysts (SACs) have emerged as a promising solution for the electrochemical nitrogen reduction reaction (NRR). A key reason for their utilization is that TMs, when used as single-atom materials, provide localized d-orbitals that weaken N₂ triple bond through efficient electron transfer between TM and N₂. Further, the low coordination number of single atom TM centers results in more accessible binding sites, thereby enhancing reactivity. However, traditional theoretical investigations into SAC systems encounter a critical limitation in accurately predicting activity, as they overlook the kinetics of TM aggregation. This oversight is significant, as aggregation plays a crucial role in understanding how activity changes due to the loss of single TM sites over time. To address this challenge, our study conducted a systematic kinetic evaluation of SACs alongside their thermodynamic and electronic properties. This approach enables comprehensive analysis of the kinetics of surface processes and of activity variations over time, thereby predicting an operational lifetime of the catalyst. Specifically, we utilized boron carbon nitride (BCN) as a substrate and thoroughly screened 216 candidate catalysts, investigating not only their activities but also TM aggregation over time. Our findings revealed that the Cr anchored to BCN exhibits a high turnover frequency (3.1 × 10^−6 s^-1) under mild conditions (300 K and 1 bar), attributed to its minimal TM aggregation over time. Therefore, our research not only addresses the lack of kinetics studies within existing SAC research but also proposes a SAC candidate distinguished by its superior kinetics, thermodynamic, and electronic properties.