Predicting the Stability of Dual-Atom Catalysts Under Electrochemical Conditions

Single-atom catalysts are emerging as a promising frontier in heterogeneous catalysis [1]. They are formed by single transition metal atoms supported by a solid matrix. Recently, this concept has expanded to include dual-atom catalysts (DACs), in which pairs of metal atoms are embedded within the supporting matrix to create cooperative active sites [2]. Density functional theory (DFT) simulations enable the rapid screening of candidate structures and the identification of activity descriptors [3]. However, most computational predictions overlook a critical aspect of catalyst design: operational stability. Stability is often estimated solely from the binding energy of the metal dimer within the support. Here, we present an approach that enables more reliable prediction of electrocatalyst stability under operating conditions. Building on the original methodology developed for single-atom catalysts, we extend a general first-principles strategy to evaluate the stability of DACs under electrochemical conditions, defined by pH and applied potential, through the simulation of Pourbaix diagrams [4]. Our approach involves building multiple thermodynamic cycles in which energetic parameters are determined from DFT calculations or measured experimentally. We applied the procedure to a set of five metals (Fe, Co, Ni, Pd, Pt) supported on nitrogen-doped graphene. The comparison with the corresponding single-atom systems indicates that, although dual-atom catalysts are generally expected to be more active, they exhibit lower stability under electrochemical conditions. Furthermore, using our method, we were able to theoretically verify the stability under operating conditions of representative electrocatalysts that are experimentally synthesized and used for electrocatalytic purposes, such as Ni2-N6@C, Figure 1 [5]. These results emphasize the importance of evaluating catalyst’s stability beyond a simple assessment of the binding energy, highlighting the importance of a more rigorous prediction of dual-atom catalysts’ stability under electrochemical operating conditions, a key requirement for the rational design of next-generation catalysts for sustainable energy applications. Figure 1: Simulated Pourbaix diagram of Ni2-N6@C dual-atom catalyst. References [1] Yang, X. F., Wang, A., Qiao, B., Li, J. U. N., Liu, J., & Zhang, T. Acc. Chem. Res., 46(8), 1740-1748 (2013). [2] Li, R., & Wang, D. Adv. Energy Mater., 12(9), 2103564 (2022). [3] Di Liberto, G., & Pacchioni, G. (2023). Adv. Mater., 35(46), 2307150 (2023). [4] Di Liberto, G., Giordano, L., & Pacchioni, G. ACS Catal., 14(1), 45-55 (2023). [5] Hao, Q., Zhong, H. X., Wang, J. Z., Liu, K. H., Yan, J. M., Ren, Z. H., ... & Zhang, X. B. Nat. Synth., 1(9), 719-728 (2022).