Predicting Catalytic Activity of Single Atom Catalysts in Oxygen Evolution Reaction via First-Principles Simulations and Symbolic Regression

Efficient energy conversion and storage require the development of effective electrocatalysts for the oxygen evolution reaction (OER). In this regard, single-atom catalysts (SACs) with 100 % active sites for OER are promising [1-6]. This study investigates the OER activities of Co single atoms (CoSA) on metallic MXenes, namely Ti₃C₂O₂ and Mo₂CO₂, considering both stoichiometric and oxygen vacancy (Ov) configurations. Spin-polarized first-principles calculations were used to determine the rate-limiting step, the conversion of oxygen from hydroxyl species. The presence of oxygen vacancies resulted in decreased OER activity and higher overpotential for CoSA on Ti₃C₂O_2-δ, while it increased OER activity for CoSA on Mo₂CO₂. Insights from the density of states, the variation of the charge density and the bonding analysis provide information about the observed results. Furthermore, the critical role of hybridization between the d states of CoSA and the transition metal sites of the catalyst bed (Ti/Mo) is demonstrated. Furthermore, we investigated the potential of designing SACs on Mo₂CO₂ MXenes for electrochemical OER using first-principles modeling simulations. The Electrochemical Step Symmetry Index (ESSI) method is used to fine-tune activity and identify optimal SACs, with both Ag and Cu showing potency in enhancing OER activity. Cu stands out among the chosen transition metals (TMs) as the best catalyst for reducing the overpotential, while Ag poses challenges in tuning its overpotential. Symbolic regression analysis is employed to identify key descriptors affecting catalytic efficiency, resulting in the derivation of mathematical formulas for the OER overpotential. This comprehensive investigation provides insights into the potential of SACs and MXenes in advanced electrocatalytic processes, offering prospects for improved OER activity and selectivity.<br/><br/><b>References:</b><br/>[1] Qu, G.; Zhou, Y.; Wu, T.; Zhao, G.; Li, F.; Kang, Y.; Xu, C. Phosphorized MXene-phase<br/>molybdenum carbide as an earth-abundant hydrogen evolution electrocatalyst. ACS Applied<br/>Energy Materials 2018, 1, 7206–7212.<br/>[2] Xiao, S.; Zhang, X.; Zhang, J.; Wu, S.; Wang, J.; Chen, J. S.; Li, T. Enhancing the lithium<br/>storage capabilities of TiO2 nanoparticles using delaminated MXene supports. Ceramics International<br/>2018, 44, 17660–17666.<br/>[3] Kan, D.; Wang, D.; Zhang, X.; Lian, R.; Xu, J.; Chen, G.; Wei, Y. Rational design of bifunctional<br/>ORR/OER catalysts based on Pt/Pd-doped Nb 2 CT 2 MXene by first-principles<br/>calculations. Journal of Materials Chemistry A 2020, 8, 3097–3108.<br/>[4] Liu, C.-Y.; Li, E. Y. Termination effects of Pt/v-Ti n+ 1C n T2 MXene surfaces for oxygen<br/>reduction reaction catalysis. ACS Applied Materials & Interfaces 2018, 11, 1638–1644.<br/>[5] Wang, Y.; Li, X.; Zhang, M.; Zhang, J.; Chen, Z.; Zheng, X.; Tian, Z.; Zhao, N.; Han, X.;<br/>Zaghib, K., et al. Highly Active and Durable Single-Atom Tungsten-Doped NiS0. 5Se0. 5<br/>Nanosheet@ NiS0. 5Se0. 5 Nanorod Heterostructures for Water Splitting. Advanced Materials<br/>2022, 34, 2107053.<br/>[6] Hu, H.; Wang, J.; Cui, B.; Zheng, X.; Lin, J.; Deng, Y.; Han, X. Atomically Dispersed<br/>Selenium Sites on Nitrogen-Doped Carbon for Efficient Electrocatalytic Oxygen Reduction.<br/>Angewandte Chemie International Edition 2022, 61, e202114441.