(Digital Presentation) Structure-Activity Relationship of M-N-C Electrocatalysts Synthesized Using a General Solution-Phase Coordination Approach

Metal- and nitrogen-doped carbon (M-N-C) catalysts have great potential in heterogeneous catalysis. They are used to catalyze various crucial electrochemical reactions, such as the oxygen reduction reaction (ORR), the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the CO 2 reduction reaction (CO 2 RR). 1-4 The nitrogen-coordinated metal sites (MN x ) have been considered the main active sites in these M-N-C catalysts. However, the synthesis of MN x moieties often undergoes a high-temperature heat-treatment step, resulting in low site density. On the other side, the coordination environment in the MN x sites is also affected by the metal species which induced the site formation. Therefore, it is challenging to single out the role of central metal in the structure-activity relationships for these MN x sites. In this presentation, we will discuss our recent progress in the development of a solution-phase coordination synthesis approach targeting M-N-C catalysts with high active-site density and well-defined coordination environments. 5, 6 A series of M-N-C catalysts are synthesized via this approach by coordinating electroactive target metal ions with the nitrogen-coordinated metal-vacancy (MVN x ) sites in N-C templated by sacrificial metals. With a combined experimental and computational approach, we explore the role of sacrificial metals, including s -, p -, 3 d -, 4 d -, and f -block metals, in forming various MVN x sites with unique coordination configurations. The structure-activity relationship between the coordination environment and the catalytic activity for ORR, HER, OER, and CO 2 RR is established by comparing the MN x site structures induced by various sacrificial metals. Furthermore, we will present the activity series of metal centers in M-N-C catalysts with the same and well-defined coordination environment for ORR, HER, OER, and CO 2 RR. These results will guide the future development of M-N-C catalysts. Acknowledgments Financial support from the State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences is greatly appreciated. This study is financially supported by the Shanxi Province grant (Grant No. 20210302123011, 202203021212007, and 202103021224442), and Key Research and Development (R&D) Projects of Shanxi Province (202102070301018). References J. Cui, Q. Chen, X. Li and S. Zhang. Recent advances in non-precious metal electrocatalysts for oxygen reduction in acidic media and PEMFCs: an activity, stability and mechanism study. Green Chemistry , 23 , 6898 (2021). H. He, H. H. Wang, J. Liu, X. Liu, W. Li and Y. Wang. Research Progress and Application of Single-Atom Catalysts: A Review. Molecules , 26 , 6501 (2021). U. Martinez, S. Komini Babu, E. F. Holby, H. T. Chung, X. Yin and P. Zelenay. Progress in the Development of Fe-Based PGM-Free Electrocatalysts for the Oxygen Reduction Reaction. Advanced Materials , 31 , 1806545 (2019). Y. Wang, X. Cui, L. Peng, L. Li, J. Qiao, H. Huang and J. Shi. Metal–Nitrogen–Carbon Catalysts of Specifically Coordinated Configurations toward Typical Electrochemical Redox Reactions. Advanced Materials , 33 , e2100997 (2021). M. Huang, R. Ding, J. Yang, W. Shi, S. Shi, L. Chen, S. Liu and X. Yin. Formation of Nitrogen-Coordinated Metal Sites (M = Fe, Co) via Solution-Phase Coordination on Nickel- And Nitrogen-Co-Doped Carbon Templates with Metal Vacancy-N x Sites. Journal of The Electrochemical Society , 169 , 106507 (2022). M. Huang, L. Chen, R. Ding, W. Shi, Q. Qin, J. Yang, S. Liu and X. Yin. Solution-Phase Synthesis of Co-N-C Catalysts Using Alkali Metals-Induced N-C Templates with Metal Vacancy-N x sites. ChemRxiv , doi: 10.26434/chemrxiv-2022-xnh88 (2022).