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Potential Dominates Structural Recombination of Single Atom Mn Sites for Promoting Oxygen Reduction Reaction |
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| Authors: | Dr. Miaomiao Tong Dr. Fanfei Sun Dr. Gengyu Xing Prof. Chungui Tian Lei Wang Prof. Honggang Fu |
| Affiliation: | 1. Key Laboratory of Functional Inorganic Materials Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin, 150080 China These authors contributed equally to this work. Contribution: Data curation (lead), Investigation (lead), Methodology (lead), Writing - original draft (lead);2. Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics Chinese Academy of Sciences, Shanghai, 201204 China Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201204 China These authors contributed equally to this work. Contribution: Data curation (lead), Formal analysis (lead);3. Key Laboratory of Functional Inorganic Materials Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin, 150080 China Contribution: Data curation (equal), Formal analysis (equal);4. Key Laboratory of Functional Inorganic Materials Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin, 150080 China Contribution: Data curation (equal), Investigation (equal);5. Key Laboratory of Functional Inorganic Materials Chemistry, Ministry of Education of the People's Republic of China, Heilongjiang University, Harbin, 150080 China |
| Abstract: | Single atom sites (SAS) often undergo structural recombination in oxygen reduction reaction (ORR), while the effect of valence state and reconstruction on active centers needs to be investigated thoroughly. Herein, the Mn-SAS catalyst with uniform and precise Mn-N4 configuration is rationally designed. We utilize operando synchrotron radiation to track the dynamic evolution of active centers during ORR. Under the applied potential, the structural evolution of Mn-N4 into Mn-N3C and further into Mn-N2C2 configurations is clarified. Simultaneously, the valence states of Mn are increased from +3.0 to +3.8 and then decreased to +3.2. When the potential is removed, the catalyst returned to its initial Mn+3.0-N4 configuration. Such successive evolutions optimize the electronic and geometric structures of active centers as evidenced by theory calculations. The evolved Mn+3.8-N3C and Mn+3.2-N2C2 configurations respectively adjust the O2 adsorption and reduce the energy barrier of rate-determining step. Thus, it can achieve an onset potential of 0.99 V, superior stability over 10,000 cycles, and a high turnover frequency of 1.59 s−1 at 0.85 VRHE. Our present work provides new insights into the construction of well-defined SAS catalysts by regulating the valence states and configurations of active centers. |
| Keywords: | Electrocatalytic Mechanism Operando Synchrotron Radiation Oxygen Reduction Reaction Single Atom Sites Structural Evolution |