期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 143, 期 36, 页码 14530-14539出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.1c03788
关键词
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资金
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDB17020100]
- National Natural Science Foundation of China [21690080, 21690084, 21721004, 21776271]
- Dalian National Laboratory for Clean Energy (DNL) Cooperation Fund
- CAS [DNL 180303]
Atomically dispersed Cu-N-C single-atom catalysts with Cu2+-N-4 structure exhibit comparable activity and superior durability to Pt/C in the electrochemical reduction of oxygen. The dynamic evolution of Cu-N-4 to Cu-N-3 and further to HO-Cu-N-2 under ORR conditions is identified, with the low-coordinated Cu+-N-3 being determined as the real active site. The findings may guide the design of more efficient low-cost catalysts.
Atomically dispersed M-N-C (M refers to transition metals) materials represent the most promising catalyst alternatives to the precious metal Pt for the electrochemical reduction of oxygen (ORR), yet the genuine active sites in M-N-C remain elusive. Here, we develop a two-step approach to fabricate Cu-N-C single-atom catalysts with a uniform and well-defined Cu2+-N-4 structure that exhibits comparable activity and superior durability in comparison to Pt/C. By combining operando X-ray absorption spectroscopy with theoretical calculations, we unambiguously identify the dynamic evolution of Cu-N-4 to Cu-N-3 and further to HO-Cu-N-2 under ORR working conditions, which concurrently occurs with reduction of Cu2+ to Cu+ and is driven by the applied potential. The increase in the Cu+/Cu2+ ratio with the reduced potential indicates that the low-coordinated Cu+-N-3 is the real active site, which is further supported by DFT calculations showing the lower free energy in each elemental step of the ORR on Cu+-N-3 than on Cu2+-N-4. These findings provide a new understanding of the dynamic electrochemistry on M-N-C catalysts and may guide the design of more efficient low-cost catalysts.
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