TY - JOUR
T1 - Microwave-Enabled Incorporation of Single Atomic Cu Catalytic Sites in Holey Graphene
T2 - Unifying Structural Requirements of a Carbon Matrix for Simultaneous Achievement of High Activity and Long-Term Durability
AU - Li, Qingdong
AU - Yang, Hongbin
AU - Ouyang, Junjie
AU - Solovyev, Mikhail
AU - Lahanas, Nicole
AU - Flach, Carol
AU - Mendelsohn, Richard
AU - Garfunkel, Eric
AU - Pavanello, Michele
AU - Lockard, Jenny V.
AU - He, Huixin
N1 - Funding Information:
H.H. and M.P. would acknowledge the support by the National Science Foundation under grant DMR-1742807. H.H. would also acknowledge the support by the ACS Petroleum Research Fund under grant 58557-ND5. J.V.L. would like to acknowledge the support by the National Science Foundation under grant no. DMR-1455127. Part of this work is based on the research conducted at the Advanced Photon Source (APS), an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory and was supported by the U.S. DOE under contract no. DE-AC02-06CH11357. Part of this research used beamline 6BM of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-SC0012704. M.S. was supported by a U.S. Department of Energy (DOE) Office of Science Graduate Student Research (SCGSR) award. We thank Dr. Chengjun Sun for support during XAS measurements at APS and Dr. Bruce Ravel for support during XAS measurements at NSLS II.
PY - 2020/9/28
Y1 - 2020/9/28
N2 - This work reports our discoveries from the first exploration in microwave pyrolysis of a metal-organic framework. A time- and energy-efficient approach was developed for direct fabrication of electrochemical single-atom catalysts (E-SACs) without the requirement of post-treatment. The most unique structure of the fabricated E-SAC is that the Cu catalytic sites were not in the amorphous carbon matrix as those achieved via traditional pyrolysis but in the basal planes of pristine holey graphene nanoplatelets. The as-prepared Cu-E-SAC exhibits excellent catalytic activity and selectivity in reducing oxygen to water in both acidic and alkaline media. The desired direct 4e- pathway is more favorable in acidic versus alkaline media, which is different from all the Cu-E-SACs reported so far and most transition-metal-based E-SACs. The superior performance is attributed to the unique structure of the catalytic sites. The large graphene domains in the holey graphene materials provide higher delocalized electron-rich πband and increase the d-orbital energy level of the Cu centers. Consequently, their binding strength for molecular oxygen is largely enhanced, improving the oxygen reduction reaction and likely promoting a direct 4e- pathway with minimized generation of a peroxide byproduct. Considering the high conductivity and excellent stability against oxidation of the holey graphene material, this work, for the first time, suggests that the contradictory structural requirement of a carbon matrix for high catalytic activity and long-term durability can be unified and simultaneously satisfied. Combined with the merits of simplicity and rapidness for fabricating both holey graphene and E-SACs, this work provides a possible strategy to address the critical challenges of precious metal-free single-atom catalysts.
AB - This work reports our discoveries from the first exploration in microwave pyrolysis of a metal-organic framework. A time- and energy-efficient approach was developed for direct fabrication of electrochemical single-atom catalysts (E-SACs) without the requirement of post-treatment. The most unique structure of the fabricated E-SAC is that the Cu catalytic sites were not in the amorphous carbon matrix as those achieved via traditional pyrolysis but in the basal planes of pristine holey graphene nanoplatelets. The as-prepared Cu-E-SAC exhibits excellent catalytic activity and selectivity in reducing oxygen to water in both acidic and alkaline media. The desired direct 4e- pathway is more favorable in acidic versus alkaline media, which is different from all the Cu-E-SACs reported so far and most transition-metal-based E-SACs. The superior performance is attributed to the unique structure of the catalytic sites. The large graphene domains in the holey graphene materials provide higher delocalized electron-rich πband and increase the d-orbital energy level of the Cu centers. Consequently, their binding strength for molecular oxygen is largely enhanced, improving the oxygen reduction reaction and likely promoting a direct 4e- pathway with minimized generation of a peroxide byproduct. Considering the high conductivity and excellent stability against oxidation of the holey graphene material, this work, for the first time, suggests that the contradictory structural requirement of a carbon matrix for high catalytic activity and long-term durability can be unified and simultaneously satisfied. Combined with the merits of simplicity and rapidness for fabricating both holey graphene and E-SACs, this work provides a possible strategy to address the critical challenges of precious metal-free single-atom catalysts.
KW - copper base catalyst
KW - holey graphene
KW - microwave synthesis
KW - ORR
KW - single-atom catalysts
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UR - http://www.scopus.com/inward/citedby.url?scp=85094826694&partnerID=8YFLogxK
U2 - 10.1021/acsaem.0c00704
DO - 10.1021/acsaem.0c00704
M3 - Article
AN - SCOPUS:85094826694
VL - 3
SP - 8266
EP - 8275
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
SN - 2574-0962
IS - 9
ER -