TY - JOUR
T1 - Redox-Mediator-Assisted Electrocatalytic Hydrogen Evolution from Water by a Molybdenum Sulfide-Functionalized Metal-Organic Framework
AU - Noh, Hyunho
AU - Kung, Chung Wei
AU - Otake, Ken Ichi
AU - Peters, Aaron W.
AU - Li, Zhanyong
AU - Liao, Yijun
AU - Gong, Xinyi
AU - Farha, Omar K.
AU - Hupp, Joseph T.
N1 - Funding Information:
This work was supported by the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC0001059. H.N. gratefully acknowledges support from the Ryan Fellowship program of the Northwestern University International Institute of Nanotechnology. C.-W.K. acknowledges support from the Postdoctoral Research Abroad Program (105-2917-I-564-046) sponsored by the Ministry of Science and Technology (Taiwan). We thank Prof. Michael R. Wasielewski and his lab group for the use of a gas chromatograph. This work made use of the IMSERC, J. B. Cohen X-ray Diffraction, EPIC, and KECK II facilities of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. Use of the Advanced Photon Source is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Materials Research Collaborative Access Team (MRCAT, Sectors 10ID) operations are supported by the U.S. Department of Energy and the MRCAT member institutions.
Funding Information:
This work was supported by the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC0001059. H.N. gratefully acknowledges support from the Ryan Fellowship program of the Northwestern University International Institute of Nanotechnology. C.-W.K. acknowledges support from the Postdoctoral Research Abroad Program (105-2917-I-564-046) sponsored by the Ministry of Science and Technology (Taiwan). We thank Prof. Michael R. Wasielewski and his lab group for the use of a gas chromatograph. This work made use of the IMSERC, J. B. Cohen X-ray Diffraction, EPIC, and KECK II facilities of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois through the IIN. Use of the Advanced Photon Source is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Materials Research Collaborative Access Team (MRCAT, Sectors 10ID) operations are supported by the U.S. Department of Energy and the MRCAT member institutions.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/10/5
Y1 - 2018/10/5
N2 - The Zr6-based metal-organic framework NU-1000 was successfully functionalized with candidate catalysts - MoSx units - via SIM (solvothermal deposition in MOFs) of molybdenum(VI), followed by reaction with H2S gas. The structure of the material, named MoSx-SIM, was characterized spectroscopically and through a single-crystal X-ray diffraction measurement. These measurements and others established that the catalyst is monometallic, with mixed oxygen and sulfur coordination, and that it forms from a MOF-node-supported molybdenum-based cluster featuring only oxy ligands. Notably, the formal potential for the MOF-grafted complex, like that for the metal-sulfur active site of hydrogenase, is nearly coincident with the formal potential for the hydrogen couple. Its effective concentration within the mesoporous MOF is several hundred millimolar, and its porous-framework-based immobilization/heterogenization obviates the need for aqueous solubility as a condition for use as a well-defined catalyst. MoSx-SIM was evaluated as an electrocatalyst for evolution of molecular hydrogen from aqueous acid. Although the MoSx-functionalized framework exhibits catalytic behavior, the highly insulating nature of the support inhibits high electrocatalytic performance. Introduction of an archetypal redox mediator (RM), methyl viologen (MV2+), resulted in more than 20-fold enhancement in its catalytic performance on a turnover frequency basis, implying efficient RM-assisted electron transfer to otherwise electrochemically non-addressable MoSx moieties. Electrochemical kinetic studies with additional viologens as mediators reveal an unexpected square-root dependence of overall reaction rate on mediator concentration, as well as sensitivity to the strength of RM•+ as a reductant. These observations, together with observations of potential-dependent H/D isotope effects and potential-dependent pH effects, provide useful insights into the catalysis mechanism and help to explain how the MOF-affixed monometallic catalyst can effectively catalyze a two-electron reduction reaction, i.e., hydrogen evolution from acidified water.
AB - The Zr6-based metal-organic framework NU-1000 was successfully functionalized with candidate catalysts - MoSx units - via SIM (solvothermal deposition in MOFs) of molybdenum(VI), followed by reaction with H2S gas. The structure of the material, named MoSx-SIM, was characterized spectroscopically and through a single-crystal X-ray diffraction measurement. These measurements and others established that the catalyst is monometallic, with mixed oxygen and sulfur coordination, and that it forms from a MOF-node-supported molybdenum-based cluster featuring only oxy ligands. Notably, the formal potential for the MOF-grafted complex, like that for the metal-sulfur active site of hydrogenase, is nearly coincident with the formal potential for the hydrogen couple. Its effective concentration within the mesoporous MOF is several hundred millimolar, and its porous-framework-based immobilization/heterogenization obviates the need for aqueous solubility as a condition for use as a well-defined catalyst. MoSx-SIM was evaluated as an electrocatalyst for evolution of molecular hydrogen from aqueous acid. Although the MoSx-functionalized framework exhibits catalytic behavior, the highly insulating nature of the support inhibits high electrocatalytic performance. Introduction of an archetypal redox mediator (RM), methyl viologen (MV2+), resulted in more than 20-fold enhancement in its catalytic performance on a turnover frequency basis, implying efficient RM-assisted electron transfer to otherwise electrochemically non-addressable MoSx moieties. Electrochemical kinetic studies with additional viologens as mediators reveal an unexpected square-root dependence of overall reaction rate on mediator concentration, as well as sensitivity to the strength of RM•+ as a reductant. These observations, together with observations of potential-dependent H/D isotope effects and potential-dependent pH effects, provide useful insights into the catalysis mechanism and help to explain how the MOF-affixed monometallic catalyst can effectively catalyze a two-electron reduction reaction, i.e., hydrogen evolution from acidified water.
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U2 - 10.1021/acscatal.8b02921
DO - 10.1021/acscatal.8b02921
M3 - Article
AN - SCOPUS:85054326383
VL - 8
SP - 9848
EP - 9858
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 10
ER -