TY - JOUR
T1 - Rational Molecular Design of Electrocatalysts Based on Single-Atom Modified Covalent Organic Frameworks for Efficient Oxygen Reduction Reaction
AU - Iwase, Kazuyuki
AU - Nakanishi, Shuji
AU - Miyayama, Masaru
AU - Kamiya, Kazuhide
N1 - Funding Information:
This research was supported by a JSPS KAKENHI Program (grants 16J09552 and 17H04798), CREST (grant JPMJCR18R3), and PRESTO Program (grant JPMJPR1415) of the Japan Science and Technology Agency (JST).
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/2/24
Y1 - 2020/2/24
N2 - The development of oxygen reduction reaction (ORR) electrocatalysts comprising abundant elements is highly desirable for achieving widespread use of fuel cells. Optimal ORR catalysts should have moderate binding strength (ΔEads) with O2-derived intermediates, where the metal species and its coordination numbers are the essential determining factors for ΔEads. However, in conventional non-noble-metal-based ORR catalysts, such as metal-nitrogen-doped carbons, the metal species and its coordination structure cannot freely be chosen. In contrast, covalent organic frameworks (COFs), which are cross-linked microporous polymers, have high design flexibility; as such, they can be purposefully designed by using a wide range of monomers. The present work investigated the adsorption strength of ORR intermediates on single 3d metal atoms (Mn, Fe, Co, Ni, and Cu) doped in COFs with different coordination structures using first-principles calculations toward the development of efficient non-noble-metal ORR catalysts. The adsorption strength of the intermediates was found to monotonically increase as either the number of d-electrons or coordination number of metal centers decreased, and a volcano-type relationship was observed between the adsorption energies of the intermediates and the theoretical ORR activities. Therefore, to develop efficient non-noble-metal-based ORR electrocatalysts, the adsorption strength should be tuned close to the volcano peak by an appropriate choice of metal species and/or coordination number as the control parameters. Considering the high designability of metal species and of its coordination numbers in COFs, COFs are expected to become the next-generation platform of supports of single-atom catalysts using the design direction provided by the present work.
AB - The development of oxygen reduction reaction (ORR) electrocatalysts comprising abundant elements is highly desirable for achieving widespread use of fuel cells. Optimal ORR catalysts should have moderate binding strength (ΔEads) with O2-derived intermediates, where the metal species and its coordination numbers are the essential determining factors for ΔEads. However, in conventional non-noble-metal-based ORR catalysts, such as metal-nitrogen-doped carbons, the metal species and its coordination structure cannot freely be chosen. In contrast, covalent organic frameworks (COFs), which are cross-linked microporous polymers, have high design flexibility; as such, they can be purposefully designed by using a wide range of monomers. The present work investigated the adsorption strength of ORR intermediates on single 3d metal atoms (Mn, Fe, Co, Ni, and Cu) doped in COFs with different coordination structures using first-principles calculations toward the development of efficient non-noble-metal ORR catalysts. The adsorption strength of the intermediates was found to monotonically increase as either the number of d-electrons or coordination number of metal centers decreased, and a volcano-type relationship was observed between the adsorption energies of the intermediates and the theoretical ORR activities. Therefore, to develop efficient non-noble-metal-based ORR electrocatalysts, the adsorption strength should be tuned close to the volcano peak by an appropriate choice of metal species and/or coordination number as the control parameters. Considering the high designability of metal species and of its coordination numbers in COFs, COFs are expected to become the next-generation platform of supports of single-atom catalysts using the design direction provided by the present work.
KW - adsorption energy
KW - covalent organic frameworks
KW - density functional theory calculation
KW - non-noble-metal catalysts
KW - oxygen reduction
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U2 - 10.1021/acsaem.9b02141
DO - 10.1021/acsaem.9b02141
M3 - Article
AN - SCOPUS:85078961042
VL - 3
SP - 1644
EP - 1652
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
SN - 2574-0962
IS - 2
ER -