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Issue 18, 2020
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Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

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Abstract

The development of high-efficiency noble-metal-free catalysts for the electrochemical nitrogen reduction reaction (NRR) to ammonia under ambient conditions has great significance in fertilizer production and energy storage. Considering the major role of Mo-nitrogenase with the FeMo cofactor in the biological N2 fixation process, the design and preparation of Mo and Fe bi-active metal based hybrid materials for the NRR under ambient conditions is proposed in this work. By using PMo12@MOF-100(Fe)@PVP (polyvinylpyrrolidone) as the precursor, two cost efficient FeMo-based electrocatalysts Fe1.89Mo4.11O7/FeS2@C and FeMoO4/FeS2@C were designed and fabricated for the NRR under room temperature and pressure conditions (RTP) via the easy-to-implement hydrothermal sulfuration method. The experiment results confirm that Fe1.89Mo4.11O7/FeS2@C (NH3 yield rate of 105.3 μg h−1 mgcat.−1, FE of 54.7% at −0.4 V vs. RHE) is more efficient towards the NRR than FeMoO4/FeS2@C (NH3 yield of 51.0 μg h−1 mgcat.−1, FE of 43.9% at −0.5 V vs. RHE) in acidic electrolytes; moreover they are all superior to most of the electrocatalysts reported to date. Further electrocatalysis of Fe1.89Mo4.11O7/FeS2@C in alkaline electrolytes (NH3 yield of 86.3 μg h−1 mgcat.−1, FE of 53.6% at −0.4 V vs. RHE) reveals the extensive NRR catalytic activity of this hybrid material. Density functional theory (DFT) calculation indicates that the NRR on Fe1.89Mo4.11O7/FeS2 has optimized nitrogen binding which facilitates the fast kinetics process through an enzymatic mechanism, and the protonation of N2 to form *N2H species is the potential-determining step (PDS) with the maximum ΔG values (+0.61 eV). This work opens up a significant opportunity to develop a family of efficient and robust FeMo-based electrocatalysts for the NRR under ambient conditions by using polyoxometalate-based metal–organic frameworks (POMOFs) as precursors by tuning metal sources.

Graphical abstract: Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

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Supplementary files

Article information


Submitted
01 Apr 2020
Accepted
17 Aug 2020
First published
18 Aug 2020

Green Chem., 2020,22, 6157-6169
Article type
Paper

Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

X. Wang, Z. Feng, B. Xiao, J. Zhao, H. Ma, Y. Tian, H. Pang and L. Tan, Green Chem., 2020, 22, 6157
DOI: 10.1039/D0GC01149E

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