Issue 33, 2023

Engineering hydrophobic–aerophilic interfaces to boost N2 diffusion and reduction through functionalization of fluorine in second coordination spheres

Abstract

Ammonia is a crucial biochemical raw material for nitrogen containing fertilizers and a hydrogen energy carrier obtained from renewable energy sources. Electrocatalytic ammonia synthesis is a renewable and less-energy intensive way as compared to the conventional Haber–Bosch process. The electrochemical nitrogen reduction reaction (eNRR) is sluggish, primarily due to the deceleration by slow N2 diffusion, giving rise to competitive hydrogen evolution reaction (HER). Herein, we have engineered a catalyst to have hydrophobic and aerophilic nature via fluorinated copper phthalocyanine (F-CuPc) grafted with graphene to form a hybrid electrocatalyst, F-CuPc-G. The chemically functionalized fluorine moieties are present in the second coordination sphere, where it forms a three-phase interface. The hydrophobic layer of the catalyst fosters the diffusion of N2 molecules and the aerophilic characteristic helps N2 adsorption, which can effectively suppress the HER. The active metal center is present in the primary sphere available for the NRR with a viable amount of H+ to achieve a substantially high faradaic efficiency (FE) of 49.3% at −0.3 V vs. RHE. DFT calculations were performed to find out the rate determining step and to explore the full energy pathway. A DFT study indicates that the NRR process follows an alternating pathway, which was further supported by an in situ FTIR study by isolating the intermediates. This work provides insights into designing a catalyst with hydrophobic moieties in the second coordination sphere together with the aerophilic nature of the catalyst that helps to improve the overall FE of the NRR by eliminating the HER.

Graphical abstract: Engineering hydrophobic–aerophilic interfaces to boost N2 diffusion and reduction through functionalization of fluorine in second coordination spheres

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Article information

Article type
Edge Article
Submitted
13 6 2023
Accepted
31 7 2023
First published
01 8 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 8936-8945

Engineering hydrophobic–aerophilic interfaces to boost N2 diffusion and reduction through functionalization of fluorine in second coordination spheres

S. Bhardwaj, S. K. Das, A. Biswas, S. Kapse, R. Thapa and R. S. Dey, Chem. Sci., 2023, 14, 8936 DOI: 10.1039/D3SC03002D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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