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Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.ORCID iD: 0000-0002-4671-205X
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.ORCID iD: 0000-0002-6212-4194
Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
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2019 (English)In: Batteries, E-ISSN 2313-0105, no 1Article in journal (Other academic) Published
Abstract [en]

Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

Place, publisher, year, edition, pages
MDPI, 2019. no 1
Keywords [en]
Iron electrodes, Cu and Sn-doped iron, SWCNT and LiOH additives, charge efficiency, hydrogen evolution, GC-MS analysis
National Category
Chemical Process Engineering
Research subject
Chemistry; Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-241278DOI: 10.3390/batteries5010001ISI: 000464125800001OAI: oai:DiVA.org:kth-241278DiVA, id: diva2:1280070
Note

QC 20190121

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-05-09Bibliographically approved
In thesis
1. Studies on Rechargeable Fe-air electrodes in Alkaline electrolyte
Open this publication in new window or tab >>Studies on Rechargeable Fe-air electrodes in Alkaline electrolyte
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy storage system is an important component in the energy system based on variable renewable energy sources into the grid. Energy storage system could contribute to decarbonization, energy security, offset the demand and supply of the electricity sector, especially for the electric grid. These can be either mechanical, electrochemical, chemical, electromagnetic or thermal devices. The most important functional characteristics of an energy storage system are capital cost, roundtrip efficiency, energy and power rating, response times and cycle life. Electrochemical energy storage systems (EES) have the following edge over the other systems: fast response time, relatively short duration of storage, size, high efficiency, a decentralized installation which is closer to generation or consumption site.

The focus of this thesis is on the development of cost-effective iron anode materials and electrocatalytic air electrodes for Fe-air batteries that potentially could become as an energy storage system. Iron-based systems are attractive due to their safety, cheapness, non-toxicity and ubiquitous availability of materials. However, both the anode and cathode parts have numerous drawbacks that need to be addressed. The anode exhibits poor charge efficiency, rate capability and low capacity utilization while the cathode has sluggish kinetics, poor activity, structural stability and the numbers of active non-noble metal catalysts are limited.

This work utilized Cu and Sn-doped iron nanomaterials and different additives (Bi2S3, CNT, LiOH) to enhance the performance of the iron electrode. The performance of the electrodes were evaluated using the charge/discharge cycling, rate capability, cyclic voltammetry (CV), galvanostatic and potentiodynamic polarization measurements, in operando charging measurements combined with mass spectrometry. The fresh and cycled electrodes and powders were characterized by ex-situ XRD, BET, SEM, TEM , XPS and Raman spectroscopy. The most striking results are the prevention of nanoparticle agglomeration, increased charging efficiency (80-91%), effect of Cu and Sn dopants on specific capacity (367-603 mAh g-1) and improved performance of the electrodes at high charge current densities.

In the subsequent air electrode part, non-precious metal La-doped CaMnOx, nano Co3O4 and NiFeOX electrocatalysts were synthesized using co-precipitation and hydrothermal methods. Both the single and mixed catalysts were used as bi-functional catalysts for oxygen reduction and evolution reactions (ORER). The catalysts were characterized by XRD, SEM, TEM, BET, Raman and XPS. The electrocatalytic activity and stability were assessed in alkaline solutions on gas diffusion electrodes and glassy carbon electrode by linear sweep voltammetry (LSV), CV and rotating disk electrode (RDE). Furthermore, the mixed catalyst and NiFeOX showed excellent bifunctional performance such as high activity and stability achieved by the hybridization of the two catalysts and the effect of catalyst loading on the electrocatalytic performance. These findings can help to develop a cost-effective material for Fe-air batteries.

Place, publisher, year, edition, pages
Stockholm: KTH, 2019. p. 108
Keywords
Fe-air battery; Cu/Sn-doped nanostructured iron electrodes, Alkaline electrolytes, Bi-functional OER/ORR catalyst, perovskite/spinel catalyst, NiFeOx, air electrode
National Category
Engineering and Technology Chemical Process Engineering Chemical Sciences
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-241534 (URN)978-91-7873-087-2 (ISBN)
Public defence
2019-03-01, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 39078-1
Note

QC 20190124

Available from: 2019-01-24 Created: 2019-01-23 Last updated: 2019-02-22Bibliographically approved

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Kiros, YohannesGöthelid, Mats

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