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Industrial grade rare-earth triple-doped ceria applied for advanced low-temperature electrolyte layer-free fuel cells
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
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2017 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 42, no 34, p. 22273-22279Article in journal (Refereed) Published
Abstract [en]

In this study, the mixed electron-ion conductive nanocomposite of the industrial-grade rare-earth material (Le(3+), Pr3+ and Nd3+ triple-doped ceria oxide, noted as LCPN) and commercial p-type semiconductor Ni0.8Co0.15Al0.05Li-oxide (hereafter referred to as NCAL) were studied and evaluated as a functional semiconductor-ionic conductor layer for the advanced low temperature solid oxide fuel cells (LT-SOFCs) in an electrolyte layer-free fuel cells (EFFCs) configuration. The enhanced electrochemical performance of the EFFCs were analyzed based on the different semiconductor-ionic compositions with various weight ratios of LCPN and NCAL. The morphology and microstructure of the raw material, as prepared LCPN as well the commercial NCAL were investigated and characterized by Xray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometer (EDS), respectively. The EFFC performances and electrochemical properties using the LCPN-NCAL layer with different weight ratios were systematically investigated. The optimal composition for the EFFC performance with 70 wt% LCPN and 30 wt% NCAL displayed a maximum power density of 1187 mW cm(-2) at 550 degrees C with an open circuit voltage (OCV) of 1.07 V. It has been found that the well-balanced electron and ion conductive phases contributed to the good fuel cell performances. This work further promotes the development of the industrial-grade rare-earth materials applying for the LTSOFC technology. It also provides an approach to utilize the natural source into the energy field.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD , 2017. Vol. 42, no 34, p. 22273-22279
Keywords [en]
Industrial-grade rare-earth doped, ceria, Electrolyte layer-free fuel cells, Ionic conductor, Electronic conductor, Electrochemical performance
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-215836DOI: 10.1016/j.ijhydene.2017.04.075ISI: 000411545300073Scopus ID: 2-s2.0-85020065957OAI: oai:DiVA.org:kth-215836DiVA, id: diva2:1149851
Conference
5th Global Conference on Materials Science and Engineering (CMSE), NOV 08-11, 2016, Tunghai Univ, Taichung, TAIWAN
Note

QC 20171017

Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2019-09-03Bibliographically approved
In thesis
1. Application of Rare-Earth Doped Ceria and Natural Minerals for Solid Oxide Fuel Cells
Open this publication in new window or tab >>Application of Rare-Earth Doped Ceria and Natural Minerals for Solid Oxide Fuel Cells
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although solid oxide fuel cell (SOFC) technology exhibits considerable advantages as compared to other energy conversion devices, e.g. high efficiency, low emission and fuel flexibility, its high operating temperature leads to rapid component degradation and has thus hampered commercialization. In recent years, intensive research interests have been devoted to lowering the operating temperature from the elevated temperature region (800-1,000 ℃) to intermediate or low-temperature range (<800 ℃). To achieve this goal, material selection plays a dominant role, involving improving the conductivity of existing electrolytes and developing new exploitable materials. This dissertation is focused on enhancing the ionic conductivity of rare-earth oxides (principally doped ceria) and exploring new candidate materials (e.g. natural minerals) for low temperature (LT) SOFCs.

In this work, the scientific contributions can be divided into four aspects:

i)                To develop desirable superionic conductors, Sm3+/Pr3+/Nd3+ triple-doped ceria is designed to realize the desired doping for Sm3+ in bulk and Pr3+/Nd3+ at surface domains via a two-step wet chemical co-precipitation method. It exhibits high ionic conductivity, 0.125 S cm-1 at 600 ℃. The SOFC device using this material as electrolyte displays a high output power density of 710 mW cm-2 at 550 ℃.

ii)              To further clarify the individual effect of Pr3+ in the doped ceria, a single-element (Pr3+) doped ceria is studied, exhibiting a mixed electronic/ionic conduction property, capable of being employed as the core component of electrolyte-layer free solid oxide fuel cells (EFFCs).

iii)             To investigate various rare-earth doped-ceria materials in double- and triple-element doping solutions for LT-SOFCs, Sm3+/Ca2+ co-doped ceria and La3+/Pr3+/Nd3+ triple-doped ceria are synthesized and then further incorporated with semiconductors, e.g. La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) or Ni0.8Co0.15Al0.05Li-oxide (NCAL), to serve as a semiconducting-ionic conducting membrane in EFFCs.

iv)             To exploit the feasibility of natural mineral cuprospinel (CuFe2O4) as an alternative material for LT-SOFCs, three different types of fuel cell devices are fabricated and tested. The device using CuFe2O4 as cathode exhibits a maximum power density of 180 mW cm-2 with an open circuit voltage of 1.07 V at 550 °C, while the device using a homogeneous mixture membrane of CuFe2O4, Li2O-ZnO-Sm0.2Ce0.8O2 (LZSDC), and LiNi0.8Co0.15Al0.05O2 (NCAL) demonstrates an improved power output, 587 mW cm-2 under the same measurement conditions.  

Based on this work, a new triple-doping strategy is exploited to improve the ionic conductivity of doped ceria materials by surface- and bulk-doping methodology. Furthermore, the material developments of single-phase mixed electronic/ionic conducting doped ceria and doped ceria/semiconductor composites are realized and verify the feasibility of EFFC technology. Investigations on CuFe2O4 indicate the utility of natural minerals in developing cost-effective materials for LT-SOFCs.    

Abstract [sv]

Även om fastoxid bränslecellers (SOFC) uppvisar signifikanta fördelar jämfört med andra energiomvandlingstekniker, t.ex. hög verkningsgrad, låga emissioner och bränsleflexibilitet, leder dess höga driftstemperatur till snabb komponentdegradering, vilken har hindrat kommersialiseringen. Under de senaste åren har intensiv forskning ägnats åt att sänka driftstemperaturerna från de höga temperaturregionerna (800-1,000 °C) till mellanliggande eller låga temperaturintervaller (<800 ℃). För att uppnå detta mål spelar materialvalet en dominerande roll, vilket bland annat innebär att man förbättrar ledningsförmågan hos befintliga elektrolyter och utvecklar nya material. Denna avhandling fokuserar på att förbättra den jonledande förmågan hos oxider av sällsynta jordartsmetaller, huvudsakligen dopad ceriumoxid, samt forskning på nya kandidatmaterial, t.ex. naturliga mineraler.

I det här arbetet kan det vetenskapliga bidraget delas in i fyra aspekter:

i)                Att utveckla en trippel-dopingmetodik för att syntetisera önskvärda superjoniska ledningsförmågor i Sm3+/Pr3+/Nd3+ dopad ceriumoxid. Detta material konstruerades med hjälp av en tvåstegs våtkemisk samutfällningsmetod för att åstadkomma en önskad dopning för Sm3+ i bulk och Pr3+/Nd3+ vid ytdomäner. Materialet uppvisar en hög jonisk ledningsförmåga, 0.125 S cm-1 vid 600 ℃. En SOFC-enhet som använder denna trippeldopade ceriumoxid som elektrolyt har uppvisat en hög effekttäthet på 710 mW cm-2 vid 550 ℃;

ii)              För att ytterligare klargöra den individuella effekten av Pr3+ i det dopade ceriummaterialet studerades enfas Pr-dopade ceria, vilken uppvisade en blandad elektronisk/jonisk ledningsegenskap som skulle användas som kärnkomponent i avancerad elektrolytskiktsfri fastoxid bränsleceller (EFFC).

iii)             Att undersöka olika sällsynta jordartade dopade ceriummaterial i lösningar med dubbel- och trippelelement (Sm3+/Ca2+ och La3+/Pr3+/Nd3+) applicerade för SOFC-teknik med låg temperatur. De dubbel- och tripeldopade ceriummaterialen var sammansatta med halvledare, dvs Ni0.8Co0.15Al0.05Li-oxid (NCAL) och La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) för att fungera som en halvledande jonisk ledande membran i EFFCs.

iv)             Att utnyttja naturligt kopparspinell (CuFe2O4) som ett alternativt material för SOFC. För första gången tillverkades tre olika typer av anordningar för att undersöka den optimala appliceringen av CuFe2O4 i SOFC. Enheten med CuFe2O4 som katodkatalysator uppvisade en maximal effekttäthet av 180 mW cm-2 med en öppen kretsspänning 1.07 V vid 550 ℃. En effekttäthet på 587 mW cm-2 emellertid uppnådes från anordningen bestående av ett homogentblandat membran med CuFe2O4, Li2O-ZnO-Sm0.2Ce0.8O2 och LiNi0.8Co0.15Al0.05O2.

Baserat på detta arbete utnyttjades en ny strategi för att förbättra jonledningsförmågan hos dopade ceriummaterial genom yt- och bulkdopningsmetodik. Vidare verifierades utvecklingen av EFFC-teknikens tillförlitlighet av enfasad, blandad elektronisk/jonledande dopade ceriumoxid samt jonledande multidopade ceria-och halvledarkompositer. Dessa resultat visar att naturliga mineraler kan spela en viktig roll för att utveckla kostnadseffektiva material för bränsleceller.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 109
Series
TRITA-ITM-AVL ; 2019:24
Keywords
Low-temperature solid oxide fuel cells; Doped ceria; Material characterizations; Electrochemical performances; Natural minerals, Lågtemperatur fastoxidbränsleceller; Dopade ceriumoxid; Materialkarakteriseringar; Elektrokemiska prestanda; Naturliga mineraler.
National Category
Engineering and Technology Energy Engineering
Research subject
Energy Technology; Materials Science and Engineering; Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-257718 (URN)978-91-7873-277-7 (ISBN)
Public defence
2019-09-27, K1, Teknikringen 56, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2019-09-03 Created: 2019-09-02 Last updated: 2019-09-03Bibliographically approved

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