別紙41 (課程博士(英文))Date of submission (month day, year)

July 121h,2019
AtsunoriMatsuda

DepaHment ofElectricaland
SludentlD

D169201

electronic informantion

HiroyukiMuto

NumberSupervisors

englneerlng

Pplicant's nameToshiakiHattori

Kyaw zayYa

Abstract (Doctor)
Effects oflnorganicAdditives on properties ofpolybenzimidazole Electrolyte
Title ofThesis

Membranes forMedium lemperature Fuelce11S

ノ,4'︑Approx.80o words

ゞ'器武Fuel ce11S are electroche111ical ce11S that directly convertthe chemical en剖'gy ofa fuel (eg. hydrog引1) andan oxidizing agent (eg. oxygen) into electl'ical en引'gy 、 ith high e仟iciency and lo、N P0ⅡUtants through theredox reaction (oxidation and l'eduction). The working principle or t11e performance of fuel ce11S are quite
different from most ofule batteries,、¥hich need a continuous s011rce offuel and oxygen (usuaⅡy h'om air) toPr010ng the chemicalreaction, W11引'eas in a bauel},the chemical en引'gy usuaⅡy comeS 介om metals and theirions or oxides that al'e commonly already pl'eS引lt in the battery, except in ao、N batteries. Fuel ce11S can yieldelectricity continuously for as long as fuel and oxygen al'e supplied.1n the proton・exchange membrane fuelCeⅡ(PEMFC) systems, the electrolyte works as a pl'oton conductor during fuel ceⅡ Operati0Π,、vhich
PI'events the electron ao、Ning through it from direct fuel gas mixing.1n this l'eseal'ch, the fabrication ofinorganic soHd composite matelials 、¥as performed using mechanochemical dry lnⅡling,、vet mⅡling, andIiquid・phase shaking to achieve potential proton conductors with hig11 Proton conductivities. Especia11y, inthe fabrication of inorganic solid acid composite materials, the e仟ect of N<1・dilnethylacetamide (DMAC)
Solvent 、Nas clearly seen in these composite materials fabricated using mechanochemical、Net miⅡing andⅡquid・phase shaking because tlw dispersing solvent DMAC 、NiⅡ Perform to 、刃eakelV愉'eak the precursor
materials bonds by partial or complete dissolution 、Nithout using high impact 引lerσy; and by extension theformation ofu〕e ne、N bonds. hl addition,、vith a highly mobile liquid dispersing lnedium it 、Nas expected dlat
reacting species 、vi11 eaSⅡy locate one another and could easily at[ain tl〕e right 01'ientations f01' e仟ective
reactions and also possibly cause a reduction in activation en引'gies needed for e仟ective reactions.
Inorganic solid acid composite materials 、vere synthesized using in01'ganic solid acid salts csHS04(CHS), and heteropoly acid (HPAS). These high pl'oton conductive composite lnatel'ials 、Nere applied as
inorganic additive fi11ers in the fabrication of in田'ganic・organic colnposite electrolytes, to improve thePhysicochemical and electrochemical performances of organic polym飢' electrolytes. phosphoric acid doped
Polybenzimidazole (PA・PBD 、和as selected as a polymer membl'ane to obtain high proton conducting state,
Since pl'oton conduction mechanism and chemicalint引'action in this polymer matrix under anhydrous
Condition at medium temperatul'es 、¥ere 、NeⅡ Understood.
In dle fabrication of cesium substituted・silicotunσStic acid composite matel'ials, high proton
Conductive xcsHS04・(1・χ)H4SiW120如(CHS、＼八IsiA) composite materials with molar rati0 χ= 0.5,0.フ, and
0.9 、¥飢'e successfUⅡy pl'epared via mechanochemical dl>, mi11ing, mechanochemical 、vet mi11ing, andHquid・phase shaking method.10n・exchange l'eactions and stl'ong chemicalinteractions were occurred
between preCⅢ'sor cHs and 、NsiA durinσ the mechanochemical mi11ing treatments and liquid‑phase
Shaking, X・ray di仟raction characterization confinned that mechanochemical treatments and liquid・phase
Shakinσ induced an ion、exchange reaction bet、veen cゞ ions in cHs and H+ ions in ＼NsiA t0 側'oduce a ne、VClass of composite materials.1he proton conductivities of c01ηPosite matel'ials 、vere significantly improved
Over t11eir precursor materials, especiaⅡy at lo、¥ temperatures, belo、N the suP引'protic phase‑transition
temP則'ature (141 ゜C) of cHS. Among these composite materials, the 09CHS・0.1圦,1SiA (in lTlole ratio)

Composites fabricated via dry mi11ing, wet miⅡing, and liquid・P1喰Se shaking sho、¥ed the highest

Conductivities of ω'ound lo‑3 S cm‑1 at 170 ゜c under dl'y nitrogen atmosphere. The enhanced anhydrous
Proton conductivities of the cs・substituted xvsiA composite matel'ials were also corroborated 、¥ith
Shortening of the hydrogen bonding distance in these composites for fast proton hoppino transpod

mechanism via lH・MAS・NMR evaluation. The pl'oton conductivities of composite materials obtained by、vet miⅡing and liquid・phase shaking 、刃ere remarkably hi旦h団' than those of the composites fabricated via
dry miⅡing, especia11y for the composites with a lo、ver cHs content (0.5CHS・0.5＼刃SiA and0.7CHS・0.3、NsiA). Thus,、Net mi11ing and liquid・phase shaking methods cooperated 、Nith DMAc e仟ectively
Promoted 小e high chemicalinteraction between cHs and xvsiA, which increased the proton conductivities

Of the obtained inorganic composites. Additiona11y, inorganic solid csHS04・H3P＼入'1?0船 Composites(CHS・、NPA)、Nere also fabricated via medlanodlemical dly mi11ing and 、Net mi川ng, and cHS、＼入IPA

doped・PBl electrolyte membranes 、Nere studied fm' the impl、ovement of acid and water retention properties

イミ

in the medium temperat11re fuel ce11S.
Forthe fabrication ofmixed alkaline・substituted phosphotungstic acid composites, MHS04 (M = K,CS) and phosphot〔mgstic (圦,'PA) solid acids 、¥a'e applied to produce anhydrous proton conductive
Composite materials via mechanical planetary dly balhηⅡling. vel'y fast proton conducting irreversible ne、¥Phase composites were obtained,、Nith 90(50KHS・50CHS)・10＼N'PA (1n01 ツ'0) mixed metalions composite
exhibiting the highest perfonnance 、vith conductivity from 49 × 10、2 t0 1.4 × 10、3 S cm、1 at 160 t040 ゜C,respectively; colnpared to those ofthe preC山'sor matel'ials (CHs and KHS) on the order of lo、3 t010、8 Under

the same temperature regime. The xRD, FT・Raman lH・MAS・NMR and HR・TEM results ofthe composites
revealed the formation of an amorphous nano‑intelface proton・conducting path圦/ay sheⅡ around anM・substituted wpA crysta11ine core, resulting in a nanoionics e仟ect leadino to the hiσh conductivities
Observed; in addition to preferred sites of alkali metal ions substitution into the ＼入,'PA 、Nith di仟er引lt
Stabilities and conductivities W北h respectto type of ion.
Inorganic・organic composite membranes wel'e fabricated using partia11y cesium・substituted

Silicotungstic acid (CHS・圦IsiA) and polybenzimidazole (PBI, MRS0810H) for medium temP引・ature
Polym引' electrolyte fuel ce11S (MT・PEFCS).0.5CHS・0.5＼NsiA composites fabl'icated via dry mi11ing'、刃etmi11ing 、Nere selected to apply inorganic composite aⅡers in the electrolyte membrane preparation. Theaexible and homogeneous composite membl'anes with several phosphoric acid doping levels (PADLS) werePrepared. A high maximum po、刃er density of 378 m圦,1Cm、2 and a good constant current stabiⅡty test (200mAcm、2) with stable voltage of o.61 V 、Nere obtained 介om a single ce11 test using the pBl composite
membrane containing 20 wtツ0 ofcHS・、NsiA from wet mⅡling and phosphoric acid doping level(PADL) ofノ"ぎψ゛气8 m01, at 150 ゜c under an anhydrous condition. wet mi11ing cHS・＼NsiA crystalHtes were 11iσhly dispersed inPBl matrix to give homogenized membranes and played a signi行Cantrole in tlw enhancemance ofacidiw byincreasing the number of proton sites in the electrolyte membl'ane. A介er adding cHS‑＼¥siA into pBI
membrane, the acid and 、Nater retention 御'opeHies 、vere significantily improved and incorporated as ne圦ノProton conduction path by adsorbing phosphoric acid in these composite electrolyte membranes. TheseObservations suggested that composite membranes with 8 m01 0f pADL are good pl'omising pA
doped・membranes 、 ith e仟ective electrochemical propedies fⅨ'the medium temP引'ature fuel ce11S.
In addition, metal oxide pa11icles (Ti02) possessing high a価nity for phosph01'ic acid are added tothe electrolyte membrane so that the pBl composite electrolyte mem愉'ane could retain phosphoric acidretention for a longer period measur引nent. The proton conductivity ofthe electrolyte m引ηbranes by theseadded padicles and the influence on the fuel ce11 P0圦ler generation characteristics in the 111edium
temperature range were investigated. chemicaⅡy stable Tio? nano・PO、¥ders 、vere added to the pBI

electrolyte membrane at various concentrations (2,10,20 wt%) to in引'ease 廿le l'etention of phosphoric acidand 、¥ater. The TioypBl electrolyte melnbrane was adlieved outP11t chal'acteristics mm'e than twice that ofthe pure pBl electrolyte membrane.1t 、Nas obsel'ved that the addition of Ti02 improved ule phosphate
holding power of d)e electroly[e membrane. TioypBl membrane retained high conductivity values at thehigher telnP引'atures as a result of itS 11igh doping level and l)igh 、Nater retention capacity. Ti02(2 、¥t%ypBI

Composite membrane showed the best perfonna11Ce 、vith a po、ver density of 434 m＼Ncm、?. These results
Suggestthat TioypBI・based composite membl'anes al'e promising electrolytes for MT‑PEFCS.