1. TOPOTACTIC SOLID-STATE SYNTHESIS METHODS: HOST-GUEST INCLUSION CHEMISTRY
Ion-exchange, injection, intercalation type synthesis
Ways of modifying existing solid state structures while maintaining the integrity of the overall structure
Precursor structure
Open structure or porous framework
Ready diffusion of guest atoms, ions, organic molecules, polymers, organometallics, coordination compounds, nanoclusters, bio(macro)molecules into and out of the structure of nanoporous crystals

2. TOPOTAXY: HOST-GUEST INCLUSION
1D- Tunnel Structures
2D- Layered Structures
-TiO2
-hWO3
-TiS3
3D-Frameworks
-Graphite
-TiS2
-TiO2(B)
-KxMnO2
-FeOCl
-HxMoO3
-b alumina
-LixCoO2
Pivotal topotactic materials and their properties for functional utility in Li solid state battery electrodes, electrochromic mirrors, windows and displays, fuel and solar cell electrolytes and electrodes, chemical sensors, superconductors, gas storage
-zeolites
-MOFs
-LiMn2O4
-cWO3

3. TOPOTACTIC SOLID-STATE SYNTHESIS METHODS: HOST-GUEST INCLUSION CHEMISTRY
Penetration into interlamellar spaces: 2-D intercalation
Into 1-D channel voids: 1-D injection
Into cavity spaces: 3-D injection
Classic materials for this kind of topotactic chemistry
Zeolites, TiO2, WO3: channels, cavities
Graphite, TiS2, NbSe2, MoO3: interlayer spaces
Beta alumina: interlayer spaces, conduction planes
Polyacetylene, NbSe3: inter chain channel spaces

4. TOPOTACTIC SOLID-STATE SYNTHESIS METHODS: HOST-GUEST INCLUSION CHEMISTRY
Ion exchange, ion-electron injection, atom, molecule, coordination complex, cluster and polymer, intercalation and occlusion, achievable by non-aqueous and aqueous solution phase, gas phase and melt techniques
Chemical and electrochemical synthesis methods
This type of topotactic solid state chemistry creates new materials with novel properties, useful functions and wide ranging applications and myriad technologies

5. GRAPHITE A B out of plane pp orbitals - p/p* delocalized bands
VDW gap 3.35Å
sp2 in plane s bonding
C-C 1.41Å, BO 1.33
ABAB stacked hexagonal graphite
Pristine graphite - filled p band - empty p* band - narrow gap - semimetal

6. GRAPHITE INTERCALATION COMPOUNDS
4x1/4 K = 1
8x1 C = 8
C8K stoichiometry
G (s) + K (melt or vapor) ® C8K (bronze)
C8K (vacuum, heat) ® C24K ® C36K ® C48K ® C60K
Staging, distinct phases, ordered guests, K  G CT
AAAA sheet stacking sequence
K nesting between parallel eclipsed hexagons,
Typical of many graphite H-G inclusion compounds

7. GRAPHITE INTERCALATION ELECTRON DONORS AND ACCEPTORS
SALCAOs of the pp –pp type create the p valence and p* conduction bands of graphite, very small band gap, essentially metallic conductivity, single crystal conductivity in-plane 104 times that of out-of plane - thermal, electrical properties tuned by degree of CB band filling or VB emptying  p p* E
N(E) C
C8Br electron depletion from C2pp VB – metallic oxidative intercalation
C8K electron transfer to C2pp CB – metallic reductive intercalation
E(F) Eg CB VB

8. G (HF/F2/25oC)  C3.3F to C40F (white)
INTERCALATION REACTIONS OF GRAPHITE Always Ask: Oxidative, Reductive or Charge Neutral?
G (HF/F2/25oC)  C3.3F to C40F (white)
intercalation via HF2- not F- - relative size, charge, ion and dipole, polarizability effects - less strongly interacting - more facile diffusion
G (HF/F2/450oC)  CF0.68 to CF (white)
G (H2SO4 conc.)  C24(HSO4).2H2SO4 + H2
G (FeCl3 vapor)  CnFeCl3
G (Br2 vapor)  C8Br

9. PROPERTIES OF INTERCALATED GRAPHITE
Structural planarity of layers often unaffected by intercalation - bending of layers has been observed - intercalation often reversible
Modification of thermal and electrical conductivity behavior by tuning degree of p*-CB filling or p-VB emptying
Anisotropic properties of graphite intercalation systems usually observed
Layer spacing varies with nature of the guest and loading
CF: 6.6 Å, C4F: 5.5 Å, C8F: 5.4 Å

10. BUTTON CELLS LITHIUM-GRAPHITE FLUORIDE BATTERY
SS contact
Li anode
Li+/PEO
CFx/C/PVDF cathode
Al contact e
Li+ F-
LiF
Composite CFx cathode with C black particles to enhance electrical conductivity and poly(vinylidenedifluoride) PVDF binder to provide mechanical stability

11. BUTTON CELLS LITHIUM-GRAPHITE FLUORIDE BATTERY
Cell electrochemistry
xLi + CFx  xLiF + C
xLi  xLi+ + e-
Cx+xF- + xLi+ + xe-  C + xLiF Nominal cell voltage 2.7 V
CFx safe storage of fluorine, intercalation of graphite by fluorine
Millions of batteries sold yearly, first commercial Li battery, Panasonic
Lightweight high energy density battery - cell requires stainless steel electrode/lithium metal anode/Li+-PEO fast ion conductor/CFx intercalate - acetylene black electrical conductor – poly(vinylidenedifluoride) mechanical support cathode/aluminum charge collector electrode

12. C60-G INTERCALATING BUCKBALL INTO GRAPHITE NEW HYDROGEN STORAGE MATERIAL???
Thermally induced 600C intercalation of C60 into G
Hexagonal close packed C60 between graphene sheets
Sieves H2 from larger N2
Physisorbed H2 in intralayer void spaces
Rapid adsorption-desorption
Dead capacity because of volume occupied by C60
Capacity possibly enhanced by reducing filling fraction of C60

14. SURPRISE-SURPRISE NATURE PHYSICS 2005, 1, 39 HIGH TC INTERCALATED SUPERCONDUCTING C6Y AND C6Ca GRAPHITES – VP ITERCALATION OF Yb AND Ca INTO GRAPHITE
XRD shows every layer filled with Yb, stage 1, interlayer spacing 4.57 Å, AA registered graphite layers and a-b offset triangular array Yb layers, superconductivity mechanism under investigation

15. SYNTHESIS OF BORON AND NITROGEN GRAPHITES - INTRALAYER DOPING
New ways of modifying the properties of graphite
Instead of tuning the degree of CB/VB filling with electrons and holes using the traditional intercalation methods focus on intralayer doping
Put B or N into the graphite layers, deficient and rich in carriers, enables intralayer doping with holes (VB) and electrons (CB) respectively
Big question delocalized intraband or localized interband dopant states???)
Also provides access to a new intercalation chemistry

16. SYNTHESIS OF BC3 THEN PROVING IT IS SINGLE PHASE?
Traditional heat and beat
xB + yC (2350oC)  BCx
Maximum 2.35 at% B incorporation in C
Poor quality not well-defined materials
New approach, soft chemistry, lower T, flow reaction, quartz tube
2BCl3 + C6H6 (800oC)  2BC3 (lustrous film on walls) + 6HCl

17. CHEMICAL AND PHYSICAL CHARACTERIZATION OF BC3
BC3 + 15/2F2  BF3 + 3CF4
Fluorine burn technique
BF3 : CF4 = 1 : 3
Shows BC3 composition
No evidence of precursors or intermediates
Electron and Powder X-Ray Diffraction Analysis
Shows graphite like interlayer reflections (00l)

18. CHEMICAL AND PHYSICAL CHARACTERIZATION OF BC3
2BC3 (polycryst) + 3Cl2 (300oC)  6C (amorph) + 2BCl3
C (cryst graphite) + Cl2 (300oC)  C (cryst graphite)
This neat experiment proves B is truly a "chemical" constituent of the graphite sheet and not an amorphous component of a "physical" mixture with graphite
Synthesis, PXRD structural analysis, chemical and physical properties all indicate a graphite like structure for BC3 with an ordered B, C arrangement in the layers

19. STRUCTURE OF BORON GRAPHITE BC3 Rietfeld PXRD Structure Refinement
4Cx1/4 + 2Cx1/2 + 10Cx1 = 12C
6Bx1/2 + 1Bx1 = 4B
Probable layer atomic arrangement with stoichiometry BC3

20. CHEMICAL AND PHYSICAL CHARACTERIZATION OF BC3
BC3 interlayer spacing similar to graphite
Also similar to graphite-like BN made from thermolysis of inorganic benzene - borazine B3N3H6 - thinking outside of the box - F doping by using fluorinated borazine!!!
Four probe basal plane resistivity on BC3 flakes
s(BC3)AB ~ 1.1 s(G)AB, (greater than 2 x 104 ohm-1cm-1)
Implies B effect is not the un-filling of VB to give a metal but rather the creation of localized states in electronic band gap making boron graphite behave like a substitution site doped graphite maybe with a larger band gap
Recall heteronuclear BN is a wide band gap insulator!!!

21. BOTTOM LINE - ELECTRONIC BAND DESCRIPTION OF BC3 p p* E
N(E) C
BC3 delocalized states in C2pp VB
E(F) Eg CB VB
BC3 localized states near C2pp VB

22. 4-PROBE CONDUCTIVITY MEASUREMENTS
I = V1/R1
Rsample = V2/I
Rsample = (V2R1)/V1
r = Rsample (A/L)
s = 1/r L A I V2 V1 R1
Constant current source
Ohmeter

23. REPRESENTATIVE BC3 INTERCALATION CHEMISTRY
BC3 + S2O6F2  (BC3)2SO3F Oxidative Intercalation
Note: O2FSO--OSO2F, peroxydisulfuryl fluoride strong oxidizing agent, weak peroxy-linkage easily reductively cleaved to stable fluorosulfonate anion 2SO3F-
(BC3)2SO3F Ic = 8.1 Å, (C7)SO3F Ic = 7.73 Å, (BN)3SO3F Ic = 8.06 Å
BC Ic = 3-4 Å , C Ic = 3.35 Å, BN Ic = 3.33 Å
More Juicy Redox Intercalation Chemistry for BC3
BC3 + Na+Naphthalide-/THF  (BC3)xNa (bronze, first stage, Ic ~ 4.3 Å)
BC3 + Br2(l)  (BC3)15/4Br (deep blue)

24. INTERCALATION SYNTHESIS OF TRANSITION METAL DICHALCOGENIDES
Group IV, V, VI MS2 and MSe2 Compounds
Layered structures
Most studied is TiS2
hcp S2-
Ti4+ in Oh sites
Van der Waals gap

25. INTERCALATION SYNTHESIS OF TRANSITION METAL DICHALCOGENIDES
Li+ intercalated between the layers
Li+ resides in well-defined Td S4 interlayer sites
Electrons injected into Ti4+ t2g CB states or localized state in electronic bandgap
LixTiS2 with tunable band filling and unfilling
Localized xLi(I)xTi(III)(1-x)Ti(IV)S2 mixed valence vs delocalized xLiTi(IV-x)S2 electronic bonding models???
Hopping semiconductor mixed valence description xLi(I)xTi(III)(1-x)Ti(IV)S2
VDW gap prized apart by 10%

26. ELECTRONIC DESCRIPTION OF LixTiS2
S(-II) 3pp VB
t2g Ti(III) localized
t2g Ti(IV) delocalized
N(E) E
DOS electronic band description LixTix(III)Ti(1-x) (IV)S2 mixed valence localized t2g states (hopping semiconductor - Day and Robin Class II) or LixTi (IV-x)S2 delocalized partially filled t2g band (metal - Day and Robin Class III)
Distinguished by s(T) temperature dependent electrical conductivity (semiconductor not metal), optical detection of Ti(III)  Ti(IV) intervalence charge transfer IVCT, and electron paramagnetic resonance EPR detection of unpaired electron on Ti(III)

27. CHEMICAL SYNTHESIS OF LixTiS2
xC4H9Li + TiS2 (hexane, N2/RT)  LixTiS2 + x/2C8H18
Filter, hexane wash
0  x  1
DOS electronic band description LixTix(III)Ti(1-x) (IV)S2 mixed valence localized t2g states (hopping semiconductor - Day and Robin Class II) or LixTi (IV-x)S2 delocalized partially filled t2g band (metal - Day and Robin Class III)
S(-II) 3pp VB
t2g Ti(III) localized
t2g Ti(IV) delocalized
N(E) E

28. SEEING INTERCALATION - DIRECT VISUALIZATION OPTICAL MICROSCOPY
Intercalating lithium - see the layers spread apart

29. ELECTROCHEMICAL SYNTHESIS OF LixTiS2 TiS2 + xLi+ + xe-  LixTiS2 AN ATTRACTIVE ENERGY STORAGE SYSTEM???
2.5V open circuit = (EF(Li)-EF(TiS2) - no current drawn - energy density 4 x Pb/H2SO4 battery of same weight
Li+ e-
Controlled potential coulometry, voltage controlled Li+ intercalation where x is number of equivalents of charge passed
Li metal anode: Li  Li+ +e-
PEO/Li(CF3SO3) polymer-salt solid electrolyte or propylene carbonate/LiClO4 non aqueous electrolyte
PVDF(filler)/C(conductor)/TiS2/Pt(contact) composite cathode – mechanical stability, electronic and ionic conductivity:
TiS2 + xLi+ +xe-  LixTiS2

30. Li/TiS2 AN ATTRACTIVE ENERGY SOURCE BUT MANY TECHNICAL OBSTACLES TO OVERCOME
Technical problems to overcome with both the Li anode, intercalation cathode and polymer-salt electrolyte
Battery cycling causes Li dendritic growth at anode - need other Li-based anode materials, Li-C composites, Li-Sn, Li-Si alloys - also rocking chair LixMO2 configuration
Mechanical deterioration at the cathode due to multiple intercalation-deintercalation lattice volume expansion-contraction cycles
Cause lifetime, corrosion, reactivity, and kaboom safety hazards – challenge for large scale electric car LSSB

31. LiCoO2
LixC6 Li
ROCKING CHAIR LSSB
TO AVOID Li DENDRITES

32. HOW TO SYNTHESIZE A BETTER LSSB
HOW TO SYNTHESIZE A BETTER LSSB? Improved Performance Cathode, Anode and Electrolyte

33. TEMPLATE SYNTHESIS OF NANOSCALE BATTERY CATHODE MATERIALS

34. A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+ DIFFUSIVE INTERCALATION
Template synthesis is a versatile nanomaterial fabrication method used to make monodisperse nanoparticles of a variety of materials including metals, semiconductors, carbons, and polymers.
The template method has been used to prepare nanostructured lithium-ion battery electrodes in which nanofibers or nanotubes of the electrode material protrude from an underlying current-collector surface like the bristles of a brush.
Nanochannel template made of Al2O3, Si, PC
Nanostructured electrodes composed of C, LiMn2O4, V2O5, Sn, TiO2 and TiS2
Prepared by precursor synthesis, chemical vapor deposition, sol-gel or melt infiltration

35. A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+ DIFFUSIVE INTERCALATION
In all cases, the nanostructured electrode showed dramatically improved rate capabilities relative to thin-film control electrodes composed of the same material.
The rate capabilities are improved because the distance that Li must diffuse in the solid state (the current- and power-limiting step in Li-ion battery electrodes) is significantly smaller in the nanostructured electrode.
For example, in a nanofiber-based electrode, the distance that Li must diffuse is restricted to the radius of the fiber, which may be as small as 50 nm.

36. A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+ DIFFUSIVE INTERCALATION
Beating mechanical stability problem of repeated intercalation-deintercalation expansion-contraction cycles
In addition to improved rate capabilities, the nanostructured electrodes do not suffer from poor cyclability observed for conventional electrodes.
This is because the absolute volume changes in the nanofibers are small, and because of the brush-like configuration, there is room to accommodate the volume expansion around each nanofiber.
Improved cycle life results show nanostructured electrode can be driven through 1400 charge/discharge cycles without loss of capacity.

37. nc-TiO2 Nanocrystal-LiX-PEO electrolytes solid plasticisers for LSSB
Ti(IV)-X- surface coordinated anion
Li+ cation
Ti(IV)-O surface coordinated oxygen of PEO polymer chain
PEO polymer chain coordinated to Li+ cation and surface Ti(IV)
Nanocrystal-LiX-PEO electrolytes solid plasticisers for LSSB

38. nc-TiO2
LiClO4-PEO-nc-TiO2
LiClO4-PEO-ncTiO2 -high surface area nanocrystalline ceramic
Brnsted and Lewis acid-base sites - surface Ti(IV) coordination to O(CH2CH2)-
Surface Ti(IV) binding to counteranion X-
Polymer-particle crosslinking - no 60oC glass transition of PEO
ncTiO2 stabilizes glassy polymer state at RT
Domains of local polymer disorder at PEO-ncTiO2 interface
Optimal anchoring promotes local structural and dynamical modifications
High Li+ conductivity at RT
Excellent mechanical stability, improved stress-strain curves
Reduced reactivity with solid ncTiO2 compared to organic liquid plasticizer
Less cooperative PEO segmental motion with enhanced interfacial mobility of Li+
Transport number t(Li+), 0.3 pristine LiClO4-PEO, 0.6 in LiClO4-PEO-nc-TiO2

39. nc-CERAMIC OXIDES: SOLID PLASTICISERS IN POLYMER-ELECTROLYTE LITHIUM BATERIES
LiClO4 : PEO = 1 : 8-10 wt% nc-TiO2 or Al2O3,
anchoring PEO oxygens and counteranions to Brnsted-Lewis acid surface sites,
enhanced corrosion resistance of electrodes,
better mechanical stability PEO,
higher Li+ conductivity & transport number,
local disorder of polymer, loss of Tg, stabilizes RT glassy state,
discards need for PEO-Li+ cooperative segmental motion

40. OTHER INTERCALATION SYNTHESES WITH TiS2
Cu+, Ag+, H+, NH3, RNH2, Cp2Co, chemical, electrochemical
Cobaltacene Cp2Co(II) especially interesting 19e guest
[Cp2Co(III)]x+Tix3+Ti1-x4+S2 chemical-electronic description consistent with structure, hopping SC, optical spectroscopy
Cp2Co almost spherical, temperature dependent 1H and 13C solid state NMR shows Cp ring wizzing (lower T) and molecule tumbling dynamics (higher T) with Cp2Co+ molecular axis orthogonal and parallel to layers, dynamics yields activation energies for the different rotational processes Co
Synthesis, Cp2Co-CH3CN (solution)-TiS2(s)

41. EXPLAINING THE MAXIMUM 3Ti: 1Co STOICHIOMETRY IN (Cp2Co)0.3TiS2
Interleaved Cp2Co(+) cations
Matching trigonal symmetry of hcp chalcogenide sheet
Maximum of third of interlayer space filled
Geometrical and steric requirements of packing transverse oriented metallocene in VDV gap

42. INTERCALATION ZOO Channel, layer and framework materials
1-D chains: TiO2 channels, (TiS3 [Ti(IV)S(2-)S2(2-)], NbSe3 [Nb(IV)Se(2-)Se2(2-)]), contain disulfide and diselenide units in Oh building blocks to form chain
2-D layers: MS2, MSe2, NiPS3 [Ni2(P2S6), ABA CdI2 type packing, alternating layers of octahedral NiS6 and trigonal P2S6 groupings with S…S Van der Waals gap], FeOCl, V2O5.nH2O, MoO3, TiO2 (layered polymorph B – see Chimie Douce later)
3D framework: zeolites, WO3, Mo6S8, Mo6Se8 (Chevrel phases)

43. LixTiO2 – LITHIUM IONS INJECTED INTO CHANNELS AND ELECTRONS INTO CONDUCTION BAND OF RUTILE CRYSTAL STRUCTURE x y z

44. Ti(IV) = S2(2-) = S(2-) = Li(+) =
FACE BRIDGING OCTAHEDRAL TITANIUM TRISULFIDE AND NIOBIUM TRISELENIDE BUILDING BLOCKS FORM 1-D CHAINS
Ti(IV) = S2(2-) = S(2-) = Li(+) =
TiS3 = Ti(IV)S(2-)S2(2-) intercalated cations like Li(+) in channels between chains to form
LixTiS3
1D high-purity TiS3 powder
is synthesized by direct stoichiometric reaction of titanium and sulfur (evacuated quartz-tube, 600 °C, 15 d) and single crystals grown by VPT with Br2 transport agent

45. 3-D OPEN FRAMEWORK TUNGSTEN OXIDE AND TUNGSTEN OXIDE BRONZES MxWO3
c-WO3 = c-ReO3 structure type with injected cation xM(q+) center of cube and charge balancing xqe-
MxWO3 Perovskite structure type M(q+) O CN = 12, O(2-) W CN = 2, W(VI) O CN = 6

46. MxMoO3 Unique 2-D layered structure of MoO3
Chains of corner sharing octahedral building blocks sharing edges with two similar chains,
Creates corrugated MoO3 layers, stacked to create interlayer VDW space,
Three crystallographically distinct oxygen sites, sheet stoichiometry 3x1/3 ( ) +2x1/2 ( )+1 ( )
xM(q+) intercalated between sheets with charge balancing xqe
MxMoO3

47. ELECTROCHEMICAL OR CHEMICAL SYNTHESIS OF MxWO3
xNa+ + xe- + WO3  NaxWx5+W1-x6+O3
xH+ + xe- + WO3  HxWx5+W1-x6+O3
Injection of alkali metal cations generates Perovskite structure types
M+ oxygen coordination number 12, resides at center of cube
H+ protonates oxygen framework, exists as MOH groups

48. SYNTHESIS DETAILS FOR Mx’MO3 WHERE M = Mo, W AND M’ = INJECTED PROTON OR ALKALI OR ALKALINE EARTH CATION
n BuLi/hexane CHEMICAL
LiI/CH3CN
Zn/HCl/aqueous
Na2S2O4 aqueous alkaline sodium dithionite
S2O4(2-) + 4OH(-)  2SO3(2-) + 2H2O + 2e
Pt/H2
Topotactic ion-exchange of Mx’MO3 with M” cation
Li/LiClO4/MO3 ELECTROCHEMICAL
Cathodic reduction in aqueous acid electrolyte
MO3 + H2SO4 (0.1M) Û HxMO3

49. VPT GROWTH OF LARGE SINGLE CRYSTALS OF MOLYBDENUM AND TUNGSTEN TRIOXIDE AND CVD GROWTH OF LARGE AREA THIN FILMS
VPT CRYSTAL GROWTH
MO3 + 2Cl2 (700°C) Û (800°C) MO2Cl2 + Cl2O
CVD THIN FILM GROWTH
M(CO)6 + 9/2O2 (500°C)  MO3 + 6CO2

50. MANY APPLICATIONS OF THIS M’xMO3 CHEMISTRY AND MATERIALS
Electrochemical devices like pH sensors, electrochromic displays, electrochromic energy saving windows, lithium solid state battery cathodes, proton conducting solid electrolytes in H2-O2 fuel cell
Behave as low dopant mixed valance hopping semiconductors
Behave as high dopant metals
Electrical and optical properties best understood by reference to simple DOS picture of
M’xMx5+M1-x6+O3

51. COLORING MOLYBDENUM TRIOXIDE WITH PROTONS, MAKING IT ELECTRONICALLY, IONICALLY CONDUCTIVE AND A SOLID BRNSTED ACID Electronic band structure in HxMoO3 molybdenum oxide bronze, tuning color, electronic conductivity, acidity with x

52. COLOR OF TUNGSTEN BRONZES, MxWO3 INTERVALENCE W(V) TO W(VI) CHARGE TRANSFER
IVCT

53. ELECTRONIC AND COLOR CHANGES BEST UNDERSTOOD BY REFERENCE TO SIMPLE BAND PICTURE OF NaxMox5+Mo1-x6+O3
SEMICONDUCTOR TO METAL TRANSITION ON DOPING MxMoO3
MoO3: Band gap excitation from O2-(2pp) VB to Mo6+ (5d) CB, LMCT in UV region, wide band gap insulator
NaxMox5+Mo1-x6+O3: Low doping level, narrow band gap hopping semiconductor, narrow localized Mo5+ (d1) VB, visible absorption, essentially IVCT Mo5+ to Mo6+ absorption, mixed valence hopping semiconductor
NaxMox5+Mo1-x6+O3: High doping level, partially filled valence band, narrow delocalized Mo5+ (d1) VB, visible absorption, IVCT Mo5+ to Mo6+ and shows metallic reflectivity (optical plasmon) and metallic conductivity

54. HxMoO3 TOPOTACTIC PROTON INSERTION
Range of compositions: 0 < x < 2, MoO3 structure largely unaltered by reaction, four phases
0.23 < x < orthorhombic
0.85 < x < monoclinic
1.55 < x < monoclinic
2.00 = x monoclinic
Similar lattice parameters by XRD, ND of HxMoO3 cf MoO3
MoO3 high resistivity semiconductor
HxMoO3 insertion material SC to M transition
HxMoO3 strong Brnsted acid: Mo-O(H)-Mo solid acid catalysts
HxMoO3 fast proton conductor: Mo-O(H)-Mo-O proton oxygen site to site hopping – useful in solid electrolyte in H2-O2 fuel cells
What happens when single crystal immersed in Zn/HCl/H2O H(+) + e(-)?

55. H2-O2 FUEL CELL WITH PROTON CONDUCTING MEMBRANE
Proton conducting membrane allows only the protons to pass
Proton conducting membrane

56. b-axis adjoining layers react
HxMoO3 TOPOTACTIC PROTON INSERTION
INTRALAYER PROTON DIFFUSION
1-D proton conduction along chains
Yellow transparent
Protons begin in basal plane
Moves from two edges along c-axis
INTERLAYER PROTON DIFFUSION
b-axis adjoining layers react
Orange transparent (semiconducting)
PROTON FILLING
Eventually proton diffusion complete and entire crystal transformed Blue bronze
Consistent with structural, electrical and optical data (metallic)

57. PROTON CONDUCTION PATHWAY IN HxMoO3
c-axis

58. PROTON CONDUCTION PATHWAY IN HxMoO3
Part of a HxMoO3 layer
Showing initial 1-D proton conduction pathway
Apical to triply bridging oxygen proton migration first
1H wide line NMR, PGSE NMR probes of structure and diffusion
Doubly to triply bridging oxygen proton migration pathway
Initial proton mobility along c-axis intralayer direction for x = 0.3
Subsequently along b-axis interlayer direction
Single protonation at x = 0.36, double protonation x = 1.7
More mobile protons higher loading D(300K) ~ vs 10-9 cm2s-1
Proton-proton repulsion

59. ION EXCHANGE SOLID STATE SYNTHESIS
Requirements: anionic open channel, layer or framework structure
Replacement of some or all of charge balancing cations by protons or simple or complex cations
Classic cation exchangers are zeolites, clays, beta-alumina, molybdenum and tungsten oxide bronzes, lithium intercalated metal dichalcogenides

60. (1+x)/2Na2O + 5.5Al2O3  Na1+xAl11O17+x/2
BETA ALUMINA
High T synthesis of beta-alumina:
(1+x)/2Na2O + 5.5Al2O3  Na1+xAl11O17+x/2
Structural reminders (x ~ 0.2):
Na2O: Antifluorite ccp Na+, O2- in Td sites
Al2O3: Corundum hcp O2-, Al3+ in 2/3 Oh sites
Na1+xAl11O17+x/2 defect Spinel, O2- vacancies in conduction plane, controlled by x ~ 0.2, Spinel blocks 9Å thick, bridging oxygen columns, mobile Na+ cations in conduction plane
2-D fast sodium ion conductor

61. Rigid Al-O-Al column spacers
3/4 O(2-) missing in conduction plane
0.9 nm Na1+xAl11O17+x/2 defect spinel blocks
Na(+) conduction plane
Spinel blocks, ccp layers of O(2-)
Every 5th. layer has 3/4 O(2-) vacant, defect spinel
4 ccp layers have 1/2Oh, 1/8Td Al( 3+) cation sites
Blocks cemented by rigid Al-O-Al spacers
Na(+) mobile in 5th open conduction plane
Centrosymmetric layer sequence in Na1+xAl11O17+x/2 (ABCA)B(ACBA)C(ABCA)B(ACBA)

62. GETTING BETWEEN THE SHEETS OF THE BETA ALUMINA FAST SODIUM CATION FAST ION CONDUCTOR: LIVING IN THE FAST LANE
Al-O-Al column spacers in conduction plane
Mobile sodium cations
Oxide wall of conduction plane
0.9 nm Spinel block

65. ION EXCHANGE IN Na1+xAl11O17+x/2
Thermodynamic and kinetic considerations
Mass, size and charge considerations
Lattice energy controls stability of ion-exchanged materials
Cation diffusion, polarizability effects control rate of ion-exchange

66. MELT ION-EXCHANGE OF CRYSTALS
Equilibria between beta-alumina and MNO3 and MCl melts, oC
Extent of exchange depends on time, T, melt composition
Monovalents: Li+, K+, Rb+, Ag+, Cu+, Tl+, NH4+, In+, Ga+, NO+, H3O+
Higher valent cations: Ca2+, Eu3+, Pb2+
Higher T melts required for exchange of higher valency cations, strong cation binding, slower cation diffusion, oC typical

67. MELT ION-EXCHANGE OF CRYSTALS
Charge-balance requirements:
2Na+ for 1Ca2+, 3Na+ for 1La3+
Controlled partial exchange by control of melt composition:
qNaNO3 : (1-q)AgNO3
Na1+x-yAgyAl11O17+x/2

68. KINETICS AND THERMODYNAMICS OF SOLID STATE ION EXCHANGE
Kinetics of Ion-Exchange
Controlled by ionic mobility of the cation
Mass, charge, radius, temperature, solvent, solid state structural properties
Thermodynamics, Extent of Ion-Exchange
Ion-exchange equilibrium for cations
Binding activities between melt and crystal phases
Site preferences
Binding energetics, lattice energies
Charge : radius ratios