SOLIDIONIC

Fig.1.

Fig.1 Different types of the presentation the same data from [3] on the conductivity of Cs2(HSO4)(H2PO4) vs temperature: Vogel-Tamman- Fulcher (black dot curve) and traditional approach for physics of unordered system (red line).

Fig.2

Fig.2 Special presentation the data on the conductivity of crystalline hydrates of potassium hydroxide in the form  as well monohydrate as dihydrate of deuterated compounds. Isotopic effect is not discussed here. In insert: the more frequently  used presentation are shown in the framework of this thesises. Ln-ln mastab allows to indicate the power law parameter.

Fig. 3

Fig.4

Fig.3 (left) and Fig.4 (right) show different forms of the presentation of the conductivity in solid individual hydroxides (NaOH left, KOH right) at temperature below approximately 500 K, i.d. phase transformations into superionic states. [8,11]. For both materials there are remarkable deviation from simple Arrenius’s form and possible using presentation based on physical theories on disoredered materials. For NaOH there is couple of interesting phenomena: 1)evident difference Arrenius’s law (insert) and power law and 2) different temperature run of conductivity (red circles) and self – diffusion of proton measured by isotopic method (blue points). The same difference take place for KOH, (but not shown here). For KOH is most interesting the strong peaks at 360 K [11] accompanied by slow relaxation of another physic-chemical properties.

Download full article here:
Nonarrenius behavior of certain hydrates of potassium hydroxide, individual alkali

Thesis for intensive discussion  from  Yurii  Baikov

^{Ioffe  Institute, St-Petersbutg, Russia}

Historical View. The question on the charge and mass transfer in hydrogen-containing materials has started to discuss more than 200 years ago  [1]. The seeming clear understanding relatively liquid phases has been formed to the middle of XIX century. However, the “barrier” to understand the ionic mobility in strongly organized crystalline lattice has been overcome. Crucial conception on the role of defects for physicochemical properties was advanced by Ya.I.Frenkel  90 years ago in Ioffe Institute  [2]. Additional efforts were performed by Bernal & Fowler [3]and  Bjerrum [4] to form the model of hydrogen ion migration. Next steps of  the development of the interest to proton mobility  were both applied aspects (J.Bokris conception of hydrogen energy) and basic research taking into account too small size and mass of proton. For example, it may be indicate the attempt to find the proton tunneling in solids. In 1979 years was predicted the protonic Hall effect by theoretician from Ioffe Institute [5]. As the result  of such brain attack the three families of inorganic proton conductors  has been discovered factually simultaneously in 1980  -1982. (Fig.1)

Fig. 1

Omitting  the detail description of applied history of these families let us take into account some subtle features of hydrogen state (i.e. protons). To model the hydrogen behavior it is necessary to take into account that hydrogen is the “quest” in perovskites and on the contrary “host” in hydroxides and acidic salts. Of course the definition “host” for proton in CsHSO₄ or in KOH means “the part of anion of “host”.

Proton behavior and stable content of hydrogen corresponds to experimental facts. Although there is different behavior relating to decomposition at heating to melt. However at first step this fact will be omitted.

The main aim of our model to evaluate the possibility to describe acidic salts and hydroxides as the composition of THREE particles,  namely 

CATIONS, 

TETRAHEDRONIC anions without protons,  

PROTONS.

The basic relations and equations of such model keeping in mind CsHSO₄. 

Anions + protons will be indicate for briefity as  HT, where Т = SO₄.  For more detailed description let us introduce three states: normal and pair of defects:

normal state             (H₁A ₂T)^-1(x)(α₁);

double proton state  (H₂A₁T)^0(•) (α₂) ;

protonless state     (A₃T)^{+1( ∕ )} (α₀).

Here:  A_i – “empty” or protonless positions on thtree vertexes of tetrahedron Charge states are indicated  by two versions: usual and  Kreger-Vink (late in margins). On the main line in marginas – atomic part of corresponding elements.

Naturally Σα_i =1, and according to electro-neutrality rules  α₂ = α₀.

The part of free energy due to protonic subsystem  F for one mole of material include chemical potentials of proton-containing components  (μ_i ) and their pair interactions with energies ε_ik :
F=Σα_i μ_i +Σε_ik α_i α_k ……………..(1).

Standard chemical potential of komponents will be parameters (μ_i⁰=Const ) (

In formulas (1) indexes i и k  are 0; 1; 2.

At considering the most important is the conditions of thermodynamic equilibrium ∂F/∂α_i=0. To get it as the controlling parameter will be chose α₂, i.d. the part of tetrahedrons with two protons. Such defects could be determined the protonic transport, allowing the idea of Frenkel [2] and Bjerrum[4]. For simplicity let us use  α  without index, i.d. α₁=(1-2α), α₂ = α₀ = α.

F = {μ₁⁰ + αƒ₁(μ_i ,ε_i)  + ½α²ƒ₂(ε_i)} + k_BT {(1-2α) ln(1-2α)+2α lnα}…….(2)

In (2) there are two parts: energetic one (first brace) and entropy second.

Let us also for convenience introduce the dimensionless energetic parameters   F, μ₁⁰,ƒ₁(μ_i ε_i) и ƒ₂(ε_i) dividing both part of (2) by k_BT,  k_B –Boltzman, but by default  keeping “previous” symbols. It is note that ƒ₁(μ_i ε_i) contain standard chemical potentials and energy of interaction, but ƒ₂(ε_i) only later. The question on sings                 ƒ₁(μ_i ε_i) and ƒ₂(ε_i) required special consideration. For example ƒ₂ = ε_2,0 – 2(ε_2,1 +ε_1,0). If ε_2,0<0 (attraction) and  ε_2,1>0 (repulson), then signƒ₂ , and  ƒ₁  are under?

Fig. 2

How to get the link between phenomenological approach  and the most  important characteristic of protonic conductors? 

Now we are only on first step and try to find the most remarkable “event” PHASE TRANSITION. Our model based on the many review like [6]. After mathematic analysis in agreement with physical sense has been found:                                   ƒ₁(μ_i ε_i) ≈ +8 ±1 and ƒ₂(ε_i)≈ -12±1. It means for 300 – 400 K  +0.25  and  –0.35 эV. It was  revealed that maximum of disorder correspond α=1/3 (ΔS=ln3), stable state at α=0 (α₁=1, ΔS=0 ) is the normal anions  HSO₄^-1  (H₁A ₂T)^-1(x), but there is the third state with α=1/2 (ΔS=ln2), which could be considered as predecessor of dehydration  (H₂SO₄ ⁰ + SO₄^-2).

These features are reflected on Fig.2. Free energy of protonic system (black line) first derivative(red) to reflect phase transformation. And second derivative to reflect stability of different phase (blue)  limiting  0.9<α₁≤1 и      0.4≤α ₂ ≤0.5. On the figures this boundaries could be seen as crossing blue line (second derivative) and grey line as Zeroth line for all curves.

Proton contribution in different part of free energy of model CsHSO₄.

References

1. de Grotthuss C.J.T. // Ann. Chim. (Paris). 1806. T. LVIII. P. 54–74.

2.  Frenkel Ya.I/.// Z.Phys. 1926. V. 35.  S. 652.

3. Bernal J. D. and Fowler R. H. //J. Chem. Phys. 1933  V.1. P.515.

4. Bjerrum N.K. //Dan.Videwisk S.M.F.Medd. 1951,  V.276, N.1. P. 3-56

5. Азизян А.О., Клингер М.И.// Теор. и Мат.Физика.1980  Т.43, N 1. С.78-90

6. Baranov A.I.// Rus Crystallographie. 2003. Т.41. N6 .  С.1081-1107.

Phenomenological model of popular solid protonic cunductors
CsHSO₄
as SOLID Solution of three components
Cations
Tetrahesdrons
PROTONS

Dear Colleagues from Solid Ionic Community!
This is the Photo of some piecies of Single Crystals
obtained by Skull technique in Ioffe Institute.
Here the single crystalls samples of Gadolinium doped Cerias
are presented for 10%. However there are another compositions.
Not  only  GDC,  but   another  oxides. We are ready to discuss if you
are able to buy such materials.
(click to view large images)

Single Crystals obtained by Skull technique pic. 1

Single Crystals obtained by Skull technique pic. 2

The piece of usual lemon is new electrolyte for discovered by us new pair of electrodes for cell
(+)C(graphite|graphene)|protonics|Sn(-)
Very interesting:
Electromotive forces (600 mV at 300 K)
is remarkably closed to one
for the cell (+)C|CsHSO4|Sn(-) at 400K.
Both electrolytes are acidic.

On the base of alkaline hydroxide Posters will be presented at autumn 2016 in Ekaternburg (XI Solid State Chemistry and XX Mengeleev Forum).

The search for and development of electrochemical cells with new electrolytes or new electrode–electrolyte assemblies  is based on fundamental investigations of the electrochemical activity of materials. This poster present a search, the novelty of which is determined by the previously unknown combination of well-known materials as membrane–electrode assembly. These are a solid electrolyte based on potassium hydroxide monohydrate and a negative semiconducting electrode (germanium).  We have prepared  electrochemically  active cells of the formula(–)Ge|KOH⋅nH2O|C(+). Ge-electrode was the thin plate of  p-Ge( 28 Ω.cm).

The solid electrolyte (KOH monohydrate) studied by us  since 2007[1,2].  As the member of  а family of water–potassium hydroxide system it is well and long known in the physical chemistry. Our interest was devoted to KOH ⋅ nH2O solid hydrates with n = 0.5, 1.0,  2.0. Graphite (C) is well known as a multifunctional electrode .   Recently, it has been shown [2] that silicon exhibitsi in heterostructures with solid potassium hydroxide mono- and dihydrate  electrochemical  activity,  the  character  of which depends on the doping level. It was naturally of interest to expand the group of previously studied electrode materials (C, Si, and Sn) in contact with solid hydroxide proton  conductors by including another group-IV element  Ge.  On three figures electrochemical data by different types are shown. Top left are cyclic voltamograms at different ranges of cell voltage and rates.  The middle picture allows to evaluate the exchange currents in a cell. On the bottom figure EIS  are shown at  some overpotential relatively  e.m.f.=0.7 V.
References
[1]Yu.M. Baikov, Solid State Ionic  208 (2012) 17.
[2] http://www.solidionic.com

Скачать или просмотреть можно по ссылке.
UNUSUAL CELL: (-)Ge-KOH.H2O – C(+)

Senior scientist of Ioffe Institute, St-Petersburg, RF baikov.solid@gmail.com http://www.solidionic.com

The pioneering investigation of the electrochemical activity of certain ionic heterostructures with solid electrolyte KOH·2H2O (Tmelt=315 K) is due to basic and applied interest in. The special study of different chemical elements of IV group (C, Si, Sn, Pb) as electrodes of electrochemical cells with hydroxide superprotonic conductor as electrolyte has been performed. EMF (1,2 – 1,3
V) and exchange currents (0,1-1 mA/cm2) of ‘C | KOH·2H2O | TiFe’ and ‘C | KOH·2H2O |
Sn’ have been shown to be adequate to work as low-power sources for electronic devices. They are factually batteries from cheap materials without any catalysts. The scientific justification of the opportunity to use such combinations in electrochemical devices has been based on the study of physical nature of different types of heterojunctions. The isotopic shift of the electromotive forces and isotopic (HD) exchange between TiFeHx – electrodes and KOH·2H2O- electrolytes have been studied specially to prove the formation of protonic heterojunction in the electrochemical cell ‘C | KOH·2H2O | TiFe’. The metal-protonic heterojunction for
‘C | KOH·2H2O | Sn’ characterized by enough high exchange current has been studied firstly.
The semiconductor-protonic heterojunction in the heterostructure ‘C | KOH·2H2O | Si’ could be considered as the opportunity of the harmonical combination of small-sized electronic devices with batteries like studied here.
Key words: low-power battery, protonic conductor, graphite, stannum, silicon
References
1. Yu.M. Baikov, J.Power Sources, 193 (2009) 1Sp 371.
2. Yu.M. Baikov, Solid State Ionics 181 (2010) 545.
3. Yu.M.Baikov, Rus. J. Electrochemistry 48 (2012) 360.
4.. Yu.M. Baikov, Solid State Ionic 208 (2012) 17.

Пдф можно скачать или просмотреть по ссылке
Advanced Solid Electrolytes: Crystalline Hydrates and-or Eutectics of Alkaline Hydroxides