Preventing pressure buildup in electrochemical cells by reacting palladium oxide with evolved hydroge

Donnelly, P. C.

Hennigan, T. J.

Palandati, C. F., Jr.

English

NASA Technical Reports Server

Nov. 22, 1966 T. J. HENNIGAN ETAL 3,287,174 
PREVENTION OF PRESSURE BUILD-UP IN EIECTROCHFPdXCkI~ CCLLS 
Fi led  Nov. 12, 1963 
1hfL'ENTORS. 
THOMAS J HENNlGAN CHATL F C PALANDATI, DONNELLY JR 
@L 
https://ntrs.nasa.gov/search.jsp?R=19700032548 2020-03-17T02:11:20+00:00Z
1 2 
3,287,174 FIGURE 1, housed within a closed chamber 15, e1e.ct-w- 
PREVENTION OF PRESSURE BUILD-UP IN chemical cell 11 having housing 12, terminals 13 and 
ELECTROCHEMICAL CELLS vent 14. A cap 16 fits about vent 14, and a coated 
Thomas J. Hennigan, Chillum Terrace, Paul C. Donnelly, member 10 is positioned within closed chamber 15. Both 
Greenbelt, and Charles F. Palandati, Jr., Hyattsville, 5 cap 16 and coated member 10 will be explained in detail 
Md., assignors to the United States of America as hereinafter. 
represented by the Administrator of the National Cap 16, s h m n  in more detail in FIGURE 2, is a closed 
Aeronautics and Space Administration 
Filed Nov. 12,1963, Ser. No. 323,182 container of plastic material o r  the like comprising a top 
2 Claims. (el. 136-179) member 17 havig a plurality of small holes 18 therein; 
10 a base member 19 including an enlarged walled aper- 
~h~ invention described herein may be manufactured ture 20 having an inner surface 21 thereof surrounding 
and by or for the Government of the United States and making a friction tight fit with outer surface 22 of 
of Amerioa for governmental purposes without the pay- vent 14; and an up-right wall 23 formed integral with and 
ment of any royalties thereon or therefor. connecting itop member 17 to base member 89. Holes IS 
The present invention relates to means for reducing 15 are provided to permit unreactive gases to escape from 
pressure build-up resulting from hydrogen gas being 12- 
evolved from electrochemical cells, and more particularly Contained within cap 16 is powdered palladium ox- 
to means for chemically reacting with the hydrogen gas ide 24 and a Porous disc 25 of filter paper or the like, 
evolving from electrochemical cells to prevent pressure the disc resting On a 26 by the 
build-up therefrom. 20 aperture 20 and behaving 'as a closure to prevenit the 
Secondary electrochemical cells such as lead-lead oxide, powdered palladium oxide 24 from falling into vent 14 
nickel oxide-cadmium, nickel oxide-iron, silver oxide-lead, while at the same time, because of being porous, per- 
silver oxide-zinc, silver oxide-cadmium and the like evolve m'itting the hydrogen gas evolved from the cell to pass 
hydrogen gas during storage, discharge or charge thereof. therethrough and react with the ~alladium oxide. ~ h o u l -  
Now, if such cells are confined in a closed space, the evolu- 25 der 26 the aperture 20 is bent 
tion of the hydrogen gas will effect a pressure rise than from the wall itself, thereby reducing the dimension of 
can destroy the housing or vessel enclosing the cells, as the ape*ure at the point where i't is by 
well as, damage surrounding equipment and be hazardous shoulder 26. 
to personnel. In addition, if oxygen or other oxidizing 30 When hydrogen gas is evolved by an electrochemical 
agents are within the closed space, there is always the cd l  11 duping the storage, oharge or discharge thereof as 
added hazard of there being a possibility of an explodon. a result of electrode reactions with the eleotrolyte, it 
ne art methods of reducing ,ae hazards caused passes through vent 14 via aperture 20 and porous disc 
by hydrogen gas being evolved from electrochemicaI cells 25 into the region of cap 16 containing the palladium 
include the use of activated charcoal to absorb the hydro- oxide 24. The hydrogen gas in diffusing through and 
gen gas and the reaction of oxygen with the hydrogen gas 35 flowing adjacent to the palladium oxide reaots therewith 
in the presence of a palladium catalyst to form water. 
Activated charcoal is not effectivc where space and weight PdO-kH2+Pd+H20 
xequirements must be taken into accsount because of the or 
large quantity of charcoal required to absorb the evolved 40 
hydrogen gases; and the reaction of oxygen with the PdOz+2Hz+Pd+2H20 
hydrogen gas in the presence of palladium catalyst has to form water and paladium depending on whether PdO 
proven to be unreliable because of the poisoning of the (palladium monoxide) or pdQ2 (palladium dioxide) is 
palladium by 'the reaction. the reactant. It should also be noted that a mixture of 
The use of palladium oxide in the manner that be 45 these reactants will work equally as well to react with 
described hereinafter has the advantage of preventing the hydrogen, thereby the pressure build-up pressure build-up and eliminating the explosion hazard in closed chamber 15. 
caused by the evolution of hydrogen gas from electro- The formation of palladium (Pd) acts to further reduce 
chemical cells. In addition, only a  mall quantity of the hydrogen pressure where oxygen is present as it will palladium oxide is required to reaat with a large volume 50 act as a catalyst and cause following reaction: 
of hydrogen gas; and the paladium oxide is not poisoned 
by the reaction. r d  2112 + Oa -----r 2TT20 The above advantages are attained by powdered pal- 
ladium oxide (PdO) being confined in the same closed However, as already explained in connection with the 
space wherein the electrochemical cells are located or 55 descniption of the prior art, presented above, the efficiency 
in contact with the cells themselves and reaching with of this reaction is limited due to the poisoning of  the 
the volved hydrogen (HZ) to form water (HzO) and palladium. 
palladium (Pd). Coated member 10, forming embodiment of the in- 
The exact nature of this invention, as well as other vention, is shown in FIGURE 3, ns comprises a base 27 
objects and advantages thereof, will be readily apparent having palladium oxide 24 in contact therewith. More 
from considera~tion of the following specification relating particularly, base member 27 can bc cho5en to be a 
to the annexed drawing in which: plastic sheet such as cellulose acetate having a thin film 
FIGURE 1 is a front view of an electrochemical cell of powdered palladium oxide encapsulated thereon; o r  a 
housed within a confined space wherein a cap is affixed palladium plated sheet of metal such a5 copper, stainless 
to the cell to form one embodiment of the invention and G5 steel or the like upon which (the oxide has been formed. 
s coated member is positioned in the confined space to Again, as described above in connection with cap ern- 
form another embodliment of the invention; bodiment of the invention, the hydrogen gas evolved by 
FIGURE 2 is a cross-sectional view of the cap of electrochemical cell 11 passes from vent 14 and reacts 
FIGURE 1 taken along line 2-2 thereof; and with palladium oxide 24 on base 27 to prevent the pressure 
FIGURE 3 is a more detailed showing of the coated 70 build-up within electrochemical cell 11 and closed 
member of FIGURE 1. &amber 15. 
Referring now to the drawing, there is shown in The foregoing disclosure relates to preferred embodi- 
3,287,174 
3 4 
ments of the invention. Numerous modificaitions or ical reaction, the improvement comprising: a palladium 
alterations may be made therein without departing from plated sheet of metal having palladium oxide formed 
the spirit and scope of the invention set forth in the ap- thereon; said palladium plated sheet with the palladium 
pended claims. oxide being positioned in said closed chamber, whereby 
What is claimed is: 5 said hydrogen gas reacts with said palladium oxide in the 
I .  In a closed chamber housing an electrochemical cell following manner: 
which oroduces a pressure build-ur, in said chamber from PdO+H3+Pd+H20 
- . - 
hydro.!& g a  evofved as a by product of its electrochem- thereby any accumulation of hydrogen gas ical retaction, the improvement c0mIXising: a plastic and preventing any pressure build-up due to hydrogen holder; powdered palladium oxide coated on said holder; 10 accumulation. 
said plastic holder with said palladium oxide coated 
thereon positioned in said closed chamber, whereby said References Cited by the Examiner 
hydrogen gas reacts with said palladium in the following 
manner: UNITED STATES PATENTS 
PdO+&-+Pd+H20 1.7 2,615,062 10/1952 Craig ------------ 136-179.1 
thereby eliminating any accumulation of hydrogen gas 2,687,449 8/1954 Galick et al. -------- 136-179.1 
and preventing any pressure build-up due to hydrogen W I N ~ T ~ N  A. DOUGLAS, P , . ~ ~ ~ , . , ,  ~~~~i~~~ 
zccumulation. 
2. In a closed chamber housing an electrochemical cell ALLEN B. CURTIS, Examiner. 
which produces a pressure build-up in said chamber from 20 D, L. WALTON, ~ ~ ~ j ~ l ~ ~ l  Examiner. 
hydrogen gas evolved as a by product of ilts e,lectrochem- 


Prevention of pressure build-up in electrochemical cells Patent

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