Electrode has silicone rubber diffusion barrier with fixed permeation constant for hydrogen. Barrier controls flow of hydrogen to anode and Faraday relationship establishes upper limit for current through cell. Electrode fabrication is described

Niedrach, L. W.

Rudek, F. P.

Rutkoneski, M. D.

English

NASA Technical Reports Server

H2 
Diffusion  
Barrier
Ion Exchange 
Membranes with 
Platinum Black 
Electrodes
02 
4
0 
LU 
cli
Ion Exchange Membrane 
Oxygen Electrode 
H2SO4 
ctrode/Electrol yte 
interface 
Diffusion Barrier v 
Vapor Deposited F 
Electrode 
April 1971	 Brief 71-10071 
•
NASA TECH BRIEF
 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology. Utilization Office, NASA, Code KT, Washington, D. F. 20546. 
Submersed Sensing Electrode Used in Fuel-Cell Type Hydrogen Detector 
The problem: 
In the past, hydrogen sensor performance in fuel 
cell operation has been seriously affected by oxygen-
laden diluent gases. A silver-palladium controlled hy-
Ion Exchange Membrane 
Configuration
Faraday relationship establishes the upper limit for 
current through the cell. In this case, a diffusion 
barrier passes a fixed amount of hydrogen for 
a given partial pressure differential. With the by-
Submersed Electrode 
Configuration 
drogen leak, for example, while having a higher	 drogen partial pressure between the barrier and 
permeation area than a small foil assembly, failed 	 anode essentially zero, the current becomes a linear 
to provide the anticipated cell output. 	 function of the hydrogen partial pressure. 
The solution:	 How it's done: 
A submersed sensing electrode used as the hydro-	 The figure presents a schematic comparison of the 
gen detector operates as a current-limited device	 ion exchange membrane (IEM) and the submersed 
with current positively controlled by a diffusion bar-	 hydrogen electrode configurations. The IEM config-
rier, such as silicone rubber; the barrier has a fixed 	 uration has a catalyst, with a finite thickness, that 
permeation constant for hydrogen. By positively 	 can act as a sink for both hydrogen and oxygen 
limiting the flow of hydrogen to the anode, the 	 atoms. In addition, the resultant pressure drop 
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19710000070 2020-03-17T02:22:37+00:00Z
across the catalyst, a drop which the hydrogen must 
overcome to reach the electrolyte interface, seriously 
retards sensor operation. 
The submersed electrode is fabricated by directly 
depositing platinum catalyst such as polyphenylene 
oxide on the diffusion barrier. The assembly is then 
used to contain the sulphuric acid electrolyte, with 
the catalyst surface facing into the acid. This con-
figuration results in the following: (a) The free 
volume between the diffusion barrier and the anode 
is eliminated, thereby decreasing sensor response 
time. (b) The 'pressure drop that the hydrogen 
atom must overcome between the point of adsorp-
tion and the electrode/electrolyte interface is ex-
tremely small. (c) The sink of catalyst to adsorb 
and store oxygen is virtually eliminated. (d) The 
configuration becomes a close approximation to the 
infinitely thin catalyst.
Note: 
Requests for further information may be directed 
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: TSP71-10071 
Patent status: 
No patent action is contemplated by NASA. 
Source: Michael D. Rutkoneski, Fred P. Rudek,

and Leonard W. Niedrach of

General Electric Company

under contract to

Marshall Space Flight Center

(MFS- 14655) 
Brief 71-10071	 Category 01


Submersed sensing electrode used in fuel-cell type hydrogen detector

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