Three-electrode hydrogen sensor containing a platinum electrode maintained in a highly catalytic state, operates with a minimal response time and maximal sensitivity to the hydrogen gas being sensed. Electronic control and readout circuitry reactivates the working electrode of the sensor to a state of maximal catalytic activity

Harman, J. N., III

English

NASA Technical Reports Server

March 1968	 Brief 68-10049 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Method of Maintaining Activity of Hydrogen-Sensing Platinum Electrode 
Hydrogen	 Operational 
Sensor	 I	 Amplifier 
I	 Bias  
Operational 
Amplifier
Pulser	 I 
.1. Readout 
The problem: 
To devise an electrochemical hydrogen sensor in 
which the platinum electrode can be maintained in a 
highly catalytic state, and thus ensure that the sensor 
will operate with a minimal response time and maxi-
mal sensitivity to the hydrogen gas being sensed. 
The solution: 
A three-electrode hydrogen sensor, consisting of an 
anodic platinum working electrode, a reference elec-
trode, and an auxiliary electrode, with electronic 
control and readout circuitry to reactivate the working 
electrode to a state of maximal catalytic activity. 
How it's done: 
The platinum working electrode is prepared by 
cathodic electrodeposition of a bright platinum or a 
platinized (platinum black) coating, from a solution 
containing a platinum coordination compound or. 
complex, on an inert metallic substrate. The platinum 
(or platinized) electrode is then subjected to repeated 
anodic-cathodic polarization cycles to effect activa-
tion. After many cycles, a film of highly energetic, 
catalytic sites is formed on the electrode. The activity 
of the electrode prepared in this manner will degrade
in time. By incorporating this working electrode in a 
sensor cell with a reference electrode and an auxiliary 
electrode, the working electrode can be restored to its 
original state of catalytic activity by means of the 
circuit shown in the block diagram. When the working 
electrode deteriorates, this circuit subjects the elec- 
trode to a series of anodic-cathodic polarization 
pulses. During the period of reactivation, the sensor 
will not ordinarily function as a quantitative hydrogen 
sensor. This problem may be circumvented by' incor-
porating a highly damped (long-time constant) read-
out device or by shorting out the readout device dur-
ing the time the polarization pulse is applied. 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: John N. Harman, Ill
of Beckman Instruments, Inc. 
under contract to
Marshall Space Flight Center 
(M FS-1422) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Method of maintaining activity of hydrogen-sensing platinum electrode

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