IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
V.B.2. Development of PEM Based Three Electrode
Amperometric Hydrogen Sensor with Control and
Measurement Electronics
Hydrogen sensors find
application in many areas of
fast reactor technology.
Hydrogen is required to be
monitored in the argon cover
gas of fast reactors and also in
the inert medium during sodium
cleaning and sodium disposal
operations. A fuel cell based
amperometric hydrogen sensor
in three electrode configuration
has been developed and tested
in chronoamperometric mode
for hydrogen monitoring during
the above processes. Three
electrode amperometric
sensors are expected to have
better selectivity, stability and
response behavior compared to
two electrode sensors. A
compact,
portable,
potentiostatic control and
measurement electronics has
Fig.1a Schematic of the hydrogen
sensor
Fig.1b Experimental set-up
been developed for the three
electrode sensor. This compact
electronics realises in-situ
industrial application of three
electrode sensors and replaces
the imported potentiostat which
is general purpose in nature
and is hence bulky and suitable
only for laboratory
applications. This is also an
import substitution step. The
circuit fixes the sensing
electrode potential with respect
to reference electrode. This is
achieved using the feed back
current between the sensing
and reference electrode and by
injecting the required current at
the counter electrode in an
analog loop. The sensor uses
Nafion as proton exchange
membrane (PEM) and platinum
as electrodes. The sensor
functions in fuel cell mode,
H 2 /Pt//Nafion//Pt/O 2 . The
reference electrode is a
platinum wire at the counter
electrode side. The supply of
hydrogen at the sensing
electrode is limited by a
physical barrier incorporated at
the sensing electrode. The
counter electrode is exposed to
air and the sensor functions as
a 'self breathing' device
requiring no air flushing at the
counter electrode. Fig. 1 shows
the schematic of the sensor and
the photograph of the
experimental setup. Fig. 2
shows the response curve and
calibration plot of the sensor.
The above design opens venues
to the development of multi
potentiostat
based
electrochemical sensors with
multi gas measurement
capability.
Fig.2a. The response curve of the
sensor
Fig.2b The calibration plot of
the sensor
ENABLING TECHNOLOGIES 125