Catalytic Micro Gas Sensor with Excellent Homogeneous Temperature Distribution and Low Power Consumption for Long-Term Stable Operation

Abstract

This paper presents a long-term stable thermoelectric micro gas sensor with ligand linked Pt nanoparticles as catalyst. The sensor design gives an excellent homogeneous temperature distribution over the catalytic layer, an important factor for long-term stability. The sensor consumes very low power, 18 mW at 100 °C heater temperature. Another thermoresistive sensor is also fabricated with same material for comparative analysis. The thermoelectric sensor gives better temperature homogeneity and consumes 23% less power than thermoresistive sensor for same average temperature on the membrane. The sensor shows linear characteristics with temperature change and has significantly high Seebeck coefficient of 6.5 mV/K. The output of the sensor remains completely constant under 15,000 ppm continuous H2 gas flow for 24 h. No degradation of sensor signal for 24 h indicates no deactivation of catalytic layer over the time. The sensor is tested with 3 different amount of catalyst at 2 different operating temperatures under 6000 ppm and 15,000 ppm continuous H2 gas flow for 4 h. Sensor output is completely stable for 3 different amount of catalyst.

Ligand-Linked Nanoparticles-Based Hydrogen Gas Sensor with Excellent Homogeneous Temperature Field and a Comparative Stability Evaluation of Different Ligand-Linked Catalysts

“…A comparative performance analysis between the thermoelectric sensor and a thermoresistive sensor fabricated with the same material as mentioned in the Section 2 (materials and methods) was performed in terms of power consumption, heater temperature and the average membrane temperature. Figure 8 a,b shows the temperature field on the membrane of the thermoelectric sensor and thermoresistive sensor respectively for a maximum temperature of 90 °C (colour legend same for both Figure 8 a,b) [ 38 ]. It is evident from Figure 8 a,b that the temperature distribution over the membrane of the thermoelectric sensor is more homogeneous than the thermoresistive sensor.…”

“…Although the highly heat conductive thermopile causes high power loss, it helps to increase the homogeneity of the temperature distribution when the thermocouples are placed evenly encircling the round membrane. If we consider a specific heater temperature, e.g., 90 °C, the thermoelectric sensor consumes 14 mW and the thermoresistive sensor consumes 12.6 mW power [ 38 ]. Therefore, the power consumption of the thermoresistive sensor is only 1.6 mW lower than the thermoelectric sensor for a specific heater temperature of 90 °C.…”

“…Interestingly, the thermoelectric sensor consumes even lower power than the thermoresistive sensor for an average temperature on the membrane as the thermopile provides more homogeneous temperature distribution. The thermoelectric sensor consumes 23% (13.3 mW) less power than the thermoresistive sensor for maintaining an average temperature of 90 °C on the membrane [ 38 ]. What is interesting here is that despite the fact of highly heat conductive thermopile; the thermoelectric sensor performs better than the thermoresistive sensor regarding an average temperature over the membrane.…”

“… Temperature field on the membrane with IR camera measurement ( a ) thermoelectric sensor; ( b ) thermoresistive sensor, ( a ) is more homogeneous than ( b ); ( c ) comparative power consumption of the thermoelectric and the thermoresistive sensor [ 38 ]. …”

Resistive gas sensors based on metal-oxide nanowires

“…36 Gas sensors are a subcategory of chemical sensors and based on the International Union of Pure and Applied Chemistry (IUPAC), a general definition for a chemical sensor 37 is "a device that transforms chemical information, ranging from concentrations of a specific sample component to total composition analysis, into an analytically useful signal". Different gas sensors have been developed for the sensing of various toxic gases, such as SAW gas sensors, 38 electrochemical gas sensors, 39,40 optical gas sensors, 41,42 gasochromic gas sensors, 43,44 quartz crystal microbalance gas sensors, 45 catalytic gas sensors, 46,47 thermal conductivity gas sensors, 48,49 cataluminescence sensors, 45,50 and resistive-based gas sensors. 51,52 In this review paper, the different aspects of resistive-based metal oxide nanowire (NW) gas sensors which work based on the resistance changes in the presence of the target gases will be presented.…”