Reaction Activator
Precious metal deposits on sensor surfaces lower the activation energy required for the chemical oxidation of combustible gases. A platinum catalyst is widely applied in catalytic bead and electrochemical sensors to accelerate reaction rates at lower temperatures. This chemical activation enables the sensor to detect lower gas concentrations with high repeatablity.
Catalytic Process
The sensor element consists of a fine coil of platinum wire embedded in a ceramic bead, which is coated with the active metal. When heated, the platinum catalyst promotes the combustion of flammable gases like hydrogen or methane on the bead surface, which increases the bead temperature. This temperature rise is directly proportional to the gas concentration, which is measured by tracking the change in electrical resistance of the underlying wire.
Poisoning Sensitivity
Exposure to specific chemicals can permanently degrade the performance of the catalytic surface. Lead compounds, silicones and sulfur-bearing gases bind to the active platinum sites, preventing further combustion reactions. This poisoning causes a drop in sensor sensitivity and requires routine calibration checks with test gases to ensure that the sensor remains functional.
Response Optimization
Optimization of the catalytic surface structure involves varying the distribution and size of the metal particles. By controlling these parameters during manufacturing, the sensor can be tuned to be more selective to specific gases.
