This part is a kind of semiconductor called MG811.

Function of this product has CO2 Sensor.

Manufacturers : ETC

Image and pinout :

Some of the text within the PDF file :

MG811 CO2 Sensor Features Good sensitivity and selectivity to CO2 Low humidity and temperature dependency Long stability and reproducibility Application Air Quality Control Ferment Process Control Room Temperature CO2 concentration Detection Structure and Testing Circuit Sensor Structure and Testing Circuit as Figure, It composed by solid electrolyte layer £¨ 1£ © £ ¬ Gold electrodes £¨ 2£ © £ ¬ Platinum Lead £¨ 3£ © £ ¬ Heater £¨ 4£ © £ ¬ Porcelain Tube £¨ 5£ © £ ¬ 100m double-layer steeless net £¨ 6£ © £ ¬ Nickel and copper plated ring £¨ 7£ © £ ¬ Bakelite (8)£¬ Nickel and copper plated pin£¨ 9£ © ¡ £ Figure 1A Figure 1B Working Principle Sensor adopt solid electrolyte cell Princip le£¬ It is composed by the f [ ... ]

MG811 PDF Datasheet Download