Oxygen Diffusion and Electrochemical Reaction: Working Principle of Oxygen Sensor

Oxygen diffusion is the first step in the operation of oxygen sensors. In the sensor structure, air windows and air chambers play a vital role. As the portal for oxygen to enter the sensor, the design and material selection of the air window are directly related to the efficiency of oxygen diffusion and the sensitivity of the sensor. When the sensor is placed in an environment containing oxygen, oxygen molecules enter the air chamber through the air window. This process seems simple, but it actually involves complex physical and chemical mechanisms. Under the action of the concentration gradient, oxygen molecules gradually penetrate into the air chamber through mutual collision and diffusion between molecules.

The design of the air chamber is also crucial. It not only ensures that oxygen can enter smoothly, but also ensures that oxygen can fully contact the chemicals inside the sensor. To achieve this goal, the air chamber is usually designed to have a large surface area and good gas permeability. In this way, when oxygen enters the air chamber, it can quickly react with the chemicals in the sensor to prepare for the subsequent electrochemical reaction.

The electrochemical reaction is the second and most critical step in the operation of the oxygen sensor. In the core part of the oxygen sensor, the ceramic tube plays a pivotal role. The inside and outside of the ceramic tube are coated with platinum electrodes, which are the main places where electrochemical reactions occur. When oxygen enters the gas chamber through diffusion and contacts the platinum electrode, the oxygen molecules combine with electrons under the catalytic action of the platinum electrode to form oxygen ions.

This reaction process seems simple, but it actually involves complex electron transfer and the formation of chemical bonds. Under the catalytic action of the platinum electrode, the electron cloud of the oxygen molecule is reorganized to form negatively charged oxygen ions. These oxygen ions migrate through the oxygen ion vacancies in the ceramic tube under the action of the electric field. The ceramic tube acts as an electrolyte, and the oxygen ion vacancies inside it provide a channel for the migration of oxygen ions. During the migration process, these oxygen ions combine with electrons on the platinum electrode on the other side of the ceramic tube to form oxygen molecules and release energy.

Due to the migration of oxygen ions in the ceramic tube, a potential difference is generated on both sides of the ceramic tube. This potential difference is closely related to the oxygen concentration and is a key parameter for oxygen sensors to measure oxygen concentration. When the oxygen concentration changes, the oxygen diffusion rate and the electrochemical reaction rate will change accordingly, resulting in a change in the potential difference. By measuring this potential difference, the oxygen concentration can be accurately calculated.

The design and manufacture of oxygen sensors is a highly complex process involving knowledge from multiple disciplines such as materials science, electrochemistry, and physics. In order to ensure the accuracy and stability of the sensor, manufacturers need to carefully design and rigorously test every detail of the sensor. From the structural design of the air window and air chamber to the material selection of the ceramic tube and platinum electrode, to the calibration and testing of the sensor, every link is crucial.

Oxygen diffusion and electrochemical reaction, as the core working principles of oxygen sensors, jointly determine the performance and accuracy of the sensor. In modern science and technology and industry, oxygen sensors play an increasingly important role. With the continuous advancement of science and technology and the continuous expansion of application fields, the performance of oxygen sensors will continue to improve, bringing more convenience and benefits to people's production and life.