Placing the working electrode of the oxygen sensor in a reducing atmosphere to produce this non-Nernstian behavior has initiated the measurement research of different gases based on the principle of mixed potential. More than 20 years ago, some people began to study hybrid potential devices for measuring the concentrations of reducing gases such as CO, H2 and CH compounds. Shimizu et al. believed that the abnormal potential observed originated from the differences in catalytic activity among different electrodes. In 1978, they developed the YSZ oxygen sensor with Pt and Pd electrodes for measuring combustible gases. However, its response was not significant above 500 ° C, and it was unstable and had poor selectivity at low temperatures. The reason for this is that the Pt electrode is an excellent oxidation catalyst, enabling the reducing gas to be completely oxidized before reaching the three-phase interface at high temperatures. At low temperatures, the oxidation of gases is mainly limited by the low ionic conductivity of YSZ. To address these issues, other metals and metal alloys have also been employed in the research as alternative materials for improving the selectivity and sensitivity of sensors. V. Schule et al. discovered that the PtAu alloy electrode exhibits better response performance to CO and H2 at temperatures above 550 ° C.

In recent years, the development and research of various electrode materials and electrolytes for hybrid potential sensors have been very active. Many device prototypes have been prepared, but commercial products that can be actually applied have not yet emerged because most devices do not have sufficient long-term stability. The way to further improve these sensors is to replace the precious metal electrodes with metal oxides that have better thermal and chemical stability. This not only enables the sensors to operate at a higher temperature but also expands the types of target gases that can be measured.

The hybrid potential sensor is affected by the electrode material, electrode morphology and the type of solid electrolyte. Many hybrid potential sensors based on Pt, Au electrodes and YSZ electrolyte operate at temperatures above 400℃. However, Au electrodes will rapidly recrystallize and grow at high temperatures, losing their catalytic activity, which makes the sensors lack long-term stability when working at high temperatures. The long-term thermal and chemical stability of electrodes and the large-scale fabrication of repeatable sensor structures are the main obstacles to hybrid potential gas sensors. Replacing metal electrodes with high-temperature resistant and well-active oxide electrode materials offers prospects for improving sensor selectivity and long-term stability.