Thin-film Au electrodes prepared by magnetron sputtering method were used to develop a potentiometric CO₂ gas sensor. The thermal evaporated Li₃PO₄ played the role of electrolyte and sensing material. This design can simplify the fabrication process compared with the conventional solid electrolyte potentiometric CO₂ sensor (c-sensor) and improve the performance compared with the thick-film Au electrodes sensor (t-sensor). The designed CO₂ sensor (d-sensor) presented good response characteristics at the CO₂ concentration range of 250–2500 ppm and the electromotive force (EMF), ΔEMF/dec, response and recovery time were investigated. The EMF values of the sensor were linearly dependent on logarithm of CO₂ partial pressure at the working temperatures between 420°C and 500°C. The d-sensor showed a sensitivity of 79.1–93.7 mV/dec at working temperatures range of 420–500°C which was much higher than the sensitivities of c-sensor and the t-sensor. The response and recovery time of the fabricated sensors were 10 and 14 s at working temperature of 500°C, respectively. The surface morphology of Au thin films was considered to increase the three-phase interface area and be good for the reaction gases to diffuse from Au film to lithium phosphate, allowing rapid chemical reaction equilibrium, getting a more stable EMF output.

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Au thin-film electrodes based potentiometric CO₂ sensor using Li₃PO₄ as both the reference material and the solid electrolyte

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Au thin-film electrodes based potentiometric CO2 sensor using Li3PO4 as both the reference material and the solid electrolyte

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Au thin-film electrodes based potentiometric CO₂ sensor using Li₃PO₄ as both the reference material and the solid electrolyte