Abstract: A two-step chemical treatment method for chemically conditioning a sensor element comprising an electrolyte in ionic communication with a first electrode and a second electrode is described. The method comprises treating at least a portion of a sensor element with a first solution comprising an inorganic base, a carbonate salt and an acid salt; heating the sensor element; treating at least a portion of the sensor element with a second solution comprising an inorganic base and a carbonate salt; and drying the sensor element. The gas sensors comprising the two-step treated sensor elements have reduced lean shift, green effect, sensor output amplitude drop, and the light-off time is improved.