NOX DECOMPOSING ELECTRODE AND NOX CONCENTRATION MEASURING APPARATUS

摘要

PROBLEM TO BE SOLVED: To stabilize impedance and NOx sensitivity by suppressing oxidation and re-metallization of Rh contained in a detection electrode. SOLUTION: In a NOx concentration measuring apparatus wherein a main pump cell 34 having an electrode (an inside pump electrode 30 and an outside pump electrode 32) not having the decomposition/reduction capacity to NOx or low in this capacity is used to control the concentration of oxygen in gas to be measured to a predetermined value incapable of substantially decomposing NO and a detection electrode 60 having the decomposition/reduction capacity to NOx or high in this capacity is used to decompose NOx and measures the amount of oxygen at this time to measure the concentration of NOx, as the detection electrode 60, a thermet electrode consisting of a Pt-Rh alloy and a ceramic component is used and a wt. ratio of Pt and Rh is set to Pt:Rh=(20:80)-(1:99).