HIGH-TEMPERATURE KELVIN PROBE FOR FLOW REACTOR STUDIES

A vibrating capacitor device (Kelvin probe) has been developed for mea surements of work-function changes Delta Phi during ongoing catalytic reactions up to high temperatures (750 K) and atmospheric pressure. Th e construction is based on the piezoelectric actuator principle, and u tilizes a lever arrangement that transfers the vibrating motion of the actuator to the reference electrode. The lever arrangement eliminates a static load on the actuator, which therefore allows a large distanc e between the actuator and the vibrating reference electrode. This mak es possible much higher temperatures in the reaction/sample zone than the piezoelectric actuator itself permits. The large actuator-electrod e distance also reduces the risk of electromagnetic pickup in the Delt a Phi measurements, from the driving circuit for the piezoelectric act uator, The reference electrode is a gold disk with 3 mm diameter and a thickness of 0.1 mm. The practical Delta Phi resolution is presently about 5 meV. The device has been combined with on-line mass spectromet ric detection of reaction rates and its performance is illustrated by results from the H-2/O-2 and CO/O-2 reactions on Pt. (C) 1995 American Institute of Physics.