Quantitative detection of trace elemental palladium in automobile exhaust catalysts through electron probe microanalysis

Abstract

Automobile exhaust catalysts containing only Pd have significant advantages over other types of catalysts, including exceptionally high activity at low temperatures, superior thermal stability at high temperatures, and resistance to sulfur toxicity. The present study employs the electron probe microanalysis (EPMA) technique to determine the trace elemental Pd in such catalysts. The particle size distribution and homogeneity of Pd in synthesised standard samples were studied after ball milling, which improved the sample uniformity. Furthermore, the impact of measurement parameters on the analysis precision was investigated. It was found that the optimal conditions are an acceleration voltage of 18 kV, a beam current of 140 nA, and a beam spot size of 40 μm. To avoid potential background interference when choosing background positions in the ZAF method, a calibration curve was established with a correlation coefficient higher than 0.99. This analysis method can be of substantial significance in the production process of automobile exhaust catalysts and in the recovery of precious metals from spent catalysts. Therefore, there is high potential to expand the applications of EPMA in this field.