Nature and evolution of Pd catalysts supported on activated carbon fibers during the catalytic reduction of bromate in water

Abstract

Catalytic hydrogenation of bromate using Pd catalysts supported on activated carbon fibers is a smart solution to treat bromate polluted water. These catalysts have been analyzed by different techniques for an in-deep characterization of the active sites. The in situ X-ray absorption spectroscopy and the CO chemisorption studies showed that Pd⁰ nanoparticles with different crystal sizes were generated on the support during hydrogen activation at 200 °C and that the PdH_x-phase was formed during the cooling to room temperature. As PdH_x species formed on Pd⁰ nanoparticles are responsible for bromate reduction, the most active catalysts are those having Pd⁰ nanoparticles with large crystal sizes, where PdH_x species are easily formed. The catalysts are fully stable in succesive reaction runs. It has been also shown that bromate reduction rate depends on the bromate concentration and on the hydrogen partial pressure, with a pseudo-first reaction order towards both reactants.