Functional Pd/reduced graphene oxide nanocomposites: effect of reduction degree and doping in hydrodechlorination catalytic activity

Abstract

Pd catalysts supported on carbon have interesting features for chlorophenols-bearing water treatment by hydrodechlorination, including high stability, activity, and tunable support. In this work, a set of materials based on reduced graphene oxide (rGO) with different degrees of reduction, surface oxygen groups, nitrogen doping, and specific surface area were decorated with Pd nanoparticles, with diameter average size between 5 and 50 nm. Ethanol, hydrazine monohydrate, and sodium borohydride were used as reducing agents, and Pd(AcO)2 was used as a Pd precursor to obtain Pd/rGO nanocomposites in our developed one-pot synthesis approach. A thorough characterization revealed that a similar degree of reduction was obtained for sodium borohydride at 25 °C and hydrazine at 60 °C, although hydrazine also led to nitrogen doping. Pd nanoparticles were homogenously nucleated on the surface of the GO and the obtained nanocomposites were tested as catalysts for hydrodechlorination of 4-chlorophenol in the aqueous phase. The materials with a higher degree of reduction showed the best specific catalytic activity at 70 °C. However, the turnover frequency (TOF) only increased with the reduction degree for the N-doped Pd/rGO, indicating the important role of the nitrogenous functionalities in the catalytic activity. Therefore, the N doping of Pd/rGO catalysts is a feasible strategy to synthesize catalysts highly active for hydrodechlorination.