Fast microwave-assisted synthesis of iron–palladium catalysts supported on graphite for the direct synthesis of H2O2

Abstract

While carbon supported noble metal catalysts have been extensively used in the direct synthesis of H2O2 (DSHP), unsatisfactory H2O2 yield remains a difficult problem to solve. In this work, a facile and efficient preparation of the FePd catalysts supported on graphite was realized by fast microwave-irradiated carbon nanotube (CNT) growth and metal reduction. For this purpose, ferrocene was used as a catalyst for microwave-assisted CNT growth as well as a carbon source, and carbon fibers and hexane were only used as carbon sources for CNT growth. The fast and localized microwave heating enabled the fast pyrolysis of ferrocene and the subsequent decomposition of other carbon sources, which efficiently regulated the Pd nanoparticle (NP) size during the microwave-irradiated reduction of Pd. The carbon sources significantly affected the geometric and electronic characteristics of Pd on carbon surface, and therefore, the catalytic activity for the DSHP reaction was affected. The additional use of hexane decreased the Pd NP size and increased the Pd2+/Pd0 ratio under microwave-assisted reduction. In the presence of FePd/GR-H catalyst, the H2O2 productivity and selectivity reached as high as 1492.3 mmol H2O2/g-Pd.h and 68.8%, respectively, in the absence of any corrosive promoters. The result clearly demonstrates that the effect of microwave irradiation for the catalyst preparation highly depended on carbon sources, and therefore, catalytic activity can be finely controlled by microwave irradiation condition.