Facile synthesis of PdAu/C by cold plasma for efficient dehydrogenation of formic acid

Abstract

Decomposition of formic acid biomass to generate hydrogen is vital for coping with fossil energy depletion, environmental pollution, and developing clean, efficient, safe, and sustainable modern energy system. In this study, a PdAu/C−C bimetallic catalyst was prepared by the co-impregnation method followed by an atmospheric pressure (AP) cold plasma treatment to synthesize PdAu/C−P catalysts. The resulting PdAu/C−P showed excellent catalytic activity for the formic acid dehydrogenation (FAD) reaction. The total volume of H2 and CO2 released from the FAD reaction was about 375 mL after 4 h at 50 °C, and the initial turnover frequency (TOFinitial) was 808.6 h−1. We used X−ray diffractometry (XRD), temperature programmed reduction (TPR) and high-resolution transmission electron microscopy (HRTEM) to show that plasma can effectively promote the redispersion of Pd−Au particles on the surface of the support. The average particle size of PdAu/C−P (3.5 ± 1.5 nm) was less than PdAu/C−C (4.4 ± 1.9 nm) and uniformly distributed. X-ray photoelectron spectroscopy (XPS), TPR, and HRTEM showed that PdAu/C−P has a higher degree of alloying. In addition, the strong electric field in the plasma facilitated more metal sites located on the outer surface of the support in PdAu/C−P, and the atomic ratio of M/C (M = Pd and Au) (0.0134) was much larger than that of PdAu/C−C (0.0060). The apparent activation energy (Ea) of PdAu/C−P for the FAD reaction was only 27.25 kJ mol−1, and it had much higher activity and stability than the commercial Pd/C (Sigma−Aldrich). The total volume of H2 and CO2 produced over the PdAu/C−P for three cycles was 1.33, 5.87, and 8.56 times that of commercial Pd/C. Overall, the cold plasma enhanced the degree of alloying, promoted the redispersion of agglomerated particles, and regulated the surface enrichment of the active metal components. This is of great significance for guiding the preparation of high−performance multi-metal catalysts by cold plasma.