A novel-Pd/CuO-Ni(OH)2/C catalyst with carbon black as support was successfully synthesized by hydrazine hydrate reduction and galvanic replacement strategies, subsequently tested for activity in the electrocatalytic oxidation of ethanol. The...

Cu–Ag core–shell nanoparticles with a size of 8 nm were synthesized by the compound method of replacement reaction and chemical reduction reaction. A fully covered Cu–Ag core–shell structure was obtained by controlling the two different silver sources and electroless silver plating time. The optimum condition uses silver ammonia reacted for 14 h. The process of electroless silver plating uses the mixed growth model of layered growth and island growth. Silver atoms firstly attach to the surface of the as-prepared copper nanoparticles to form the dotted Ag atom structure by galvanic displacement reaction between Cu and [Ag(NH3)2]+, and then more silver atoms, reduced by sodium citrate, gradually deposit on the copper surface to form a fully covered structure. The morphology and core–shell structure of the nanoparticles was observed by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The simultaneous thermal analyzer results confirmed that the weight gain of Cu–Ag core–shell nanoparticles was 2.2% when heated up to 400 °C, which was lower than pure Cu nanoparticles. According to the x-ray photoelectron spectroscopy results, the Cu–Ag core–shell nanoparticles exhibited good anti-oxidation performance compared with the pure copper nanoparticles after being stored for one month under the ambient conditions.

Nanostructures of the multimetallic catalysts offer great scope for fine tuning of heterogeneous catalysis, but clear understanding of the surface chemistry and structures is important to enhance their selectivity and efficiency. Focussing on a typical Pt−Pd−Ni trimetallic system, we comparatively examined the Ni/C, Pt/Ni/C, Pd/Ni/C and Pt−Pd/Ni/C catalysts synthesized by impregnation and galvanic replacement reaction. To clarify surface chemical/structural effect, the Pt−Pd/Ni/C catalyst was thermally treated at X=200, 400 or 600 °C in a H2 reducing atmosphere, respectively termed as Pt−Pd/Ni/C−X. The as‐prepared catalysts were characterized complementarily by XRD, XPS, TEM, HRTEM, HS‐LEIS and STEM‐EDS elemental mapping and line‐scanning. All the catalysts were comparatively evaluated for benzaldehyde and styrene hydrogenation. It is shown that the “PtPd alloy nanoclusters on Ni nanoparticles” (PtPd/Ni) and the synergistic effect of the trimetallic Pt−Pd−Ni, lead to much improved catalytic performance, compared with the mono‐ or bi‐ metallic counterparts. However, with the increase of the treatment temperature of the Pt−Pd/Ni/C, the catalytic performance was gradually degraded, which was likely due to that the favourable nanostructure of fine “PtPd/Ni” was gradually transformed to relatively large “PtPdNi alloy on Ni” (PtPdNi/Ni) particles, thus decreasing the number of noble metal (Pt and Pd) active sites on the surface of the catalyst. The optimum trimetallic structure is thus the as synthesised Pt−Pd/Ni/C. This work provides a novel strategy for the design and development of highly efficient and low‐cost multimetallic catalysts, e. g. for hydrogenation reactions.