Noble metal nanomaterials with hierarchical structures are considered to be promising catalysts owing to its controlling crystal morphology, good chemical stability and environmental-friendly. In order to improve the electrocatalytic activity of catalysts and maximize the utilization of nobel metal, Pd-based catalysts with hierarchically structures were successfully synthesized in the presence of different organic additives at ordinary temperature. And the influence of the component and morphology on the electrocatalytic properties of catalysts was also studied.

Firstly, a series of Pd hollow nanospheres and nanopaticles with different particle size were prepared in the presence of conducting polymers or different organic additives. Compared with the solid nanoparticles, Pd hollow nanospheres show a very high electrochemically-active surface area and significant increase in electrocatalytic activity (160 mA cm^-2) towards formic acid oxidation, which make them the preferable catalysts for direct formic acid fuel cells (DFAFC).

Secondly, a series of Pd-based (PdCu, PdCo, PdRh et al.) bimetallic alloyed hollow nanospheres composed with nanopaticles were successfully synthesized by a novel one-pot template-free strategy. According to cyclic voltammograms, the maximal peak current density of hollow PdCu alloyed nanocubes is 190 mA cm^-2, greater than those of PdCu alloy catalyst (143.1 mA cm^-2) and Pd nanopaticles (106.8 mA cm^-2). The results reveal that the alloy hollow nanostructures have high electrochemical activity, good stability and excellent anti-CO toxic ability during the process of formic acid oxidation. At the same time, it is one of the effective approaches to reduce the loading of noble metals and lower the cost of the catalysts.

Thirdly, a series of Pd-MeO_x (Pd-Fe₂O₃, Pd-CeO₂, Pd-SnO₂ et al.) hybrid nanostructured electrocatalysts were successfully prepared in the presence of different organic additives at ordinary temperature. On the surface of such metal oxides, hydroxyl species (OH^-) could form easily and assist oxidization of the adsorbed intermediate species during the electrooxidation. In short, the Pd-MeO_x catalyst not only lowers the cost by means of less Pd dosage but also shows good performance for electrooxidation with the assistance of oxide additives.

Overall, the component and morphology are key factors to the excellent performance of the catalysts. The results reveal that hollow nanostructures composed with nanopaticles represent a new class of powerful catalysts because of the increased surface area, low density and surface permeability. As a result, the catalyst with bimetallic alloy is an effective approach to enhance the catalytic activity, and reduce the cost of catalysts. Obviously, design and synthesis of hollow bimetallic nanosphere catalysts represent a promising way to effectively improve the performance and utilization of catalysts, while the cost can be further decreased.