How to reduce the usage of precious metals in electrocatalysts is a big challenge for the development of fuel cells. Metal nanoclusters (NCs) are highly desirable as active catalysts, but palladium nanoclusters (Pd NCs) have been less well developed than other metal clusters, such as gold, silver and copper, owing partly to the difficulties in size-controlled synthesis. Here, based on N, N-dimethylformamide (DMF)-mediation and ligand-exchange reaction, atomically precise Pd₅(C₁₂H₂₅S)₁₃ nanoclusters are successfully synthesized. By loading the as-prepared Pd₅ nanoclusters on multiwalled carbon nanotubes (MWCNTs) and the following pyrolysis to remove the thiolate ligands, the surface-cleaned Pd₅ clusters (Pd₅ NCs/MWCNTs) can serve as efficient electrocatalysts for the oxygen reduction reaction (ORR) and the ethanol oxidation reaction (EOR). With ultra-low mass loading of Pd (2%), the Pd₅ NCs showed higher mass and specific activities and better durability than the commercial Pd/C catalyst (5 wt%) for the ORR. At 0.8 V, the mass and specific activities of Pd₅ NCs/MWCNTs are 5.70 and 4.53 times higher than the commercial Pd/C catalyst, respectively. As for the EOR, the Pd₅ NCs/MWCNTs exhibited lower onset potential (0.39 V) and peak potential (0.81 V) than the commercial Pd/C catalyst (0.44 and 0.89 V). Electrochemical impedance spectroscopy (EIS) measurements indicated that for the EOR, the Pd₅ nanoclusters have a much smaller charge transfer resistance (R_ct) than the commercial Pd/C. The high-performance electrocatalytic properties of Pd₅ NCs for the ORR and EOR could be ascribed to the relatively high surface area-to-volume ratio and high density of exposed surface atoms of the Pd₅ nanoclusters.

如何减少电催化剂中贵金属的使用是燃料电池发展的一大挑战。金属纳米团簇（NCs）作为活性催化剂是非常理想的，但是钯纳米团簇（Pd NCs）比其他金属簇（如金，银和铜）的发展欠佳，部分原因是尺寸控制合成的困难。在这里，基于N，N-二甲基甲酰胺（DMF）介导和配体交换反应，成功地合成了原子精确的Pd ₅（C ₁₂ H ₂₅ S）₁₃纳米团簇。通过将制备好的Pd ₅纳米团簇负载在多壁碳纳米管（MWCNT）上，然后进行热解以去除硫醇盐配体，表面清洁的Pd ₅簇（Pd ₅ NCs / MWCNT）可以用作氧还原反应（ORR）和乙醇氧化反应（EOR）的有效电催化剂。与ORR的商用Pd / C催化剂（5 wt％）相比，Pd ₅ NCs的超低质量负载量（2％）显示出更高的质量和比活度以及更好的耐久性。在0.8 V时，Pd ₅ NCs / MWCNT的质量和比活分别比市售Pd / C催化剂高5.70倍和4.53倍。至于EOR，Pd ₅ NCs / MWCNTs的起始电势（0.39 V）和峰值电势（0.81 V）比市售Pd / C催化剂（0.44和0.89 V）低。电化学阻抗谱（EIS）测量表明，对于EOR，Pd ₅纳米团簇的电荷转移阻力（R _ct）比市售Pd / C小得多。Pd ₅ NCs对ORR和EOR的高性能电催化性能可归因于Pd ₅纳米团簇的相对较高的表面积体积比和较高的暴露表面原子密度。