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Developing high-performance non-Pt electrocatalysts toward the oxygen reduction reaction (ORR) is highly desirable but still challenging for industrial application in fuel cells. Here, we report a facile approach for the synthesis of Au-doped Pd3Pb wavy nanowires (WNWs) with different amounts of Au. We found that the oriented attachment dictated the formation of the WNWs. Such WNWs with several attractive features including a high density of defects, anisotropic one-dimensional nanostructures, ordered intermetallic structures, and Au doping exhibited substantially enhanced catalytic properties in terms of activity and durability towards the ORR in alkaline media compared to commercial Pt/C. Interestingly, the Au doped Pd3Pb WNWs showed a volcano-like relationship in ORR activity as a function of the amount of Au with the 2% Au-doped Pd3Pb WNWs being the best ORR electrocatalysts. Specifically, the 2% Au doped Pd3Pb WNWs achieved the highest mass activity (0.75 mA μg−1) at 0.9 V, which was 1.25 and 7.5 times higher than that of the Pd3Pb WNWs and commercial Pt/C, respectively. More importantly, the 2% Au-doped Pd3Pb WNWs displayed higher durability with only 22.7% loss in mass activity after 10 000 cycles compared to the commercial Pt/C (38% loss in mass activity) due to their chemically stable intermetallic structures and the effect of Au doping.

The strain effect is a critical knob to tune the catalytic performance and has received unprecedented research interest recently. However, it is difficult to distinguish the strain effect from the synergistic effect, especially in alloyed catalysts. Here we have synthesized Pd@PdAg icosahedra and {111} truncated bi-pyramids with only different surface strains between them as electrocatalysts for the ethanol oxidation reaction (EOR). Due to the same exposed facets and compositions of the two electrocatalysts, their EOR performances are mainly determined by the surface strains of PdAg alloys. These two electrocatalysts provide a perfect model to investigate the role of the strain effect in tuning the EOR performance. It is indicated that Pd@PdAg {111} truncated bi-pyramids with a surface strain of 0.3% show better catalytic activity and durability than Pd@PdAg icosahedra with a surface strain of 2.1% including commercial Pd/C. Density functional theory (DFT) calculations reveal that the lowered d-band center of 0.3% strained PdAg alloys relative to 2.1% strained ones reduced the adsorption energy of the acetate-evolution key intermediate *CH

Although tremendous efforts have been devoted to exploring non-Pt based electrocatalysts toward the oxygen reduction reaction (ORR), achievements in both catalytic activity and durability are still far from satisfactory. Here, we report a facile approach for the synthesis of intermetallic Pd3Pb ultrathin nanoplate-constructed flowers. Such highly opened hierarchical nanostructures with an ordered phase and low-coordinated edge sites exhibited a substantially enhanced activity toward the ORR. Especially, the intermetallic Pd3Pb nanoflowers achieved a record-breaking mass activity (1.14 mA μgPd−1) in an alkaline solution at 0.9 V vs. a reversible hydrogen electrode among the reported Pd-based ORR electrocatalysts to date, which was 1.8, 3.9 and 11.4 times higher than those of intermetallic Pd3Pb nanocubes, Pd3Pb dendrites and commercial Pt/C, respectively. More importantly, the intermetallic Pd3Pb nanoflowers also showed a higher durability with only 23.7% loss in mass activity after 10 000 cycles compared to the commercial Pt/C (35% loss in mass activity) due to their chemically stable intermetallic structures.

Pd is generally regarded as an alternative catalyst material to Pt for the oxygen reduction reaction (ORR). However, its catalytic activity and durability are much lower than those of Pt. Here, we report a facile approach for the synthesis of intermetallic Pd3Pb square nanoplates enclosed by {100} facets. The use of oleylamine (OAm), oleic acid (OA), and 1-octadecene (ODE) played important roles in the formation of the Pd3Pb intermetallic square nanoplates in high-quality. The Pd3Pb square nanoplates exhibited substantially enhanced ORR properties in terms of activity and durability. In particular, such nanoplates showed higher mass activity (0.62 mA μgPd−1) and specific activity (3.59 mA cm−2), which were 10.3 and 32.6 times higher than those of the commercial Pt/C, respectively, due to ligand and geometry effects. Significantly, the Pd3Pb square nanoplates/C were highly stable with 23% loss in specific activity and 21% loss in mass activity after 10 000 cycles compared to the Pd3Pb alloy dendritic nanocrystals/C (over 50% loss in specific and mass activities) due to their unique intermetallic structure with high chemical stability.

Pt-based multimetallic nanorings with a hollow structure are attractive as advanced catalysts due to their fantastic structure feature. However, the general method for the synthesis of such unique nanostructures is still lack. Here we report the synthesis of Pd@PtM (M = Rh, Ni, Pd, Cu) multimetallic nanorings by selective epitaxial growth of Pt alloyed shells on the periphery of Pd nanoplates in combination with oxidative etching of partial Pd in the interior. In situ generation of CO and benzoic acid arising from interfacial catalytic reactions between Pd nanoplates and benzaldehyde are critical to achieve high-quality Pt-based multimetallic nanorings. Specifically, the in-situ generated CO promotes the formation of Pt alloyed shells and their epitaxial growth on Pd nanoplates. In addition, the as-formed benzoic acid and residual oxygen are responsible for selective oxidative etching of partial Pd in the interior. When evaluated as electrocatalysts, the Pd@PtRh nanorings exhibit remarkably enhanced activity and stability for ethanol oxidation reaction (EOR) compared to the Pd@PtRh nanoplates and commercial Pt/C due to their hollow nanostructures.

Pd@Pt core–shell nanocrystals with ultrathin Pt layers have received great attention as active and low Pt loading catalysts for oxygen reduction reaction (ORR). However, the reduction of Pd loading without compromising the catalytic performance is also highly desired since Pd is an expensive and scarce noble-metal. Here we report the epitaxial growth of ultrathin Pt shells on PdxCu truncated octahedra by a seed-mediated approach. The Pd/Cu atomic ratio (x) of the truncated octahedral seeds was tuned from 2, 1 to 0.5 by varying the feeding molar ratio of Pd to Cu precursors. When used as catalysts for ORR, these three PdxCu@Pt core–shell truncated octahedra exhibited substantially enhanced catalytic activities compared to commercial Pt/C. Specifically, Pd2Cu@Pt catalysts achieved the highest area-specific activity (0.46 mA cm−2) and mass activity (0.59 mA μgPt−1) at 0.9 V, which were 2.7 and 4.5 times higher than those of the commercial Pt/C. In addition, these PdxCu@Pt core–shell catalysts showed a similar durability with the commercial Pt/C after 10 000 cycles due to the dissolution of active Cu and Pd in the cores.

Developing an efficient electrocatalyst for the hydrogen evolution reaction (HER) working in both acidic and alkaline solutions is highly desirable, but still remains challenging. Here, Ptx Ni ultrathin nanowires (NWs) with tunable compositions (x = 1.42, 3.21, 5.67) are in situ grown on MXenes (Ti3 C2 nanosheets), serving as electrocatalysts toward HER. Such Ptx Ni@Ti3 C2 electrocatalysts exhibit excellent HER performance in both acidic and alkaline solutions, with the Pt3.21 Ni@Ti3 C2 being the best one. Specifically, Pt3.21 Ni@Ti3 C2 achieves record-breaking performance in terms of lowest overpotential (18.55 mV) and smallest Tafel slope (13.37 mV dec-1 ) for HER in acidic media to date. Theory calculations and X-ray photoelectron spectroscopy analyses demonstrate that the coupling of MXenes with the NWs not only approaches the Gibbs free energy for hydrogen adsorption close to zero through the electron transfer between them in acidic media, but also provides additional active sites for water dissociation in alkaline solution, both of them being beneficial to the HER performance.