Search

There is an urgent need to develop cost‐effective electrocatalysts based on Pt for a broad spectrum of applications, including those vital to the operation of fuel cells. Hollowing out the interior of Pt nanocrystals offers a simple and viable strategy for maximizing the utilization efficiency of this precious metal while enhancing the electrocatalytic performance. Herein, we report the synthesis and electrocatalytic evaluation of Pt−Ag icosahedral nanocages with an average wall thickness of 1.6 nm. The Pt atoms are coated on the surface of Ag icosahedral seeds, leading to the formation of Ag@PtnL core‐shell icosahedral nanocrystals with tunable shell thicknesses. The core‐shell nanocrystals are then converted to icosahedral nanocages by selectively etching away the Ag in the core. The as‐obtained nanocages with a composition of Pt4.5Ag exhibit an almost 3‐fold enhancement in specific activity toward oxygen reduction relative to the commercial Pt/C in acid media. [ABSTRACT FROM AUTHOR]

We report a simple route based upon seed‐mediated growth to the synthesis of Pd@AuxPd1−x (0.8≤x≤1) core–shell nanocubes. Benefiting from the well‐defined {100} facets and an optimal Au/Pd ratio for the surface, the nanocubes bearing a shell made of Au0.95Pd0.05 work as an efficient electrocatalyst toward H2O2 production, with high selectivity of 93–100 % in the low‐overpotential region of 0.4–0.7 V. When the Au0.95Pd0.05 alloy is confined to a shell of only three atomic layers in thickness, the electrocatalyst is able to maintain its surface structure and elemental composition, endowing continuous and stable production of H2O2 during oxygen reduction at a high rate of 1.62 mol g(Pd+Au)−1 h−1. This work demonstrates a versatile route to the rational development of active and durable electrocatalysts based upon alloy nanocrystals. [ABSTRACT FROM AUTHOR]

We report a facile synthesis of Ag@Pd core−shell icosahedral nanocrystals for the development of cost‐effective electrocatalysts toward formic acid oxidation. With 12.4 nm Ag icosahedra serving as seeds, Pd shells of controlled thicknesses in the range of 3.6–5.8 atomic layers are grown by adjusting the experimental parameters. When examined as catalysts toward formic acid oxidation, all the Ag@Pd nanocrystals exhibit enhanced mass activities relative to a commercial Pd/C catalyst, with the Ag@Pd4.2L nanocrystals showing enhanced mass activity that is almost twice that of a commercial Pd/C. The chronoamperometry measurements indicate that all the Ag@Pd/C catalysts are more robust than the Pd/C, with the catalyst based on Ag@Pd4.2L nanocrystals showing a mass activity greater than that of the pristine Pd/C after holding in a mixture of HCOOH and HClO4 at 0.75 V for 1,000 s. We believe that the strategy demonstrated here can also be extended to the development of other types of advanced electrocatalysts. [ABSTRACT FROM AUTHOR]

We report a highly active and durable water oxidation electrocatalyst based on cubic nanocages with a composition of Ir44Pd10, together with well‐defined {100} facets and porous walls of roughly 1.1 nm in thickness. Such nanocages substantially outperform all the water oxidation electrocatalysts reported in literature, with an overpotential of only 226 mV for reaching 10 mA cm−2geo at a loading of Ir as low as 12.5 μgIr cm−2 on the electrode in acidic media. When benchmarked against a commercial Ir/C electrocatalyst at 250 mV of overpotential, such a nanocage‐based catalyst not only shows enhancements (18.1‐ and 26.2‐fold, respectively) in terms of mass (1.99 A mg−1Ir) and specific (3.93 mA cm−2Ir) activities, but also greatly enhanced durability. The enhancements can be attributed to a combination of multiple merits, including a high utilization efficiency of Ir atoms and an open structure beneficial to the electrochemical oxidation of Ir to the active form of IrOx. [ABSTRACT FROM AUTHOR]

Platinum icosahedral nanocrystals are intriguing catalytic materials owing to the presence of a large number of twin boundaries and well‐defined {111} facets on the surface. However, there are only two protocols available for their synthesis and the protocols required either the involvement of a metal carbonyl as the reductant or a very long reaction time up to one week. Here we report a facile route to the quick synthesis of Pt icosahedral nanocrystals with tunable sizes. The synthesis only involved Pt(acac)2, tetraethylene glycol, poly(vinyl pyrrolidone), and as the metal precursor, solvent/reductant, and colloidal stabilizer, respectively. Noticeably, the synthesis could be completed within 20 min. By simply varying the amount of the precursor, we were able to tune the size of the Pt icosahedral nanocrystals in the range of 10–25 nm. Additionally, when ascorbic acid was introduced as a co‐reductant to facilitate the reduction of the precursor, the size of the Pt icosahedral nanocrystals could be further reduced down to 7–12 nm. When used as a catalyst towards the oxygen reduction reaction, the Pt icosahedral nanocrystals with different sizes all exhibited a specific activity more than 2.4 times greater than that of commercial Pt/C. Moreover, their specific activity increased with the particle size. After 5,000 cycles of the accelerated durability test, the specific activities of the Pt icosahedral nanocrystals with three different sizes were still more than 2 times as high as that of the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Development of renewable energy technologies requires advanced catalysts for efficient electrical-chemical energy conversion reactions. Here we report the study of Pt-Re alloy nanoparticles as an electrocatalyst for the oxygen reduction reaction (ORR). An organic solution approach is developed to synthesize monodisperse and homogeneous Pt 3 Re alloy nanoparticles. Electrochemical studies show that these nanoparticles exhibit an improvement factor of 4 in catalytic activity for the ORR compared to commercial Pt catalysts of similar particle sizes. Fundamental understanding of the structure-property relationship is established by combining material characterization using X-ray spectroscopy and atomically resolved electron microscopy, as well as Density Functional Theory (DFT) calculations. Our work revealed that an electronic modification of the surface properties of Pt by subsurface Re ( ligand effect ) accounts for the catalytic enhancement. [ABSTRACT FROM AUTHOR]

The fine balance between activityand durability is crucial forthe development of high performance electrocatalysts. The importanceof atomic structure and compositional gradients is a guiding principlein exploiting the knowledge from well-defined materials in the designof novel class of core–shell electrocatalysts comprising Nicore, Au interlayer, and PtNi shell (Ni@Au@PtNi). This multimetallicsystem is found to have the optimal balance of activity and durabilitydue to the synergy between the stabilizing effect of subsurface Auand modified electronic structure of surface Pt through interactionwith subsurface Ni atoms. The electrocatalysts with Ni@Au@PtNi core-interlayer-shellstructure exhibit high intrinsic and mass activities as well as superiordurability for the oxygen reduction reaction with less than 10% activityloss after 10 000 potential cycles between 0.6 and 1.1 V vsthe reversible hydrogen electrode. [ABSTRACT FROM AUTHOR]