Control of structure at the atomic level can precisely and effectively tune catalytic properties of materials, enabling enhancement in both activity and durability. We synthesized a highly active and durable class of electrocatalysts by exploiting the structural evolution of platinum-nickel (Pt-Ni) bimetallic nanocrystals. The starting material, crystalline PtNi3 polyhedra, transforms in solution by interior erosion into Pt3Ni nanoframes with surfaces that offer three-dimensional molecular accessibility. The edges of the Pt-rich PtNi3 polyhedra are maintained in the final Pt3Ni nanoframes. Both the interior and exterior catalytic surfaces of this open-framework structure are composed of the nanosegregated Pt-skin structure, which exhibits enhanced oxygen reduction reaction (ORR) activity. The Pt3Ni nanoframe catalysts achieved a factor of 36 enhancement in mass activity and a factor of 22 enhancement in specific activity, respectively, for this reaction (relative to state-of-the-art platinum-carbon catalysts) during prolonged exposure to reaction conditions.

Advancement in heterogeneous catalysis relies on the capability of altering material structures at the nanoscale, and that is particularly important for the development of highly active electrocatalysts with uncompromised durability. Here, we report the design and synthesis of a Pt-bimetallic catalyst with multilayered Pt-skin surface, which shows superior electrocatalytic performance for the oxygen reduction reaction (ORR). This novel structure was first established on thin film extended surfaces with tailored composition profiles and then implemented in nanocatalysts by organic solution synthesis. Electrochemical studies for the ORR demonstrated that after prolonged exposure to reaction conditions, the Pt-bimetallic catalyst with multilayered Pt-skin surface exhibited an improvement factor of more than 1 order of magnitude in activity versus conventional Pt catalysts. The substantially enhanced catalytic activity and durability indicate great potential for improving the material properties by fine-tuning of the nanoscale architecture.

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Colloidal nanoparticles prepared by solution synthesis with robust control over particle size, shape, composition, and structure have shown great potential for catalytic applications. However, such colloidal nanoparticles are usually capped with organic ligands (as surfactants) and cannot be directly used as catalyst. We have studied the effect of surfactant removal on the electrocatalytic performance of Pt nanoparticles made by organic solution synthesis. Various methods were applied to remove the oleylamine surfactant, which included thermal annealing, acetic acid washing, and UV-Ozone irradiation, and the treated nanoparticles were applied as electrocatalysts for the oxygen reduction reaction. It was found that the electrocatalytic performance, including electrochemically active surface area and catalytic activity, was strongly dependent on the pretreatment. Among the methods studied here, lowtemperature thermal annealing (∼185 °C) in air was found to be the most effective for surface cleaning without inducing particle size and morphology changes.

Monodisperse and homogeneous PtxNi1‐x alloy nanoparticles of various compositions are synthesized via an organic solution approach in order to reveal the correlation between surface chemistry and their electrocatalytic properties. Atomic‐level microscopic analysis of the compositional profile and modeling of nanoparticle structure are combined to follow the dependence of Ni dissolution on the initial alloy composition and formation of the Pt‐skeleton nanostructures. The developed approach and acquired knowledge about surface structure‐property correlation can be further generalized and applied towards the design of advanced functional nanomaterials.

Interest in the low-cost production of clean hydrogen is growing. Anion exchange membrane water electrolyzers (AEMWEs) are considered one of the most promising sustainable hydrogen production technologies because of their...

The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (RhP/C) by a facile solvo-thermal approach. The RhP/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the RhP NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.

The oxygen reduction reaction (ORR) is an important cathode reaction used in fuel cells and metal-air batteries for renewable energy applications. [1][2][3] Platinum has been studied extensively as an essential catalytic component to reduce undesired overpotentials observed in the ORR. [4] Previous computational and experimental investigations have revealed that once alloyed with first-row transition metals, such as Fe, Co, and Ni, Pt alloy thin films and nanoparticles (NPs) can show dramatic activity enhancement in ORR catalysis, [5,6] especially when the Pt-skin structure is formed on the surface of MPt. [7] This enhancement is believed to originate from the downshift of the d-band center of Pt in the alloy structure; this downshift results in a decrease of the bonding strength between Pt and the oxygenated species (often called blocking species or spectators) and an increased number of available Pt sites for oxygen adsorption. [5] Recent experiments also indicate that elongated Pt nanostructures are less subject to dissolution, Ostwald ripening, and aggregation than the Pt NPs in acidic conditions, [8][9][10][11] and that they may be robust for catalyzing the ORR with high activity and durability.Herein, we report an advanced organic-phase synthesis of thin FePt and CoPt alloy nanowires (NWs) for enhanced catalysis of the ORR. Different from the previous approach to FePt NPs [12] and FePt NWs, [13] the current synthesis through decomposition of metal pentacarbonyl and reduction of platinum acetylacetonate, [Pt(acac) 2 ], was performed in sodium oleate solution of 1-octadecene (ODE) and oleylamine (OAm). Depending on the metal carbonyl used, FePt or CoPt NWs were obtained at a high synthetic yield and with the desired control over alloy composition. Electrochemical studies showed that these NWs were active catalysts for the ORR. The specific activity and the mass activity of the 2.5 nm wide FePt NWs reached 1.53 mA cm À2 and 844 mA mg À1 Pt at 0.9 V (vs. reversible hydrogen electrode, RHE; 0.2 mA cm À2 and 110 mA mg À1 Pt at 0.95 V), while those of the benchmark Pt catalyst reached 0.32 mA cm À2 and 155 mA mg À1 Pt at 0.9 V (0.080 mA cm À2 and 35 mA mg À1 Pt at 0.95 V). The annealed 6.3 nm wide FePt NWs showed an even higher specific activity of 3.9 mA cm À2 at 0.9 V and 0.46 mA cm À2 at 0.95 V.