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Pt-based intermetallics exhibit excellent activity in electrocatalysis. However, their controlled syntheses remain difficult. Herein, carbon-supported PtM (M = Fe, Co, Ni, Zn and Mn) intermetallics with small size (3 nm) were prepared at the gramscale and applied as a highly effective electrocatalyst for the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

LiCoO2 (LCO) can deliver ultrahigh discharge capacities as a cathode material for Li-ion batteries when the charging voltage reaches 4.6 V. However, establishing a stable LCO cathode at a high cut-off voltage is a challenge in terms of bulk and surface structural transformation. O2 release, irreversible structural transformation, and interfacial side reactions cause LCO to experience severe capacity degradation and safety problems. To solve these issues, a strategy of gradient Ta doping is proposed to stabilize LCO against structural degradation. Additionally, Ta1-LCO that was tuned with 1.0 mol% Ta doping demonstrated outstanding cycling stability and rate performance. This effect was explained by the strong Ta-O bonds maintaining the lattice oxygen and the increased interlayer spacing enhancing Li+ conductivity. This work offers a practical method for high-energy Li-ion battery cathode material stabilization through the gradient doping of high-valence elements. [ABSTRACT FROM AUTHOR]

The fundamental understanding and precise control of catalytic sites are challenging yet essential to explore advanced electrocatalysts for the formic acid oxidation reaction (FAOR). Herein, this work demonstrates a new and promising catalyst prototype of antiperovskite‐type PdFe3N which possesses ordered and isolated Pd sites. The as‐synthesized PdFe3N/N‐rGO exhibits significant enhancement in catalytic activity, robust stability, and Fe anti‐dissolution properties when compared with PdFe3/rGO and Pd/C. Density functional theory (DFT) calculations reveal that isolated and ordered Pd sites are beneficial for high formate coverage and thus suppressing CO formation/poisoning. Moreover, the strong Fe–N covalent bonds improve the vacancy formation energy of Fe, which ensures superior Fe anti‐dissolution properties. Beyond offering a promising candidate for catalyzing FAOR, these findings provide deeper insights into the structure of CO tolerance relationships and benefit the theory‐guided design of highly efficient catalysts. [ABSTRACT FROM AUTHOR]

Controllable synthesis of atomically ordered intermetallic nanoparticles (NPs) is crucial to obtain superior electrocatalytic performance for fuel cell reactions, but still remains arduous. Herein, we demonstrate a novel and general hydrogel‐freeze drying strategy for the synthesis of reduced graphene oxide (rGO) supported Pt3M (M=Mn, Cr, Fe, Co, etc.) intermetallic NPs (Pt3M/rGO‐HF) with ultrasmall particle size (about 3 nm) and dramatic monodispersity. The formation of hydrogel prevents the aggregation of graphene oxide and significantly promotes their excellent dispersion, while a freeze‐drying can retain the hydrogel derived three‐dimensionally (3D) porous structure and immobilize the metal precursors with defined atomic ratio on GO support during solvent sublimation, which is not afforded by traditional oven drying. The subsequent annealing process produces rGO supported ultrasmall ordered Pt3M intermetallic NPs (≈3 nm) due to confinement effect of 3D porous structure. Such Pt3M intermetallic NPs exhibit the smallest particle size among the reported ordered Pt‐based intermetallic catalysts. A detailed study of the synthesis of ordered intermetallic Pt3Mn/rGO catalyst is provided as an example of a generally applicable method. This study provides an economical and scalable route for the controlled synthesis of Pt‐based intermetallic catalysts, which can pave a way for the commercialization of fuel cell technologies. [ABSTRACT FROM AUTHOR]

Hierarchically structured materials have special properties and possess potential in applications in the catalytic and electrochemical fields. Herein, two kinds of hierarchical core–shell nanostructures, lavender-like α-MnO2@α-MnO2 and balsam pear-like α-MnO2@γ-MnO2, were prepared by a facile room-temperature method using α-MnO2 nanowires as a backbone under acidic and alkaline conditions, respectively. When being used as a catalyst for dimethyl ether combustion, α-MnO2@γ-MnO2 exhibited a better performance than α-MnO2@α-MnO2 (T10 = 171 vs. 196 °C; T90 = 220 vs. 258 °C, SV = 30, 000 mL g−1 h−1). It is concluded that the larger surface area, higher reducibility/oxygen mobility, richer surface oxygen species, and the relatively smaller apparent activation energy are responsible for the superior performance of α-MnO2@γ-MnO2. [ABSTRACT FROM AUTHOR]

Manganese dioxide is one of the important electrode materials used for oxygen reduction reaction (ORR) in fuel-cell and metal-air batteries, and its electrochemical activity is greatly influenced by its crystalline structure. To elucidate the crystalline structure effect on the ORR, herein, we designed a facile method to obtain α-MnO2 and γ-MnO2via adjusting the acid under hydrothermal conditions using the same starting materials and reagents. The prepared α-MnO2 and γ-MnO2 have a similar morphology composed of 3D microscopic spheres made up of numerous nanorods. X-ray photoelectron spectroscopy, temperature programmed desorption of oxygen characterization and conductivity measurements demonstrate that the α-MnO2 material has a relatively higher ratio of surface oxygen species, higher oxygen mobility and higher electrical conductivity. When compared with γ-MnO2, α-MnO2 displays superior ORR activity with a higher electron transfer number and lower yield of peroxide species in alkaline solutions. The obtained results shed new light on the crystalline structure-dependent ORR activity of MnO2. [ABSTRACT FROM AUTHOR]

Although Mo 2 C and earth-abundant 3d transition metals are regarded as potential catalysts to replace noble metal catalysts for effective hydrogen evolution reaction, their large-scale application is still inhibited by their own defects. Here, a facile thermal treatment method for nonprecious metal catalysts is developed to prepare a porous Ni/Mo 2 C composite catalyst. The loading density of Ni nanoparticles on the Mo 2 C surface has an important effect on the activity of the catalyst. By optimizing the Ni doping ratio, the Ni-40/Mo 2 C-17 sample exhibits the lowest onset overpotential and lowest overpotential at 10 mA cm -2 in both acidic and alkaline electrolytes, compared to other reported Ni- and Mo 2 C-based catalysts. In addition, theoretical calculations have also confirmed the synergistic effect between Ni nanoparticles and Mo 2 C, which can balance the thermodynamics between H adsorption and desorption of H 2 . This work provides an avenue for designing high-performance water-splitting catalytic materials using low-cost species, which exhibit excellent HER activity in a wide pH range.

Hierarchically structured materials have special properties and possess potential in applications in the catalytic and electrochemical fields. Herein, two kinds of hierarchical core-shell nanostructures, lavender-like α-MnO 2 @α-MnO 2 and balsam pear-like α-MnO 2 @γ-MnO 2 , were prepared by a facile room-temperature method using α-MnO 2 nanowires as a backbone under acidic and alkaline conditions, respectively. When being used as a catalyst for dimethyl ether combustion, α-MnO 2 @γ-MnO 2 exhibited a better performance than α-MnO 2 @α-MnO 2 (T 10 = 171 vs. 196 °C; T 90 = 220 vs. 258 °C, SV = 30, 000 mL g -1 h -1 ). It is concluded that the larger surface area, higher reducibility/oxygen mobility, richer surface oxygen species, and the relatively smaller apparent activation energy are responsible for the superior performance of α-MnO 2 @γ-MnO 2 .