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The rational design and facile synthesis of highly activated and stable electrocatalysts toward the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) are extremely demanded but remain challenging. Herein, a highly efficient bifunctional electrocatalyst composed of rhodium (Rh), cobalt (Co), and iron (Fe) alloy nanoparticles embedded in nitrogen-doped graphene (RhFeCo@NG) is prepared through sequential annealing and the substitution reaction. The as-prepared Rh2.6Fe3Co2.6@NG electrocatalyst achieves an overpotential as low as 25 mV for reaching a current density of 10 mA cm–2 and an ultralow Tafel slope of 29.8 mV dec–1 in 1 M KOH solution for HER, which is even superior to the state-of-the-art platinum (Pt) catalyst. With regard to ORR, for the Rh2.6Fe3Co2.6@NG electrocatalyst, a half-wave potential (E1/2) of 0.82 V versus reversible hydrogen electrode and excellent long-term stability are achieved. The experimental results illustrate that alloying the Rh atom with the FeCo nanoalloy is mainly responsible for the excellent HER and ORR performances. This study not only provides a robust and promising electrocatalyst for HER and ORR in alkaline media but also sheds light on the devising of efficient and multifunctional 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]

The high cost and poor durability of Pt nanoparticles (NPs) have always been great challenges to the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt-based intermetallic NPs with a highly ordered structure are considered as promising catalysts for PEMFCs due to their high catalytic activity and stability. Here, we reported a facile method to synthesize N-doped carbon encapsulated PtZn intermetallic (PtZn@NC) NPs via the pyrolysis of Pt@Zn-based zeolitic imidazolate framework-8 (Pt@ZIF-8) composites. The catalyst obtained at 800 °C (10%-PtZn@NC-800) was found to exhibit a half-wave potential (E1/2) up to 0.912 V versus reversible hydrogen electrode (RHE) for the cathodic oxygen reduction reaction in an acidic medium, which shifted by 26 mV positively compared to the benchmark Pt/C catalyst. Besides, the mass activity and specific activity of 10%-PtZn@NC-800 at 0.9 V versus RHE were nearly 3 and 5 times as great as that of commercial Pt/C, respectively. It is worth noting that the PtZn@NC showed excellent stability in ORR with just 1 mV of the E1/2 loss after 5,000 cycles, which is superior to that of most reported PtM catalysts (especially those disordered solid solutions). Furthermore, such N-doped carbon shell encapsulated PtZn intermetallic NPs showed significantly enhanced performances towards the anodic oxidation reaction of organic small molecules (such as methanol and formic acid). The synergistic effects of the N doped carbon encapsulation structure and intermetallic NPs are responsible for outstanding performances of the catalysts. This work provides us a new engineering strategy to acquire highly active and stable multifunctional catalysts for PEMFCs. [ABSTRACT FROM AUTHOR]

A facile method to prepare Pt–Ti intermetallic nanoparticles supported on carbon was developed. Starting from a commercial Pt/C catalyst, TiO 2 layers were formed on the Pt/C then thermal annealing under a reducing condition successfully produced intermetallic Pt–Ti nanoparticles with an average size of 4.2 nm. The intermetallic Pt–Ti/C showed enhanced activity and durability for oxygen reduction reaction due to the change in electronic structure and less aggregation. [ABSTRACT FROM AUTHOR]