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Mesoporous Pt-containing nanocomposites with well-organized pores are desirable for fuel cells as well as sensors, electronics, and various chemical reactions. However, it remains challenging to construct three-dimensional (3D) ordered honeycomb-like (OHC) nanostructures with Pt species anchored in the mesopores. Herein, we show for the first time an in situ strategy of developing an N-doped ordered honeycomb (N-OHC) nanopattern with well-dispersed Pt–N2 moieties by using the self-assembly of a block copolymer (BCP). The as-mentioned Pt including Pt single atoms (SAs) and Pt ∼2.5 nm ultrafine nanoparticles (NPs) was hierarchically located on the inner walls and the outer surfaces of the N-OHC mesopores (Pt/N-OHC), forming well-dispersed Pt–N active sites and showing efficient catalytic activity towards the oxygen reduction reaction (ORR). By changing the film thickness of the pristine Pt/BCP template, double-layered Pt/N-OHC could be designed and the ORR activity could be correspondingly improved, for which a current density of 1.60 A cm−2@0.6 V and a peak power density of 1.07 W cm−2 were observed at a very low Pt-loading of 0.04 mg cm−2, better than 1.21 A cm−2@0.6 V and 0.79 W cm−2 of the commercial Pt/C catalyst at a Pt-loading of 0.15 mg cm−2. The electron donating behavior of Pt–N2 and the pathway for O2 reduction were investigated via the density functional theory (DFT) computation. The electron transfer from Pt to N gave rise to the formation of Pt–N covalent bonds, which resulted in a lower d band center and a weaker O adsorption energy and endowed the Pt/N-OHCs with enhanced ORR activity. [ABSTRACT FROM AUTHOR]

The low-cost sodium (Na) metal anode has high specific capacity and is one of the most promising electrode materials for next generation high-energy density batteries. Unfortunately, it is also extremely reactive and suffers from severe side reactions with almost all electrolytes, which results in detrimental failures including uncontrollable growth of mossy structures, fast electrolyte depletion and short cycle life. We report here the in situ synthesis of composite sponges with sodiated NaxSnSb particles embedded in N-doped graphene (NG) frameworks for modulating Na anodes with significantly improved stability and fast charging capability. The sodiated NaxSnSb composites function as seeding particles that guide low-overpotential and smooth growth of Na metal whereas the NG wrapping layers protect the freshly plated Na metal from detrimental side reactions with the battery electrolyte. As a result, as high as 95% of the freshly plated Na metal can be reversibly stripped during battery operation and this efficiency can last hundreds of cycles. We further show that the Na3Sb phase in the NaxSnSb composites played critical roles as sponges with only the Na15Sn4 phase have much lower performance. Overall, the synergy of guided growth from NaxSnSb and shielding from NG allows multifunctional hosts that support Na anodes to cycle with nearly unchanged overpotential and charge transfer resistance for >500 cycles in both symmetric cells and full cells. The Na metal remained dense without measurable formation of unsafe dendrite or inactive mossy structures in these novel sponges even after aggressive cycling. [ABSTRACT FROM AUTHOR]

Bimetallic CuAg nanoparticles were synthesized using uric acid as a stabilizer, Fe3O4 loaded CuAg nanoparticles (Fe3O4–CuAg NPs) were also fabricated, and the morphology and content of both CuAg NPs and Fe3O4–CuAg NPs were investigated. The bimetallic CuAg NPs can be used as a catalyst and exhibited superior catalytic performance in the hydrogenation of nitrophenols and potassium ferricyanide(III). Notably, the bimetallic CuAg NPs and Fe3O4–CuAg NPs showed better catalytic activity compared with the same amount of Ag NPs in the hydrogenation of 4-nitrophenol, with rate constants k of 20.02 × 10−3 s−1 and 20.19 × 10−3 s−1, respectively. The magnetic Fe3O4–CuAg NPs can be re-used as a catalyst at least five times, promoting the concept of recycling by improving the deficiency in the disposable use of colloidal nanoparticles. [ABSTRACT FROM AUTHOR]