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Vesicle, a microscopic unit that encloses a volume with an ultrathin wall, is ubiquitous in biomaterials. However, it remains a huge challenge to create its inorganic metal-based artificial counterparts. Here, inspired by the formation of biological vesicles, we proposed a novel biomimetic strategy of curling the ultrathin nanosheets into nanovesicles, which was driven by the interfacial strain. Trapped by the interfacial strain between the initially formed substrate Rh layer and subsequently formed RhRu overlayer, the nanosheet begins to deform in order to release a certain amount of strain. Density functional theory (DFT) calculations reveal that the Ru atoms make the curling of nanosheets more favorable in thermodynamics applications. Owing to the unique vesicular structure, the RhRu nanovesicles/C displays excellent hydrogen oxidation reaction (HOR) activity and stability, which has been proven by both experiments and DFT calculations. Specifically, the HOR mass activity of RhRu nanovesicles/C are 7.52 A mg(Rh+Ru)−1 at an overpotential of 50 mV at the rotating disk electrode (RDE) level; this is 24.19 times that of commercial Pt/C (0.31 mA mgPt−1). Moreover, the hydroxide exchange membrane fuel cell (HEMFC) with RhRu nanovesicles/C displays a peak power density of 1.62 W cm−2 in the H2-O2 condition, much better than that of commercial Pt/C (1.18 W cm−2). This work creates a new biomimetic strategy to synthesize inorganic nanomaterials, paving a pathway for designing catalytic reactors. [ABSTRACT FROM AUTHOR]

Anion-exchange membrane fuel cells and Zn–air batteries based on non-Pt group metal catalysts typically suffer from sluggish cathodic oxygen reduction. Designing advanced catalyst architectures to improve the catalyst's oxygen reduction activity and boosting the accessible site density by increasing metal loading and site utilization are potential ways to achieve high device performances. Herein, we report an interfacial assembly strategy to achieve binary single-atomic Fe/Co-Nx with high mass loadings through constructing a nanocage structure and concentrating high-density accessible binary single-atomic Fe/Co–Nx sites in a porous shell. The prepared FeCo-NCH features metal loading with a single-atomic distribution as high as 7.9 wt% and an accessible site density of around 7.6 × 1019 sites g−1, surpassing most reported M–Nx catalysts. In anion exchange membrane fuel cells and zinc–air batteries, the FeCo-NCH material delivers peak power densities of 569.0 or 414.5 mW cm−2, 3.4 or 2.8 times higher than control devices assembled with FeCo-NC. These results suggest that the present strategy for promoting catalytic site utilization offers new possibilities for exploring efficient low-cost electrocatalysts to boost the performance of various energy devices. An interfacial assembly strategy was developed to construct single-atom binary Fe/Co-Nx sites with a high accessible site density of 7.6 × 1019 sites per gram which results in increased power densities in fuel cells and Zn/air batteries. [ABSTRACT FROM AUTHOR]

To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt‐free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn‐Pyrrolic‐N4 moieties and abundant mesoporous structure. The ZnNC‐based anion‐exchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm−2 in H2‐O2 and H2‐air (CO2‐free), and also exhibits long‐term stability with more than 120 and 100 h for H2‐air (CO2‐free) and H2‐O2, respectively. Density functional calculations further unveil that the Zn‐Pyrrolic‐N4 structure is the origin of high activity of as‐synthesized ZnNC catalyst, while the Zn‐Pyridinic‐N4 moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn‐metal‐organic framework ‐derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn‐Pyridinic‐N4 moieties. This work offers a new route for speeding up development of AEMFCs. [ABSTRACT FROM AUTHOR]

The microstructure of an electrode plays a critical role in the electrochemical performance of lithium‐ion batteries, including the energy and power density. Using a micrometer‐scale Wadsley–Roth phase TiNb2O7 active material with Li intercalation chemistry as a model system, the relationship between electrochemical performance and microstructure of calendared electrodes with same mass loading but different electrode parameters is studied by both experimental investigation and theoretical modeling, providing a paradigm of calendaring‐driven electrode microstructure for balanced battery energy density and power density. Along with the reduction in porosity, ion and electron diffusion distance decreases, which is beneficial for charge transfer and rate capability. Nevertheless, the narrowed ion diffusion pathway increases the resistance for ion diffusion. The rate capability, volumetric capacity, and materials utilization are thus predominantly restricted by the microstructures of the electrode, providing fundamental insights into electrode microstructure design for different applications. As an example, an optimized TiNb2O7 electrode with compaction density of ≈2.5 g cm‐3 and mass loading of ≈8.5 mg cm‐2 provides the highest specific charge capacity of 271.3 mAh g‐1 at 0.2 C in half cell configuration and 70.4% capacity retention at 6 C in full configuration, enabling balanced energy density and power density of batteries. [ABSTRACT FROM AUTHOR]