Scheme 1. Schematic of the synthesis of graphitic-shell-coated Pt catalysts through in situ ligand carbonization.

This contribution describes the self-assembly of colloidal nanodumbbells (NDs) with tunable shapes within cylindrical channels. We present that the intrinsic concave geometry of NDs endows them with peculiar packing and interlocking behaviors, which, in conjunction with the adjustable confinement constraint, leads to a variety of superstructures such as tilted-ladder chains and crossed-chain superlattices. A mechanistic investigation, corroborated by geometric calculations, reveals that the phase behavior of NDs under strong confinement can be rationalized by the entropy-driven maximization of the packing efficiency. Based on the experimental results, an empirical phase diagram is generated, which could provide general guidance in the design of intended superstructures from NDs. This study provides essential insight into how the interplay between the particle shape and confinement conditions can be exploited to direct the orientationally ordered assembly of concave nanoparticles into unusual superlattices.

The lifespan of proton‐exchange membrane fuel cells heavily relies on the durability of the carbon support of cathode catalysts. However, commercial carbon supports like ketjenblack (KB) and Vulcan carbon (VC) face the challenge of balancing porosity, surface area, and electrochemical stability. To address this issue, a 3D porous wrinkled graphitic carbon (PWGC) is designed and synthesized using a catalyst‐free, plasma‐enhanced chemical vapor deposition approach. The resulting PWGC possesses a hierarchically porous structure with a high surface area, a high degree of graphitization, and exceptional corrosion resistance. As a result, the Pt/PWGC catalysts with the use of PWGC as the carbon support demonstrate superior high potential stability compared to those made with KB and VC as the carbon support. Additionally, a sacrificial layer strategy is introduced to further reduce PWGC corrosion, resulting in Pt@C/PWGC catalysts that show significantly improved durability in membrane electrode assembly tests. After 5K voltage cycles from 1.0 to 1.5 V, the retention of electrochemically active surface area approaches 56.8%, surpassing the 23.6% retention of commercial Pt/C catalysts tested under the same conditions.

Two-dimensional (2D) covalent organic polymers (COPs) featuring large surface areas and exposed active sites are desirable in the modification of electrode materials for electrochemical reactions. However, the rigid and planar conformation of 2D COPs limits the wrap of one-dimensional electrodes. Herein, we have proposed a molecular strategy to regulate in situ encapsulation of carbon nanotubes (CNTs) with 2D polyphosphazene. The stoichiometric control over the nucleophilic substitution reaction between hexachlorocyclophosphazene and amines allows for the oriented evolution around the surface of CNTs. The formed COP sheath is an ultrathin and uniform coating without granular deposition. Upon carbonization, the well-defined core/shell CNT composite was converted into the N,P-codoped carbon, exhibiting outstanding electrocatalytic oxygen reduction performance with a diffusion-limiting current density of 5.4 mA cm–2 and an electron transfer number of 3.97. The improved electrocatalytic activity originates from a high content of active N,P-containing catalytic sites uniformly distributed on porous carbon. This study provides a viable strategy to develop functional composite materials by modulating the flexibility of 2D COPs for 1D substrates, contributing to broad applicability.

Monodisperse nanoparticles have attracted great attention in fundamental and applied research. Current protocols for the synthesis of monodisperse nanoparticles typically involve hydrocarbon molecules as surface-capping ligands. Utilizing platinum (Pt)-based nanoparticles for the oxygen reduction reaction (ORR), however, hydrocarbon ligands must be removed in order to expose the surface sites. Here, highly active and durable Pt catalysts are realized without removing the ligands; instead, the native surface ligands are directly converted into uniform, bilayered graphitic shells conformally coated on individual Pt nanoparticles by simple thermal annealing. Strikingly, the annealing temperature is found to be a critical factor dictating the ORR performance of Pt catalysts. Pt nanoparticles thermally treated at 500 oC show a very poor ORR activity, whereas those annealed at 700 oC become highly active along with exceptional stability. In-depth characterization reveals that thermal treatment from 500 to 700 oC triggers the subtle structural reconstruction of carbon shells through graphitization, gradually opening up the porosity without affecting the carbon shell thickness. Additionally, the ligand-derived graphitic shells can effectively prevent Pt nanoparticles from detachment, agglomeration, and dissolution while largely maintaining the accessibility of surface sites. As a result, such graphitic-shell-coated Pt catalysts can exhibit superior long-term stability, largely retaining the activity after 20,000 accelerated durability test cycles in a membrane electrode assembly. Moreover, this ligand carbonization strategy is amenable to Pt-based alloy nanoparticles and can further be extended to modify commercial Pt/C catalysts with substantially enhanced durability. Our work shows that boosting the ORR performance of common Pt nanoparticles is certainly possible by harnessing the native surface ligands, thus offering a robust approach of designing highly durable catalysts for proton-exchange membrane fuel cells.