Zeolitic‐imidazolate‐frameworks‐8 (ZIF‐8) derivatives have recently been demonstrated as one of the most ideal precursors to prepare single‐atom metal catalysts for oxygen reduction reaction (ORR). However, abundant single‐atom metal sites are buried in the derived carbon nanoparticles, rendering them useless for ORR. Here a novel ZIF‐8 “thermal melting” strategy is proposed to prepare a high specific surface area of Fe‐N‐doped graphene nanosheets (Fe‐N/GNs) with single‐atom Fe‐sites on the surface which are accessible to electrolytes, optimizing their utilization and improving ORR activity. As a result, the Fe‐N/GNs material exhibits excellent ORR activity with half‐wave potentials of 0.903 V in alkaline media and 0.837 V in acidic media, which are comparable to commercial Pt/C catalysts.

Hydrogel electronics have attracted growing interest for emerging applications in personal healthcare management, human‐machine interaction, etc. Herein, a “doping then gelling” strategy to synthesize supramolecular PANI/PAA hydrogel with a specific strand entangled network is proposed, by doping the PANI with acrylic acid (AA) monomers to avoid PANI aggregation. The high‐density electrostatic interaction between PAA and PANI chains serves as a dynamic bond to initiate the strand entanglement, enabling PAA/PANI hydrogel with ultra‐stretchability (2830%), high breaking strength (120 kPa), and rapid self‐healing properties. Moreover, the PAA/PANI hydrogel‐based sensor with a high strain sensitivity (gauge factor = 12.63), a rapid responding time (222 ms), and a robust conductivity‐based sensing behavior under cyclic stretching is developed. A set of strain sensing applications to precisely monitor human movements is also demonstrated, indicating a promising application prospect as wearable devices.

High internal phase emulsion (HIPE) technique has been of great interest for fabrication of polymer foams with controlled porous structures. However, for fluoropolymers, it has been a challenge to fabricate high-performance foams with controllable porous structures by HIPE due to the lack of suitable surfactant. Here, for the first time, a new type of cationic fluorosurfactant (CFS) is proposed to address this issue. The cationic fluorosurfactant is a diblock copolymer, Poly(2-dimethylamino)ethyl methacrylate-b-Poly(hexafluorobutyl acrylate) (PDMAEMA-b-PHFBA) synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization. For the prepared fluoro-diblock copolymer having similar fluorosegments to fluoro-monomer, this cationic fluorosurfactant can effectively stabilize high internal phase

Hydrogels have been attracting increasing attention in wearable electronics, due to their intrinsic biomimetic features, highly tunable chemical-physical properties (mechanical, electrical, etc), and excellent biocompatibility. Among many proposed varieties, conductive...

No abstract