Polyhedral Carbon Anchored on Carbon Nanosheet with Abundant Atomic Fe-Nx Moieties for Oxygen Reduction

Carbon-based single-atom iron electrocatalysts with nitrogen coordination (CSAIN) have recently shown enormous promise to replace the costly Pt for boosting the cathodic oxygen reduction reaction (ORR) in fuel cells. However, there remains a great challenge to achieve highly efficient CSAIN catalysts for the ORR in acidic electrolytes. Herein, a novel CSAIN catalyst is synthesized by pyrolyzing a precursor mixture consisting of metal–organic framework and conductive polymer hybrid. After pyrolysis at a high temperature, the CSAIN with a structure of carbon nanosheet supported polyhedral carbon is achieved, where the unique structure endows CSAIN with expediting electron transfer and mass transport, as well as largely exposed surface to host atomically dispersed iron active sites. As a result, the optimal CSAIN catalyst shows a high ORR activity with its half-wave potential of 0.77 V (vs RHE) and a Tafel slope of 74.1 mV dec–1, which are comparable to that of commercial Pt/C catalyst (0.80 V and 81.9 mV dec–1)

Conductive polymer based hydrogels and their application in wearable sensors: a review

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 polymer-based hydrogels (CPHs) have emerged as a promising candidate for future wearable sensor designs, with a capability of realizing desired features using different tuning strategies ranging from molecular design (with a low lengthscale of 10-10 m) to micro-structural configuration (up to a lengthscale of 10-2 m). However, considerable challenges remain to be overcome, such as the limited strain sensing range due to the mechanical strength, the signal loss/instability caused by swelling/deswelling, the significant hysteresis of sensing signal, the de-hydration induced malfunctions, the surface/interfacial failure during manufacturing/processing, etc. This review aims to offer a targeted scan of recent advancements in CPH based wearable sensor technology, from the establishment of dedicated structure-property relationships in the lab to the advanced manufacturing routes for potential scale-up production. The application of CPHs in wearable sensors is also explored, with suggested new research avenues and prospects for CPHs in the future also included.Abstract text goes here

Porous multifunctional fluoropolymer composite foams prepared via humic acid modified Fe3O4 nanoparticles stabilized Pickering high internal phase emulsion using cationic fluorosurfactant as co-stabilizer

Fluoropolymers are very important owing to their excellent application performances, especially in extreme conditions. On the other hand, the preparation of porous fluoropolymers is a difficult task due to unavailability of suitable surfactants as well as tedious synthesis steps. Here we prepared multifunctional porous fluoropolymer composite foams with a simple process of “high internal phase emulsion (HIPE)” by using humic acid modified iron oxide nanoparticles (HA-Fe3O4 NPs) and cationic fluorosurfactant (CFS) (PDMAEMA-b-PHFBA) as co-stabilizer. The inclusion of HA-Fe3O4 NPs in the system made fluoro-HIPE more stable than the emulsion prepared using only CFS or other conventional stabilizers. Morphology of the prepared polyHIPE was easily controlled by altering the concentration of HA-Fe3O4 and/or CFS in the original formulation. Adjustment of the porous structure with open/close cells was performed and the average diameter of the pores tuned between 4.9 and 23 μm. With the increase in specific surface area by using nanoparticles (NPs) and CFS as co-surfactants, Pickering HIPE monoliths adsorbed double amount of oil compared to foams based solely on HIPE template. Multiple functional groups were bound onto Fe3O4 NPs through HA modification that made the fluoro-monolith capable of adsorbing dye, i.e. methylene blue, from water. A simple centrifugation enabled regeneration of the oil soaked foams and adsorption capacity was not decreased after 10 adsorption/regeneration cycles. Keywords: HIPE, Co-stabilization, Fluoropolymer, Adsorption, Hydrophobic, Functional porous polyme

A Strand Entangled Supramolecular PANI/PAA Hydrogel enabled Ultra-stretchable Strain Sensor

Hydrogel electronics have attracted growing interests for the emerging applications in personal healthcare management, human-machine interaction, etc. Herein, we propose a novel ‘doping then gelling’ strategy to synthesize supramolecular PANI/PAA hydrogel with a specific strand entangled network, by doping the PANI with acrylic acid (AA) monomers to avoid the PANI aggregation. The high-density electrostatic interaction between PAA and PANI chains serve as 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, we develop 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. We also demonstrate a set of strain sensing applications to precisely monitor human movements, indicating a promising application prospect as wearable devices