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Abstract Considering their simplicity, processibility, and tunable rheological properties, polymer composite‐type precursors hold exceptional promise in the processing of polymers, ceramics, metals, and their composites. This large variety of precursors used in many different applications cover a large compositional space with dramatically varying rheological properties. Understanding how precursor composition influences their rheological properties is a key need towards streamlining the design and implementation of these precursors. With regard to this design advancement, this study elucidates the composition‐rheology relationships of graphene‐poly(ethylene) oxide (PEO) composite inks as a sample polymer composite‐type precursor. To this end, shear and extensional rheology of numerous compositions were studied across a wide compositional space, which varied graphene concentration, total solid concentration, and binder molecular weight. These studies showed that composition greatly affected various rheological parameters, such as the overall presence of yielding behavior. Specifically, this study illustrated the influence of (i) binder structure, (ii) total solid loading, and (iii) binder‐filler interactions on ink rheology. Extensional rheology was studied to examine how relaxation behaviors were dependent on composition and explicate how relaxation behaviors coincide with responses to shear forces. In tandem, our results illuminate significant composition‐rheology relationships in polymer composite‐type precursors. HighlightsRheology of polyethylene oxide‐graphene composite precursors were studied.Shear and extensional rheology, and their correlations were investigated.Composition‐binder molecular weight‐yielding relationships were elucidated.Extensional relaxation regimes were identified with respect to composition.Results can be used to determine compositional ranges for different processes. 

To address a long‐existing debate on what copper species are responsible for efficient CC coupling, especially ethanol formation, in electrochemical CO₂reduction reaction, herein, a comprehensive study using Cu₃N nanocubes with a uniform size and shape, alongside a single crystalline phase is reported. The Cu₃N nanoensemble electrode has a remarkable Faradaic efficiency (FE) of 64% for ethanol production at a relatively low potential of −0.6 V versus reversible hydrogen electrode. Throughin‐operandoX‐ray absorption spectroscopy study, a dynamic phase evolution that directly correlates with changes in FE across varying applied potentials is observed. Notably, the nanoensemble with a composition of ≈71% Cu⁺and 29% Cu⁰is identified as being selective for ethanol formation at the low overpotential. Conversely, a predominantly metallic Cu phase formed at potentials more negative than −0.6 V favors the hydrogen evolution reaction. Density functional theory calculations at the Cu₃N–Cu interface substantiate that the coexistence of Cu⁰–Cu⁺not only energetically favors the ethanol reaction pathway but also destabilizes the intermediates for ethylene pathway. 

Abstract Fe–N–C single‐atom catalysts (SACs) exhibit excellent peroxidase (POD)‐like catalytic activity, owing to their well‐defined isolated iron active sites on the carbon substrate, which effectively mimic the structure of natural peroxidase's active center. To further meet the requirements of diverse biosensing applications, SAC POD‐like activity still needs to be continuously enhanced. Herein, a phosphorus (P) heteroatom is introduced to boost the POD‐like activity of Fe–N–C SACs. A 1D carbon nanowire (FeNCP/NW) catalyst with enriched Fe–N₄active sites is designed and synthesized, and P atoms are doped in the carbon matrix to affect the Fe center through long‐range interaction. The experimental results show that the P‐doping process can boost the POD‐like activity more than the non‐P‐doped one, with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can greatly enhance POD‐like activity initially, but its effect becomes insignificant with increasing amount of P. As a proof of concept, FeNCP/NW is employed in an enzyme cascade platform for highly sensitive colorimetric detection of the neurotransmitter acetylcholine.