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In this study, a straightforward, eco-friendly strategy for the phase modulation of MoS2 in 2D materials was developed for green-solvent-phase co-exfoliation and subsequent solvent-free drying/annealing processes, yielding binary-metal oxide nanoparticulate-decorated heterolayered 2D nanohybrids. As a green solvent, ethanol with poly(N-vinyl-2-pyrrolidone) provided an effective surface tension for liquid-phase exfoliation of the 2D materials (MoS2 and graphene). Electron injection of binary metal oxides (NiFe2O4) and graphene functional groups to the Mo 4d orbital played an important role in the modulating phase conversion of semiconductive MoS2 to metallic MoS2 in the nanohybrids. Moreover, the introduction of MoS2 and graphene tuned the diameter (∼6 nm) and effective crystalline domains of the NiFe2O4 nanoparticles in the resulting nanohybrid. The electrocatalytic activity of the nanohybrids exhibited outstanding performance in the hydrogen and oxygen evolution reactions due to the synergetic effects of the modified MoS2/graphene/NiFe2O4 components. Density functional theory calculations and the Tafel slope indicated that the combination of 1T-MoS2/graphene/NiFe2O4 nanohybrids achieved a lower activation barrier at the first hydrogen absorption step and the RDS for the interaction of adsorbed oxygen atoms with hydroxide in the hydrogen and oxygen evolution reactions. The nanohybrids were prepared as symmetric electrodes to assemble an environmentally-benign hydrogel cell for water-splitting systems, exhibiting excellent stability in deswelling–swelling cycles. We believe that the proposed process allows for phase-modulating 2D materials while alleviating the negative impact on the environment, creating desirable functionality for various catalytic applications. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs), owing to their superior electrical and mechanical properties, are a promising alternative to nonmetallic electrically conducting materials. In practice, cellulose as a low-cost sustainable matrix has been used to prepare the aqueous dispersion of cellulose-CNT (C-CNT) nanocomposites. However, the compatibility with conventional solution-processing and structural rearrangement for improving conductivity has yet to be determined. Herein, a straightforward route to prepare a conductive composite material from single-walled CNTs (SWCNTs) and natural pulp is reported. High-power shaking realizes the self-alignment of individual SWCNTs in a cellulose matrix, resulting from the structural change in molecular orientations owing to countless collisions of zirconia beads in the aqueous mixture. The structural analysis of the dried C-CNT films confirms that the entanglement and dispersion of C-CNT nanowires determine the mechanical and electrical properties. Moreover, the rheological behavior of C-CNT inks explains their coating and printing characteristics. By controlling shaking time, the electrical conductivity of the C-CNT films with only 9 wt.% of SWCNTs from 0.9 to 102.4 S cm -1 are adjusted. the optimized C-CNT ink is highly compatible with the conventional coating and printing processes on diverse substrates, thus finding potential applications in eco-friendly, highly flexible, and stretchable electrodes is also demonstrated., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The functionalization of nanocarbon materials such as graphene has attracted considerable attention over the past decades. In this work, we designed and synthesized a unique N-heterocyclic carbene compound with a pyrene tail group (NHCp) to investigate how carbene species can be used for the functionalization of graphene. Although the carbene moiety of NHCp has the ability to covalently bond to graphene, the pyrene tail can noncovalently interact with graphene and allows monitoring its surrounding microenvironment. The major characteristics of the resulting nanohybrids were highly dependent on the type of graphene and the NHCp-to-graphene weight ratio. Importantly, despite the covalent functionalization of graphene, an anomalous decrease in the intensity of the Raman D peak and improved conductivity were observed for the nanohybrids. It was found that the covalent bond of NHCp to the graphene edge may allow the hybridization of their orbitals, which affects electronic energy levels and alters the double resonance process that originates the D peak at the edge defect. Importantly, the NHCp compound can act as a π acceptor (not just as a σ donor) via the NHCp-graphene covalent bridge. This is the first report showing that the concept of π-backdonation can be realized in two-dimensional materials, such as graphene, and rationally designed carbene molecules can functionalize graphene without losing their beneficial sp2 hybridization characteristics.