Applying electrochemical nitrate reduction reaction (NO3RR) to produce ammonia offers a sustainable alternative to the energy-intensive Haber-Bosch process, which is crucial for clean energy and agricultural applications. While 2D MXenes hold great promise as electrocatalysts for NO3RR, their application for ammonia production remains underexplored. This study combines experimental and theoretical approaches to evaluate the catalytic performance of a series of MXenes with different central metal atoms for NO3RR. Among the materials studied (Ti3C2Tx, Ti3CNTx, Ti2CTx, V2CTx, Cr2CTx, Nb2CTx, and Ta2CTx), Ti3-based MXenes exhibit superior faradaic efficiency, ammonia yield rate, and stability. Density functional theory calculations offer further insights explaining the structure-activity-based observations. This research establishes a foundation for future studies aimed at leveraging MXenes for electrochemical nitrate reduction for green synthesis of ammonia.

• Klíčová slova
• 2D materials, catalysis, electrochemistry,
• Publikační typ
• časopisecké články MeSH

The selective reduction of molecular oxygen to superoxide is one of the key reactions in electrochemistry and photocatalysis. Here the effect of Pt co-catalysts, dispersed on titania, either as single atoms or as nanoparticles, on the photocatalytic superoxide (•O2 -) formation in O2 containing solutions is investigated. The •O2 - formation is traced by nitroblue tetrazolium (NBT) assays and in detail by EPR measurements using TEMPO as •O2 - radical scavenger. The results show that the photocatalytic formation rate of •O2 - on titania can strongly be enhanced by using Pt single atoms as a co-catalyst, whereas Pt nanoparticles hardly exhibit any accelerating effect. This finding is of considerable significance regarding photocatalytic degradation and photocatalytic oxidative synthesis processes.

• Klíčová slova
• Pt single atoms, degradation, photocatalysis, superoxide, titanium dioxide,
• Publikační typ
• časopisecké články MeSH

Soft robots have demonstrated exceptional potential in various applications, particularly in biomedicine, which is attributed to their motional agility and machinability. However, their potential applications in water remediation have not been fully explored. The main challenge is to achieve both precise motion and efficient pollutant degradation. Herein, a modular design is reported for fabricating soft robots. These robots are designed with spatially separated components. One is superparamagnetic iron oxide nanoparticles for magnetic actuation and the other is photocatalysts for targeted pollutant degradation (i.e., methyl orange, congo red, rhodamine B, tetracycline, and soybean oil). The helical structure enables diverse programmable motional modes, including high-speed propulsion up to 3.54 mm s-1. At the same time, the photocatalytic module enables efficient degradation of multiple pollutants with excellent reusability. The modular design combines structural stability with multifunctionality and opens new opportunities for soft robots in environmental remediation.

• Klíčová slova
• dual‐component, finite element simulation, magnetic manipulation, soft robot, water remediation,
• Publikační typ
• časopisecké články MeSH

2D materials have rapidly gained attention due to their exceptional properties like high surface area, flexibility, and tunable electronic characteristics. These attributes make them highly versatile for applications in energy storage, electronics, and biomedicine. Inspired by graphene's success, researchers are exploring other 2D materials from bulk crystals. Electrochemical exfoliation (ECE) is an efficient method for producing these materials, offering more sustainable mild conditions, quick processing, simple equipment, and high yields. While substantial progress has been made in the ECE of layered van der Waals (L-vdW) crystals, the exploration of layered non-van der Waals (L-NvdW) materials remains in its early stages. This review delves into using ECE to create 2D nanoplatelets from L-NvdW crystals. A comparative analysis of exfoliation techniques is provided for L-vdW and L-NvdW materials, followed by a comprehensive overview of recent advances in ECE methods applied to L-NvdW crystals. The discussion is organized around key categories, including the selective extraction of "M" and "A" layers respectively from MAX phases, decalcification of Zintl phases, and oxide delocalization from metal oxides. It is concluded by highlighting the potential applications of these 2D materials and discussing the challenges and future directions in this evolving field.

• Klíčová slova
• 2D materials, delocalization, electrochemical exfoliation, layered non‐van der Waals,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Spatially separated palladium nanocubes (Pd NCs) terminated by {100} facets are synthesized using direct micelles approach. The stepwise seed-mediated growth of Pd NCs is applied for the first time. The resulting Pd NCs are thoroughly characterized by HR-TEM, XPS, Raman, ATR-FTIR, TGA, and STEM-EDX spectroscopies. Some traces of residual stabilizer (polyvinylpyrrolidone, PVP) attached to the vertices of Pd NCs are identified after the necessary separation-washing procedure, however, it is vital to avoid aggregation of the NCs. Pd NCs are subsequently and uniformly loaded on Vulcan carbon (≈20 wt.%) for the electrochemical hydrogen cycling. By post-mortem characterizations, it is revealed that their shape and size remained very stable after all electrochemical experiments. However, a strong effect of the NCs size on their hydrogen interaction is revealed. Hydrogen absorption capacity, measured as the H:Pd ratio, ranges from 0.28 to 0.48, while hydrogen evolution and oxidation reactions (HER and HOR) kinetics decrease from 15.5 to 4.6 mA.mg Pd -1 between ≈15 and 34 nm of Pd NCs, respectively. Theoretical calculations further reveal that adsorption of H atoms and their penetration into the Pd lattice tailors the NCs electronic structure, which in turn controls the kinetics of HER, experimentally observed by the electrochemical tests. This work may pave the way to the design of highly active electrocatalysts for efficient HER stable for a long reactive time. In particular, obtained results might be transferred to active Pd-alloy-based NCs terminated by {100} facets.

• Klíčová slova
• colloidal synthesis, hydrogen adsorption, nanocubes, palladium, reaction mechanism, surface analysis,
• Publikační typ
• časopisecké články MeSH

Many printed electronic applications require strain-independent electrical properties to ensure deformation-independent performance. Thus, developing printed, flexible devices using 2D and other nanomaterials will require an understanding of the effect of strain on the electrical properties of nano-networks. Here, novel AC electrical techniques are introduced to fully characterize the effect of strain on the resistance of high-mobility printed networks, fabricated from of electrochemically exfoliated MoS2 nanosheets. These devices are initially characterized using DC piezoresistance measurements and show good cyclability and a linear strain response, consistent with a low gauge factor of G ≈ 3. However, AC impedance spectroscopy measurements, performed as a function of strain, allow the measurement of the effects of strain on both the nanosheets and the inter-nanosheet junctions separately. The junction resistance is found to increase linearly with strain, while the nanosheet resistance remains constant. This response is consistent with strain-induced sliding of the highly-aligned nanosheets past one another, without any strain being transferred to the sheets themselves. The approach allows for the individual estimation of the contributions of dimensional factors (G ≈ 1.4) and material factors (G ≈ 1.9) to the total gauge factor. This novel technique may provide insights into other piezoresistive systems.

• Klíčová slova
• impedance spectroscopy, junction resistance, nanosheet network, straining,
• Publikační typ
• časopisecké články MeSH

Light-induced water splitting (hν-WS) for the production of hydrogen as a solar fuel is considered a promising sustainable strategy for the replacement of fossil fuels. An efficient system for hν-WS involves a photoactive material that, upon shining light, is capable of separating and transferring charges to catalysts for the hydrogen and oxygen evolution processes. Covalent triazine-based frameworks (CTFs) represent an interesting class of 2D organic light-absorbing materials that have recently emerged thanks to their tunable structural, optical and morphological properties. Typically, catalysts (Cat) are metallic nanoparticles generated in situ after photoelectroreduction of metal precursors or directly drop-casted on top of the CTF material to generate Cat-CTF assemblies. In this work, the synthesis, characterization and photocatalytic performance of a novel hybrid material, Ru-CTF, is reported, based on a CTF structure featuring dangling pyridyl groups that allow the Ru-tda (tda is [2,2':6',2'"-terpyridine]-6,6'"-dicarboxylic acid) water oxidation catalyst (WOC) unit to coordinate via covalent bond. The Ru-CTF molecular hybrid material can carry out the light-induced water oxidation reaction efficiently at neutral pH, reaching values of maximum TOF of 17 h-1 and TONs in the range of 220 using sodium persulfate as a sacrificial electron acceptor.

• Klíčová slova
• covalent triazine frameworks, hybrid molecular materials, molecular catalyst, redox catalysis, solar fuels, water oxidation,
• Publikační typ
• časopisecké články MeSH

Noble gases, notably xenon, play a pivotal role in diverse high-tech applications. However, manufacturing xenon is an inherently challenging task, due to its unique properties and trace abundance in the Earth's atmosphere. Consequently, there is a pressing need for the development of efficient methods for the separation of noble gases. Using mild fluorographene chemistry, nitrogen-doped graphene (GNs) materials are synthesized with abundant aromatic regions and extensive nitrogen doping within the vacancies and holes of the aromatic lattice. Due to the organized interlayer "nanochannels", nitrogen functional groups, and defects within the two-dimensional (2D) structures, GNs exhibits effective selectivity for Xe over Kr at low pressure. This enhanced selectivity is attributed to the stronger binding affinity of Xe to GN compared to Kr. The adsorption is governed by London dispersion forces, as revealed by theoretical calculations using symmetry-adapted perturbation theory (SAPT). Investigation of other GNs differing in nitrogen content, surface area, and pore sizes underscores the significance of nitrogen functional groups, defects, and interlayer nanochannels over the surface area in achieving superior selectivity. This work offers a new perspective on the design and fabrication of functionalized graphene derivatives, exhibiting superior noble gas storage and separation activity exploitable in gas production technologies.

• Klíčová slova
• 2D materials, defect engineering, noble gas separation, selectivity, symmetry‐adapted perturbation theory (SAPT), xenon,
• Publikační typ
• časopisecké články MeSH

Flexible power supply devices present significant potential for wearable bioelectronics within the Internet of Things. Aqueous zinc-ion batteries have emerged as a viable and safe alternative for power supply in flexible electronics. Nevertheless, typical battery behaviors are generally detrimental with unfavorable phase transition of electrodes, which invariably lead to rapid performance degradation. Here, extraordinary capacity enhancement of 150% is presented, sustained over 60 000 cycles, attained using vanadium carbide MXene (V2C)/vanadium pentoxide (V2O5) heterostructure as cathode. The unique cathode material is created through the rational engineering of MAX (V2AlC), employing a single-step laser writing process. The ultrastable Zn ion battery stands in stark contrast to all previously reported counterparts, which typically exhibit capacity degradation within a few hundred/thousand cycles. The primary mechanisms driving this enhancement include the delamination of V2C MXene and an unexpected favorable phase transition during cycling. Additionally, a wearable power supply is constructed using a series configuration and is integrated with a commercial temperature sensor for wireless, real-time body temperature monitoring. This study highlights the critical role of electrode design for advanced wearable bioelectronics.

• Klíčová slova
• aqueous zinc ion battery, cyclic stability, temperature sensor, vanadium carbide, vanadium oxide, wearable bioelectronics,
• Publikační typ
• časopisecké články MeSH

The recent prediction of the new magnetic class, altermagnetism, has drawn considerable interest, fueled by its potential to host novel phenomena and to be utilized in next-generation spintronics devices. Among many promising candidates, rutile RuO2 is a prototypical candidate for realizing the prospects of altermagnetism. However, the experimental studies on RuO2 are still in the early stages. In this study, the magnetic responses in RuO2 film are investigated by the Planar Hall effect (PHE). By rotating the external field (Hext), the PHE exhibits twofold behaviors. Moreover, the planar Hall conductivity shows a nonlinear response to the Hext. These observed features in PHE resemble those in ferromagnet and topologically nontrivial systems, suggesting the field-induced magnetic response in rutile antiferromagnet. The work provides a strategy for detecting intriguing magnetic responses in altermagnetic materials, promoting further research in altermagnet-based spintronics and novel phenomena.

• Klíčová slova
• RuO2, altermagnetism, oxide thin film, spin‐orbit coupling, transport,
• Publikační typ
• časopisecké články MeSH