The development of new catalysts with high selectivity and efficiency for the electrocatalytic nitrate reduction reaction (NtRR) to produce ammonia (NH
) at room temperature and ambient pressure is ...still a challenge. Herein, we report a simple
growth method for the controlled synthesis of a GDY-MnO
heterointerface by selectively anchoring and growing MnO
on GDY surfaces. Experimental results show that the incomplete charge-transfer between GDY and Mn atoms at the interface structures largely increases the number of active sites, improves the electrical conductivity, and therefore results in excellent electrocatalytic performance for NH
synthesis with a maximum FE of 95.4%, an NH
yield rate of 463.4 μmol h
cm
and high long-term stability in 0.1 M KOH + 0.1 M NO
aqueous electrolytes at room temperature and ambient pressure.
Hierarchical organization plays an important role in the stunning physical properties of natural and synthetic composites. Limits on the physical properties of such composites are generally defined ...by percolation theory and can be systematically altered using the volumetric filler fraction of the inorganic/organic phase. In natural composites, organic materials such as proteins that interact with inorganic filler materials can further alter the hierarchical order and organization of the composite
topological interactions, expanding the limits of the physical properties defined by percolation theory. However, existing polymer systems do not offer a topological parameter that can systematically modulate the assembly characteristics of composites. Here, we present a composite based on proteins and titanium carbide (Ti
C
T
) MXene that manifests a topological network that regulates the organization, and hence physical properties, of these biomimetic composites. We designed, recombinantly expressed, and purified synthetic proteins consisting of polypeptides with repeating amino acid sequences (tandem repeats) that have the ability to self-assemble into topologically networked biomaterials. We demonstrated that the interlayer distance between MXene sheets can be controlled systematically by the number of tandem repeat units. We varied the filler fraction and number of tandem repeat units to regulate the in-plane and out-of-plane electrical conductivities of these composites. Once Ti
C
T
MXene sheets are separated enough to facilitate formation of cross-links in our proteins with the number of tandem repeat units reaching 11, the linear
characteristics of the composites switched into nonlinear
curves with a distinct hysteresis for out-of-plane electron transport, while the in-plane
characteristics remained linear. This highlights the impact of synthetic protein templates, which can be designed to modulate electronic transport in composites both isotropically and anisotropically.
Exploration of high-performance aqueous ammonium-ions hybrid supercapacitor has attracted tremendous research attention recently. Herein, structural reconstructed cobalt-iron layered double ...hydroxides (SR-CoFe LDHs) featuring copious structure defects (i. e., oxygen-vacancies, M-O bonds, MOO
bonds, coexistence of Co
/Co
and Fe
/Fe
) are reported as a high-capacity cathode for NH
storage. The resulting SR-CoFe LDHs can deliver a reversible capacity of 167.9 mAh g
at 0.5 A g
, which is 3.3 folds higher than that of pristine CoFe-LDHs. Ex-situ experimental results and theoretical studies denote that the presence of structural defects in the CoFe-LDHs can lower the NH
adsorption energy and induced electron delocalization to enhance the electrical conductivity, rendering the CoFe-LDHs exhibits excellent performance for NH
storage. As a proof of concept, ammonium-ion hybrid supercapacitor has been assembled with CoFe-LDHs as the cathode and hierarchical carbon as the anode, which can deliver a large specific capacitance of 238.3 F g
, long cycle stability over 10000 cycles, and high energy density of 66.2 Wh kg
within a wide working voltage of 2 V. Overall, this work offers some insights into the design of high capacity cathode for aqueous NH
storage and also illustrates the construction of aqueous hybrid devices with NH
as the charge carrier.
Hydrogen transport in solids, applied in electrochemical devices such as fuel cells and electrolysis cells, is key to sustainable energy societies. Although using proton (H
) conductors is an ...attractive choice, practical conductivity at intermediate temperatures (200-400 °C), which would be ideal for most energy and chemical conversion applications, remains a challenge. Alternatively, hydride ions (H
), that is, monovalent anions with high polarizability, can be considered a promising charge carrier that facilitates fast ionic conduction in solids. Here, we report a K
NiF
-type Ba-Li oxyhydride with an appreciable amount of hydrogen vacancies that presents long-range order at room temperature. Increasing the temperature results in the disappearance of the vacancy ordering, triggering a high and essentially temperature-independent H
conductivity of more than 0.01 S cm
above 315 °C. Such a remarkable H
conducting nature at intermediate temperatures is anticipated to be important for energy and chemical conversion devices.
MXene-based structural materials with high mechanical robustness and excellent electrical conductivity are highly desirable for multifunctional applications. The incorporation of macromolecular ...polymers has been verified to be beneficial to alleviate the mechanical brittleness of pristine MXene films. However, the intercalation of a large amount of insulating macromolecules inevitably compromises their electrical conductivity. Inspired by wood, short-chained hemicellulose (xylo-oligosaccharide) acts as a molecular binder to bind adjacent MXene nanosheets together; this work shows that this can significantly enhance the mechanical properties without introducing a large number of insulating phases. As a result, MXene–hemicellulose films can integrate a high electrical conductivity (64,300 S m–1) and a high mechanical strength (125 MPa) simultaneously, making them capable of being high-performance electrode materials for supercapacitors and humidity sensors. This work proposes an alternative method to manufacture robust MXene-based structural materials for multifunctional applications.
The rapid development of consumer electronics, artificial intelligence, and clinical medicine generates an increasing demand for flexible pressure sensors, whose performance depends significantly on ...sensitive materials with high flexibility and proper conductivity. MXene, a type of 2D nanomaterial, has attracted extensive attention due to its good electrical conductivity, hydrophilicity, and flexibility. The synthesis methods for MXenes make it relatively easy to control their microstructure and surface termination groups. Hence, MXenes can obtain peculiar microstructures and facilely combine with other functional materials, making them promising prospects for use in flexible pressure sensors. In this Review, recent advances in MXenes are summarized, mainly focusing on the synthesis methods and their application in flexible pressure sensors. Finally, the challenges and potential solutions for future development are also discussed.
Topological materials Yan, Binghai; Zhang, Shou-Cheng
Reports on progress in physics,
09/2012, Letnik:
75, Številka:
9
Journal Article
Recenzirano
Recently, topological insulator materials have been theoretically predicted and experimentally observed in both 2D and 3D systems. We first review the basic models and physical properties of ...topological insulators, using HgTe and Bi(2)Se(3) as prime examples. We then give a comprehensive survey of topological insulators which have been predicted so far, and discuss the current experimental status.
Expanding the toolbox of the biology and electronics mutual conjunction is a primary aim of bioelectronics. The organic electrochemical transistor (OECT) has undeniably become a predominant device ...for mixed conduction materials, offering impressive transconduction properties alongside a relatively simple device architecture. In this review, we focus on the discussion of recent material developments in the area of mixed conductors for bioelectronic applications by means of thorough structure–property investigation and analysis of current challenges. Fundamental operation principles of the OECT are revisited, and characterization methods are highlighted. Current bioelectronic applications of organic mixed ionic–electronic conductors (OMIECs) are underlined. Challenges in the performance and operational stability of OECT channel materials as well as potential strategies for mitigating them, are discussed. This is further expanded to sketch a synopsis of the history of mixed conduction materials for both p- and n-type channel operation, detailing the synthetic challenges and milestones which have been overcome to frequently produce higher performing OECT devices. The cumulative work of multiple research groups is summarized, and synthetic design strategies are extracted to present a series of design principles that can be utilized to drive figure-of-merit performance values even further for future OMIEC materials.
Artificial ion channels with ion permeability and selectivity comparable to their biological counterparts are highly desired for efficient separation, biosensing, and energy conversion technologies. ...In the past two decades, both nanoscale and sub-nanoscale ion channels have been successfully fabricated to mimic biological ion channels. Although nanoscale ion channels have achieved intelligent gating and rectification properties, they cannot realize high ion selectivity, especially single-ion selectivity. Artificial angstrom-sized ion channels with narrow pore sizes <1 nm and well-defined pore structures mimicking biological channels have accomplished high ion conductivity and single-ion selectivity. This review comprehensively summarizes the research progress in the rational design and synthesis of artificial subnanometer-sized ion channels with zero-dimensional to three-dimensional pore structures. Then we discuss cation/anion, mono-/di-valent cation, mono-/di-valent anion, and single-ion selectivities of the synthetic ion channels and highlight their potential applications in high-efficiency ion separation, energy conversion, and biological therapeutics. The gaps of single-ion selectivity between artificial and natural channels and the connections between ion selectivity and permeability of synthetic ion channels are covered. Finally, the challenges that need to be addressed in this research field and the perspective of angstrom-scale ion channels are discussed.
This review summarizes angstrom-scale ion channels with 0D-3D pore structures and their charge, mono/divalent, and single-ion selectivities and potential applications.
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