The exploration of novel systems for the electrochemical CO2 reduction reaction (CO2RR) for the production of hydrocarbons like CH4 remains a giant challenge. Well‐designed electrocatalysts with ...advantages like proton generation/transferring and intermediate‐fixating for efficient CO2RR are much preferred yet largely unexplored. In this work, a kind of Cu‐porphyrin‐based large‐scale (≈1.5 μm) and ultrathin nanosheet (≈5 nm) has been successfully applied in electrochemical CO2RR. It exhibits a superior FECH4
of 70 % with a high current density (−183.0 mA cm−2) at −1.6 V under rarely reported neutral conditions and maintains FECH4
>51 % over a wide potential range (−1.5 to −1.7 V) in a flow cell. The high performance can be attributed to the construction of numerous hydrogen‐bonding networks through the integration of diaminotriazine with Cu‐porphyrin, which is beneficial for proton migration and intermediate stabilization, as supported by DFT calculations. This work paves a new way in exploring hydrogen‐bonding‐based materials as efficient CO2RR catalysts.
A Cu‐porphyrin‐based large‐scale, ultrathin nanosheet with numerous hydrogen‐bonding networks was developed for the highly selective electroreduction of CO2 to CH4 under neutral conditions. This catalyst exhibits a superior FECH4
of 70 % with a high current density (−183.0 mA cm−2) at −1.6 V under rarely reported neutral conditions and maintains FECH4
>51 % over a wide potential range (−1.5 to −1.7 V) in a flow cell.
Strategies that enable simultaneous morphology‐tuning and electroreduction performance boosting are much desired for the exploration of covalent organic frameworks in efficient CO2 electroreduction. ...Herein, a kind of functionalizing exfoliation agent has been selected to simultaneously modify and exfoliate bulk COFs into functional nanosheets and investigate their CO2 electroreduction performance. The obtained nanosheets (Cu−Tph−COF−Dct) with large‐scale (≈1.0 μm) and ultrathin (≈3.8 nm) morphology enable a superior FECH4 (≈80 %) (almost doubly enhanced than bare COF) with large current‐density (−220.0 mA cm−2) at −0.9 V. The boosted performance can be ascribed to the immobilized functionalizing exfoliation agent (Dct groups) with integrated amino and triazine groups that strengthen CO2 absorption/activation, stabilize intermediates and enrich the CO concentration around the Cu active sites as revealed by DFT calculations. The point‐to‐point functionalization strategy for modularly assembling Dct‐functionalized COF catalyst for CO2 electroreduction will open up the attractive possibility of developing COFs as efficient CO2RR electrocatalysts.
A kind of functionalizing exfoliation agent has been selected to simultaneously modify and exfoliate bulk COFs into functional nanosheets and the obtained materials can be applied in highly selective CO2 electroreduction into CH4.
Glycans play important roles in all major kingdoms of organisms, such as archea, bacteria, fungi, plants, and animals. Cellulose, the most abundant polysaccharide on the Earth, plays a predominant ...role for mechanical stability in plants, and finds a plethora of applications by humans. Beyond traditional use, biomedical application of cellulose becomes feasible with advances of soluble cellulose derivatives with diverse functional moieties along the backbone and modified nanocellulose with versatile functional groups on the surface due to the native features of cellulose as both cellulose chains and supramolecular ordered domains as extractable nanocellulose. With the focus on ionic cellulose‐based compounds involving both these groups primarily for biomedical applications, a brief introduction about glycoscience and especially native biologically active glycosaminoglycans with specific biomedical application areas on humans is given, which inspires further development of bioactive compounds from glycans. Then, both polymeric cellulose derivatives and nanocellulose‐based compounds synthesized as versatile biomaterials for a large variety of biomedical applications, such as for wound dressings, controlled release, encapsulation of cells and enzymes, and tissue engineering, are separately described, regarding the diverse routes of synthesis and the established and suggested applications for these highly interesting materials.
Ionic cellulose‐based compounds as either polymeric cellulose derivatives or ionic nanocellulose have gained tremendous attention within the last years due to their remarkable properties, especially their biological properties. Recent advances about various ionic cellulose‐based compounds with diverse functional moieties either along the cellulose chains or on the surface of nanocellulose for biomedical applications are systematically summarized.
Understanding the reaction mechanism of nonaqueous oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to increase the low round-trip efficiency and power capability of ...rechargeable Li-air batteries. Here we show that the ORR kinetics are much faster than OER kinetics and OER occurs in two distinct stages upon Li-air battery charging. The first OER stage occurs at low overpotentials (<400 mV) with a slopping voltage profile, whose kinetics are relatively insensitive to charge rates and catalysts. This OER stage could be attributed to the delithiation of the outer part of Li2O2 forming lithium-deficient Li2–x O2, which is chemically disproportionate to evolve O2. The second stage takes place at high overpotentials (400–1200 mV), whose kinetics are sensitive to discharge/charge rates and catalysts, which can be attributed to the oxidation of bulk Li2O2 particles. Our study provides insights into bridging current two schools of thought on the OER mechanism.
Improving evaporation rate is extremely important to promote the application of solar steam generation in clean water production through seawater desalination. However, the theoretical evaporation ...rate limit of a normal two-dimensional (2D) photothermal evaporator is only about 1.46 kg m–2 h–1. While 3D evaporators can break the limit, they require much more raw materials. In this work, an effective approach for achieving high-yield solar steam generation via the synergy of 2D nanostructure-embedded all-in-one hybrid hydrogel evaporator and surface patterning is reported. This improved surface-patterned evaporator is able to simultaneously lower the enthalpy of vaporization and induce the Marangoni effect near the evaporation surface, thus delivering a high evaporation rate of 3.62 kg m–2 h–1, which is more than twice the theoretical limit of the normal 2D photothermal evaporator. This hybrid hydrogel offers a cost-effective and energy-efficient pathway to mitigate clean water shortages.
New BN‐heterocyclic compounds have been found to undergo double arene photoelimination, forming rare yellow fluorescent BN‐pyrenes that contain two BN units. Most significant is the discovery that ...the double arene elimination can also be driven by excitons generated electrically within electroluminescent (EL) devices, enabling the in situ solid‐state conversion of BN‐heterocycles to BN‐pyrenes and the use of BN‐pyrenes as emitters for EL devices. The in situ exciton‐driven elimination (EDE) phenomenon has also been observed for other BN‐heterocycles.
Arene elimination reactions of BN‐heterocycles (A) in an electroluminescent device result in the in situ formation of BN‐pyrenes (B) and BN‐phenanthrenes. This is a novel approach to the creation of functional EL devices.
Porous heterostructured electrocatalysts with multifunctionality and synergistic effect have much benefit for efficient electrocatalytic CO2 reduction reaction (CO2RR), yet it still remains a ...daunting challenge to explore heterostructures based on covalent organic frameworks (COFs) and metal–organic frameworks (MOFs) in this field. Here, a series of honeycomb‐like porous crystalline hetero‐electrocatalysts (MCH‐X, X = 1–4, X stands for the numbered sample obtained from different MOF doses in the synthesis of the MCH) are synthesized, and these are successfully applied in electrocatalytic CO2RR. The specially designed heterostructures with integrated porous MOF‐template and ultrathin COF‐coating enable efficient CO2 adsorption/activation and conversion into CH4. The best of them, MCH‐3, shows greatly inhibited H2 evolution, excellent current density (−398.1 mA cm−2), and superior FECH4${\rm{F}}{{\rm{E}}_{{\rm{C}}{{\rm{H}}_4}}}$ (76.7%) to the physical mixture (38.0%), the MOF@COF without the honeycomb‐like morphology (47.7%), and the bare COF (37.5%) and MOF (15.9%) at −1.0 V. Based on the density functional theory calculations and various characterizations, the vital roles of the MOF in facilitating CO2 adsorption/activation, stabilizing intermediates, and conquering the energy barrier of rate‐determining step are intensively studied.
A series of honeycomb‐like metal–organic framework (MOF)@covalent organic framework (COF) heterostructures with integrated porous MOF template and ultrathin COF coating are synthesized and successfully applied in efficient CO2 electroreduction to CH4.
Strategy that can design powerful photothermal‐catalysts to achieve photothermal‐effect assisted coupling‐catalysis is much desired for the improvement of energy conversion efficiency and redox ...product value in CO2 electroreduction system. Herein, a kind of bifunctional viologen‐containing covalent organic framework (Ni‐2CBpy2+‐COF) has been prepared and successfully applied in photothermal‐assisted co‐electrolysis of CO2 and methanol. Specifically, the FECO (cathode) and FEHCOOH (anode) for Ni‐2CBpy2+‐COF can reach up to ≈100 % at 1.9 V with ≈31.5 % saved overall electricity‐consumption when the anodic oxygen evolution reaction (OER) is replaced by methanol oxidation. The superior performance could be attributed to the cyclic diquats in Ni‐2CBpy2+‐COF that enhance the photothermal effect (ΔT=49.1 °C) to accelerate faster charge transfer between catalyst and immediate species as well as higher selectivity towards desired products as revealed by DFT calculations and characterizations.
A kind of bifunctional viologen‐containing covalent‐organic‐framework has been prepared and successfully applied in photothermal‐assisted co‐electrolysis of CO2 and methanol. The superior performance could be attributed to the cyclic diquats in Ni‐2CBpy2+‐COF that enhance the photothermal effect to accelerate faster charge‐transfer between catalyst and immediate species as well as higher selectivity towards desired products.
Recently, significant progress has been made in (2+1 )-dimensional conformal field theories without supersymmetry. In particular, it was realized that different Lagrangians may be related by hidden ...dualities; i.e., seemingly different field theories may actually be identical in the infrared limit. Among all the proposed dualities, one has attracted particular interest in the field of strongly correlated quantum-matter systems: the one relating the easy-plane noncompact CP1 model (NCCP1 ) and noncompact quantum electrodynamics (QED) with two flavors (N=2 ) of massless two-component Dirac fermions. The easy-plane NCCP1 model is the field theory of the putative deconfined quantum-critical point separating a planar (XY ) antiferromagnet and a dimerized (valence-bond solid) ground state, while N=2 noncompact QED is the theory for the transition between a bosonic symmetry-protected topological phase and a trivial Mott insulator. In this work, we present strong numerical support for the proposed duality. We realize the N=2 noncompact QED at a critical point of an interacting fermion model on the bilayer honeycomb lattice and study it using determinant quantum Monte Carlo (QMC) simulations. Using stochastic series expansion QMC simulations, we study a planar version of the S=1/2 J−Q spin Hamiltonian (a quantum XY model with additional multispin couplings) and show that it hosts a continuous transition between the XY magnet and the valence-bond solid. The duality between the two systems, following from a mapping of their phase diagrams extending from their respective critical points, is supported by the good agreement between the critical exponents according to the proposed duality relationships. In the J−Q model, we find both continuous and first-order transitions, depending on the degree of planar anisotropy, with deconfined quantum criticality surviving only up to moderate strengths of the anisotropy. This explains previous claims of no deconfined quantum criticality in planar two-component spin models, which were in the strong-anisotropy regime, and opens doors to further investigations of the global phase diagram of systems hosting deconfined quantum-critical points.
We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO4 1,2-dimethoxyethane via rotating ...disk electrode measurements. The nonaqueous Li+-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a “volcano-type” trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O2 cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li+-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications.
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