Latest ArticlesPyrolyzed Fe-Nx-C with atomically dispersed Fe-Nx sites are hailed as the most promising alternative to the noble metal Pt-based catalysts towards oxygen reduction reaction (ORR). However, the conventional micropore-confinement synthetic approach usually causes the insufficient utilization of active sites and mass transport resistance as the sites are located inside the micropore. We herein report a polymer-chelation strategy to directly disperse the Fe-Nx active sites onto the carbon surface. The N-rich monomer was in-situ polymerized on the carbon support and then chelated with Fe. The strong Fe-N chelating interaction is crucial to suppress Fe aggregation when undergoing the high-temperature pyrolysis. Due to the enriched surface sites, hierarchically porous structure and excellent conductivity of carbon support, the optimal catalyst (denoted as Fe-Nx-C@C-900) exhibits impressive ORR activity of onset and half-wave potential of 1.02 and 0.87 V, respectively, superior to the Pt/C benchmark.
Metal-doped carbon materials, as one of the most important electrocatalytic catalysts for CO2 reduction reaction (CO2RR), have attracted increasing attention. Herein, a series of Cu cluster embedded highly porous nanofibers have been prepared through the carbonization of electro-spun MOF/PAN nanofibers. The obtained Cu cluster doped porous nanofibers possessed fibrous morphology, high porosity, conductivity, and uniformly dispersed Cu clusters, which could be applied as promising CO2RR catalysts. Specifically, best of them, MCP-500 exhibited high catalytic performance for CO2RR, in which the Faradaic efficiency of CO (FECO) was as high as 98% at −0.8 V and maintained above 95% after 10 h continuous electrocatalysis. The high performance might be attributed to the synergistic effect of tremendously layered graphene skeleton and uniformly dispersed Cu clusters that could largely promote the electron conductivity, mass transfer and catalytic activity during the electrocatalytic CO2RR process. This attempt will provide a new idea to design highly active CO2RR electrocatalyst.
Metal-organic frameworks (MOFs) have showed high promise in CO2-electroreduction, yet their generally insufficient conductivity or low electron-transfer efficiency have largely restricted the wide-spread applications. Herein, fullerene molecules (i.e., C60 and C70) have been successfully introduced into the pore-channels of a Co-porphyrin based MOF through a facile strategy. Thus-obtained hybrid materials present higher electron-transfer ability, enhanced CO2 adsorption-enthalpy and CO2 electroreduction activity. Notably, the charge transfer resistance (Rct) of C60@MOF-545-Co is almost 5 times lower of than that of MOF-545-Co, as well as 1.5 times increased for the CO2 adsorption enthalpy. As expect, the FECO of C60@MOF-545-Co (97.0%) is largely higher than MOF-545-Co (70.2%), C60@MOF-545 (19.4%), C60 (11.5%) and physical mixture (70.3%) and presented as one of the best CO2 electroreduction catalysts reported in H-cell system. The facile strategy would give rise to new insight into the exploration of powerful MOF-based hybrid materials in high-efficiency CO2 electroreduction.
Sodium-ion batteries (SIB) have attracted widespread attention in large-scale energy storage fields owing to the abundant reserve in the earth and similar properties of sodium to lithium. Biomass-based carbon materials with low-cost, controllable structure, simple processing technology, and environmental friendliness tick almost all the right boxes as one of the promising anode materials for SIB. Herein, we present a simple novel strategy involving tea tomenta biomass-derived carbon anode with enhanced interlayer carbon distance (0.44 nm) and high performance, which is constructed by N, P co-doped hard carbon (Tea-1100-NP) derived from tea tomenta. The prepared Tea-1100-NP composite could deliver a high reversible capacity (326.1 mAh/g at 28 mA/g), high initial coulombic efficiency (ICE = 90% at 28 mA/g), stable cycle life (262.4 mAh/g at 280 mA/g for 100 cycles), and superior rate performance (224.5 mAh/g at 1400 mA/g). Experimental results show that the excellent electrochemical performance of Tea-1100-NP due to the high number of active N, P-containing groups, and disordered amorphous structures provide ample active sites and increase the conductivity, meanwhile, large amounts of microporous shorten the Na+ diffusion distance as well as quicken ion transport. This work provides a new type of N, P co-doped high-performance tomenta-derived carbon, which may also greatly promote the commercial application of SIB.
Hydrogel-based quasi-solid-state electrolytes (Q-SSEs) swollen with electrolyte solutions are important components in stretchable supercapacitors and other wearable devices. This work fabricates a super-tough, fatigue-resistant, and alkali-resistant multi-bond network (MBN) hydrogel aiming to be an alkaline Q-SSE. To synthesize the hydrogel, a 2-ureido-4[1H]-pyrimidone (UPy) motif is introduced into a poly(acrylic acid) polymer chain. The obtained MBN hydrogels with 75 wt% water content exhibit tensile strength as high as 2.47 MPa, which is enabled by the large energy dissipation ability originated from the dissociation of UPy dimers due to their high bond association energy. Owing to the high dimerization constant of UPy motifs, the dissociated UPy motifs are able to partially re-associate soon after being released from external forces, resulting in excellent fatigue-resistance. More importantly, the MBN hydrogels exhibit excellent alkali-resistance ability. The UPyGel-10 swollen with 1 mol/L KOH display a tensile strength as high as ~1.0 MPa with elongation at break of ~550%. At the same time, they show ionic conductivity of ~17 mS/cm, which do not decline even when the hydrogels are stretched to 500% strain. The excellent mechanical property and ionic conductivity of the present hydrogels demonstrate potential application as a stretchable alkaline Q-SSE.
The intercalation behavior of spiro-(1,1′)-bipyrrolidinium cation (SBP+) into graphite electrode from spiro-(1,1′)-bipyrrolidinium tetrafluoroborate-ethylene carbonate (SBPBF4-EC) solutions is investigated by conventional electrochemical tests and in situ X-ray diffraction measurements. Two kinds of graphite intercalation compounds (GICs) with discrete characteristic intercalated gallery heights (IGHs) (ca. 0.95 and 0.75 nm) can be obtained with varying the salt concentration. The effect of graphite type is also addressed.
Developing highly efficient photocatalysts for selective oxidation of benzene to phenol is of great significance. However, it is still challenging to simultaneously achieve high conversion rate and selectivity. Herein, we demonstrate 99.9% of benzene photoconversion and 99.1% of phenol selectivity under the illumination of AM 1.5 for 12 h. For this purpose, an advanced CuO@CN photocatalyst has been fabricated by loading tubular carbon nitride (CN) with CuO nanoparticles thermally polymerized from Cu-based metal-organic frameworks (MOFs). The sluggish photocharge carrier recombination rate and the excellent stability indicate that the as-prepared nanocomposite is an ideal photocatalyst for benzene oxidation application. This work paves a new avenue for designing novel photocatalyst based on MOFs and carbon nitride materials.
Luminescent spin crossover (SCO) materials have attracted significant interest owing to their potential applications in magneto-optical switches. However, the majority of previously reported FeⅡ-based SCO complexes are adversely affected by fluorescence quenching in the solid-state. Here, we have constructed the first mononuclear FeⅡ complex decorated with an aggregation-induced emission (AIE) luminophore (i.e., tetraphenylethylene) that exhibits synergistic SCO and fluorescence behavior. Intriguingly, we obtained two types of crystals in different solvent systems, both displaying distinct magnetic bistability and fluorescence properties. The fluorescence intensity was observed to track the magnetic susceptibility, which confirmed that SCO and solid-state fluorescence operate synergistically. We introduce a novel approach for the construction of luminescent SCO compounds using an AIEgen as a luminophore, which leads to fluorescence emission in the solid-state, thus allowing us to study the synergy between SCO and fluorescence.
Lithium rich layered oxide (LRLO) has been considered as one of the promising cathodes for lithium-ion batteries (LIBs). The high voltage and large capacity of LRLO depend on Li2MnO3 phase. To ameliorate the electrochemical performance of Li2MnO3, also written as Li(Li1/3Mn2/3)O2, we propose a strategy to substitute Mn4+ and Li+ in Mn/Li transition metal layer with Ti4+, which can stabilize the structure of Li2MnO3 by inhibiting the excessive oxidation of O2− above 4.5 V. More significantly, the unequal-valent substitution brings about the emergence of interlayer Li vacancies, which can promote the Li-ion diffusion based on the enlarged interlayer and increase the capacity by activating the Mn3+/4+ redox. We designed Li0.7[Li1/3Mn2/3]0.7Ti0.3O2 with high interlayer Li vacancies, which presents a high capacity (290 mAh/g at 10 mA/g) and stable cycling performance (84% over 60 cycles at 50 mA/g). We predict that this strategy will be helpful to further improve the electrochemical performance of LRLOs.
We use a single-molecule self-assembled layer of an aromatic organophosphonic acid (2PACz) to modify the cathode interface layer in inverted organic solar cells (OSCs). The modified OSCs not only have an obvious improvement in power conversion efficiency (PCE), but also demonstrate greatly enhanced air stability. Ultraviolet photoelectron spectroscopy shows that the work function of cathode interlayer after modification by 2PACz is more suitable for electron extraction. In addition, the surface energy is reduced without affecting the film deposition, which will be beneficial to reduce the interfacial traps. As a result, the PCE of OSCs based on the PBDB-T: IT-M system is increased, and its stability in air is greatly improved (remaining 88% of its initial PCE after 555 h in air). Therefore, we provide a new strategy for constructing high-performance non-fullerene OSCs with enhanced air stability.
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