Latest ArticlesEfficient and stable electrocatalyst for oxygen evolution reaction (OER) in acidic environment is vital for polymer electrolyte membrane water electrolysis (PEMWE). In this work, we have devised the formation of heterostructured RuO2/MnO2 with nanoflower structure for acidic OER catalysis. Compared to commercial RuO2, the overpotential at 50 mA/cm2 is decreased by 36 mV, corresponding to a 3.7-fold better mass activity. The boosted acidic OER performance is attributed to the heterostructure inducing more electrons are filled in eg orbital of Ru atom triggering a better deprotonation of bridge oxygen atom in Ru-Obri-Mn structure evidenced by pH-independent cyclic voltammetry test. Moreover, RuO2/MnO2 sustains its acidic OER activity within 20 h, longer than commercial RuO2. The membrane electrode assembly (MEA) test suggests than only 2.18 V is required to achieve a current density of 5 A/cm2. The theoretical calculation reveals that the eg filling of Ru atom is increased from 2.18 to 2.39 after MnO2 incorporation, reducing the energy for the formation of *OOH moiety.
Manganese dioxide (MnO2) electrode material possesses the advantages of high energy density, structural diversity and high modification potential. This allows it become one of the important cathodes for aqueous zinc ion battery. However, the applications are limited by the poor electrical conductivity, narrow layer spacing and the ease of dissolution. Herein, we prepare MnO2-PVP@0.03GO composites by the co-modification of polyvinylpyrrolidone (PVP) pre-insertion layer and graphene oxide (GO) self-assembly layer. The Zn//MnO2-PVP@0.03GO cells deliver a discharge specific capacity of 442 mAh/g at a current density of 0.2 A/g. It also maintains 100% capacity for 1000 times cycling at 1 A/g. The assembled soft package batteries demonstrate superior flexibility and adaptability under different bending conditions.
Sluggish conversion reaction kinetics and spontaneous shuttle effect of lithium polysulfides (LiPSs) are deemed as the two big mountains that hinder the practical application of lithium-sulfur batteries (LSBs). Herein, dual-defect engineering strategy is implemented by introducing boron-doping and phosphorus-vacancy sites with MoP@NC composite as the precursor. Based on the experimental characterizations and theoretical calculations, B-MoP1-x@NC-based electrode presents low oxidation potential, high lithium diffusivity, small Tafel slope and strong adsorption capability for polysulfides, which is beneficial to enhance the adsorption capability for LiPSs, reduce the lithium diffusion energy barriers and Gibbs free energy for the conversion reactions of LiPSs. As demonstrated, the corresponding Li-S/B-MoP1-x@NC batteries can remain high reversible capacity of 753 mAh/g at 0.5 C after 300 cycles, and keep a stable capacity of 520 mAh/g at 0.5 C after 100 cycles even at the high-loading content of 5.1 mg/cm2. According to the results of in-situ UV–vis spectra, the satisfactory battery performance majorly originates from the existence of dual-defect characteristics in B-MoP1-x@NC catalyst, which effectively promotes the conversion reaction kinetics of LiPSs, and restrains the shuttle behavior of LiPSs. The key ideas of this work will enlighten the development of catalytic cathode materials for sulfur-based secondary batteries.
We propose and investigate a novel stable two-dimensional (2D) AlO2 with anomalous stoichiometric ratios based on first-principles calculation. 2D AlO2 has metallic properties. It possesses the rare in-plane and out-of-plane negative Poisson's ratio (NPR) phenomenon, originating from its special sawtooth-like structure. The absolute value of the NPR decreases as the number of layers increases. The adsorption of volatile organic compounds (VOCs) including CH2O, C2H3Cl and C6H6 by AlO2 exhibit small adsorption distance, large adsorption energy, large charge transfer and significant density of states (DOS) changes, indicating the presence of strong interactions. The desorption time of each gas molecule on the AlO2 surface is also evaluated, and the results further suggest that the desorption of VOCs can be controlled by changing the temperature to achieve the recycling of AlO2. These interesting properties make 2D AlO2 a promising material for electronic, mechanical and sensing applications for VOCs.
Defects at the grain boundaries (GBs) of perovskite film highly restrict both the efficiency and stability of perovskite solar cells (PSCs). Herein, organic small molecules of butanedioic acid (BA) and acetylenedicarboxylic acid (AA), containing two carbonyl (C=O) groups and different core-units, were incorporated into perovskite as additives for PSCs application. Thanks to the strong coordination interaction between CO group and under-coordinated Pb2+, the additives can effectively passivate film defects and regulate the perovskite crystallization, yielding high-quality perovskite films with lower defect densities. More importantly, the additives can efficiently regulate the charge transport behaviors in PSCs. Benefiting from the defects passivation and the regulation of charge carrier dynamics, the BA and AA-treaded PSCs show the power conversion efficiencies of 21.52% and 20.50%, which are higher than that of the control device (19.41%). Besides, the optimal devices exhibit a remarkable enhanced long-term stability and moisture tolerance compared to the pristine devices. Furthermore, the transient absorption spectrum reveals the mechanism of enhanced photovoltaic performances, attributing to the improvement of charge transport capability at the perovskite/Spiro-OMeTAD interfaces. This work affords a promising strategy to improve the efficiency and stability of PSCs through regulating the charge-carrier dynamic process in perovskite film.
Lithium metal is one of the most promising anodes for lithium batteries because of their high theoretical specific capacity and the low electrochemical potential. However, the commercialization of lithium metal anodes (LMAs) is facing significant obstacles, such as uncontrolled lithium dendrite growth and unstable solid electrolyte interface, leading to inferior Coulombic efficiency, unsatisfactory cycling stability and even serious safety issues. Introducing low-cost natural clay-based materials (NCBMs) in LMAs is deemed as one of the most effective methods to solve aforementioned issues. These NCBMs have received considerable attention for stabilizing LMAs due to their unique structure, large specific surface areas, abundant surface groups, high mechanical strength, excellent thermal stability, and environmental friendliness. Considering the rapidly growing research enthusiasm for this topic in the last several years, here, we review the recent progress on the application of NCBMs in stable and dendrite-free LMAs. The different structures and modification methods of natural clays are first summarized. In addition, the relationship between their modification methods and nano/microstructures, as well as their impact on the electrochemical properties of LMAs are systematically discussed. Finally, the current challenges and opportunities for application of NCBMs in stable LMAs are also proposed to facilitate their further development.
Two CoⅡ-based complexes, {[Co(dps)2(N3)2]·H2O} (1) and [Co(dps)2(N3)2] (2), show a 1D chain and a 3D network, respectively. The central CoⅡ ions in the complexes have the same coordination environment with the [Co(dps)4(N3)2] unit. Although the differences in crystal parameters are nearly negligible, their magnetic properties are very different. AC susceptibility data show that 1 behaves as a typical field-induced single-ion magnet (SIM) with the out-of-phase (χM'') signals, while 2 shows ac signals of χM'' without peaks even under applied dc filed within our measurement window. Far-IR magneto-spectra (FIRMS) show strong spin-phonon couplings at 0 T in 2, likely making the magnetic relaxation in 2 fast, while the couplings are negligible in 1. Small spin-phonon coupling in 1 likely leads to slower magnetic relaxation, making 1 a SIM. The difference in the properties is due to the structural rigidity of 2 in its 3D network, leading to stronger spin-phonon coupling. Combined high-field EPR (HF-EPR) and FIRMS studies give spin-Hamiltonian parameters, including D = 64.0(9) cm-1, E = 15.7(2) cm-1 for 1 and D = 80.0(2) cm-1, E = 19.0(1) cm-1 for 2.
Dion–Jacobson (DJ) phase hybrid perovskites have been proven to improve the photovoltaic performance of the devices due to its unique structure. At present, some DJ hybrid perovskites have been reported and used for photodetection filed, but most of them are based on lead-bromide systems, which is not conducive to construct broadband photodetection devices due to the limitation of intrinsic absorption. Herein, we constructed a bilayered DJ hybrid perovskite (3AMPY)(EA)Pb2I7 (3AMPY2+ is 3-(aminomethyl)pyridinium, EA+ is ethylammonium) using an aromatic spacer, which exhibit large current on/off ratios of ~104 under 520 and 637 nm illumination. In particular, the single crystal device based on (3AMPY)(EA)Pb2I7 shows a distinguished detectivity of 7.4 × 1012 Jones and a high responsivity of 0.89 A/W under 637 nm illumination. Such finding not only enriches the quantities of DJ hybrid perovskites, but also provides useful assistance for constructing high-performance optoelectronic device in the future.
Atomically dispersed Cu-based single-metal-site catalysts (Cu-N-C) have emerged as a frontier for electrocatalytic oxygen reduction reactions (ORR) because they can effectively optimize the d-band center of the Cu active site and provide appropriate adsorption/desorption energy for oxygen-containing intermediates. Metal-organic frameworks (MOFs) show excellent prospects in many fields because of their structural regularity and designability, but their direct use for electrocatalysis has been rarely reported due to the low intrinsic conductivity. Here, a MOF material (Cu-TCNQ) with highly regular single-atom copper active centers was successfully prepared using a solution chemical reaction method. Subsequently, Cu-TCNQ and graphene oxide (GO) were directly self-assembled to form a Cu-TCNQ/GO composite, which improved the conductivity of the catalyst while maintained the atomically precise controllability. The resistivity of the Cu-TCNQ/GO decreased by three orders of magnitude (1663.6–2.7 W/cm) compared with pure Cu-TCNQ. The half-wave potential was as high as 0.92 V in 0.1 mol/L KOH, even better than that of commercial 20% Pt/C. In alkaline polymer electrolyte fuel cells (APEFCs), the open-circuit voltage and power density of Cu-TCNQ/GO electrode reached 0.95 V and 320 mW/cm2, respectively, which suggests that Cu-TCNQ/GO has a good potential for application as a cathode ORR catalyst.
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