Latest ArticlesSulfurized polyacrylonitrile (SPAN) is proposed as a promising cathode material for lithium sulfur batteries. However, the continuous side reactions at the electrolyte-electrode interfaces as well as the slow redox kinetics of SPAN cathode deteriorate the electrochemical performance. In this study, an electrolyte with dual-additives comprising 2-fluoropyridine (2-FP) and lithium difluorobis (oxalato) phosphate (LiDFBOP) was used to improve the performance of Li||SPAN cells. 2-FP has a lower lowest occupied molecular orbital energy than that of the solvents in the electrolyte, leading to its prior reduction. A LiF-rich film can be formed on the electrode, effectively improving the stability of the electrolyte-electrode interfaces and prolonging the life. Simultaneously, LiDFBOP could form an electrolyte-electrode interface film containing a large amount of LixPOyFz species, compensating for the kinetic deterioration caused by the lower ionic conductive of LiF formed at the electrolyte-electrode interface. Hence, an electrode-interface film with good chemical stability and high Li+ transport was established by LiF and LixPOyFz-rich species. The Li||SPAN cell with the electrolyte containing dual-additives demonstrates an excellent capacity retention of 97.5% after 200 cycles at 1.0 C, 25 ℃, comparing to 56.2% capacity retention without additives. Moreover, the rate capacities of cells with dual-additives can reach 1128.1 mAh/g at 5 C, comparing to only 813.5 mAh/g using electrolyte without additives. Our results shown that the dual-additives in electrolyte provide a promising strategy for practical application of lithium sulfur batteries with SPAN cathodes.
In persulfate-based advanced oxidation process (PS-AOPs), fixing nanosized metal oxide on processable substrates is highly desirable to avoid the aggregation and loss of nanocatalysts during the practical application. However, it is still challenging to develop a versatile strategy for the deposition of metal oxide nanocatalysts on various substrates with different physicochemical properties. Herein, polyphenols are utilized as a "molecular glue" and reductant to mediate the interfacial deposition of MnO2 nanocatalysts on different substrates. MnO2 nanocatalysts were in-situ grown on macroscope mineral substrates (e.g., airstone) via an interfacial redox strategy between tannic acid (TA) and oxidized KMnO4, and then employed as a fixed catalyst of peroxymonosulfate (PMS) activation for treating pharmaceutical and personal care products (PPCPs) in water. The fixed MnO2 exhibited superior catalytic performance toward different PPCPS via a singlet oxygen (1O2)-dominated nonradical oxidation pathway. PPCPs in the secondary effluent of wastewater treatment plants could be effectively removed by a fixed-bed column of the fixed MnO2 with long term stability. Redox cycle of Mn4+/Mn3+ and surface hydroxyl group of the fixed MnO2 was proved to be responsible for the activation of PMS. This work provides a new avenue for developing fixed metal oxides for sustainable water treatment.
The development of highly efficient catalysts in the cathodes of rechargeable Li-O2 batteries is a considerable challenge. To enhance the electrochemical performance of the Li-O2 battery, it is essential to choose a suitable catalyst material. Copper selenide (CuSe) is considered as a more promising cathode catalyst material for Li-O2 battery due to its better conductivity and rich electrochemical active sites. However, its electrochemical reaction and fundamental catalytic mechanism remain unclear till now. Herein, in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the CuSe nanosheets in Li-O2 batteries during discharge and charge processes. It is found that Li2O was formed and decomposed around the ultrafine-grained Cu during the discharge and charge processes, respectively, demonstrating excellent cycling. This indicate that the freshly formed ultrafine-grained Cu in the conversion reaction catalyzed the latter four-electron-transfer oxygen reduction reaction, leading to the formation of Li2O. Our study provides important understanding of the electrochemistry of the Li-O2 nanobatteries, which will aid the development of high-performance Li-O2 batteries for energy storage applications.
Grain boundary (GB), as a kind of lattice defect, widely exists in two-dimensional transition metal dichalcogenides (2D TMDs), which has complex and diverse influences on the physical/chemical properties of 2D TMDs. GBs are universally considered to be a double-edged sword, although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality, certain structure-oriented applications could be realized based on its unique properties. In this review, we first detailed the atomic structure characteristics of GBs and the corresponding techniques, then we systematically summarized the methods of introducing GBs into 2D TMDs. Next, we expounded unique electrical, mechanical, and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure. Moreover, the application of GB structure in hydrogen evolution reaction (HER) is also discussed. In the end, we make a conclusion and put forward outlooks, hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.
Ultra-high nickel material is considered to be a promising cathode material. However, with the increase of nickel content, the interfacial side reactions between the cathode and electrolyte become increasingly serious. Herein, an atomically controllable ionic conductor Li3PO4 (LPO) coating is deposited on the LiNi0.90Co0.06Mn0.04O2 (NCM9064) based electrode by the atomic layer deposition method. The results shows that the LPO coating is uniformly and densely covered on the surface of secondary particles of NCM9064, helping to prevent the direct contact between the electrolyte and cathode during the charging-discharging process. In addition, the coating layer is electrochemically stable. As a result, the interfacial side reactions during the long cycle are effectively suppressed, and the solid electrolyte interphase layer at the interface is stabilized. The electrode with 20 layers of LPO deposition (ALD-LPO-20) exhibits an excellent capacity retention of 81% after 200 cycles in 2.8-4.3 V at 25 ℃, which is 18% higher than the unmodified material (ALD-LPO-0). Besides, the moderate LPO coating improves the rate capability and high temperature cycling performance of NCM9064. This study provides a method for the modification of ultra-high nickel cathode materials and corresponding electrodes.
A new bismuth-based halide double perovskite Cs2KBiCl6 was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction. Rather than an ordered structure, the crystal structure consists of shifted Cs, K, Bi, and Cl sites from the ideal positions with fractional occupancy in compensation, leading to variable local coordination of Cs+ ions, as revealed by 133Cs solid-state nuclear magnetic resonance spectroscopy. Cs2KBiCl6 displays volume hysteresis at 5–298 K range upon heating and cooling. The Cs2KBiCl6 has a direct bandgap of 3.35(2) eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue. The stabilization of disordered structure in Cs2KBiCl6 is related to two factors including the large-sized K+ cation which prefers to coordinate with more than six Cl−, and the Bi3+ with 6s2 lone pair which has a preference for a local asymmetric environment. These findings could have general application and help to understand the structure and property of halide perovskites.
Electrocatalytic nitrogen reduction reaction (NRR) is considered as an attractive approach for ammonia synthesis under mild conditions. A bottleneck of NRR is the exploration of efficient catalysts for accelerating reaction kinetics, among which heterogeneous structures possessing distinct atomic arrangement could modify electronic structure, and therefore altering their NRR activity. Here, we report a facile strategy for fabricating hetero-phase metal oxides derived from metal organic framework that are further integrated with Au nanoparticles as NRR catalysts. The phase composition of zirconia can be easily adjusted by simply changing the reaction temperature, where the monoclinic and tetragonal phases with the roughly close proportions have a distinct interface, leading to a strong interaction between Au and ZrO2. The enhanced interaction renders Au to be more electropositive and facilitates stronger binding to N2. As a result, a remarkable ammonia yield of 22.32 µg h−1 mgcat.−1 and a Faradaic efficiency of 31.92% can be achieved at low overpotential. This work is expected to pave the way for the design of heterogeneous structures and the exploration of hetero-phase nanostructures in boosting the electrocatalytic NRR.
Single crystallization is an important strategy to resolve intergranular cracks and unnecessary side reactions with electrolytes in layered transition metal oxide cathodes LiNi0.8Mn0.1Co0.1O2 (NMC811). Due to the limitations of high-temperature sintering and multi-step calcination, single crystal NMC811 generally shows irregular particles with a size of 2–3 µm. However, the prolonged Li-ion diffusion pathway and the stress generated by the uneven de-/intercalation sluggish Li-ion diffusion kinetics, what is more, cause structural damage such as intragranular cracks. A slow Li extraction rate or particle size reduction will ameliorate the structural damage and improve the cycling stability. As the most promising cathodes for next-generation power batteries, NMC811 required fast charge performance and cycle stability. Particle size reduction appears to be the displacement option. Nanonization is an effective strategy to mitigate intragranular cracks of single crystal NMC811. However, the serious aggregation and increased specific surface area become new challenges. In this article, we synthesized monodisperse nanoscale single crystal NMC811 by molten salt method and modified the surface by LiNbO3 coating. The electrochemical performance shows that nanoscale single crystal NMC811 has faster kinetic and higher capacity retention, so the strategy of combining nanonization and surface coating is an alternative way to prepare high specific capacity and cycle stable single crystal NMC811.
Photosensitization related to energy/electron transfer process is of great importance to natural photosynthesis. Herein, we proposed a promising strategy to improve the sensitizing ability of the typical photoactive MOFs (UiO-Ir) by engineering its metal coordination center with NBI (1, 8-naphthalenebenzimidizole) chromophore. The resulting MOFs (UiO-Ir-NBI) exhibited a strong sensitizing ability for significantly boosting photosynthesis. Impressively, the catalytic yield of 2-chloroethyl ethyl sulfoxide with UiO-Ir-NBI can reach 99%, over 6 times higher than that with UiO-Ir (16.4%). Moreover, UiO-Ir-NBI exhibited an excellent catalytic stability and a broad substrate tolerance, highlighting its great application prospect. Systematic investigations revealed that the strong visible light absorption, long excited state lifetime and efficient electron-hole separation of UiO-Ir-NBI greatly contributed to harvesting visible light and facilitating interface electron/energy transfer for efficient solar energy utilization. This work provides a new horizon to boost photosythesis of MOFs by engineering their metal sensitizing centers at a molecular level.
Conversion of CO2 into high-value products using electrochemical CO2 reduction (ECR) technology is an effective way to alleviate global warming and reach carbon neutrality. The oxygen vacancies in heterogenous catalysis are generally considered as a powerful method to enhance the performance of ECR by promoting CO2 adsorption and activation. However, the extent of defects in oxygen vacancies-activity relation has rarely been studied. Herein, we prepared Cu–Cd bimetallic catalysts with adjustable oxygen defect degree by controlling the amount of cadmium addition. Fourier transform infrared spectroscopy characterization results reveal that the formation of oxygen vacancies is attributed to the asymmetric stretching of Cu–O by the addition of cadmium. Electrochemical results show that the oxygen defect degree can modulate the selectivity of ECR products. A low degree of oxygen defects (CuO) is generally associated with lower product Faraday efficiency (FEC2/FEC1 ≈ 114%), but overabundant oxygen vacancies (CuO2.625–CdO0.375) are not entirely favorable to improving ECR activity (FEC2/FEC1 ≈ 125%) and single selectivity, while an appropriate degree of oxygen vacancies (CuO2.75–CdO0.25) can facilitate the ECR process toward single product selective production (FEC2/FEC1 ≈ 296%). The theoretical calculation showed that the O vacancy formed on CuO and the interface between CdO and CuO were conducive to enhancing the formation of *COOH intermediate and promoting the generation of ethylene products. This study provides a new approach and insight into the selective production of single products for future industrial applications of ECR.
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