Reinforcing the Adsorption and Conversion of Polysulfides in Li-S Battery by Incorporating Molybdenum into MnS/MnO Nanorods.

The Sabatier principle suggests that an excessive adsorption of lithium polysulfides (LiPSs) by metal compounds may hinder their conversion in the absence of a conversion module. Therefore, it is imperative to establish a synergetic effect mechanism between "strong adsorption" and "rapid conversion" for LiPSs. To achieve this coexistence, a molybdenum-doped MnS/MnO@C porous structure is designed as a multifunctional coating on the polypropylene (PP) separator. The incorporation of MnS/MnO@C enhances the adsorption capacity towards LiPSs, while molybdenum facilitates subsequent conversion. Benefiting from the synergistic effect of each component and its large specific surface area, the cell with Mo-doped MnS/MnO@C coating achieves smooth adsorption-diffusion-conversion processes and exhibits an appreciable rate performance with outstanding cycling stability. Even when sulfur loading increases to 9.68 mg cm-2 , the modified battery delivers an excellent initial areal capacity of 11.69 mAh cm-2 and maintains 6.97 mAh cm-2 after 50 cycles at 0.1 C. This study presents a promising approach to simultaneously accomplish "strong adsorption" and "rapid conversion" of polysulfides, offering novel perspectives for devising dual-functional modified separators.

Integrated PtxCoy-Hierarchical Carbon Matrix Electrocatalyst for Efficient Hydrogen Evolution Reaction.

Pt-based catalysts are regarded as state-of-the-art electrocatalysts for producing clean hydrogen energy; however, their wide application is restricted by their low abundance, high cost, and poor stability. Herein, we report an integrated PtxCoy-hierarchical carbon matrix electrocatalyst (Pt/Co@NCNTs, Pt3Co@NCNTs, PtCo@NCNTs, and PtCo3@NCNTs) that is developed using a thermally driven Co migration strategy forming alloy nanoparticles to achieve efficient hydrogen evolution reaction (HER). Benefiting from its electronic regulation effect and unique hierarchical hollow structure, the Pt3Co@NCNTs catalyst loaded with 11.5 wt % Pt exhibits superior catalytic performance and durability for HER compared with commercial 20 wt % Pt/C. Under both alkaline and acidic conditions, Pt3Co@NCNTs exhibits excellent HER activity with overpotentials of 21 and 45 mV at 10 mA cm-2, respectively. Density functional theory (DFT) results further verify that the interaction between Pt and Co in Pt3Co@NCNTs can modulate electronic rearrangement, optimize the d-band center, and accelerate water dissociation and *H desorption, thereby enhancing HER activity.

Reinforcement of Electrocatalytic Oxygen Evolution Activity Enabled by Constructing Silver-Incorporated NiCo-PBA@NiFe-LDH Hierarchical Nanoboxes.

Complicated oxygen evolution reaction (OER) poses the bottleneck in improving the efficiency of hydrogen production through water electrolysis. Herein, an integrated strategy to modulate the electronic structure of NiFe layered double hydroxide (NiFe-LDH) is reported by constructing Ag-incorporated NiCo-PBA@NiFe-LDH heterojunction with a hierarchical hollow structure. This "double heterojunction" facilitates local charge polarization at the interface, thereby promoting electron transfer and reducing the adsorption energy of intermediates, ultimately enhancing the intrinsic activity of the catalyst. It is noteworthy that an exchange bias field is observed between NiCo-PBA and NiFe-LDH, which will be conducive to regulating the electron spin states of metals and facilitating the production of triplet oxygen. Additionally, the unique hierarchical nanoboxes provide a large specific surface area that ensures adequate exposure to adsorption sites and active sites. Profiting from the synergistic advantages, the overpotential is as low as 190 mV at a current density of 10 mA cm-2 , with a low Tafel slope of 21 mV dec-1 . Moreover, density functional theory (DFT) calculation further substantiated that the incorporation of Ag in the heterojunction can effectively reduce the adsorption energy of reactant intermediates and enhance the conductivity.

A Highly-Lithiophilic Mn3O4/ZnO-Modified Carbon Nanotube Film for Dendrite-Free Lithium Metal Anodes.

Lithium metal anode is deemed as a potential candidate for high energy density batteries, which has attracted increasing attention. Unfortunately, Li metal anode suffers from issues such as dendrite grown and volume expansion during cycling, which hinders its commercialization. Herein, we designed a porous and flexible self-supporting film comprising of single-walled carbon nanotube (SWCNT) modified with a highly-lithiophilic heterostructure (Mn3O4/ZnO@SWCNT) as the host material for Li metal anodes. The p-n-type heterojunction constructed by Mn3O4 and ZnO generates a built-in electric field that facilitates electron transfer and Li+ migration. Additionally, the lithiophilic Mn3O4/ZnO particles serve as the pre-implanted nucleation sites, dramatically reducing the lithium nucleation barrier due to their strong binding energy with lithium atoms. Moreover, the interwoven SWCNT conductive network effectively lowers the local current density and alleviates the tremendous volume expansion during cycling. Thanks to the aforementioned synergy, the symmetric cell composed of Mn3O4/ZnO@SWCNT-Li can stably maintain a low potential for more than 2500 h at 1 mA cm-2 and 1 mAh cm-2. Furthermore, the Li-S full battery composed of Mn3O4/ZnO@SWCNT-Li also shows excellent cycle stability. These results demonstrate that Mn3O4/ZnO@SWCNT has great potential as a dendrite-free Li metal host material.

Boosting oxygen evolution reaction activity and durability of phosphate doped Ni(OH)2/FeOOH hierarchical microtubes by morphology engineering and reconstruction strategy.

Developing electrocatalysts with remarkable activity and durability is significant for efficient oxygen evolution reaction (OER). Herein, we designed phosphate doped Ni(OH)2/FeOOH hierarchical microtubes (denoted as POx-Ni(OH)2/FeOOH HMTs), obtained by phosphate doped NiFe Prussian blue analogue hierarchical microtubes (denoted as P-NF-PBA HMTs) completely reconstructing in OER process. POx-Ni(OH)2/FeOOH HMTs possess an extremely low overpotential of 237 mV at 30 mA cm-2 in alkaline electrolyte with the Tafel slope of 35 mV dec-1, and the catalysts can maintain excellent durability for 100 h at 30 mA cm-2. The remarkable electrochemical catalytic activity comes from the advantages of the hierarchical hollow structure, the modulation of electronic structure caused by phosphate doping, and the synergistic effect of Ni(OH)2 and FeOOH species produced by catalyst complete reconstruction in the OER process. This work may provide an effective strategy to develop highly efficient and durable electrocatalysts towards OER.

Lithiophilic hollow Co3[Co(CN)6]2 embedded carbon nanotube film for dendrite-free lithium metal anodes.

Lithium metal is considered to be an ideal anode material due to its ultra-high theoretical capacity and extremely low electric potential. Unfortunately, the infinite volume expansion and unregulated formation of lithium dendrites in the plating/stripping process restrict its practical utilization. Herein, we designed a hollow Co3[Co(CN)6]2 (CoCoPBA) embedded high-conductivity carbon film as a three-dimensional (3D) lithiophilic current collector (h-CoCoPBAs@SWCNT). The interwoven carbon nanotubes with hollow nanoparticles can effectively promote electron transfer and reduce local current density, adapting to the huge volume expansion in long-term electrochemical cycling. At the same time, lithiophilic hollow CoCoPBA nanoparticles provide abundant active sites due to their large surface area, efficiently reducing nucleation overpotential and making lithium deposition easier and more uniform, both confirmed by theoretical calculation and experiment. Accordingly, compared with bare Cu electrodes, h-CoCoPBAs@SWCNT electrodes have a flat and uniform Li deposition morphology, which is beneficial to enhance the cycle life of lithium metal anodes. And the symmetrical cell assembled by h-CoCoPBAs@SWCNT shows stable cycling performance of more than 500 h at 2 mA cm-2 with 1 mAh cm-2. Besides, the assembled lithium-sulfur full cell also has higher cycle stability and rate performance.

Polarized Laser Switching with Giant Contrast in MOF-Based Mixed-Matrix Membrane.

Nonlinear optical (NLO) switch materials have attracted considerable attention in photonics. Although various materials based on complex structural transitions have been developed extensively, the studies on light-driven up-conversion laser switches are rare, which have advantages including easy operations at room temperature and high contrasts. Here, the concept of photoswitch building unit is proposed to construct a novel sandwich-like mixed-matrix membrane. Dye@metal-organic framework (MOF) crystals and spirooxazine are regarded as the laser emission and absorption units, followed by their hierarchical encapsulation into the polydimethylsiloxane carrier unit. Excited MOF microcrystals exhibit two-photon pumped lasing anisotropy, with an ultrahigh degree of linear polarization (≈99.9%). Photochromic molecules can be interconverted by the external ultraviolet stimulus, causing sharp absorption-band variations and inducing the laser emission or quenching. Such up-conversion polarized laser switch material is reported for the first time. Record-high NLO contrast (≈6.1 × 104 ) among the solid-state NLO switch materials can be obtained through simultaneously controlling the ultraviolet irradiation and the emission-detected polarization direction at room temperature.

Boosting Hydrogen Evolution through the Interface Effects of Amorphous NiMoO4-MoO2 and Crystalline Cu.

The rational design and synthesis of a highly efficient and cost-effective electrocatalyst for hydrogen evolution reaction (HER) are of great importance for the efficient generation of sustainable energy. Herein, amorphous/crystalline heterophase Ni-Mo-O/Cu (denoted as a/c Ni-Mo-O/Cu) was synthesized by a one-pot electrodeposition method. Thanks to the introduction of metallic Cu and the formation of amorphous Ni-Mo-O, the prepared electrocatalyst exhibits favorable conductivity and abundant active sites, which are favorable to the HER progress. Moreover, the interfaces consisting of Cu and Ni-Mo-O show electron transfers between these components, which might modify the absorption/desorption energy of H atoms, thus accelerating HER activity. As expected, the prepared a/c Ni-Mo-O/Cu possesses excellent HER performance, which affords an ultralow overpotential of 34.8 mV at 10 mA cm-2, comparable to that of 20 wt % Pt/C (35.0 mV), and remarkable stability under alkaline conditions.

Benchmark C2 H2 /CO2 Separation in an Ultra-Microporous Metal-Organic Framework via Copper(I)-Alkynyl Chemistry.

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)-alkynyl chemistry within an ultra-microporous MOF (CuI @UiO-66-(COOH)2 ) to achieve ultrahigh C2 H2 /CO2 separation selectivity. The anchored CuI ions on the pore surfaces can specifically and strongly interact with C2 H2 molecule through copper(I)-alkynyl π-complexation and thus rapidly adsorb large amount of C2 H2 at low-pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2 H2 /CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU-74a (36.5) and ATC-Cu (53.6). Theoretical calculations reveal that the unique π-complexation between CuI and C2 H2 mainly contributes to the ultra-strong C2 H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2 H2 /CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)-alkynyl chemistry for highly selective separation of C2 H2 over CO2 .

Boosting hydrogen generation by anodic oxidation of iodide over Ni-Co(OH)2 nanosheet arrays.

For overall water electrolysis, the hydrogen evolution reaction (HER) is severely limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER). Therefore, replacing the OER with a more favorable anodic oxidation reaction with remarkable kinetics is of paramount significance, especially the one that can produce value-added chemicals. Moreover, time-saving and cost-effective strategies for the fabrication of electrodes are helpful for the wide application of electrolysis. Herein, thermodynamically more favorable iodide electrooxidation over Ni doped Co(OH)2 nanosheet arrays (NSAs) in alkaline solution is presented as the alternative to the OER to boost the HER. And the active species are determined to be the reverse redox of the Co(iv)/Co(iii) couple. Remarkably, a negative shift of voltage of 320 mV is observed at a current density of 10 mA cm-2 after using iodide electrolysis to replace ordinary water splitting. The synthetic strategy and iodide oxidation in this work expand the application of Co-based materials in the field of energy-saving hydrogen production.

Boosting Ethylene/Ethane Separation within Copper(I)-Chelated Metal-Organic Frameworks through Tailor-Made Aperture and Specific π-Complexation.

The development of new materials for separating ethylene (C2H4) from ethane (C2H6) by adsorption is of great importance in the petrochemical industry, but remains very challenging owing to their close molecular sizes and physical properties. Using isoreticular chemistry in metal-organic frameworks (MOFs) enables the precise design and construction of target materials with suitable aperture sizes and functional sites for gas separations. Herein, it is described that fine-tuning of pore size and π-complexation simultaneously in microporous copper(I)-chelated MOFs can remarkably boost the C2H4/C2H6 adsorption selectivity. The judicious choice of organic linkers with a different number of carboxyl groups in the UiO-66 framework not only allows the fine tuning of the pore size but also immobilizes copper(I) ions onto the framework. The tailor-made adsorbent, CuI@UiO-66-(COOH)2, thus possesses the optimal pore window size and chelated Cu(I) ions to form π-complexation with C2H4 molecules. It can rapidly adsorb C2H4 driven by the strong π-complexation interactions, while effectively reducing C2H6 uptake due to the selective size-sieving. Therefore, this material exhibits an ultrahigh C2H4/C2H6 selectivity (80.8), outperforming most previously described benchmark materials. The exceptional separation performance of CuI@UiO-66-(COOH)2 is validated by breakthrough experiments for 50/50 v/v C2H4/C2H6 mixtures under ambient conditions.

Facile in-situ growth of Ni2P/Fe2P nanohybrids on Ni foam for highly efficient urea electrolysis.

Urea electrolysis is regarded as an alternative energy-saving hydrogen production technique to replace the conventional water splitting method due to the predicted lower thermodynamic potential. Herein, we demonstrate a robust and mass-produced strategy to in-situ grow Ni2P/Fe2P nanohybrids on Ni foam (Ni2P/Fe2P/NF) as an advanced electrode for overall urea electrolysis via a 30 s manual shaking reaction of FeCl3·6H2O, K3[Fe(CN)6] and pre-treated NF, followed by a facile phosphorization treatment. The as-prepared Ni2P/Fe2P/NF electrode exhibits high activity for the HER at 115 mV and UOR at 1.36 V with the current density of 10 mA cm-2, and only a cell voltage of 1.47 V is required to deliver the current density of 10 mA cm-2. This work reveals a promising industrializable pathway to develop non-noble materials as bifunctional catalysts.

A Room-Temperature Postsynthetic Ligand Exchange Strategy to Construct Mesoporous Fe-Doped CoP Hollow Triangle Plate Arrays for Efficient Electrocatalytic Water Splitting.

Hollow nanostructures with mesoporous shells are attractive for their advantageous structure-dependent high-efficiency electrochemical catalytic performances. In this work, a novel nanostructure of Fe-doped CoP hollow triangle plate arrays (Fe-CoP HTPAs) with unique mesoporous shells is designed and synthesized through a room-temperature postsynthetic ligand exchange reaction followed by a facile phosphorization treatment. The mild postsynthetic ligand exchange reaction of the presynthesized ZIF-67 TPAs with K4 [Fe(CN)6 ] in an aqueous solution at room temperature is of critical importance in achieving the final hollow nanostructure, which results in the production of CoFe(II)-PBA HTPAs that not only determine the formation of the interior voids in the nanostructure, but also provide the doping of Fe atoms to the CoP lattice. As expected, the as-prepared mesoporous Fe-CoP HTPAs exhibit pronounced activity for water splitting owing to the advantages of abundant active reaction sites, short electron and ion pathways, and favorable hydrogen adsorption free energy (ΔGH* ). For the hydrogen and oxygen evolution reactions with the Fe-CoP HTPAs in alkaline medium, the low overpotentials of 98 and 230 mV are observed, respectively, and the required cell voltage toward overall water splitting is only as low as 1.59 V for the driving current density of 10 mA cm-2 .

Facile formation of mesoporous BiVO4/Ag/AgCl heterostructured microspheres with enhanced visible-light photoactivity.

In this study, we demonstrate a facile and novel dual-ion-exchange method together with subsequent visible-light induced reduction for synthesis of mesoporous BiVO4/Ag/AgCl ternary heterostructured microspheres (HSMSs) with uniform size distribution. Using flower-like BiOCl microspheres as the starting material, and introducing NaVO3 and AgNO3 by a facile impregnation method, mesoporous BiVO4/AgCl HSMSs have been obtained through solid-phase dual-ion-exchange reactions at 400 °C for 2 h. Interestingly, it has been found that Ag(+) ions play an indispensable role on the dual-ion-exchange reactions, and then the BiVO4/AgCl HSMSs are converted into BiVO4/Ag/AgCl ternary HSMSs by a facile visible-light illumination for 2 h. The as-prepared mesoporous BiVO4/Ag/AgCl ternary HSMSs manifest high photocatalytic activity in degrading methyl orange (MO) and phenol under visible-light illumination, and a possible Z-scheme photocatalytic mechanism is proposed to understand the enhanced photochemical properties.