Microfluidic‐Assisted Blade Coating of Compositional Libraries for Combinatorial Applications: The Case of Organic Photovoltaics

Microfluidic technologies are highly adept at generating controllable compositional gradients in fluids, a feature that has accelerated the understanding of the importance of chemical gradients in biological processes. That said, the development of versatile methods to generate controllable compositional gradients in the solid‐state has been far more elusive. The ability to produce such gradients would provide access to extensive compositional libraries, thus enabling the high‐throughput exploration of the parametric landscape of functional solids and devices in a resource‐, time‐, and cost‐efficient manner. Herein, the synergic integration of microfluidic technologies is reported with blade coating to enable the controlled formation of compositional lateral gradients in solution. Subsequently, the transformation of liquid‐based compositional gradients into solid‐state thin films using this method is demonstrated. To demonstrate efficacy of the approach, microfluidic‐assisted blade coating is used to optimize blending ratios in organic solar cells. Importantly, this novel technology can be easily extended to other solution processable systems that require the formation of solid‐state compositional lateral gradients.     

Spontaneous Atomic Ruthenium Doping in Mo2CTX MXene Defects Enhances Electrocatalytic Activity for the Nitrogen Reduction Reaction

The electrochemical nitrogen reduction reaction (NRR) process usually suffers extremely low Faradaic efficiency and ammonia yields due to sluggish N?N dissociation. Herein, single‐atomic ruthenium modified Mo₂CT_X MXene nanosheets as an efficient electrocatalyst for nitrogen fixation at ambient conditions are reported. The catalyst achieves a Faradaic efficiency of 25.77% and ammonia yield rate of 40.57 µg h^?1 mg^?1 at ‐0.3 V versus the reversible hydrogen electrode in 0.5 m K₂SO₄ solution. Operando X‐ray absorption spectroscopy studies and density functional theory calculations reveal that single‐atomic Ru anchored on MXene nanosheets act as important electron back‐donation centers for N₂ activation, which can not only promote nitrogen adsorption and activation behavior of the catalyst, but also lower the thermodynamic energy barrier of the first hydrogenation step. This work opens up a promising avenue to manipulate catalytic performance of electrocatalysts utilizing an atomic‐level engineering strategy.     

Osteoclastogenesis Modulatory Steroids from the South China Sea Gorgonian Coral Iciligorgia sp.

A new 9,11‐secosteroid, (22R)‐22‐acetoxy‐3β,6α,11‐trihydroxy‐9,11‐seco‐5α‐cholest‐7‐en‐9‐one, along with twelve known analogues were isolated from the South China Sea gorgonian coral Iciligorgia sp. Their structures were determined by the spectroscopic analysis and comparison with reported data. In an in vitro test of osteoclastic differentiation, three compounds exhibited significant down‐regulating effect whereas two compounds showed significant up‐regulating effect at 0.5 and 1.0 μm . This is the first report of the chemical investigation of the gorgonian Iciligorgia sp. The acetoxy substitution at C‐22 seems to play an important role in the regulating activity.     

Synthesis of Novel Aryloxyethylamine Derivatives and Evaluation of Their in Vitro and in Vivo Neuroprotective Activities

A series of aryloxyethylamine derivatives were designed, synthesized and evaluated for their biological activity. Their structures were confirmed by ¹H‐NMR, ¹³C‐NMR, FT‐IR and HR‐ESI‐MS. The preliminary screening of neuroprotection of compounds in vitro was detected by MTT, and the anti‐ischemic activity in vivo was tested using bilateral common carotid artery occlusion in mice. Most of these compounds showed potential neuroprotective effects against the glutamate‐induced cell death in differentiated rat pheochromocytoma cells (PC12 cells), especially for (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone, (4‐bromophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone, (4‐chlorophenyl)(1‐{2‐[(naphthalen‐2‐yl)oxy]ethyl}piperidin‐4‐yl)methanone, (4‐chlorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone and {1‐[2‐(4‐bromophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone, which exhibited potent protection of PC12 cells at three doses (0.1, 1.0, 10 μM). Compounds (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, (4‐fluorophenyl){1‐[2‐(naphthalen‐2‐yloxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone and {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone possessed the significant prolongation of the survival time of mice subjected to acute cerebral ischemia and decreased the mortality rate at all five doses tested (200, 100, 50, 25, 12.5 mg/kg) and had significant neuroprotective activity. In addition, (4‐fluorophenyl){1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}methanone, {1‐[2‐(4‐methoxyphenoxy)ethyl]piperidin‐4‐yl}(4‐methoxyphenyl)methanone and {1‐[2‐(4‐chlorophenoxy)ethyl]piperidin‐4‐yl}(4‐chlorophenyl)methanone possessed outstanding neuroprotection in vitro and in vivo. These compounds can be used as a promising neuroprotective agents for future development of new anti‐ischemic stroke agents. Basic structure–activity relationships are also presented.     

Oxygen‐Deficient Blue TiO2 for Ultrastable and Fast Lithium Storage

Developing a titanium dioxide (TiO₂)‐based anode with superior high‐rate capability and long‐term cycling stability is important for efficient energy storage. Herein, a simple one‐step approach for fabricating blue TiO₂ nanoparticles with oxygen vacancies is reported. Oxygen vacancies can enlarge lattice spaces, lower charge transfer resistance, and provide more active sites in TiO₂ lattices. As a result, this blue TiO₂ electrode exhibits a highly reversible capacity of 50 mAh g^?1 at 100 C (16 800 mA g^?1) even after 10 000 cycles, which is attributable to the combination of surface capacitive process and remarkable diffusion‐controlled insertion revealed by the kinetic analysis. The strategy of employing oxygen‐deficient nanoparticles may be extended to the design of other robust semiconductor materials as electrodes for energy storage.     

Superior Oxygen Reduction Reaction on Phosphorus‐Doped Carbon Dot/Graphene Aerogel for All‐Solid‐State Flexible Al–Air Batteries

Carbon dots have been recognized as one of the most promising candidates for the oxygen reduction reaction (ORR) in alkaline media. However, the desired ORR performance in metal–air batteries is often limited by the moderate electrocatalytic activity and the lack of a method to realize good dispersion. To address these issues, herein a biomass‐deriving method is reported to achieve the in situ phosphorus doping (P‐doping) of carbon dots and their simultaneous decoration onto graphene matrix. The resultant product, namely P‐doped carbon dot/graphene (P‐CD/G) nanocomposites, can reach an ultrahigh P‐doping level for carbon nanomaterials. The P‐CD/G nanocomposites are found to exhibit excellent ORR activity, which is highly comparable to the commercial Pt/C catalysts. When used as the cathode materials for a primary liquid Al–air battery, the device shows an impressive power density of 157.3 mW cm^?2 (comparing to 151.5 mW cm^?2 of a similar Pt/C battery). Finally, an all‐solid‐state flexible Al–air battery is designed and fabricated based on our new nanocomposites. The device exhibits a stable discharge voltage of ≈1.2 V upon different bending states. This study introduces a unique biomass‐derived material system to replace the noble metal catalysts for future portable and wearable electronic devices.     

Conductive Hole‐Selective Passivating Contacts for Crystalline Silicon Solar Cells

Defect state passivation and conductivity of materials are always in opposition; thus, it is unlikely for one material to possess both excellent carrier transport and defect state passivation simultaneously. As a result, the use of partial passivation and local contact strategies are required for silicon solar cells, which leads to fabrication processes with technical complexities. Thus, one material that possesses both a good passivation and conductivity is highly desirable in silicon photovoltaic (PV) cells. In this work, a passivation‐conductivity phase‐like diagram is presented and a conductive‐passivating‐carrier‐selective contact is achieved using PEDOT:Nafion composite thin films. A power conversion efficiency of 18.8% is reported for an industrial multicrystalline silicon solar cell with a back PEDOT:Nafion contact, demonstrating a solution‐processed organic passivating contact concept. This concept has the potential advantages of omitting the use of conventional dielectric passivation materials deposited by costly high‐vacuum equipment, energy‐intensive high‐temperature processes, and complex laser opening steps. This work also contributes an effective back‐surface field scheme and a new hole‐selective contact for p‐type and n‐type silicon solar cells, respectively, both for research purposes and as a low‐cost surface engineering strategy for future Si‐based PV technologies.     

Boosting Superior Lithium Storage Performance of Alloy‐Based Anode Materials via Ultraconformal Sb Coating–Derived Favorable Solid‐Electrolyte Interphase

Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy‐based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li₃Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF‐dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb‐coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g^?1 after 200 cycles at 500 mA g^?1, compared to only 72% and 170 mAh g^?1 for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long‐term cycling stability for alloy‐based anode materials.     

Enhanced Rate Capability of Ion‐Accessible Ti3C2Tx‐NbN Hybrid Electrodes

Although 2D Ti₃C₂T_x is a good candidate for supercapacitors, the restacking of nanosheets hinders the ion transport significantly at high scan rates, especially under practical mass loading (>10 mg cm^?2) and thickness (tens of microns). Here, Ti₃C₂T_x‐NbN hybrid film is designed by self‐assembling Ti₃C₂T_x with 2D arrays of NbN nanocrystals. Working as an interlayer spacer of Ti₃C₂T_x, NbN facilitates the ion penetration through its 2D porous structure; even at extremely high scan rates. The hybrid film shows a thickness‐independent rate performance (almost the same rate capabilities from 2 to 20 000 mV s^?1) for 3 and 50 µm thick electrodes. Even a 109 µm thick Ti₃C₂T_x‐NbN electrode shows a better rate performance than 25 µm thick pure Ti₃C₂T_x electrodes. This method may pave a way to controlling ion transport in electrodes composed of 2D conductive materials, which have potential applications in high‐rate energy storage and beyond.     

Revisiting the Role of Conductivity and Polarity of Host Materials for Long‐Life Lithium–Sulfur Battery

Despite their high theoretical energy density and low cost, lithium–sulfur batteries (LSBs) suffer from poor cycle life and low energy efficiency owing to the polysulfides shuttle and the electronic insulating nature of sulfur. Conductivity and polarity are two critical parameters for the search of optimal sulfur host materials. However, their role in immobilizing polysulfides and enhancing redox kinetics for long‐life LSBs are not fully understood. This work has conducted an evaluation on the role of polarity over conductivity by using a polar but nonconductive platelet ordered mesoporous silica (pOMS) and its replica platelet ordered mesoporous carbon (pOMC), which is conductive but nonpolar. It is found that the polar pOMS/S cathode with a sulfur mass fraction of 80 wt% demonstrates outstanding long‐term cycle stability for 2000 cycles even at a high current density of 2C. Furthermore, the pOMS/S cathode with a high sulfur loading of 6.5 mg cm^?2 illustrates high areal and volumetric capacities with high capacity retention. Complementary physical and electrochemical probes clearly show that surface polarity and structure are more dominant factors for sulfur utilization efficiency and long‐life, while the conductivity can be compensated by the conductive agent involved as a required electrode material during electrode preparation. The present findings shed new light on the design principles of sulfur hosts towards long‐life and highly efficient LSBs.