Enhancement in Oxygen Reduction Reaction Activity of Nitrogen‐Doped Carbon Nanostructures in Acidic Media through Chloride‐Ion Exposure

Enhancing Electrochemical CO2 Reduction via Redox Non-Innocent Spheres in Copper-Coordinated Covalent Organic Frameworks

Significant efforts have been dedicated to the development of highly efficient electrocatalysts for electrochemical CO2 reduction reactions (eCO2RR). The outer coordination spheres of catalytic centers may play a pivotal role in the reaction pathway and kinetics for eCO2RR. Herein, three single copper sites coordinated Aza-fused conjugated organic frameworks (Aza-COFs-Cu) with different outer coordination spheres around Cu sites are designed. Experiment and density functional theory (DFT) calculation results reveal that the redox non-innocent outer spheres around Cu sites significantly influence the catalytic performance of Aza-COFs-Cu for eCO2RR. When adjacent redox non-innocent groups of uncoordinated aromatic-N and quinone around the Cu centers act as the symmetry-breaking sites, the energy-consuming activation process of CO2 molecules can be accelerated via the H+/e- transfer process to form *COOH intermediates, which will significantly improve the performance for eCO2RR. This study provides a new perspective on the design of more advanced electrocatalysts for eCO2RR through redox non-innocent spheres engineering.

N-P covalent bond regulation of mesoporous carbon-based catalyst for lowered oxygen reduction overpotential and enhanced zinc-air battery performance

Developing sustainable metal-free carbon-based electrocatalysts is essential for the deployment of metal-air batteries such as zinc-air batteries (ZABs), among which doping of heteroatoms has attracted tremendous interest over the past decade. However, the effect of the heteroatom covalent bonds in carbon matrix on catalysis was neglected in most studies. Here, an efficient metal-free oxygen reduction reaction (ORR) catalyst is demonstrated by the N-P bonds anchored carbon (termed N,P-C-1000). The N,P-C-1000 catalyst exhibits superior specific surface area of 1362 m2 g-1 and ORR activity with a half-wave potential of 0.83 V, close to that of 20 wt% Pt/C. Theoretical computations reveal that the p-band center for C-2p orbit in N,P-C-1000 has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. The N,P-C-1000 assembled primary ZAB can attain a large peak power density of 121.9 mW cm-2 and a steady discharge platform of ∼1.20 V throughout 120 h. Besides, when served as the cathodic catalyst in a solid-state ZAB, the battery shows flexibility, conspicuous open circuit potential (1.423 V), and high peak power density (85.8 mW cm-2). Our findings offer a strategy to tune the intrinsic structure of carbon-based catalysts for improved electrocatalytic performance and shed light on future catalysts design for energy storage technologies beyond batteries.

Coexistence of Electrochromism and Bipolar Nonvolatile Memory in a Single Viologen

Viologens are fascinating redox-active organic compounds that have been widely explored in electrochromic devices (ECDs). However, the combination of electrochromic and resistive random-access memory in a single viologen remains unexplored. We report the coexistence of bistate electrochromic and single-resistor (1R) memory functions in a novel viologen. A high-performance electrochromic function is achieved by combining viologen (BzV2+2PF6) with polythiophene (P3HT), enabling a "push-pull" electronic effect due to the efficient intermolecular charge transfer in response to an applied bias. The ECDs show high coloration efficiency (ca. 1150 ± 10 cm2 C-1), subsecond switching time, good cycle stability (>103 switching cycles), and low-bias operation (±1.5 V). The ECDs require low power for switching the color states (55 μW cm-2 for magenta and 141 μW cm-2 for blue color). The random-access memory devices (p+2-Si/BzV2+2PF6/Al) exhibit distinct low and high resistive states with an ON/OFF ratio of ∼103, bipolar and nonvolatile characteristics that manifest good performances, and "Write"-"Read"-"Erase" (WRE) functions. The charge conduction mechanism of the RRAM device is elucidated by the Poole-Frenkel model where SET and RESET states arise at a low transition voltage (VT = ±1.7 V). Device statistics and performance parameters for both electrochromic and memory devices are compared with the literature data. Our findings on electrochromism and nonvolatile memory originated in the same viologen could boost the development of multifunctional, smart, wearable, flexible, and low-cost optoelectronic devices.

Microwave-Assisted Synthesis as a Promising Tool for the Preparation of Materials Containing Defective Carbon Nanostructures: Implications on Properties and Applications

In this review, we focus on a small section of the literature that deals with the materials containing pristine defective carbon nanostructures (CNs) and those incorporated into the larger systems containing carbon atoms, heteroatoms, and inorganic components.. Briefly, we discuss only those topics that focus on structural defects related to introducing perturbation into the surface topology of the ideal lattice structure. The disorder in the crystal structure may vary in character, size, and location, which significantly modifies the physical and chemical properties of CNs or their hybrid combination. We focus mainly on the method using microwave (MW) irradiation, which is a powerful tool for synthesizing and modifying carbon-based solid materials due to its simplicity, the possibility of conducting the reaction in solvents and solid phases, and the presence of components of different chemical natures. Herein, we will emphasize the advantages of synthesis using MW-assisted heating and indicate the influence of the structure of the obtained materials on their physical and chemical properties. It is the first review paper that comprehensively summarizes research in the context of using MW-assisted heating to modify the structure of CNs, paying attention to its remarkable universality and simplicity. In the final part, we emphasize the role of MW-assisted heating in creating defects in CNs and the implications in designing their properties and applications. The presented review is a valuable source summarizing the achievements of scientists in this area of research.

Hexachloro-1,3-butadiene as a Functional Additive for Constructing an Efficient Solid Electrolyte Interface Layer for Long-Life Stable Li Anodes

Lithium (Li) metal is considered as one of the attractive anodes for next-generation high-energy-density batteries due to its ultrahigh theoretical specific capacity and low potential. However, many great challenges including uncontrolled dendrite growth and undesired side reactions during repeated cycling still seriously hinder its practical application in Li metal secondary batteries. Herein, we report the hexachloro-1,3-butadiene (HCBD) molecule as a functional additive to stabilize the Li anode by forming a stable solid electrolyte interface (SEI) layer with high Li ion conductivity via in situ surface and electrochemical reactions. Density functional theory calculations demonstrate that HCBD can preferentially react with the Li anode, which generates an ionic conducting species (LiCl) into an SEI layer. The LiCl-rich SEI layer effectively regulates Li⁺ deposition/stripping kinetics and then induces uniform nucleation of Li⁺ and reduces the side reactions between the Li anode and electrolyte. With an optimal amount of HCBD in an ether-based electrolyte, an excellent cycling lifespan (7000 h) was achieved with a low hysteresis voltage of ∼10 mV at 1.0 mA cm^-2 in a Li||Li symmetrical cell. Furthermore, the LiFePO₄-based cell with the additive-functionalized Li anode displays obviously improved cycling stability (with a high specific capacity of 141.1 mAh g^-1 after 350 cycles at 1 C).

Reusing Face Covering Masks: Probing the Impact of Heat Treatment

The COVID-19 pandemic resulted in imminent shortages of personal protective equipment such as face masks. To address the shortage, new sterilization or decontamination procedures for masks are quickly being developed and employed. Dry heat and steam sterilization processes are easily scalable and allow treatment of large sample sizes, thus potentially presenting fast and efficient decontamination routes, which could significantly ease the rapidly increasing need for protective masks globally during a pandemic like COVID-19. In this study, a suite of structural and chemical characterization techniques, including scanning electron microscopy (SEM), contact angle, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman were utilized to probe the heat treatment impact on commercially available 3M 8210 N95 Particulate Respirator and VWR Advanced Protection surgical mask. Unique to this study is the use of the synchrotron-based In situ and Operando Soft X-ray Spectroscopy (IOS) beamline (23-ID-2) housed at the National Synchrotron Light Source II at Brookhaven National Laboratory for near-edge X-ray absorption spectroscopy (NEXAFS).

Reusing Face Covering Masks: Probing the Impact of Heat Treatment

The COVID-19 pandemic resulted in imminent shortages of personal protective equipment such as face masks. To address the shortage, new sterilization or decontamination procedures for masks are quickly being developed and employed. Dry heat and steam sterilization processes are easily scalable and allow treatment of large sample sizes, thus potentially presenting fast and efficient decontamination routes, which could significantly ease the rapidly increasing need for protective masks globally during a pandemic like COVID-19. In this study, a suite of structural and chemical characterization techniques, including scanning electron microscopy (SEM), contact angle, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman were utilized to probe the heat treatment impact on commercially available 3M 8210 N95 Particulate Respirator and VWR Advanced Protection surgical mask. Unique to this study is the use of the synchrotron-based In situ and Operando Soft X-ray Spectroscopy (IOS) beamline (23-ID-2) housed at the National Synchrotron Light Source II at Brookhaven National Laboratory for near-edge X-ray absorption spectroscopy (NEXAFS).

Incorporation of Cesium Lead Halide Perovskites into g-C3N4 for Photocatalytic CO2 Reduction

CsPbBr₃ perovskite-based composites so far have been synthesized by postdeposition of CsPbBr₃ on a parent material. However, in situ construction offers enhanced surface contact, better activity, and improved stability. Instead of applying a typical thermal condensation at highly elevated temperatures, we report for the first time CsPb(Br _x Cl_1-x )₃/graphitic-C₃N₄ (CsPbX₃/g-C₃N₄) composites synthesized by a simple and mild solvothermal route, with enhanced efficacy in visible-light-driven photocatalytic CO₂ reduction. The composite exhibited a CO production rate of 28.5 μmol g^-1 h^-1 at an optimized loading amount of g-C₃N₄. This rate is about five times those of pure g-C₃N₄ and CsPbBr₃. This work reports a new in situ approach for constructing perovskite-based heterostructure photocatalysts with enhanced light-harvesting ability and improved solar energy conversion efficiency.