Enhancing Efficiency of Low-Grade Heat Harvesting by Structural Vibration Entropy in Thermally Regenerative Electrochemical Cycles

The majority of waste-heat energy exists in the form of low-grade heat (<100 °C), which is immensely difficult to convert into usable energy using conventional energy-harvesting systems. Thermally regenerative electrochemical cycles (TREC), which integrate battery and thermal-energy-harvesting functionalities, are considered an attractive system for low-grade heat harvesting. Herein, the role of structural vibration modes in enhancing the efficacy of TREC systems is investigated. How changes in bonding covalency, influenced by the number of structural water molecules, impact the vibration modes is analyzed. It is discovered that even small amounts of water molecules can induce the A1g stretching mode of cyanide ligands with strong structural vibration energy, which significantly contributes to a larger temperature coefficient (ɑ) in a TREC system. Leveraging these insights, a highly efficient TREC system using a sodium-ion-based aqueous electrolyte is designed and implemented. This study provides valuable insights into the potential of TREC systems, offering a deeper understanding of the intrinsic properties of Prussian Blue analogs regulated by structural vibration modes. These insights open up new possibilities for enhancing the energy-harvesting capabilities of TREC systems.

Microstructure and Oxygen Evolution Property of Prussian Blue Analogs Prepared by Mechanical Grinding

Solvent-free mechanochemical synthesis of efficient and low-cost double perovskite (DP), like a cage of Prussian blue (PB) and PB analogs (PBAs), is a promising approach for different applications such as chemical sensing, energy storage, and conversion. Although the solvent-free mechanochemical grinding approach has been extensively used to create halide-based perovskites, no such reports have been made for cyanide-based double perovskites. Herein, an innovative solvent-free mechanochemical synthetic strategy is demonstrated for synthesizing Fe4[Fe(CN)6]3, Co3[Fe(CN)6]2, and Ni2[Fe(CN)6], where defect sites such as carbon-nitrogen vacancies are inherently introduced during the synthesis. Among all the synthesized PB analogs, the Ni analog manifests a considerable electrocatalytic oxygen evolution reaction (OER) with a low overpotential of 288 mV to obtain the current benchmark density of 20 mA cm-2. We hypothesize that incorporating defects, such as carbon-nitrogen vacancies, and synergistic effects contribute to high catalytic activity. Our findings pave the way for an easy and inexpensive large-scale production of earth-abundant non-toxic electrocatalysts with vacancy-mediated defects for oxygen evolution reaction.

Heterostructured CoFeP/CoP as an Electrocatalyst for Hydrogen Evolution in Alkaline Media

Developing highly efficient and persistent transition-metal-phosphide (TMP)-based electrocatalysts is critical for the hydrogen evolution reaction (HER) via water splitting in alkaline media. Herein, we constructed a unique heterostructured CoFeP/CoP grown on a nickle foam (NF) via hydrothermal and dipping methods followed by phosphorization at different temperatures for HER. The experimental results exhibit that the HER activity of CoFeP/CoP-400 is accelerated after the construction of heterostructures. The unique heterostructure provides plentiful active sites and a large surface area, which are beneficial for HER in 1.0 M KOH. CoFeP/CoP-400 displays a small overpotential of 78 mV at a current density of 10 mA cm^-2 and a smaller Tafel slope of 55.5 mV dec^-1. Moreover, CoFeP/CoP-400 shows excellent stability with a long-term operating time of 12 h. This work provides an effective method for the construction of TMPs with heterostructures for promoting energy conversion.

The facile fabrication and high-performance sensing of glucose of sea-urchin-like CoFeLDH/PBA/NF heterojunction

The sea-urchin-like CoFeLDH/PBA/NF heterojunction was successfully synthesized, exhibiting excellent glucose sensing performance with ultra-high sensitivity, outstanding reproducibility, stability and selectivity.

Chiral tetranuclear copper(ii) complexes: synthesis, optical and magnetic properties

The chiral tetranuclear Cu(ii) cubane complexes with the general molecular formula [Cu₄(R-L₁)₄] (R-1) and [Cu₄(S-L₁)₄] (S-1) exhibit ferromagnetic exchange coupling, which is in contrast to the literature reports. This is corroborated by theoretical calculations.

Preparation of Prussian Blue Containing Polymeric Nanocapsule via Interfacial Confined Coordination in Crosslinked Inverse Miniemulsion

This work presents a simple and facile strategy for the creation of Prussian blue containing polymeric nanocapsules. An crosslinked inverse miniemulsion with a formula of water/ K₄Fe(CN)₆/1,2-bis-(-2-iodoethyl) ethane(BIEE)/ toluene/ PDMAEMA-b-PS stabilizer mixture was prepared as soft template firstly. A crosslinking nanocapsule structure with K₄Fe(CN)₆ in water core could be achieved by a crosslinking reaction between PDMAEMA-b-PS stabilizers and BIEE. Upon the following addition of FeCl₃ ether solution into the oil phase of this inverse miniemulsion, a coordination reaction between two iron salts occurred immediately to form a Prussian blue complex. Due to the solubility limitation of FeCl₃ in the oil phase of the miniemulsion, forcing the coordination reaction of K₄Fe(CN)₆ and FeCl₃ mainly occurred at the oil-water interface of the nanocapsules, resulting in a soft polymer/Prussian blue(PB) hybrid nanocapsule.

A breakthrough in the intrinsic multiferroic temperature region in Prussian blue analogues

Thin films of [(Fe^II_xCr^II_1−x)]_1.5[Cr^III(CN)₆]·yH₂O (x ≈ 0.30–0.35, y ≈ 1.77) (1) on FTO substrates (namely film 1) were synthesized with an electrochemical method. Investigation of the ferroelectricity of film 1 at different temperatures reveals that it exhibits ferroelectric behaviour in the temperature range from 10 K to 310 K. Study of the X-ray absorption (XAS) of the crushed film 1 and simulation of the structure of film 1 and crushed film 1 by using the Materials Studio software indicate that the vacancy defects and interactions between the film and FTO substrate make a key contribution to the ferroelectricity of film 1. Owing to the magnetic phase transition point being up to 210 K, film 1 is a multiferroic material and its magneto/electric coexistence temperature can be as high as 210 K.

Prussian blue analogue film exhibits ferroelectric from 10 to 310 K and works up to 210 K as a molecular-based multiferroic material.

Electrical and room temperature multiferroic properties of polyvinylidene fluoride nanocomposites doped with nickel ferrite nanoparticles

The higher values of magneto-dielectric coupling is observed in flexible multiferroic polyvinylidene fluoride (PVDF) nanocomposites doped with nickel ferrite (NFO) nanoparticles.

Coordinating gallium hexacyanocobaltate: Prussian blue-based nanomaterial for Li-ion storage

Prussian blue analogs (PBAs) are a type of metal–organic framework and have drawn significant attention recently. To date, most are constructed with divalent transition metal ions coordinated to the N end of a cyanide bridge. In this report, we studied a trivalent gallium ion-based Ga hexacyanocobaltate (GaHCCo), which depicted a face-centered cubic crystal structure. In addition, the synthesized GaHCCo was demonstrated as a cathode material of lithium-ion batteries (LIBs) and was found to exhibit long-term stability, having a capacity retention of 75% after 3000 cycles of repeated charge–discharge cycling and an extremely high coulombic efficiency of 98%, which was achieved because of a solid-state diffusion controlled Li-ion storage process. After ex situ XRD analysis on the different charge stages, the Li-ion storage in the GaHCCo was attributed to the Co species via the formation of a Li/Co compound. This work will pave the way toward the study of PBAs constructed with trivalent metal ions and provide more insights into the development of high-performance LIBs in the future.

A newfound Prussian blue analog, gallium hexacyanocobaltate, has been demonstrated as an electrode material for Li-ion storage.