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In this work, platinum group metal-free (PGM-free) electrocatalysts were synthesized, characterized, and tested for hydrogen evolution reaction (HER). These materials were mono, bi and trimetallic Ni-based electrocatalysts with the addition of a second or a third transition metal (TM) such as iron and cobalt. TM-phthalocyanine (TMPc) was used as a metal precursor, mixed with a conductive carbon backbone and subjected to pyrolysis in a controlled temperature and atmosphere. Two temperatures of pyrolysis (600°C and 900°C) were used. The effect of TM loading in the precursors and the different pyrolysis temperatures on the surface chemistry and morphology and the electrocatalytic activity towards HER were evaluated. The increase of NiPc in the initial mixture is beneficial to improve the electrocatalytic activity. The addition of a second and a third metal reflects positively on the HER performance. Interestingly, the pyrolysis temperature influences both the formation and growth of the nanoparticles and this information is supported by high-resolution transmission electron microscopy (HR-TEM) and light synchrotron X-ray Absorption Spectroscopy (XAS) measurement.

Ionic skin, as an emerging subclass of artificial skin, has been proposed and developed for nearly a decade, which makes up for the partial shortcomings of electronic skin to some extent. Highly similar to the ion-sensing mechanism of natural skin, the ionic skin also acquires and conducts perceptual signals in the form of ions. During this decade, a great deal of effort has been devoted to the species amplification of ionic soft matter and the discovery of new mechanisms of artificial ion sensing. It is worth emphasizing that the deciphering of the perceptual mechanisms of natural skin has inspired a great number of bionic studies in pursuit of the reproduction of natural touch in ionic skin. Ionic skin, as a multi-functional operating platform, is also endowed with attractive functions that are beyond natural skin. The birth and appearance of ionic skin greatly promote the vigorous development of products in the era of the internet of things, such as human-machine interaction, prosthetics and wearable devices. In this review, on the basis of explaining the perceptual mechanism of natural skin, we deeply analyze the progressive sensing mechanism of bionic ionic skin. The typical cases of ionic skin that are beyond the ability of natural skin are also summarized in detail. Finally, constructive perspectives and common issues are presented for the future development of ionic skin.

The influences of increasing the number of d-electrons in the single metal (Fe-like) substituted (111)n surface of γ-Al2O3 on its possible catalytic effects were explored. The energetic properties, local structures, and in-site electron configurations of the most active tri-coordinated Co and Ni single-site (111)n surface of γ-Al2O3 have been studied using the density functional theory (DFT) approach under periodic boundary conditions. The replacement of Al by a Co or Ni atom on the I position of the (111)n surface leads to significant elongations of metal–O distances. The energy released from the substitution process on the AlI site of the (111)n surface follows the sequence NiI (164.85 kcal mol?1) > CoI (113.17 kcal mol?1) > FeI (44.30 kcal mol?1). The triplet and quintet (ground state) of the CoI substituted complex are energy degenerate. Also, the doublet and quartet (ground state) of the NiI substituted complex have the same stable energy. This energy degeneracy comes from the α–β electron flipping on the p-orbital of the neighboring O that is next to the substituted CoI or NiI site on the (111)n surface of γ-Al2O3. Different from the FeI substituted single-site (111)n surface, in which the electron configuration of FeI varies according to its spin-multiplicity state, substituted NiI has a unique d8 electron configuration in all three spin states, and similarly, CoI has a unique d7 electron configuration in all three open shell spin states. An increase of the population of d-electrons in the single metal substituted (111)n surface of γ-Al2O3 is likely to provide a more stable electron configuration in the metal catalytic center.

Ionic liquids (ILs) provide a promising way for efficient absorption and separation of ammonia (NH3) due to their extremely low vapor pressures and adjustable structures. However, the understanding of absorption mechanisms especially in terms of theoretical insights is still not very clear, which is crucial for designing targeted ILs. In this work, a universal method that integrates density functional theory and molecular dynamic simulations was proposed to study the mechanisms of NH3 absorption by protic ionic liquids (PILs). The results showed that the NH3 absorption performance of the imidazolium-based PILs ([BIm][X], X= Tf2N, SCN and NO3) is determined by not only the hydrogen bonding between the N atom in NH3 and the protic site (H–N3) on the cation but also the cation–anion interaction. With the increase in NH3 absorption capacity, the hydrogen bonding between [BIm][Tf2N] and NH3 changed from orbital dominated to electrostatic dominated, so 3.0 mol NH3 per mol IL at 313.15 K and 0.10 MPa was further proved as a threshold for NH3 capacity of [BIm][Tf2N] by the Gibbs free energy results, which agrees well with the experimental results. Furthermore, the anions of [BIm][X] could also compete with NH3 for interaction with H-N3 of the cation, which weakens the interaction between the cation and NH3 and then decreases the NH3 absorption ability of PILs. This study provides further understanding on NH3 absorption mechanisms with ILs, which will guide the design of novel functionalized ILs for NH3 separation and recovery.

Direct regeneration is a low-cost and environmentally friendly way of recycling spent Li-ion batteries. In this study, a new method is adopted to regenerate spent LiFePO4. First, the spent LiFePO4 powder is homogenized, and then, small amounts of a lithium source and a carbon source are thoroughly mixed by spray drying. After that, a high-temperature solid-phase method is used to regenerate the carbon-coated lithium iron phosphate. Compared with traditional regeneration methods, the proposed method significantly improves the universality of spent LiFePO4 having different degrees of damage. The regenerated LiFePO4 is characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electrochemical measurements. The results show that the regenerated sample has a stable morphology, structure, and electrochemical performance. Under the conditions of 0.1C, the initial capacity exceeds 160 mA h g?1. After 800 cycles under the conditions of 1C, the capacity retention is 80%, which satisfies the requirements for regenerated LiFePO4 batteries.

Two-dimensional metal-organic-framework (2D MOF) nanosheets with modular nature and tunable structures exhibit bright future for the sensor, separation, and catalysis. Developing ultrathin 2D MOF nanosheets with unique physical and chemical properties are urgently requested but very challenging. Although the chemical exfoliation strategy has been regarded as a promising way to the exfoliation of large amounts of three-dimensional (3D) pillar-layered MOFs, this method still faces many problems and remains insufficient. In this work, a novel chemical exfoliation method is developed for target preparation of 2D MOF monolayers from the 3D pillar-layered MOFs. The Co/Zn/Cu-MOFs with pillar ligand of trans-1,2-bis(4-pyridyl)ethylene (bipyen) are subjected to be broken by the cleavage of C=C bonds in the bipyen ligands via an ozone oxidation reaction. As chemical exfoliation is processed via oxidation of the pillar ligand by ozone, the thickness of the 2D MOFs can be tuned by the control of oxidation time and the obtained 2D Co/Zn/Cu-MOF monolayers are functionalized with -COOH group. This work provides an effective and generality chemical exfoliation method to prepare monolayer MOFs from the 3D pillar-layered MOFs with bipyen as pillar ligand.

Carbon capture and storage (CCS) technology is believed to be a promising solution for global CO2 emission control and climate change. However, the application of CCS projects is facing a dilemma due to their negative cash flow. To address the challenge, it is critical to adopt an innovative technology that can capture and convert CO2 simultaneously with satisfying efficiencies and can make a profit for the end users. Recently, molten salt CO2 electrolysis that splits CO2 into carbon and oxygen has been extensively studied. This study reviews the process mechanisms, the salt selection, and the effects of operating conditions, including temperature and voltage. In most reported articles, the CO2 to carbon conversion efficiency reached at least 80%, and the current efficiency is over 90%, proving the promising potential of the molten salt CO2 electrolysis method. Still, some aspects, such as the impurities' influences and electrode corrosion, have not been thoroughly investigated. Therefore, some suggestions are recommended for future work.

Yolk–shell urchin-like porous Co3O4/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere. High reversible specific capacity, long cycling stability, and excellent rate capability were achieved for the material due to its specific yolk–shell urchin-like porous structure and coated carbon layers. The pores distributed on the yolk and shell, as well as the gap between the yolk and shell, provide numerous pathways for the penetration of electrolyte, and enhance the reversible specific capacity (the initial discharge specific capacity was as high as 1405.7 mA h g?1 at 0.1 C). Meanwhile, the stress and volume expansion could be greatly released and relieved through the pores, and long cycling stability was achieved (a high reversible specific capacity of 502.7 mA h g?1 was maintained after 1000 cycles at 5 C). The coated carbon layers greatly enhance the conductivity of the yolk–shell urchin-like porous Co3O4/NiO microspheres, accelerate the transmission of electrons, and improve their rate performance (a reversible specific capacity of 397.5 mA h g?1 was achieved when the current density was increased to 10 C).

Organic materials with room-temperature phosphorescence (RTP) emission have attracted extensive attention owing to their extraordinary properties, including long lifetime, large Stokes shift, and stimuli-responsiveness, and show bright prospects in broad fields. Numerous design strategies, such as creating a rigid environment through crystallization and supramolecular assembly, can be employed to improve the luminescent characteristics of RTP materials by restricting nonradiative transition, enhancing intersystem crossing, and so forth. This review summarizes recent progress with organic room-temperature phosphorescent materials from the perspective of practical applications, including luminescence and display, environmental detection, and bioimaging, and the challenges and prospects will be discussed at the end, which should assist with future research on the application of RTP materials.

To develop graphene-based nanomaterials as reliable catalysts for electrochemical energy conversion and storage systems ( e.g. PEM fuel cells, metal–air batteries, etc. ), it is imperative to critically understand their performance changes and correlated material degradation processes under different operational conditions. In these systems, hydrogen peroxide (H 2 O 2 ) is often an inevitable byproduct of the catalytic oxygen reduction reaction, which can be detrimental to the catalysts, electrodes, and electrolyte materials. Here, we studied how the electrocatalytic performance changes for a heterogeneous nanocatalyst named nitrogen-doped graphene integrated with a metal–organic framework (N-G/MOF) by the effect of H 2 O 2 , and correlated the degradation process of the catalyst in terms of the changes in elemental compositions, chemical bonds, crystal structures, and morphology. The catalyst samples were treated with five different concentrations of H 2 O 2 to emulate the operational conditions and examined to quantify the changes in electrocatalytic performances in an alkaline medium, elemental composition and chemical bonds, crystal structure, and morphology. The electrocatalytic performance considerably declined as the H 2 O 2 concentration reached above 0.1 M. The XPS analyses suggest the formation of different oxygen functional groups on the material surface, the breakdown of the material's C–C bonds, and a sharp decline in pyridinic-N functional groups due to gradually harsher H 2 O 2 treatments. In higher concentrations, the H 2 O 2 -derived radicals altered the crystalline and morphological features of the catalyst. Keywords: Nitrogen-doped graphene-based electrocatalyst; Metal–organic framework; Hydrogen peroxide effect on catalyst; Electrocatalytic performance; Material degradation.