Since the emergence of organic-inorganic hybrid perovskite materials as light harvesters, the perovskite solar cells have attained a considerable efficiency improvement due to notable achievements in optimizing the fabrication process and device structure, while nevertheless been suffering increasingly serious challenges, especially instability. Layered (low-dimensional) perovskite materials are constructed based on a periodical (or quasi-periodical, or hybridized) structure which is composed of alternate layers of organic amines and metal halide perovskite crystals. The layered structure approximates to a two-dimensional structure whilst the number (n) of planes, which consist of the pyramids’ squares of the perovskite octahedrons, within one separated perovskite layer approaches 1. For photovoltaic application, these low-dimensional perovskite structures have two advantages compared to their three-dimensional counterparts: I. remarkably enhanced moisture resistance and thermal stability; II. tunable optical and electrical characteristics by varying n and selecting different organic amines.

On the other hand, poor carrier mobility (a consequence of the inhibition of out-of-plane charge transport by the organic amine cations) and wide band gap contribute to a far lower efficiency of low-dimensional perovskite solar cell than three-dimensional perovskite device. This urges intensive research endeavors to seek favorable organic amines and optimize perovskite film fabrication process, aiming at boosting photovoltaic efficiency while exploiting layered perovskite’s stability. And in the past three years, impressive strides have been made in promoting the low-dimensional perovskite solar cells, with a giant leap in the reported power conversion efficiency (PCE) from 4.37% to 13.7%.

Phenethylamine (PEA), n-butylamine (n-BA), isobutylamine (iso-BA), polyethylenimine (PEI), etc. have been found to be satisfactory as the hydrophobic amine interlayers for relatively-high-efficiency layered perovskite solar cells. PEA is the first to be involved in the attempts, and the n-BA-intercalated perovskite hold the currently highest efficiency of this new type of photovoltaic devices. PEI intercalation appears to result in narrower band gap and higher moisture resistance, but also leads to a larger inhibition to the carrier transport. Although one-step spin coating provides a facile route to obtain layered perovskite films, this method will cause the horizontal growth (i.e. interlayers parallel to substrate) of the layered structure and in consequence, an extremely low cell efficiency. Works in the past two years have established a new avenue to overcome the low-efficiency bottleneck, by introducing various techniques into the spin coating process, e.g. hot casting, immersion (in short-chain amines), antisolvent dripping, all of which have successfully achieved the preferential out-of-plane alignment of the inorganic perovskite layers. Besides, researchers also have demonstrated that the 2D-3D hybrid perovskite structures, which can be constructed on the basis of 3D perovskite with the presence of organic amine additives, can gain improvements in terms of both efficiency and stability.

This review offers a retrospection of the research efforts with respect to the layered (low-dimensional) perovskite photovoltaic devices, and provides elaborate descriptions about the structure of low-dimensional perovskite, the selection of the intercalating organic amines, and the film fabrication process. We then pay attention to the problems confronting the current state-of-the-art low-dimensional perovskite solar cells. We have confidence that the low-dimensional perovskite solar cells have a bright future in the development and innovation of stable and environmental-friendly photovoltaic devices.

The over-exploitation and over-utilization of fossil fuel resources such as petroleum and coal has aggravated energy and environment problem in the 21st century, and urged the development of highly-efficient and cost-effective energy conversion and storage devices to become the research topic of this new era. Among many candidates of energy conversion and storage devices, metal-air batteries and intermediate-low temperature solid oxide fuel cells can efficiently convert chemical energy into electric energy, and enjoy the advantages of low cost, high efficiency and environmental friendliness. Hence, they have provoked intensive and fruitful research endeavors with amazing achievements over the past decade. However, the sluggish kinetics of the oxygen reduction and evolution reactions greatly reduces the energy conversion efficiency, and consequently increases the application cost and severely hinders the commercialization of these two devices. Cobalt-based electrocatalysts, as highly efficient cathode materials with lower cost than noble metals, feature mixed ionic and electronic conductivity which can effectively reduce polarization and contribute to high catalytic activity for oxygen reduction and evolution reactions, and thereby have been holding growing interest recently.

　For metal-air batteries, cobalt-based electrocatalysts such as simple oxides, spinel oxides, perovskite oxides, and others can significantly improve the discharge capacity and cycle life, and simultaneously, lower the charge voltage and polarization. On the other hand, the catalytic activity and stability need to be further enhanced, and the catalytic mechanisms and active sites deserve further rational exploration and ascertainment. Similarly, cobalt-based electrocatalysts including La_1-xSr_xCoO_3-δ, La_1-xSr_xCo_1-yFe_yO_3-δ, Ba_1-xSr_xCo_yFe_1-yO_3-δ and cobalt-based double perovskites show evident efficacy in reducing the cathode polarization resistance and area specific resistance as well as increasing the power density, while nonetheless sustaining a generally higher thermal expansion coefficient and a rather poor stability compared to some other competitors.

　To further improve the catalytic performance of cobalt-based electrocatalysts for metal-air batteries and intermediate-low tempe-rature solid oxide fuel cells, researchers have developed many useful and productive methods, exemplified by metal elements doping, composite cathode materials preparation, and noble metals decoration.

　This review provides a brief introduction of the structure and working principle of metal-air batteries and intermediate-low temperature solid oxide fuel cells, and a vivid description upon the latest attempts and achievements for the fabrication, modification and performance of the rich variety of cobalt-based electrocatalysts, mainly including simple oxides, perovskites oxides, spinel oxides and double perovskites.

The lithium-ion battery anode material have been prepared from humic acid through high-temperature heat treatment. The morphology, microcrystalline structure and electrochemical properties of as-prepared activated material were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical testing system. The results indicated that the humic acid-based graphitized materials showed a more regular graphite lamellar structure, and the degree of graphitization of the materials was also getting higher and higher with the increase of graphitization temperature. The humic acid-based graphitized mate-rials all presented good electrochemical performance. The graphitized material with the temperature of 2 800 ℃ had a first discharge specific capacity of 356.7 mAh/g and a charge capacity of 277.6 mAh/g, and the initial coulombic efficiencies was 77.81%. The capacity retention rate after 50 cycles at 1C and 2C rates was as high as 99.4% and 95.9%, respectively. The above results suggest that the humic acid-based graphitized material is an ideal lithium ion battery anode material.

It is difficult and urgent task to develop a high-performance plasma facing materials for current nuclear fusion research by the irradiation behavior of PFMs, which is suitable for advanced experiment superconducting tokamak (EAST), international thermonuclear fusion reactor (ITER) and China fusion engineering experiment reactor (CFETR). Tungsten is considered to be the primary candidate for plasma facing materials in future fusion reactors owing to its superiority to other materials including high melting point, high thermal conductivity, low sputter corrosion rate, high sputtering threshold, low vapor pressure and low tritium inventory. In this paper, we review the research progress of damage of tungsten and tungsten alloy irradiated by various particles. The defects caused by irradiation are accumulate in tungsten and tungsten alloy. The formation and quantity of defects are closely related to the microstructure of the tungsten and the second phase components, the situation of defects are diverse. At the same time, the irradiation conditions, for instance, the kinds of particles, energy, flux and temperature, will also have an important impact on the morphology and defect of the irradiated sample.

The behaviors of fatigue crack initiation of 316LN and Z3CN20.09M austenite stainless steels (ASSs) were studied by corrosion fatigue test system in high temperature water. The results indicated that the fatigue cracks were mainly initiated at the persistent slip bands (PSBs) on the surface of 316LN ASS. Only a few cracks were initiated at the sub-grain boundaries. While the fatigue cracks were sequentially initiated at PSBs, phase boundaries and corrosion pits of the Z3CN20.09M ASS containing a little part of ferrite, and they were also mainly initiated at PSBs. The crack initiation mechanism at PSBs was analyzed based on composition of oxide film and morphology of cross section of the specimens tested in high temperature water. Moreover, the difference of the crack initiation mechanisms for two kinds of stainless steel was analyzed. Finally, the effect of the ferrite phase on corrosion fatigue property was summarized.

During the process of the aniline polymerization, bivalent cobalt salt with different anionic groups such as (C₂H₃O₂)₂^2-, Cl₂^2-, (NO₃)₂^2-, SO₄^2- and C₂O₄^2- were added into the solution and then different polyaniline cobalt (PANI-Co) coordination polymer were obtained. Finally, Co-N-C catalysts were prepared through pyrolysis of PANI-Co coordination polymer. The morphology, structure, chemical composition and chemical valence of the Co-N-C catalysts were characterized by scanning electron microscopy (SEM), X-ray spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectra (Raman). The electrocatalytic activity of Co-N-C catalysts were tested by electrochemical method. The results showed that the cobalt salt anionic groups had little impact on the morphology of Co-N-C catalysts, but had a great influence on the composition and surface chemistry of Co-N-C catalysts, carbon structure, degree of graphitization and the valence of Co. The cobalt salt anionic groups could affect the electrocatalytic activity of Co-N-C catalysts. The catalytic activities decreased as (C₂H₃O₂)₂^2-＞Cl₂^2-＞(NO₃)₂^2-＞SO₄^2-＞C₂O₄^2-. The Co-N-C catalysts prepared by cobalt salt containing (C₂H₃O₂)₂^2- and Cl₂^2- anions had higher ORR activity, which possibly due to the higher content of graphite nitrogen and pyridine nitrogen.

High-rate SiO₂/C composite (called SiO₂-130/C) was synthesized using tetraethyl orthosilicate (TEOS) as SiO₂ precursor in a amphiphilic carbonaceous material (ACM)-polyethylene glycol 400(PEG 400) mixture. Confinement effect of smaller cells formed by ACM and PEG 400 on diameter of SiO₂ was studied. The results showed that the diameter of SiO₂ nanospheres was reduced from 500 nm (without confinement effect) to 130 nm (with confinement effect),and carbon framework resulting from carbon-rich ACM was constructed on the surface of SiO₂. Electrochemical performance of SiO₂-130/C composite was evaluated as anode material for lithium ion batteries. The reversible capacities of the SiO₂-130/C composite were 527 mAh ·g ^-1 and 347 mAh·g ^-1 at current densities of 0.1 A·g ^-1and 1 A·g ^-1, respectively. Moreover, the SiO₂-130/C composite, after the process of electrochemical activation, exhibited reversible capacitance as high as 483 mAh·g ^-1 at a current density of 1 A·g ^-1 over 400 cycles,indicating great rate performance and long-term cycling stability of the as-prepared SiO₂-130/C composite.

The nano-Au@PANI was prepared via a two-step method of oxidative polymerization by controlling the diffusion of oxidizing agents. The morphology of nano-Au@PANI was characterized by TEM, and the performances of supercapacitor were measured by electrochemical work-station (CHI660E). Furthermore, the relationship of reaction time and the performances of supercapacitor were also studied. The results showed that the nano-Au@PANI composites possessed yolk-shell structure, and with extension of reaction time the specific capacitance first increased and then decreased. When the reaction time was 12 h, the shell thickness of PANI was about 21 nm, the specific capacitance was up to 79 F·g ^-1.

Advanced fission and fusion reactors require high-performance alloys with outstanding microstructure and property stability in ultra-severe service environment including high temperature and high pressure, intense neutron irradiation and long service life. Oxide dispersion strengthened (ODS) steels have been considered as the most promising candidate as fuel cladding in Gen. Ⅳ reactor and structural materials in fusion blanket. Based on neutron irradiation damage, this paper reviews the latest research progress of irradiation-resistant ODS steels, focusing on the alloy design and advanced nanoscale second-phase particles characterization techniques.

V₂O₅ is suitable for lithium ion storage due to its unique layered structure. Compared with traditional cathode materials such as LiMn₂O₄, LiCoO₂ and LiFePO₄, V₂O₅ has the advantages of high theoretical specific capacity, excellent power density, low-cost and abundance, and has attracted extensive attention in the field of cathode materials for lithium-ion batteries. However, its low inherent conductivity and slow lithium ion diffusion coefficient cause the poor capacity retention and rate capability. In addition, repeated phase change will lead to the structural instability during the charge-discharge process, moreover, vanadium oxides can partially dissolve into electrolyte, which are detrimental to long-term cycling performance in electrochemical devices. Because of these restricting factors, it has been an important research hot spot for modifying the V₂O₅ inherent defects to improve the electrochemical performance of electrode materials. It will be possible for V₂O₅ cathode materials to exhibit excellent electrochemical performance by preparing nanostructured vanadium oxides to enlarge surface area and shorten the ion diffusion distance, and integrating with conductive materials and doping to enhance the electrical conductivity and cycle stability of materials. In this work, we introduce the improvement on vanadium oxides inherent defects from four aspects, including making nanostructured electrode materials, integrating with conductive materials, adjusting working voltage window and doping metal ions. The influence of various methods on the change of electrochemical performance is discussed as well.