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Recycling of spent lithium-ion batteries has recently become a critical issue based on environmental concerns and a desire to reutilize resources. Among the existing recycling strategies, direct regeneration is largely encouraged from an economic and environmental perspective. However, current procedures used to separate the active cathode materials from the aluminum foil have some limitations for direct regeneration because they either destroy the structure of the cathode or use too many toxic and expensive reagents. Hence, we conducted comprehensive research on the microstructural evolution of the LiNi1−x−yCoxMnyO2 degraded electrode and then proposed a targeted method to recycle the spent cathode materials based on the increased residual lithium compounds. This separation process involves no other reagents but water, and toxic organic solvents, complicated processes, and waste treatments are unnecessary compared with the existing pretreatment strategies. Moreover, the separated cathodes are suitable for direct regeneration. Satisfactory capacity recovery of the cathode was achieved via simple sintering. Such a recycling process enables a sustainable closed-loop for the spent cathodes and provides new inspiration for the design of LIB recycling.

Sulfide-based solid-state electrolytes (SSEs) matched with alloy anodes are considered as promising candidates for application in all-solid-state batteries (ASSBs) to overcome the bottlenecks of the lithium (Li) anode. However, an understanding of the dynamic electrochemical processes on alloy anode in SSE is still elusive. Herein, in situ atomic force microscopy gives insights into the block-formation and stack-accumulation behaviors of Li precipitation on an Li electrode, uncovering the morphological evolution of nanoscale Li deposition/dissolution in ASSBs. Furthermore, two-dimensional Li-indium (In) alloy lamellae and the homogeneous solid electrolyte interphase (SEI) shell on the In electrode reveal the precipitation mechanism microscopically regulated by the alloy anode. The flexible and wrinkle-structure SEI shell further enables the electrode protection and inner Li accommodation upon cycles, elucidating the functional influences of SEI shell on the cycling behaviors. Such on-site tracking of the morphological evolution and dynamic mechanism provide an in-depth understanding and thus benefit the optimizations of alloy-based ASSBs.

With the increasing demands for energy utilization and storage, the secondary lithium batteries with high energy-density and high safety performance are being continuously developed and improved. An in-depth understanding of the electrochemical process and corresponding micro-mechanism at the electrode/electrolyte interface of lithium batteries during charging and discharging is beneficial to open new avenues of guiding the optimal design of battery materials. In situ electrochemical atomic force microscopy (AFM) combines high-resolution surface-imaging of AFM with electrochemical characterizations, unraveling the direct visualization and dynamic evolution of the electrode/electrolyte interface in a working battery at nanoscale. This article reviews the latest research progress of in situ electrochemical AFM investigations into the electrode processes of lithium batteries, including the interfacial reaction process of the conversion-type cathode, the dynamic evolution of the solid electrolyte interphase film at the electrode/electrolyte interface, and the structural evolution in solid-state lithium batteries.

The development of advanced transition metal/nitrogen/carbon-based (M/N/C) catalysts with high activity and extended durability for oxygen reduction reaction (ORR) is critical for platinum-group-metal (PGM) free fuel cells but still remains great challenging. In this review, we summarize the recent progress in two typical M/N/C catalysts (atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts and carbon-supported metal nanoparticles with N-doped carbon shells (M@NC)) with an emphasis on their potential applications in fuel cells. Starting with understanding the active sites in these two types of catalysts, the representative innovative strategies for enhancing their intrinsic activity and increasing the density of these sites are systematically introduced. The synergistic effects of M-N-C and M@NC are subsequently discussed for those M/N/C catalysts combining both of them. To translate the material-level catalyst performance into high-performance devices, we also include the recent progress in engineering the porous structure and durability of M/N/C catalysts towards efficient performance in fuel cell devices. From the viewpoint of industrial applications, the scale-up cost-effective synthesis of M/N/C catalysts has been lastly briefed. With this knowledge, the challenges and perspectives in designing advanced M/N/C catalysts for potential PGM-free fuel cells are proposed.

Recent advances in spherical mesoporous metal oxides (SMMOs) have demonstrated their enormous potential in a large variety of research fields. However, a direct creation of these materials with precise control on their key shape features, particularly pore architectures, remains a major challenge as compared to the widely explored counterpart of silica. Here, using Al

Unstable electrode/solid-state electrolyte interfaces and internal lithium dendrite penetration hamper the applications of solid-state lithium-metal batteries (SSLMBs), and the underlying mechanisms are not well understood. Herein, in situ optical microscopy provides insights into the lithium plating/stripping processes in a gel polymer electrolyte and reveals its dynamic evolution. Spherical lithium deposits evolve into moss-like and branch-shaped lithium dendrites with increasing current densities. Remarkably, the on-site-formed solid electrolyte interphase (SEI) shell on the lithium dendrite is distinctly captured after lithium stripping. Inducing an on-site-formed SEI shell with an enhanced modulus to wrap the lithium precipitation densely and uniformly can regulate dendrite-free behaviors. An in-depth understanding of lithium dendrite evolution and its functional SEI shell will aid in the optimization of SSLMBs.

Because of its high theoretical specific capacity and low reduction potential, Li metal is considered to be key to reaching high energy density in rechargeable batteries. In this context, most of the research has focused on suppressing dendrite formation during Li deposition to improve the cycling reversibility and safety of the batteries. Here, covalent organic framework (COF) film coating on a commercial polypropylene separator is applied as an ion redistributor to eliminate Li dendrites. The COF crystallites consist of ordered nanochannels that hinder the movement of anions while allowing Li-ions to transport across, leading to a high Li-ion transference number of 0.77±0.01. The transport of Li-ions across the COF film can be considered to be analogous to beads passing through a Galton Board, a model that demonstrates a statistical concept of a normal distribution. Thus, an even distribution of Li-ions is obtained at the COF Li metal interface. The controlled Li-ion flux yields a smooth Li metal surface after 1,000 h (500 times) of cycling, leading to a significantly improved cycling stability and reversibility, as demonstrated by Cu||Li half cells, Li||Li symmetric cells, and LiFePO4||Li full cells. These results suggest that, following the principle of a Galton Board, nanopore insulators such as COF-based materials are effective ion distributors for the different energy storage or conversion systems.

We report a molecular investigation of a cobalt phthalocyanine (CoPc)-catalyzed CO2 reduction reaction by electrochemical scanning tunneling microscopy (ECSTM). An ordered adlayer of CoPc was prepared on Au(111). Approximately 14 % of the adsorbed species appeared with high contrast in a CO2 -purged electrolyte environment. The ECSTM experiments indicate the proportion of high-contrast species correlated with the reduction of CoII Pc (-0.2 V vs. saturated calomel electrode (SCE)). The high-contrast species is ascribed to the CoPc-CO2 complex, which is further confirmed by theoretical simulation. The sharp contrast change from CoPc-CO2 to CoPc is revealed by in situ ECSTM characterization of the reaction. Potential step experiments provide dynamic information for the initial stage of the reaction, which include the reduction of CoPc and the binding of CO2 , and the latter is the rate-limiting step. The rate constant of the formation and dissociation of CoPc-CO2 is estimated on the basis of the in situ ECSTM experiment.

Single-molecule conductance of a B-N substituted phenanthrene derivative and its isoelectronic C═C counterpart was investigated by the scanning tunneling microscopy break junction (STM-BJ) technique. The incorporation of the B-N motif results in a better single-molecule conductivity than the C═C analogue. Furthermore, the Lewis acid-base reaction between F

Lithium metal batteries are vital devices for high-energy-density energy storage, but the Li metal anode is highly reactive with electrolyte and forms uncontrolled dendrite that can cause undesirable parasitic reactions and, thus, poor cycling stability and raise safety concerns. Despite remarkable progress to partially solve these issues, the Li metal still plates at the electrode/electrolyte interface where the parasitic reactions and dendrite formation invariably occur. Here, we demonstrate the inward-growth plating of Li atoms into a metal foil of thickness of tens of micrometers while avoiding surface deposition, which is driven by the reversible solid-solution-based alloy phase change. Lithiation of the solid-solution alloy phase allows the freshly generated Li atoms at the surface to sink into the metal foil, while the reversible alloy phase change is companied by the dealloying reaction during delithiation, which extracts Li atoms from inside of the metal foil. The yielded dendrite free Li anode produces an enhanced Coulombic efficiency of 99.5 ± 0.2% with a reversible capacity of 1660 mA h g-1 (3.3 mA h cm-2).

Sodium-ion batteries (SIBs) are promising candidates for large-scale electric energy storage with abundant sodium resources. However, their development is challenged by the availability of satisfac...

With the potential to circumvent the need for scarce and cost-prohibitive platinum-based catalysts in proton-exchange membrane fuel cells, anion-exchange membrane fuel cells (AEMFCs) are emerging as alternative technologies with zero carbon emission. Numerous noble metal-free catalysts have been developed with excellent catalytic performance for cathodic oxygen reduction reaction in AEMFCs. However, the anodic catalysts for hydrogen oxidation reaction (HOR) still rely on noble metal materials. Since the kinetics of HOR in alkaline media is 2-3 orders of magnitude lower than that in acidic media, it is a major challenge to either improve the performance of noble metal catalysts or to develop high-performance noble metal-free catalysts. Additionally, the mechanisms of alkaline HOR are not yet clear and still under debate, further hampering the design of electrocatalysts. Against this backdrop, this review starts with the prevailing theories for alkaline HOR on the basis of diverse activity descriptors

The development of potassium-ion batteries (PIBs) is challenged by the shortage of stable cathode materials capable of reversibly hosting the large-sized K

Layered LiCoO

The complexity of chemical compounds in lithium-ion batteries (LIBs) results in great difficulties in the extraction of multiple transition metals, which have similar physicochemical characteristics. Here, we propose a novel strategy for selective extraction of nickel, cobalt, and manganese from spent LiNi

The application of solid-state batteries (SSBs) is challenged by the inherently poor interfacial contact between the solid-state electrolyte (SSE) and the electrodes, typically a metallic lithium anode. Building artificial intermediate nanofilms is effective in tackling this roadblock, but their implementation largely relies on vapor-based techniques such as atomic layer deposition, which are expensive, energy-intensive, and time-consuming due to the monolayer deposited per cycle. Herein, an easy and low-cost wet-chemistry fabrication process is used to engineer the anode/solid electrolyte interface in SSBs with nanoscale precision. This coordination-assisted deposition is initiated with polyacrylate acid as a functional polymer to control the surface reaction, which modulates the distribution and decomposition of metal precursors to reliably form a uniform crack-free and flexible nanofilm of a large variety of metal oxides. For demonstration, artificial Al

The increasing demand for high-energy Li-ion batteries (LIBs) continues to push the development of electrode materials, particularly cathode materials, towards their capacity limits. Despite the enormous success, the stability and reliability of LIBs are becoming a serious concern due to the much-aggravated side reactions between electrode materials and organic electrolytes. How to stabilize the cathode/electrolyte interface is therefore an imperative and urgent task drawing considerable attention from both academia and industry. An active treatment on the surface of cathode materials, usually by introducing an inert protection layer, to diminish their side reaction with electrolytes turns out to be a reasonable and effective strategy. This Feature Article firstly outlines our synthesis efforts for the construction of a uniform surface nanocoating on various cathode materials. Different wet chemical routes have been designed to facilitate the control of growth kinetics of targeted coating species so that a precise surface coating could be achieved with nanometer accuracy. Furthermore, we showed the possibility to transform the outer coating layer into a surface doping effect through surface solid reaction at high temperature. A detailed discussion on the structure-performance relationship of these surface-controlled cathode materials is introduced to probe the stabilization mechanism. Finally, perspectives on the development tendency of high-energy cathodes for stable LIBs are provided.

To investigate the genotypes and clinical characteristics of thalassemia on children in Wuhan region.A total of 159 patients diagnosed as thalassemia in Maternal and Child Health Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology from December 2017 to December 2019. The patients were retrospectively analyzed for their types of mutations, detection rates and clinical characteristics.Among the 422 samples, 159 samples were finally diagnosed as thalassemia through genetic testing, the total detection rate was 37.68%. The detection rate of α, β and αβ-thalassemia was 17.30%, 20.14% and 0.24% respectively. Among α-thalassemia, αα/-SEA was the most common one, with a composition ratio of 68.49%(50/73), followed by αα/-α3.7 (19.18%), αα/-α4.2 (6.85%) and αα/ QS (1.37%). 9 types of β-thalassemia gene mutations were detected, and the most common three mutations were IVSII-654(C→T), with a composition ratio of 40.00%, CD41-42(-TTCT) (20.00%) and CD17(A→T)(16.47%). Two novel mutations of β-thalassemia, HBB: c.92-2A＞T and HBB:c.-23A＞G were detected. Among all the positive patients, 134 (84.28%) were 0-3 years old, 19 (11.95%) were 4-6 years old, and 6 (3.77%) were 7 years of age or older. There were 147 patients with mild anemia (92.45%), 11 patients with moderate anemia (6.92%), and 1 patients with severe anemia (0.63%). The MCV of 94(59.12%) patients was lower than 65 fL, and that of 51(32.08%) patients was between 65 fL and 80 fL, while 14(8.81%) patients was higher than 80 fL. MCV in β-thalassemia group was lower than that in α-thalassemia group, and the difference showed statistically significant (P0.05).The genotypes of thalassemia in children in Wuhan area are diverse, and most of them are mild thalassemia, and diagnosed under 3 years old. Children with β-thalassemia have smaller red blood cell volumes than those with α-thalassemia.中国武汉地区儿童地中海贫血基因类型及临床特征分析.分析武汉地区儿童地中海贫血的基因型及临床特征.回顾性选取2017年12月至2019年12月于本院儿科就诊并确诊为地中海贫血的159例患儿，分析本地区儿童地贫基因型、检出率及其临床特征.共送检422份样品，其中159例通过基因检测确诊为地中海贫血，总检出率为37.68%。其中α-地中海贫血检出率为17.30%，β-地中海贫血检出率为20.14%，αβ-复合地中海贫血检出率为0.24%。α-地中海贫血中αα/-SEA最常见，共检出50例，构成比为68.49%，其次为αα/-α3.7 14例（19.18%），αα/-α4.2 5例 (6.85%)，αα/ QS 1例 (1.37%)；检出9种β-地中海贫血基因突变类型，最常见的3种突变类型依次为IVSⅡ-654(C→T) 34例（40.00%）、CD41-42(-TTCT) 17例（20.00%）、CD17(A→T) 14例（16.47%），检测出2例新发突变：HBB：c.92-2A＞T、HBB：c.-23A＞G。送检样本年龄在0-3岁者134例（84.28 %），4-6岁者19例（11.95%），＞7岁者6例（3.77%）。轻度贫血147例（92.45%），中度贫血11例（6.92%），重度贫血1例（0.63%）。MCV＜65 fL组94例（59.12%），65-80 fL组51例（32.08%），≥80 fL组14例（8.81%）。β-地中海贫血组MCV小于α-地贫组，差异有统计学意义（P＜0.05）.武汉地区儿童地中海贫血基因型具有多样性，与其他地区存在差异，且以轻型为主，多数于3岁以内确诊；β-地中海贫血患儿红细胞体积较α-地中海贫血更小.

Li‐based secondary batteries are now attracting soaring research attention as a promising energy storage system with high energy density for commercial applications. However, the high‐energy systems meanwhile are causing serious concerns on safety issues due to unstable interfaces on both cathodes and anodes. To improve interphase stability upon extended cycles, surface fluorinated treatment becomes highly desirable due to its unique capability in modulating the chemistry of electrode/electrolyte interface to ensure a stable electrochemical performance. Accordingly, it is essential that a deeper understanding on the solid electrolyte interphase (SEI), especially the role of fluorine‐containing components, is demanded to guide the interface design. This review begins with an introduction to the fundamental knowledge on the structure of SEI with focus on the unique physiochemical properties of fluorides. Detailed discussions are then taken on the control strategies for a reliable construction of fluoride‐based interfaces, which typically includes the surface coating of metal fluorides on cathodes and ex situ/in situ fluorination on lithium, based on which the structure–performance relationship is elaborated to inspire a rational interface engineering. Finally, perspectives are provided to give insights into the possible research directions of fluorinated SEI for further development of rechargeable Li batteries.

Solid-state Li-metal batteries offer a great opportunity for high-security and high-energy-density energy storage systems. However, redundant interfacial modification layers, intended to lead to an overall satisfactory interfacial stability, dramatically debase the actual energy density. Herein, a dual-interface amorphous cathode electrolyte interphase/solid electrolyte interphase CEI/SEI protection (DACP) strategy is proposed to conquer the main challenges of electrochemical side reactions and Li dendrites in hybrid solid-liquid batteries without sacrificing energy density via LiDFOB and LiBF4 in situ synergistic conversion. The amorphous CEI/SEI products have an ultralow mass proportion and act as a dynamic shield to cooperatively enforce dual electrodes with a well-preserved structure. Thus, this in situ DACP layer subtly reconciles multiple interfacial compatibilities and a high energy density, endowing the hybrid solid-liquid Li-metal battery with a sustainably brilliant cycling stability even at practical conditions, including high cathode loading, high voltage (4.5 V), and high temperature (45 °C) conditions, and enables a high-energy-density (456 Wh kg-1) pouch cell (11.2 Ah, 5 mA h cm-2) with a lean electrolyte (0.92 g Ah-1, containing solid and liquid phases). The compatible modification strategy points out a promising approach for the design of practical interfaces in future solid-state battery systems.

A hybrid solid/liquid electrolyte with superior security facilitates the implementation of high-energy-density storage devices, but it suffers from inferior chemical compatibility with cathodes. Herein, an optimal lithium difluoro(oxalato)borate salt was introduced to build in situ an amorphous cathode electrolyte interphase (CEI) between Ni-rich cathodes and hybrid electrolyte. The CEI preserves the surface structure with high compatibility, leading to enhanced interfacial stability. Meanwhile, the space-charge layer can be prominently mitigated at the solid/solid interface via harmonized chemical potentials, acquiring promoted interfacial dynamics as revealed by COMSOL simulation. Consequently, the amorphous CEI integrates the bifunctionality to provide an excellent cycling stability, high Coulombic efficiency, and favorable rate capability in high-voltage Li-metal batteries, innovating the design philosophy of functional CEI strategy for future high-energy-density batteries.

Hollow carbon nanospheres (HCNs) have found broad applications in different kinds of electrochemical storage devices. The characteristic hollow structure can endow carbon electrode materials with good reaction kinetics, high mechanical reliance against structural deformation, and powerful capability toward loading functional materials, which makes them particularly interesting for different energy storage systems. In this review, we summarize the recent progresses made in the research of HCNs, focusing on the synthesis strategies and corresponding applications as high-performance electrode materials in post lithium-ion battery (LIB) systems. Besides the widely implemented template-based routes, self-template routes based on the chemical design of polymeric precursors are also introduced. Efforts directed toward the shape evolution mechanism during synthesis, as well as the control capability of different methodologies on the key structural features of HCNs (such as shape, compositions, and architectures), will also be highlighted. Furthermore, we introduce the representative applications of the prepared HCNs in post LIBs, such as lithium–sulfur batteries, sodium-ion batteries, and potassium-ion batteries. We attempt to correlate the battery performance with the structural characteristics of HCNs so as to not only make good use of the advantage of shape control, but also facilitate understanding regarding the charge storage mechanism in the newly emerging technologies.

Although the significance of charge diffusion has been recognized in many high-performance energy devices, it has received very less attention in the design of electrocatalysts for the oxygen evolution reaction (OER), which is particularly crucial for highly active but less conductive OER electrocatalysts, such as two-dimensional metal hydroxides (MHs) with anisotropic conductivity. Herein, we report the elaborate design of a series of CoFe hydroxide nanosheets on graphene (CFH@G) composites to demonstrate the importance of charge diffusion regulation in improving the OER activity of MHs. It was discovered that the few-layer-thick CFH nanosheets lying on the graphene substrate provided an effective in-plane charge diffusion pathway, while keeping the substrate surface entirely covered by the laid nanosheets is necessary for providing sufficient active sites. The overly thick or stacked nanosheets are not favourable for charge diffusion, especially at large current outputs. By regulating the charge diffusion properties, the best-performing CFH@G-based material can deliver a steady OER current density of 2000 mA cm−2 at a cost of only 1.507 V under near-industrial conditions (6 M KOH and 60 °C). A practical water electrolyzer also demonstrated an impressive current output of 400 mA cm−2 at 1.694 V as well as a steady solar-to-hydrogen efficiency of 17.41%. These findings provide new insights into the role of charge diffusion in water oxidation and may open up an avenue for developing low-cost, stable and efficient electrocatalysts for practical water electrolysis and diverse energy devices.

The electrochromic property and device construction of a triphenylamine-based oriented two-dimensional covalent organic framework (2D COF) film on indium tin oxide (ITO) coated glass was reported. The characterization of the 2D COF3PA-TT film revealed that the film was uniform, with good crystallinity, and oriented with its 2D plane parallel to the substrate. For the first time, the electrochromic properties of 2D COF3PA-TT film were studied. 2D COF3PA-TT film on ITO exhibited reversible color transition between deep red and dark brown during redox process. Spectroelectrochemical experiments revealed color changes in the absorption spectra of 2D COF3PA-TT film in the visible and near-infrared regions and showed the characteristics of intervalence charge transfer. The quasi-solid-state electrochromic device was prepared based on the COF3PA-TT film, and it exhibited moderate performance and stability in the near-infrared region.

Alkaline hydrogen evolution reaction (HER), consisting of Volmer and Heyrovsky/Tafel steps, requires extra energy for water dissociation, leading to more sluggish kinetics than acidic HER. Despite the advances in electrocatalysts, how to combine active sites to synergistically promote both steps and understand the underlying mechanism remain largely unexplored. Here, Density Functional Theory (DFT) calculations predict that NiO accelerates the Volmer step while metallic Ni facilitates the Heyrovsky/Tafel step. A facile strategy is thus developed to control Ni/NiO heterosurfaces in uniform and well-dispersed Ni-based nanocrystals, targeting both reaction steps synergistically. By systematically modulating the surface composition, we find that steering the elementary steps through tuning the Ni/NiO ratio can significantly enhance alkaline HER activity, and Ni/NiO nanocrystals with a Ni/NiO ratio of 23.7% deliver the best activity, outperforming other state-of-the-art analogues. The results suggest that integrating bicomponent active sites for elementary steps is effective for promoting alkaline HER, but they have to be balanced.

High energy density batteries are urgently required for sustainable life. The intrinsic understanding of the reaction mechanism at the interfaces is essential for the progress. In this short overview, recent advances in rechargeable batteries by in situ atomic force microscopy are summarized, providing nanoscale information on the solid product evolution and metal plating/stripping inside working batteries. Besides, the multifunctional imaging of the morphology along with mechanical and electrical properties can be achieved to assist further interfacial design. Extensive applications of in situ atomic force microscopy are encouraged to explore the electrochemical mechanism and advanced engineering.

Li-metal anodes are one of the most promising energy storage systems that can considerably exceed the current technology to meet the ever-increasing demand of power applications. The apparent cycling performances and dendrite challenges of Li-metal anodes are highly influenced by the interface layer on the Li-metal anode because the intrinsic high reactivity of metallic Li results in an inevitable solid-state interface layer between the Li-metal and electrolytes. In this review, we summarize the recent progress on the interfacial chemistry regarding the interactions between electrolytes and ion migration through dynamic interfaces. The critical factors that affect the interface formation for constructing a stable interface with a low resistance are reviewed. Moreover, we review emerging strategies for rationally designing multiple-structured solid-state electrolytes and their interfaces, including the interfacial properties within hybrid electrolytes and the solid electrolyte/electrode interface. Finally, we present scientific issues and perspectives associated with Li-metal anode interfaces toward a practical Li-metal battery.

Silicon (Si) has been considered as one of the most promising anodes in secondary high-energy rechargeable lithium-ion batteries (LIBs) owing to its high theoretical specific capacity and abundant reserves, whereas it suffers from an unstable solid electrolyte interphase (SEI) film and dramatic volume expansion. Herein, in situ electrochemical atomic force microscopy (AFM) and visual videos were used to reveal the interphasial properties of SEI film and anisotropic dynamics upon lithiation/delithiation processes on the single-crystalline Si electrodes with different crystal plane orientations. Lithiation of Si (111) prefer to grow along the direction in the XY plane with the shape of oriented rods, in contrast, that of Si (100) form cone-like structure with the axial direction of perpendicular to the (100) surface. Quantitative dynamic processes elucidate the preferable reversibility in Si (111) system, revealing the corresponding structure-reactivity correlations.

K-ion batteries (KIBs) are drawing increasing research interest as a promising supplement of Li-ion batteries due to the natural abundance of K resource. However, due to the large size of K+, high-capacity anodes are challenged by the structural stability of the active materials which are susceptible to large volumetric deformation after incorporating with a sufficient number of K+. Herein, using SnS2/graphene as an example, we demonstrated that high-performance KIBs anode could be achieved through collaborative efforts targeting on both the active material and the prepared electrode film. The electrochemically-active species of SnS2 were controlled into small nanoparticles with their size below 5 nm to provide sufficient reactive sites for K+ storage. Meanwhile, highly-resilient electrode film based on the prepared SnS2/graphene nanocomposite was built on aluminum (Al) current collector rather than the widely-used copper foil, forming a strong anode film with high peel strength to endure the potassiation/depotassiation process. In this way, the active species was able to deliver an extraordinary reversible capacity of 610 mAh g−1 with unprecedented high-rate capability (around 290 mAh g−1 at 2A g−1) and promising cycling stability. This contribution sheds light on the rational design of high-performance electrode for KIBs and beyond.

We report an electrochemical scanning tunneling microscopy (ECSTM) study of the 5,10,15,20-tetraphenyl-21 H,23 H-porphyrin cobalt(II) (CoTPP) catalyzed oxygen evolution reaction (OER). A highly ordered self-assembled monolayer of CoTPP is formed on the Au(111) electrode. Cyclic voltammetry results show the OER activity of the electrode is enhanced with the increasing alkalinity of the electrolytes. The CoTPP molecules appear as two symmetric bright spots in STM images in alkaline solution, which is in sharp contrast to that in acidic solution. The molecular contour changes are attributed to the formation of the CoTPP-OH- species before OER, which is further confirmed by UV-vis absorption spectroscopy. In situ ECSTM results reveal the evolution from the CoTPP-OH- species to CoTPP molecules during OER.

Understanding catalytic mechanisms at the nanoscale is essential for the advancement of lithium-oxygen (Li-O2) batteries. Using in situ electrochemical atomic force microscopy, we explored the interfacial evolution during the Li-O2 electrochemical reactions in dimethyl sulfoxide-based electrolyte, further revealing the surface catalytic mechanism of the soluble catalyst 2,5-di- tert-butyl-1,4-benzoquinone (DBBQ). The real-time views showed that during discharge flower-like Li2O2 formed in the electrolyte with DBBQ but small toroid without DBBQ. Upon charge, Li2O2 decomposes at a slow rate from bottom to top in the absence of DBBQ, yet with an outside-in approach in the presence of DBBQ. Bigger discharge products and more efficient decomposition pathways in the DBBQ-containing system reveal the catalytic activity of DBBQ straightforwardly. Our work provides a direct insight into the surface effect of soluble catalyst DBBQ on Li-O2 reactions at the nanoscale, which is critical for the performance optimization of Li-O2 batteries.

Ni or Co is commonly required in efficient electrocatalysts for oxygen evolution reaction (OER). Although Fe is much more abundant and cheaper, full-Fe or Fe-rich catalysts suffer from insufficient activity. Herein, we discover that Se-doping can drastically promote OER on FeOOH and develop a facile on-site electrochemical activation strategy for achieving such a Se-doped FeOOH electrode via an FeSe precatalyst. Theoretical analysis and systematic experiments prove that Se-doping enables FeOOH as an efficient and low-cost OER electrocatalyst. By optimizing the electrode structure, an industrial-level OER current output of 500 mA cm-2 is secured at a low overpotential of 348 mV. The application of such an Fe-rich OER electrode in a practical solar-driven water splitting system demonstrates a high and stable solar-to-hydrogen efficiency of 18.55%, making the strategy promising for exploring new cost-effective and highly active electrocatalysts for clean hydrogen production.

The development of high energy electrode materials for lithium ion batteries is challenged by their inherent instabilities, which become more aggravated as the energy densities continue to climb, accordingly causing increasing concerns on battery safety and reliability. Here, taking the high voltage cathode of LiNi0.5Mn1.5O4 as an example, we demonstrate a protocol to stabilize this cathode through a systematic phase modulating on its particle surface. We are able to transfer the spinel surface into a 30 nm shell composed of two functional phases including a rock-salt one and a layered one. The former is electrochemically inert for surface stabilization while the latter is designated to provide necessary electrochemical activity. The precise synthesis control enables us to tune the ratio of these two phases, and achieve an optimized balance between improved stability against structural degradation without sacrificing its capacity. This study highlights the critical importance of well-tailored surface phase property for the cathode stabilization of high energy lithium ion batteries.

Although single-atomically dispersed metal-Nx on carbon support (M-NC) has great potential in heterogeneous catalysis, the scalable synthesis of such single-atom catalysts (SACs) with high-loading metal-Nx is greatly challenging since the loading and single-atomic dispersion have to be balanced at high temperature for forming metal-Nx. Herein, we develop a general cascade anchoring strategy for the mass production of a series of M-NC SACs with a metal loading up to 12.1 wt%. Systematic investigation reveals that the chelation of metal ions, physical isolation of chelate complex upon high loading, and the binding with N-species at elevated temperature are essential to achieving high-loading M-NC SACs. As a demonstration, high-loading Fe-NC SAC shows superior electrocatalytic performance for O2 reduction and Ni-NC SAC exhibits high electrocatalytic activity for CO2 reduction. The strategy paves a universal way to produce stable M-NC SAC with high-density metal-Nx sites for diverse high-performance applications., Although single atom catalysts (SACs) with high-loading metal-Nx have great potential in heterogeneous catalysis, their scalable synthesis remains challenging. Here, the authors develop a general cascade anchoring strategy for the mass production of a series of metal-Nx SACs with a metal loading up to 12.1 wt%.

Hollow metal oxide microspheres (HMMs) have drawn enormous attention in different research fields. Reliable and scalable synthetic protocols applicable for a large variety of metal oxides are in emergent demand. Here we demonstrated that polymer hydrogel, such as the resorcinol formaldehyde (RF) one, existed as an efficient synthetic platform to build HMMs. Specifically, the RF gel forms stacked RF microspheres enlaced with its aqueous phase, where the following evaporation of the highly dispersed water leads to a gel-assisted precipitation (GAP) of the dissolved metal precursor onto the embedded polymeric solids suited for the creation of HMMs. By taking advantage of the structural features of hydrogel, this synthesis design avoids the delicate control on the usually necessitated coating process and provides a simple and effective synthetic process versatile for functional HMMs, particularly Nb2 O5 as a high-performance electrode material in Li-ion intercalation pseudocapacitor.

Wide-bandgap semiconductors exhibiting a bandgap of ∼1.7-1.9 eV have generated great interest recently due to their important applications in tandem solar cells as top cells and emerging indoor photovoltaics. However, concerns about the stability and toxicity especially in indoor application limit the choice of these materials. Here we report a new member of this family, germanium monosulfide (GeS); this material displays a wide bandgap of 1.7 eV, nontoxic and earth-abundant constituents, and high stability. We find that the little success of GeS solar cells to date is primarily attributed to the challenge in fabricating high-quality polycrystalline GeS films, wherein the high thermal expansion coefficient (α = 3.1 × 10-5 K-1) combined with high crystallization temperature (375 °C) of GeS induces large tensile strain in the GeS film that peels off GeS from the substrate. By introducing a high-α buffer layer between GeS and substrate, we achieve a high-quality polycrystalline GeS thin film that compactly adheres to substrate with no voids. Solar cells fabricated by these GeS films show a power conversion efficiency of 1.36% under AM 1.5G illumination (100 mW cm-2). The unencapsulated devices are stable when stored in ambient atmosphere for 1500 h. Their efficiencies further increase to 3.6% under indoor illumination of 1000 lux.

Understanding the mechanism of electrocatalytic reaction is important for the design and development of highly efficient electrocatalysts for energy technology. Investigating the surface structures of electrocatalysts and the surface processes in electrocatalytic reactions at the atomic and molecular scale is helpful to identify the catalytic role of active sites and further promotes the development of emerging electrocatalysts. Since it was invented, scanning tunnelling microscopy (STM) has become a powerful technique to investigate surface topographies and electronic properties at the nanoscale resolution. STM can be operated in diversified environments. Electrochemical STM can be used to investigate the surface processes during electrochemical reactions. Moreover, the critical intermediates in catalysis on catalyst surfaces can be identified by STM at low temperature or ultrahigh vacuum. STM has been extensively utilized in electrocatalysis research, including the structure–activity relationship of electrocatalysts, the distribution of active sites, and surface processes in electrocatalytic reactions. In this review, progress in the application of STM in electrocatalysis is systematically discussed. The construction of model electrocatalysts and electrocatalytic systems are summarized. Then, we present the STM investigation of electrocatalyst structures and surface processes related to electrocatalysis. Challenges and future developments in the field are discussed in the outlook.

Li

Hollow carbon-based nanospheres (HCNs) have been demonstrated to show promising potential in a large variety of research fields, particularly electrochemical devices for energy conversion/storage. The current synthetic protocols for HCNs largely rely on template-based routes (TBRs), which are conceptually straightforward in creating hollow structures but challenged by the time-consuming operations with a low yield in product as well as serious environmental concerns caused by hazardous etching agents. Meanwhile, they showed inadequate ability to build complex carbon-related architectures. Innovative strategies for HCNs free from extra templates thus are highly desirable and are expected to not only ensure precise control of the key structural parameters of hollow architectures with designated functionalities, but also be environmentally benign and scalable approaches suited for their practical applications.In this Account, we outline our recent research progress on the development of template-free protocols for the creation of HCNs with a focus on the acquired mechanical insight into the hollowing mechanism when no extra templates were involved. We demonstrated that carbon-based particles themselves could act as versatile platforms to create hollow architectures through an effective modulation of their inner chemistry. By means of reaction control, the precursor particles were synthesized into solid ones with a well-designed inhomogeneity inside in the form of different chemical parameters such as molecular weight, crystallization degree, and chemical reactivity, by which we not only can create hollow structures inside particles but also have the ability to tune the key features including compositions, porosity, and dimensional architectures. Accordingly, the functionalities of the prepared HCNs could be systematically altered or optimized for their applications. Importantly, the discussed synthesis approaches are facile and environmentally benign processes with potential for scale-up production.The nanoengineering of HNCs is found to be of special importance for their application in a large variety of electrochemical energy storage and conversion systems where the charge transfer and structural stability become a serious concern. Particular attention in this Account is therefore directed to the potential of HCNs in battery systems such as sodium ion batteries (NIBs) and potassium ion batteries (KIBs), whose electrochemical performances are plagued by the destructive volumetric deformation and sluggish charge diffusion during the intercalation/deintercalation of large-size Na+ or K+. We demonstrated that precise control of the multidimensional factors of the HCNs is critical to offer an optimized design of sufficient reactive sites, excellent charge and mass transport kinetics, and resilient electrode structure and also provide a model system suitable for the study of complicated metal-ion storage mechanisms, such as Na+ storage in a hard carbon anode. We expect that this Account will spark new endeavors in the development of HCNs for various applications including energy conversion and storage, catalysis, biomedicine, and adsorption.

Intensive understanding of the surface mechanism of cathode materials, such as structural evolution and chemical and mechanical stability upon charging/discharging, is crucial to design advanced solid-state lithium batteries (SSLBs) of tomorrow. Here, via

The use of catalysts is the key to boost electrode reactions in lithium–oxygen (Li–O2) batteries. In-depth understanding of the nanoscale catalytic effect at electrode/electrolyte interfaces is of ...

Investigation of chirality in on-surface synthesis is of significance not only for fabricating atomically precise covalently bonded chiral species but also for unveiling chiral phenomena involving chemical reactions. In this contribution, we present the growth of single-layered homochiral 2D covalent organic frameworks (COFs) on surfaces based on a steric hindrance strategy, by which both the chiral expression of the prochiral precursor and the newly formed C═N bonds are successfully steered. When coupling a tritopic monomer with the prochiral ditopic molecule with phenyl substituents, two enantiomers of the precursor are randomly integrated in the product via variable C═N linkages, resulting in distorted hexagonal frameworks without chiral expression. After equipping the prochiral precursor with more hindered bulky substituents, highly regular homochiral 2D COFs are fabricated, in which only one of the enantiomers of the prochiral precursor is integrated, and all C═N linkages possess the same configuration. Structural analysis based on high resolution scanning tunneling microscopy images and theoretical simulations indicate that the homochiral 2D COFs are generated through an enantioselective on-surface polymerization driven by the steric hindrance effect. This result not only benefits understanding and controlling chirality in on-surface synthesis but also provides a new approach for the growth of highly regular COFs on surfaces.

The rechargeable aluminium-sulfur (Al-S) battery is regarded as a potential alternative beyond lithium-ion battery system owing to its safety, promising energy density, and the high earth abundance of the constituent electrode materials, however, sluggish kinetic response and short life-span are the major issues that limit the battery development towards applications. In this article, we report CoII,III as an electrochemical catalyst in the sulfur cathode that renders a reduced discharge-charge voltage hysteresis and improved capacity retention and rate capability for Al-S batteries. The structural and electrochemical analysis suggest that the catalytic effect of CoII,III is closely associated with the formation of cobalt sulfides and the changes in the valence states of the CoII,III during the electrochemical reactions of the sulfur species, which lead to improved reaction kinetics and sulfur utilization in the cathode. The Al-S battery, assembled with the cathode consisting of CoII,III decorated carbon matrix, demonstrates a considerably reduced voltage hysteresis of 0.8 V, a reversible specific capacity of ≈500 mAh g-1 at 1 A g-1 after 200 discharge-charge cycles and of ≈300 mAh g-1 at 3 A g-1 .