One-step Synthesis of Organic Terminal 2D Ti3C2T x MXene Nanosheets by Etching of Ti3AlC2 in an Organic Lewis Acid Solvent.

The surface and interface chemistry are critical for controlling the properties of two-dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the functionalization of MXenes with small inorganic ligands; however, few etching methods have been reported on the direct bonding of organic groups to MXene surfaces. In this work, we demonstrated an efficient and rapid strategy for the direct synthesis of 2D Ti3C2Tx MXene nanosheets with organic terminal groups in an organic Lewis acid (trifluoromethanesulfonic acid) solvent, without introducing additional intercalations. The dissolution of aluminum and the subsequent in-situ introduction of trifluoromethanesulfonic acid resulted in the extraction of Ti3C2Tx MXene (T = CF3SO3-) (denoted as CF3SO3H-Ti3C2Tx) flakes with sizes reaching 15 µm and high productivity (over 70%) of monolayers or few layers. More importantly, the large CF3SO3H-Ti3C2TxMXene nanosheets had high colloidal stability, making them promising as efficient electrocatalysts for the hydrogen evolution reaction.

A universal and scalable transformation of bulk metals into single-atom catalysts in ionic liquids.

Single-atom catalysts (SACs) with maximized metal atom utilization and intriguing properties are of utmost importance for energy conversion and catalysis science. However, the lack of a straightforward and scalable synthesis strategy of SACs on diverse support materials remains the bottleneck for their large-scale industrial applications. Herein, we report a general approach to directly transform bulk metals into single atoms through the precise control of the electrodissolution-electrodeposition kinetics in ionic liquids and demonstrate the successful applicability of up to twenty different monometallic SACs and one multimetallic SAC with five distinct elements. As a case study, the atomically dispersed Pt was electrodeposited onto Ni3N/Ni-Co-graphene oxide heterostructures in varied scales (up to 5 cm × 5 cm) as bifunctional catalysts with the electronic metal-support interaction, which exhibits low overpotentials at 10 mA cm-2 for hydrogen evolution reaction (HER, 30 mV) and oxygen evolution reaction (OER, 263 mV) with a relatively low Pt loading (0.98 wt%). This work provides a simple and practical route for large-scale synthesis of various SACs with favorable catalytic properties on diversified supports using alternative ionic liquids and inspires the methodology on precise synthesis of multimetallic single-atom materials with tunable compositions.

Electronic Modulation in Cu Doped NiCo LDH/NiCo Heterostructure for Highly Efficient Overall Water Splitting.

Layered double hydroxides (LDHs), promising bifunctional electrocatalysts for overall water splitting, are hindered by their poor conductivity and sluggish electrochemical reaction kinetics. Herein, a hierarchical Cu-doped NiCo LDH/NiCo alloy heterostructure with rich oxygen vacancies by electronic modulation is tactfully designed. It extraordinarily effectively drives both the oxygen evolution reaction (151 mV@10 mA cm-2 ) and the hydrogen evolution reaction (73 mV@10 mA cm-2 ) in an alkaline medium. As bifunctional electrodes for overall water splitting, a low cell voltage of 1.51 V at 10 mA cm-2 and remarkable long-term stability for 100 h are achieved. The experimental and theoretical results reveal that Cu doping and NiCo alloy recombination can improve the conductivity and reaction kinetics of NiCo LDH with surface charge redistribution and reduced Gibbs free energy barriers. This work provides a new inspiration for further design and construction of nonprecious metal-based bifunctional electrocatalysts based on electronic structure modulation strategies.

Manipulating Zn Metal Texture with Guided Zincophilic Sites via Electrochemical Stripping for Dendrite-Free Zn Anodes.

Constructing a three-dimensional (3D) structure along with Zn (002) texture selective exposure is a promising strategy to tackle the issues faced by Zn metal anodes. Herein, for the first time, we proposed an electrochemical stripping strategy to achieve controlled modification of the texture and microstructure of zinc foils in one step, building a hierarchical structure with (002) texture preferred exposed Zn (SZ). The SZ with favorable zincophilic properties not only can reduce the concentration polarization at the interface but also allow Zn to grow horizontally on the edge of the (002) texture by guiding the adsorption sites for Zn2+. Moreover, the honeycomb-like structure is beneficial to rearrange the distribution of the Zn2+ flux as well as alleviating stress changes during cycling. Thus, the SZ||Cu cell exhibits excellent stability with a Coulombic efficiency of 99.76% over 1800 cycles. The SZ||NaV3O8·xH2O cell with inconspicuous self-discharge effect maintains a high areal capacity of 3.67 mA h cm-2 even after 700 cycles with a low N/P ratio of 3.6. This work achieves texture architecture and structure designing on Zn foils simultaneously by metallurgical electrochemical methods and opens up a potential strategy to implement the practicality of zinc metal anodes.

Realization of tunable-performance in atomic layer deposited Hf-doped In2O3 thin film transistor via oxygen vacancy modulation.

Due to the limitation of inherent ultra-high electron concentration, the electrical properties of In2O3 resemble those of conductors rather than semiconductors prior to special treatment. In this study, the effect of various annealing treatments on the microstructure, optical properties, and oxygen vacancies of the films and transistors is systematically investigated. Our finding reveals a progressive crystallization trend in the films with increasing annealing temperature. In addition, a higher annealing temperature is also associated with the reduction in the concentration of oxygen vacancies, as well as an elevation in both optical transmittance and optical bandgap. Furthermore, with the implementation of annealing process, the devices gradually transform from no pronounced gate control to exhibit with excellent gate control and electrical performances. The atomic layer deposited Hf-doped In2O3 thin film transistor annealed at 250 °C exhibits optimal electrical properties, with a field-effect mobility of 18.65 cm2 V-1 s-1, a subthreshold swing of 0.18 V/dec, and an Ion/Ioff ratio of 2.76 × 106. The results indicate that the impact of varying annealing temperatures can be attributed to the modulation of oxygen vacancies within the films. This work serves as a complementary study for the existing post-treatment of oxide films and provides a reliable reference for utilization of the annealing process in practical applications.

Tunable-performance all-oxide structure field-effect transistor based atomic layer deposited Hf-doped In2O3 thin films.

The relocation of peripheral transistors from the front-end-of-line (FEOL) to the back-end-of-line (BEOL) in fabrication processes is of significant interest, as it allows for the introduction of novel functionality in the BEOL while providing additional die area in the FEOL. Oxide semiconductor-based transistors serve as attractive candidates for BEOL. Within these categories, In2O3 material is particularly notable; nonetheless, the excessive intrinsic carrier concentration poses a limitation on its broader applicability. Herein, the deposition of Hf-doped In2O3 (IHO) films via atomic layer deposition for the first time demonstrates an effective method for tuning the intrinsic carrier concentration, where the doping concentration plays a critical role in determine the properties of IHO films and all-oxide structure transistors with Au-free process. The all-oxide transistors with In2O3: HfO2 ratio of 10:1 exhibited optimal electrical properties, including high on-current with 249 µA, field-effect mobility of 13.4 cm2 V-1 s-1, and on/off ratio exceeding 106, and also achieved excellent stability under long time positive bias stress and negative bias stress. These findings suggest that this study not only introduces a straightforward and efficient approach to improve the properties of In2O3 material and transistors, but as well paves the way for development of all-oxide transistors and their integration into BEOL technology.

Improving Electrocatalytic Oxygen Evolution through Local Field Distortion in Mg/Fe Dual-site Catalysts.

Transition metal single atom electrocatalysts (SACs) with metal-nitrogen-carbon (M-N-C) configuration show great potential in oxygen evolution reaction (OER), whereby the spin-dependent electrons must be allowed to transfer along reactants (OH- /H2 O, singlet spin state) and products (O2 , triplet spin state). Therefore, it is imperative to modulate the spin configuration in M-N-C to enhance the spin-sensitive OER energetics, which however remains a significant challenge. Herein, we report a local field distortion induced intermediate to low spin transition by introducing a main-group element (Mg) into the Fe-N-C architecture, and decode the underlying origin of the enhanced OER activity. We unveil that, the large ionic radii mismatch between Mg2+ and Fe2+ can cause a FeN4 in-plane square local field deformation, which triggers a favorable spin transition of Fe2+ from intermediate (dxy 2 dxz 2 dyz 1 dz2 1 , 2.96 µB ) to low spin (dxy 2 dxz 2 dyz 2 , 0.95 µB ), and consequently regulate the thermodyna-mics of the elementary step with desired Gibbs free energies. The as-obtained Mg/Fe dual-site catalyst demonstrates a superior OER activity with an overpotential of 224 mV at 10 mA cm-2 and an electrolysis voltage of only 1.542 V at 10 mA cm-2 in the overall water splitting, which outperforms those of the state-of-the-art transition metal SACs.

The Effect of Alkali Metals (Li, Na, and K) on Ni/CaO Dual-Functional Materials for Integrated CO2 Capture and Hydrogenation.

Ni/CaO, a low-cost dual-functional material (DFM), has been widely studied for integrated CO2 capture and hydrogenation. The core of this dual-functional material should possess both good CO2 capture-conversion performance and structural stability. Here, we synthesized Ni/CaO DFMs modified with alkali metals (Na, K, and Li) through a combination of precipitation and combustion methods. It was found that Na-modified Ni/CaO (Na-Ni/CaO) DFM offered stable CO2 capture-conversion activity over 20 cycles, with a high CO2 capture capacity of 10.8 mmol/g and a high CO2 conversion rate of 60.5% at the same temperature of 650 °C. The enhanced CO2 capture capacity was attributed to the improved surface basicity of Na-Ni/CaO. In addition, the incorporation of Na into DFMs had a favorable effect on the formation of double salts, which shorten the CO2 capture and release process and promoted DFM stability by hindering their aggregation and the sintering of DFMs.

Building Negative-Thermal-Expansion Protective Layers on the Grain Boundary of Ni-rich Cathodes Enables Safe and Durable High Voltage Lithium-Ion Batteries.

Ni-rich layered oxide cathode materials demonstrate high energy densities for Li-ion batteries, but the electrochemically driven thermal runaway and mechanical degradation remain their long-standing challenges in practical applications. Herein, it presents a novel ZrV2 O7  (ZVO) coating with negative thermal expansion properties along the secondary particles and primary particle grain boundaries (GBs), to simultaneously enhance the structural and thermal stability of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811). It unveils that, such an architecture can significantly enhance the electronic conductivity, suppress the microcracks of GBs, alleviate the layered to spinel/rock-salt phase transformation, and meanwhile relieve the lattice oxygen loss by increasing the oxygen vacancy formation energy increased (1.43 vs 1.90 eV). Consequently, the ZVO-coated NCM811 material demonstrates a remarkable cyclability with 86.5% capacity retention after 100 cycles, and an outstanding rate performance of 30 C under a high-voltage of 4.6 V, outperforming the state-of-the-art literature. More importantly, the Li+ transportation can be readily blocked at 120 °C by the negative-thermal-expansion ZVO coating, thus avoiding the high-temperature thermal runaway.

CO2 capture by Li2CaSiO4 and enhancement with alkali carbonates.

Alkali and alkali earth oxides show good CO2 capture performance for carbonation, while their regeneration occurs at high temperatures, leading to a high energy penalty. When alkali oxides and alkali earth oxides combine with SiO2 to form oxysalts, the regeneration temperatures can be reduced, and the CO2 adsorption capacity is maintained. In this study, the reaction between CO2 and Li2CaSiO4, composed of stoichiometric CaO, Li2O, and SiO2, was evaluated thermodynamically by DFT. The synthesized Li2CaSiO4 with and without alkali carbonates was used as CO2 sorbents, and their CO2 adsorption performances were examined using thermal analyses. The phase and morphology of Li2CaSiO4 before and after CO2 adsorption were characterized by XRD and SEM. According to the thermodynamic evaluation and the XRD results, Li2CaSiO4 could adsorb CO2 and form CaCO3 and Li2SiO3. The thermal analyses showed that the regeneration of Li2CaSiO4 started from 575 °C, at which it was difficult to realize the CO2 diffusion through the solid CaCO3 product layer. The mixed alkali carbonates can improve the kinetics and facilitate the CO2 adsorption of Li2CaSiO4. Alkali carbonates were effective in reducing the activation energy of the reaction and CO2 diffusion at low temperatures and improving the cyclic stability because of the dispersing carbonation products.

Effects of pressure and temperature on topological electronic materials X2Y3 (X = As, Sb, Bi; Y = Se, Te) using first-principles.

We systematically study the thermal and topological properties of X2Y3 (X = As, Sb, Bi; Y = Se, Te) and the effects of pressure and temperature on their electronic properties using first-principles. We find that the external pressure-induced electronic topological transition occurs at about 5 GPa for Bi2Se3, and the type of band gap tends to become indirect with the increase of pressure. We also investigate the lattice expansion with temperature in quasi-harmonic approximation and further explore the effect of temperature on the volume, band gap, and volumetric thermal expansion coefficient of the studied selenides and tellurides. Finally, we calculate the evolution of the Wannier charge center of X2Y3 to determine their topological invariants, and theoretically suggest that Bi2Se3 changes from a topological to an ordinary insulator when the pressure decreases to -8 GPa; As2Se3 is found to be an ordinary insulator, while all other four compounds are always strong topological insulators at any pressure or temperature.

Chemically bonding inorganic fillers with polymer to achieve ultra-stable solid-state sodium batteries.

Inorganic/organic composite solid electrolytes (CSEs) have attracted ever-increasing attentions due to their outstanding mechanical stability and processibility. However, the inferior inorganic/organic interface compatibility limits their ionic conductivity and electrochemical stability, which hinders their application in solid-state batteries. Herein, we report a homogeneously distributed inorganic fillers in polymer by in-situ anchoring SiO2 particles in polyethylene oxide (PEO) matrix (I-PEO-SiO2). Compared with ex-situ CSEs (E-PEO-SiO2), SiO2 particles and PEO chains in I-PEO-SiO2 CSEs are closely welded by strong chemical bonds, thus addressing the issue of interfacial compatibility and realizing excellent dendrite-suppression ability. In addition, the Lewis acid-base interactions between SiO2 and salts facilitate the dissociation of sodium salts and increase the concentration of free Na+. Consequently, the I-PEO-SiO2 electrolyte demonstrates an improved Na+ conductivity (2.3 × 10-4 S cm-1 at 60 °C) and Na+ transference number (0.46). The as constructed Na3V2(PO4)3 ‖ I-PEO-SiO2 ‖ Na full-cell demonstrates a high specific capacity of 90.5 mAh g-1 at 3C and an ultra-long cycling stability (>4000 cycles at 1C), outperforming the state-of-the-art literatures. This work provides an effective way to solve the issue of interfacial compatibility, which can enlighten other CSEs to overcome their interior compatibility.

Recent Advances in Electrochemical-Based Silicon Production Technologies with Reduced Carbon Emission.

Sustainable and low-carbon-emission silicon production is currently one of the main focuses for the metallurgical and materials science communities. Electrochemistry, considered a promising strategy, has been explored to produce silicon due to prominent advantages: (a) high electricity utilization efficiency; (b) low-cost silica as a raw material; and (c) tunable morphologies and structures, including films, nanowires, and nanotubes. This review begins with a summary of early research on the extraction of silicon by electrochemistry. Emphasis has been placed on the electro-deoxidation and dissolution-electrodeposition of silica in chloride molten salts since the 21st century, including the basic reaction mechanisms, the fabrication of photoactive Si films for solar cells, the design and production of nano-Si and various silicon components for energy conversion, as well as storage applications. Besides, the feasibility of silicon electrodeposition in room-temperature ionic liquids and its unique opportunities are evaluated. On this basis, the challenges and future research directions for silicon electrochemical production strategies are proposed and discussed, which are essential to achieve large-scale sustainable production of silicon by electrochemistry.

Optoelectronic Devices of Large-Scale Transferred All-Inorganic Lead Halide Perovskite Thin Films.

We report the large-scale transfer process for monocrystalline CsPbBr3 thin films prepared by chemical vapor deposition (CVD) with excellent optical properties and stability. The transfer process is robust, simple, and effective, in which CsPbBr3 thin films could be transferred to several substrates and effectively avoid chemical or physical fabrication processes to damage the perovskite surface. Moreover, the transfer process endows CsPbBr3 and substrates with atomically clean and electronically flat interfaces. We utilize this transfer process to realize several optoelectronic devices, including a photonic laser with a threshold of 61 µJ/cm2, a photodetector with a responsivity of 2.4 A/W, and a transistor with a hole mobility of 11.47 cm2 V-1 s-1. High device performances mainly originate from low defects of high-quality single-crystal perovskite and seamless contact between CsPbBr3 and target substrates. The large-scale nondestructive transfer process provides promising opportunities for optoelectronic applications based on monocrystalline perovskites.

Molten salt electrosynthesis of Cr2GeC nanoparticles as anode materials for lithium-ion batteries.

The two-dimensional MAX phases with compositional diversity are promising functional materials for electrochemical energy storage. Herein, we report the facile preparation of the Cr2GeC MAX phase from oxides/C precursors by the molten salt electrolysis method at a moderate temperature of 700°C. The electrosynthesis mechanism has been systematically investigated, and the results show that the synthesis of the Cr2GeC MAX phase involves electro-separation and in situ alloying processes. The as-prepared Cr2GeC MAX phase with a typical layered structure shows the uniform morphology of nanoparticles. As a proof of concept, Cr2GeC nanoparticles are investigated as anode materials for lithium-ion batteries, which deliver a good capacity of 177.4 mAh g-1 at 0.2 C and excellent cycling performance. The lithium-storage mechanism of the Cr2GeC MAX phase has been discussed based on density functional theory (DFT) calculations. This study may provide important support and complement to the tailored electrosynthesis of MAX phases toward high-performance energy storage applications.

Design Strategies toward High-Performance Zn Metal Anode.

Rechargeable aqueous Zn-ion batteries (AZIBs) are one of the most promising alternatives for traditional energy-storage devices because of their low cost, abundant resources, environmental friendliness, and inherent safety. However, several detrimental issues with Zn metal anodes including Zn dendrite formation, hydrogen evolution, corrosion and passivation, should be considered when designing advanced AZIBs. Moreover, these thorny issues are not independent but mutually reinforcing, covering many technical and processing parameters. Therefore, it is necessary to comprehensively summarize the issues facing Zn anodes and the corresponding strategies to develop roadmaps for the development of high-performance Zn anodes. Herein, the failure mechanisms of Zn anodes and their corresponding impacts are outlined. Recent progress on improving the stability of Zn anode is summarized, including structurally designed Zn anodes, Zn alloy anodes, surface modification, electrolyte optimization, and separator design. Finally, this review provides brilliant and insightful perspectives for stable Zn metal anodes and promotes the large-scale application of AZIBs in power grid systems.

Microstructural Evolution of SK85 Pearlitic Steel Deformed by Heavy Cold Rolling.

The microstructural evolution of SK85 pearlitic steel cold-rolled up to a 90% rolling reduction was characterized by scanning electron microscopy with electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). SK85 steel exhibits excellent cold rolling performance. The interlamellar spacing of pearlite is refined obviously and a tensile strength of 2318 MPa can be reached for SK85 steel after 90% rolling reduction, an increase of 83% from 1264 MPa before rolling. The EBSD observation indicates that the {001} <110> texture becomes pronounced at a 90% rolling reduction in cold-rolled Sk85 steel. A propagation and multiplication of dislocations occur during rolling as the kernel average misorientation (KAM) angles significantly increase from 0.72° to 2.11°. The XRD analysis reveals that bcc ferrite is transformed into a bct structure at a 90% rolling reduction. The strengthening mechanism was discussed.

Water interaction with B-site (B = Al, Zr, Nb, and W) doped SrFeO3-δ-based perovskite surfaces for thermochemical water splitting applications.

Density functional theory (DFT) calculations were performed to study the interaction of water with the SrO and FeO2 terminations of the SrFeO3-δ (001) surface, where the effects of the metal dopants (Al, Zr, Nb, and W), surface oxygen vacancies, and oxygen ion migration were investigated. Our calculations showed that the metal dopants benefited the molecular and dissociative adsorptions of H2O on both the perfect and oxygen-vacancy-containing surfaces. The surface oxygen vacancies were predicted to promote the dissociative adsorption of H2O and the formation of H2. For all structures studied, H2 release was found to be always an overall endothermic process, except for the W-doped structure which will become exothermic at high temperature. On the oxygen-vacancy-containing surface, H2 generation was predicted to be easier at the SrO termination than the FeO2 termination. Furthermore, we also investigated the oxygen ion migration mechanism on all surface structures, predicted the behaviour of oxygen migration and the effect of oxygen vacancy defects. Our results showed that Al doping facilitated not only the formation of surface oxygen vacancies, but also oxygen migration from the surface to the subsurface, in contrast to the Zr, Nb and W-doped structures. This study provided significant insights into the interaction of water with the surfaces of doped SrFeO3-δ perovskite materials for thermochemical water splitting applications.

Proton Storage in Metallic H1.75MoO3 Nanobelts through the Grotthuss Mechanism.

The proton, as the cationic form of the lightest element-H, is regarded as most ideal charge carrier in "rocking chair" batteries. However, current research on proton batteries is still at its infancy, and they usually deliver low capacity and suffer from severe acidic corrosion. Herein, electrochemically activated metallic H1.75MoO3 nanobelts are developed as a stable electrode for proton storage. The electrochemically pre-intercalated protons not only bond directly with the terminal O3 site via strong O-H bonds but also interact with the oxygens within the adjacent layers through hydrogen bonding, forming a hydrogen-bonding network in H1.75MoO3 nanobelts and enabling a diffusion-free Grotthuss mechanism as a result of its ultralow activation energy of ∼0.02 eV. To the best of our knowledge, this is the first reported inorganic electrode exhibiting Grotthuss mechanism-based proton storage. Additionally, the proton intercalation into MoO3 with formation of H1.75MoO3 induces strong Jahn-Teller electron-phonon coupling, rendering a metallic state. As a consequence, the H1.75MoO3 shows an outstanding fast charging performance and maintains a capacity of 111 mAh/g at 2500 C, largely outperforming the state-of-art battery electrodes. More importantly, a symmetric proton ion full cell based on H1.75MoO3 was assembled and delivered an energy density of 14.7 Wh/kg at an ultrahigh power density of 12.7 kW/kg, which outperforms those of fast charging supercapacitors and lead-acid batteries.

Experimental and computational approaches to study the chlorination mechanism of pentlandite with ammonium chloride.

Pentlandite (Fe4.5Ni4.5S8) is the primary source for the metallurgical production of nickel worldwide, however it usually coexists with copper sulfide in nature. To develop an efficient and green process for the separation and extraction of valuable metals from the nickel sulfide concentrate, herein we conducted experimental studies and density functional theory (DFT) calculations to elucidate the chlorination mechanism of pentlandite using ammonium chloride (NH4Cl). First, low-temperature chlorination roasting experiments with NH4Cl were performed in which pentlandite was successfully converted into the corresponding metal chlorides (FeCl2 and NiCl2). Then, the chlorination product was analyzed via energy dispersive spectrometry to reveal the elemental distribution at the cross-section. Results reveal that Fe atoms in pentlandite underwent preferential chlorination to form a chloride layer, whereas Ni atoms remained at the center of the grain. Furthermore, density functional theory calculations were performed to investigate the chlorination mechanism of pentlandite by exploring two possible pathways, involving the adsorption of oxygen (O2), ammonium chloride (NH4Cl) and chlorine (Cl2) on both the (001) and (010) surfaces of pentlandite. Considering that the chlorination of pentlandite was achieved in air atmosphere, we first consider the direct chlorination of pentlandite by NH4Cl in the presence of oxygen. Dissociative oxygen adsorption was found to promote the chlorination process by providing oxygen sites for the dissociation of HCl, which is decomposed from NH4Cl, eventually leading to the formation of H2O and FeCl2 species. Alternatively, the reaction between pentlandite and Cl2 was proved to be feasible thermodynamically.