Element Screening of High-Entropy Silicon Anodes for Superior Li-Storage Performance of Li-Ion Batteries

The high-entropy silicon anodes are attractive for enhancing electronic and Li-ionic conductivity while mitigating volume effects for advanced Li-ion batteries (LIBs), but are plagued by the complicated elements screening process. Inspired by the resemblances in the structure between sphalerite and diamond, we have selected sphalerite-structured SiP with metallic conductivity as the parent phase for exploring the element screening of high-entropy silicon-based anodes. The inclusion of the Zn in the sphalerite structure is crucial for improving the structural stability and Li-storage capacity. Within the same group, Li-storage performance is significantly improved with increasing atomic number in the order of BZnSiP3 < AlZnSiP3 < GaZnSiP3 < InZnSiP3. Thus, InZnSiP3-based electrodes achieved a high capacity of 719 mA h g-1 even after 1,500 cycles at 2,000 mA g-1, and a high-rate capacity of 725 mA h g-1 at 10,000 mA g-1, owing to its superior lithium-ion affinity, faster electronic conduction and lithium-ion diffusion, higher Li-storage capacity and reversibility, and mechanical integrity than others. Additionally, the incorporation of elements with larger atomic sizes leads to greater lattice distortion and more defects, further facilitating mass and charge transport. Following these screening rules, high-entropy disordered-cation silicon-based compounds such as GaCuSnInZnSiP6, GaCu(or Sn)InZnSiP5, and CuSnInZnSiP5, as well as high-entropy compounds with mixed-cation and -anion compositions, such as InZnSiPSeTe and InZnSiP2Se(or Te), are synthesized, demonstrating improved Li-storage performance with metallic conductivity. The phase formation mechanism of these compounds is attributed to the negative formation energies arising from elevated entropy.

State-of-the-Art Two-Dimensional Metal Phosphides for High Performance Lithium-ion Batteries: Progress and Prospects

Lithium-ion batteries (LIBs) with high energy density, long cycle life and safety have earned recognition as outstanding energy storage devices, and have been used in extensive applications, such as portable electronics and new energy vehicles. However, traditional graphite anodes deliver low specific capacity and inferior rate performance, which is difficult to satisfy ever-increasing demands in LIBs. Very recently, two-dimensional metal phosphides (2D MPs) emerge as the cutting-edge materials in LIBs due to their overwhelming advantages including high theoretical capacity, excellent conductivity and short lithium diffusion pathway. This review summarizes the up-to-date advances of 2D MPs from typical structures, main synthesis methods and LIBs applications. The corresponding lithium storage mechanism, and relationship between 2D structure and lithium storage performance is deeply discussed to provide new enlightening insights in application of 2D materials for LIBs. Several potential challenges and inspiring outlooks are highlighted to provide guidance for future research and applications of 2D MPs.

Research progress on direct borohydride fuel cells

The rapid development of industry has accelerated the utilization and consumption of fossil energy, resulting in an increasing shortage of energy resources and environmental pollution. Therefore, it is crucial to explore new energy storage devices using renewable and environment-friendly energy as fuel. Direct borohydride fuel cells (DBFCs) are expected to be a feasible and efficient energy storage device by virtue of the read availability of raw materials, non-toxicity of products, and excellent operational stability. Moreover, while utilizing H2O2 as an oxidant, a significant theoretical energy density of 17 kW h kg-1 can be achieved, indicating the broad application prospect of DBFCs in long-range operation and oxygen-free environment. This review summarizes the research progress on DBFCs in term of reaction kinetics, electrode materials, membrane materials, architecture, and electrolytes. In addition, we predict the future research challenges and feasible research directions, considering both performance and cost. We hope this review will help guide future studies on DBFCs.

Highly Efficient and Stable Mo-CoP3 @FeOOH Electrocatalysts for Alkaline Seawater Splitting

The introduction of high-valence state elements and highly active species is promisingly desired to design superior electrocatalysts for water electrolysis. Exploring scalable synthetic strategies is necessary for an in-depth understanding of the mechanism of improving electrocatalytic performance. But it remains challenging. Herein, several electrocatalysts through element doping are prepared. The obtained Mo-CoP3 -2@FeOOH samples show the overpotentials (OER) of 232 mV (alkaline seawater) and 262 mV (KOH electrolyte). As HER catalyst, it also presents an excellent electrocatalytic performance. The above electrocatalysts are utilized as anode/cathode to assemble devices for alkaline seawater/water electrolysis, which delivers a cell voltage of 1.58 V and durability of 350 h. Density functional theory calculations reveal that Mo ion doping and FeOOH significantly enhance the density states of the Fermi level and tune the position of the d-band center. It expedites the charge transfer and decreases the adsorption energy of intermediates. It demonstrates that transition-metal phosphides coated with highly active FeOOH offer an effective route to fabricate high-performance and durable catalysts for seawater/water electrolysis.

Graphene cladded cobalt phosphide nanoparticles with a sandwich structure by plasma for lithium and sodium storage

Graphene cladded cobalt phosphide nanoparticles with a sandwich structure are synthesized using Ar-H2-P plasma. In situ phosphorization and graphene reduction are achieved at the same time. Benefitting from the sandwich structure and heterointerface between CoP and RGO, the electrode delivered a high reversible capacity and durable lifespan for both lithium and sodium storage.

Phonons in Copper Diphosphide (CuP2): Raman Spectroscopy and Lattice Dynamics Calculations

Copper diphosphide (CuP₂) is an emerging binary semiconductor with promising properties for energy conversion and storage applications. While functionality and possible applications of CuP₂ have been studied, there is a curious gap in the investigation of its vibrational properties. In this work, we provide a reference Raman spectrum of CuP₂, with a complete analysis of all Raman active modes from both experimental and theoretical perspectives. Raman measurements have been performed on polycrystalline CuP₂ thin films with close to stoichiometric composition. Detailed deconvolution of the Raman spectrum with Lorentzian curves has allowed identification of all theoretically predicted Raman active modes (9A_g and 9B_g), including their positions and symmetry assignment. Furthermore, calculations of the phonon density of states (PDOS), as well as the phonon dispersions, provide a microscopic understanding of the experimentally observed phonon lines, in addition to the assignment to the specific lattice eigenmodes. We further provide the theoretically predicted positions of the infrared (IR) active modes, along with the simulated IR spectrum from density functional theory (DFT). Overall good agreement is found between the experimental and DFT-calculated Raman spectra of CuP₂, providing a reference platform for future investigations on this material.

Terminal Group-Oriented Self-Assembly to Controllably Synthesize a Layer-by-Layer SnSe2 and MXene Heterostructure for Ultrastable Lithium Storage

Heterostructured materials integrate the advantages of adjustable electronic structure, fast electron/ions transfer kinetics, and robust architectures, which have attracted considerable interest in the fields of rechargeable batteries, photo/electrocatalysis, and supercapacitors. However, the construction of heterostructures still faces some severe problems, such as inferior random packing of components and serious agglomeration. Herein, a terminal group-oriented self-assembly strategy to controllably synthesize a homogeneous layer-by-layer SnSe₂ and MXene heterostructure (LBL-SnSe₂ @MXene) is designed. Benefitting from the abundant polar terminal groups on the MXene surface, Sn²⁺ is induced into the interlayer of MXene with large interlayer spacing, which is selenized in situ to obtain LBL-SnSe₂ @MXene. In the heterostructure, SnSe₂ layers and MXene layers are uniformly intercalated in each other, superior to other heterostructures formed by random stacking. As an anode for lithium-ion batteries, the LBL-SnSe₂ @MXene is revealed to possess strong lithium adsorption ability, the small activation energy for lithium diffusion, and excellent structure stability, thus achieving outstanding electrochemical performance, especially with high specific capacities (1311 and 839 mAh g^-1 for initial discharge and charge respectively) and ultralong cycling stability (410 mAh g^-1 at 5C even after 16 000 cycles). This work conveys an inspiration for the controllable design and construction of homogeneous layered heterostructures.

Crystallize It before It Diffuses: Kinetic Stabilization of Thin-Film Phosphorus-Rich Semiconductor CuP2

Numerous phosphorus-rich metal phosphides containing both P–P bonds and metal–P bonds are known from the solid-state chemistry literature. A method to grow these materials in thin-film form would be desirable, as thin films are required in many applications and they are an ideal platform for high-throughput studies. In addition, the high density and smooth surfaces achievable in thin films are a significant advantage for characterization of transport and optical properties. Despite these benefits, there is hardly any published work on even the simplest binary phosphorus-rich phosphide films. Here, we demonstrate growth of single-phase CuP₂ films by a two-step process involving reactive sputtering of amorphous CuP_2+x and rapid annealing in an inert atmosphere. At the crystallization temperature, CuP₂ is thermodynamically unstable with respect to Cu₃P and P₄. However, CuP₂ can be stabilized if the amorphous precursors are mixed on the atomic scale and are sufficiently close to the desired composition (neither too P poor nor too P rich). Fast formation of polycrystalline CuP₂, combined with a short annealing time, makes it possible to bypass the diffusion processes responsible for decomposition. We find that thin-film CuP₂ is a 1.5 eV band gap semiconductor with interesting properties, such as a high optical absorption coefficient (above 10⁵ cm^–1), low thermal conductivity (1.1 W/(K m)), and composition-insensitive electrical conductivity (around 1 S/cm). We anticipate that our processing route can be extended to other phosphorus-rich phosphides that are still awaiting thin-film synthesis and will lead to a more complete understanding of these materials and of their potential applications.

Hierarchical Pores-Confined Ultrasmall Cu Nanoparticles for Efficient Oxidation of 5-Hydroxymethylfurfural

Pyrolysis is one of the most widely utilized protocols for the preparation of nanoconfined metal species for heterogeneous catalysis, but it still suffers from the uncontrollable composition evolution process with undesired metal sintering and porous structure collapse. Herein, a novel and versatile molten salt-assisted pyrolysis strategy was demonstrated for the preparation of ultrasmall transition-metal nanoparticles embedded in hollow hierarchical carbon skeletons. The preparation only involved the fabrication of metal-organic framework templates and subsequent pyrolysis with the addition of KCl-KBr molten salt, which played a crucial role in pore size extending and metal sintering inhibiting. Benefitting from the encapsulation effect, the as-synthesized Cu@HHC materials exhibited remarkable catalytic performance and recycling stability in the selective oxidation of biomass-derived 5-hydroxymethylfurfural into 2,5-diformylfuran under mild reaction conditions.

Acidity-responsive nanocages as robust reactive oxygen species generators with butterfly effects for maximizing oxidative damage and enhancing cancer therapy

Recently, with the rational design of transition metal-containing nanoagents, chemodynamic therapy (CDT) has been developed and considered a promising method for cancer therapy through Fenton and Fenton-like reaction-induced hydroxyl radical (·OH) generation and cellular oxidative damage. However, it is still a great challenge to realize high reactive oxygen species (ROS) generation and therapeutic efficiency under the strict conditions of the tumor microenvironment (TME). Herein, we design and fabricate a TME-responsive core-shell nanocage composed of a CaCO₃ nanolayer and a heterogeneous CoP core (CaCO₃@CoP, CCP) with the synergy of CDT and calcium overload to maximize oxidative damage and enhance cancer therapy. The CaCO₃ nanoshell is sensitive to pH and can be rapidly degraded upon endocytosis, leading to intracellular Ca²⁺ accumulation, which further triggers the production of mitochondrial ROS. Subsequently, the CoP hollow nanocage with fully exposed Co active sites has high Fenton-like reactive activity to produce ·OH and induce mitochondrial damage. Mitochondrial damage and ROS elevation, in turn, can modulate Ca²⁺ dynamics and augment calcium overload. The reciprocal interaction and loop feedback between calcium overload and photoenhanced ROS generation via photothermal therapy (PTT) can further trigger the immunogenic cell death (ICD) process to activate the maturation of dendritic cells (DCs), activation of cytotoxic and helper T cells, and excretion of proinflammatory cytokines to enhance antitumor immunity in vivo. With the butterfly effect, CCP finally brings forth a greatly enhanced cancer therapeutic outcome in murine models.

Interfacial Covalent Bonding Endowing Ti3 C2 -Sb2 S3 Composites High Sodium Storage Performance

Antimony sulfide is attracting enormous attention due to its remarkable theoretical capacity as anode for sodium-ion batteries (SIBs). However, it still suffers from poor structural stability and sluggish reaction kinetics. Constructing covalent chemical linkage to anchor antimony sulfide on two-dimension conductive materials is an effective strategy to conquer the challenges. Herein, Ti₃ C₂ -Sb₂ S₃ composites are successfully achieved with monodispersed Sb2S3 uniformly pinned on the surface of Ti₃ C₂ T_x MXene through covalent bonding of Ti-O-Sb and S-Ti. Ti₃ C₂ T_x MXene serves as both charge storage contributor and flexible conductive buffer to sustain the structural integrity of the electrode. Systematic analysis indicates that construction of efficient interfacial chemical linkage could bridge the physical gap between Sb2S3 nanoparticles and Ti₃ C₂ T_x MXene, thus promoting the interfacial charge transfer efficiency. Furthermore, the interfacial covalent bonding could also effectively confine Sb2S3 nanoparticles and the corresponding reduced products on the surface of Ti₃ C₂ T_x MXene. Benefited from the unique structure, Ti₃ C₂ -Sb₂ S₃ anode delivers a high reversible capacity of 475 mAh g^-1 at 0.2 A g^-1 after 300 cycles, even retaining 410 mAh g^-1 at 1.0 A g^-1 after 500 cycles. This strategy is expected to shed more light on interfacial chemical linkage towards rational design of advanced materials for SIBs.

In-Situ Templating Growth of Homeostatic GeP Nano-Bar Corals with Fast Electron-Ion Transportation Pathways for High Performance Li-ion Batteries

We propose an in situ template method to directionally induce the construction of germanium phosphide nanobar (GeP-nb) corals with an adjustable aspect ratio. The GeP nanobars grown onto conductive matrix with high aspect ratio expose more quickest electron-ion transportation facets for fast reaction dynamics. The customized GeP-nb electrode delivers a self-healable homeostatic behavior by reversibly stabilizing GeP crystalline structure through multi-phase reactions to maintain structural integrity and cycling stability (850 mAh g^-1 at 1 A g^-1 after 500 cycles). As a result, the GeP-nb presents the highest Li⁺ diffusion coefficient (6.21×10^-11  cm²  s^-1 ) among all the Ge-based anode materials studied so far, rendering an excellent rate performance (620 mAh g^-1 at 5 A g^-1 ) as a lithium-ion battery (LIB) anode.

Understanding the Effect of Second Metal on CoM (M = Ni, Cu, Zn) Metal-Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction

Co-based bimetallic metal-organic frameworks (MOFs) have emerged as a kind of promising electrocatalyst for oxygen evolution reaction (OER). However, most of present works for Co-based bimetallic MOFs are still in try-and-wrong stage, while the OER performance trend and the underlying structure-function relationship remain unclear. To address this challenge, Co-based MOFs on carbon cloth (CC) (CoM MOFs/CC, M = Zn, Ni, and Cu) are prepared through a room-temperature method, and their structure and OER performance are compared systematically. Based on the results of overpotential and Tafel slope, the order of OER activity is ordered in the decreasing sequence: CoZn MOF > CoNi MOF > CoCu MOF > Co MOF. Spectroscopic studies clearly show that the better OER performance of CoM MOFs results from the higher oxidation state of Co, which is related to the choice of second metal. Theoretical calculations indicate that CoZn MOFs possess strengthened adsorption for O-containing intermediate, and lower energy barrier towards OER. This study figures out the effect of second metal on the OER performance of Co-based bimetallic MOFs and suggests that tuning the electronic structure of the metal site can be an effective strategy for other MOFs-based OER catalysts.

Spatial Isolation-Inspired Ultrafine CoSe2 for High-Energy Aluminum Batteries with Improved Rate Cyclability

Transition-metal selenides are attractive cathode materials for rechargeable aluminum batteries (RABs) because of their high specific capacity, superior electrical properties, and low cost. To overcome the associated challenges of low structural stability and poor reaction kinetics, a spatial isolation strategy was applied to develop RAB cathodes comprising ultrafine CoSe₂ particles embedded in nitrogen-doped porous carbon nanosheet (NPCS)/MXene hybrid materials; the two-dimensional NPCS structures were derived from the self-assembly of metal frameworks on MXene surfaces. This synthetic strategy enabled control over the particle size of the active materials, even at high pyrolysis temperature, thereby allowing investigations into the effect of size on the electrochemical behavior. Spectroscopic analysis revealed that the CoSe₂-NPCS electrode exhibited a high discharge capacity (436 mAh g^-1 at 1 A g^-1), excellent rate capability (122 mA h g^-1 at 5 A g^-1), and long-term cycling stability (212 mAh g^-1 after 500 cycles at 1 A g^-1). Theoretical calculations regarding the Co adsorption affinities at various N-doping sites elucidated the synergistic effects of N-C/MXene hybrids for boosting the reaction kinetics and Co adsorption behavior in this system. This work offers an effective material engineering approach for designing electrodes with high rate stability for high-energy RABs.

Nitrogen doped porous carbon coated antimony as high performance anode material for sodium-ion batteries

Sb holds the promise of being a high performance anode for sodium ion batteries(SIBs), while effective preparation of decent antimony(Sb) based anode materials for sodium storage is still under exploration. Herein, we propose a simple approach to achieve a high performance anode, using polyaniline as the carbon source and SbCl₃as the metal source. Synergetic polymerization and hydrolysis reactions combined with subsequent thermal reduction endow Sb/C-PANI electrode possessing ultrafine Sb nanoparticles symmetrically distributed in the nitrogen(N) doped porous carbon matrix. The Sb/C-PANI electrode exhibits excellent sodium storage performance, featured for a high reversible capacity of 469.5 mAh g^-1after 100 cycles at 100 mA g^-1and 336.5 mAh g^-1after 300 cycles under 500 mA g^-1. Such impressive performance will advance the development of Sb based anode materials for sodium storage. The present approach provides a compatible strategy for preparation of anode materials with high reversible capacity and long lifespan.

General molten-salt route to three-dimensional porous transition metal nitrides as sensitive and stable Raman substrates

Transition metal nitrides have been widely studied due to their high electrical conductivity and excellent chemical stability. However, their preparation traditionally requires harsh conditions because of the ultrahigh activation energy barrier they need to cross in nucleation. Herein, we report three-dimensional porous VN, MoN, WN, and TiN with high surface area and porosity that are prepared by a general and mild molten-salt route. Trace water is found to be a key factor for the formation of these porous transition metal nitrides. The porous transition metal nitrides show hydrophobic surface and can adsorb a series of organic compounds with high capacity. Among them, the porous VN shows strong surface plasmon resonance, high conductivity, and a remarkable photothermal conversion efficiency. As a new type of corrosion- and radiation-resistant surface-enhanced Raman scattering substrate, the porous VN exhibits an ultrasensitive detection limit of 10^-11 M for polychlorophenol.

Nanostructured metal phosphides: from controllable synthesis to sustainable catalysis

Metal phosphides (MPs) with unique and desirable physicochemical properties provide promising potential in practical applications, such as the catalysis, gas/humidity sensor, environmental remediation, and energy storage fields, especially for transition metal phosphides (TMPs) and MPs consisting of group IIIA and IVA metal elements. Most studies, however, on the synthesis of MP nanomaterials still face intractable challenges, encompassing the need for a more thorough understanding of the growth mechanism, strategies for large-scale synthesis of targeted high-quality MPs, and practical achievement of functional applications. This review aims at providing a comprehensive update on the controllable synthetic strategies for MPs from various metal sources. Additionally, different passivation strategies for engineering the structural and electronic properties of MP nanostructures are scrutinized. Then, we showcase the implementable applications of MP-based materials in emerging sustainable catalytic fields including electrocatalysis, photocatalysis, mild thermocatalysis, and related hybrid systems. Finally, we offer a rational perspective on future opportunities and remaining challenges for the development of MPs in the materials science and sustainable catalysis fields.

A porous material excited by near-infrared light for photo/chemodynamic and photothermal dual-mode combination therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) are well-developed light therapy methods for cancer; however, both have a few areas that need improvement. A sustained PDT effect depends on the sustained generation of reactive oxygen species (ROS); therefore, adjusting the type of photosensitizer or the reaction mechanism to prolong the duration of the oxidation-reduction reaction is a possible solution for the continuation of the PDT effect. Further, if PTT could be combined with other treatments, it would bring about a more satisfactory therapeutic effect. To increase the treatment effect of the above two therapeutic methods, a collaborative treatment model of photo/chemodynamic therapy (PCDT) and PTT is needed and is the focus of this study. On the one hand, PCDT is a therapy that integrates PDT with Fenton-like reactions, and Fenton-like reactions can help PDT to produce more ROS by making better use of H₂O₂ in the tumor microenvironment. On the other hand, the PTT effect can also promote PCDT effects to some extent because rising temperature can elevate the redox reaction rate. Therefore, a copper oxide semiconductor photosensitizer was selected in this research to realize the abovementioned therapeutic purposes and experimental concepts. A porous silica carrier can facilitate the uniform attachment of the copper oxide photosensitizer to the SiO₂ surface to form a relatively uniform nanostructure, and the nanoporous structure can increase the performance of the whole material to a certain extent. Based on these perspectives, SiO₂@CuO nanotube (NT), an agent of both Fenton-like photosensitization and photothermal reagent, is synthesized by the hydrothermal co-precipitation template approach to shrink the tumor through the combined effect of PCDT and PTT. In this system, copper ions can participate in the Fenton-like reactions and make better use of H₂O₂ to generate more ROS. Herein, 808 nm light was chosen for irradiation because of its suitable excitation ability, applicable penetration and low intrinsic damage. The experimental results show that SiO₂@CuO NT is a promising agent that combines PCDT and PTT for cancer treatment. This work provides guidance for the synthesis of Fenton-like photosensitizers for the PCDT effect.