Metal Borides Research Articles

Harnessing MBene termination for superior anode interfaces in Li/Ca-ion batteries

The elevation of two-dimensional (2D) transition metal borides, specifically MBenes, as anode materials for lithium-ion batteries (LIBs) and calcium-ion batteries (CIBs) can be achieved through strategic functionalization with appropriate groups. Utilizing a first-principles approach, we conducted an in-depth investigation into the electrochemical properties of chlorine-terminated V2B (V2BCl2) as a candidate anode material for LIBs and CIBs. V2BCl2 exhibits metallic behavior, as demonstrated by band structure analysis, which endows it with exceptional conductivity due to the free electron surface of the system, thereby embodying ideal anode characteristics. The dynamic and thermal stability of the system was assessed through comprehensive phonon dispersion analyses and ab-initio molecular dynamics (AIMD) calculations. High net charge transfer rates of Li/Ca ions towards the monolayer, augmented electron localization function (ELF) near system atoms, and the presence of ionic bonds between Ca/Li and the V2BCl2 monolayer contribute to the enhanced conductivity observed in these anode systems. This is corroborated by metrics such as the projected crystal orbital Hamiltonian population (-pCOHP), low diffusion energy barriers (< 0.35 eV) facilitating rapid charging mechanisms, and low open circuit voltages (< 0.32 V) ensuring robust battery performance stability. Furthermore, V2BCl2 exhibits notable specific storage capacities of 875.67 mAh g−1 for Ca ions and 1167.75 mAh g−1 for Li ions, surpassing the benchmarks set by recent MBene systems. These promising results strongly advocate for V2BCl2 as a viable candidate for anode material in both LIB and CIB applications, highlighting its potential significance in advancing battery technology.

Novel design of nickel cobalt boride nanosheets-decorated molybdenum disulfide hollow spheres as efficient battery-type materials of hybrid supercapacitors

Transition metal borides (TMBs) with high theoretical capacitances and excellent electronic properties have attracted much attention as a promising active material of supercapacitors (SCs). However, TMB nanoparticles are prone to conduct self-aggregation, which significantly deteriorates the electrochemical performance and structural stability. To address the severe self-aggregation in TMBs and improve the active material utilization, it is imperative to provide a conductive substrate that promotes the dispersion of TMB during growths. In this work, sheet-like nickel cobalt boride (NCB) was grown on molybdenum disulfide (MoS2) hollow spheres (H-MoS2) by using simple template growth and chemical reduction methods. The resultant NCB/H-MoS2-50 was observed with uniform NCB nanosheets structure on the surface of the H-MoS2 and stronger MB bonding. After optimizing the loading amount of H-MoS2, the optimal composite (NCB/H-MoS2-50) modified nickel foam (NF) exhibits a superior specific capacity (1302 C/g) than that of the NCB electrode (957 C/g) at 1 A/g. Excellent rate capability of 84.8% (1104 C/g at 40 A/g) is also achieved by the NCB/H-MoS2-50 electrode. The extraordinary electrochemical performance of NCB/H-MoS2-50 is credited to the unique nanosheet-covered hollow spheres structure for facilitating ion diffusion and versatile charge storage mechanisms from the pseudocapacitive behavior of H-MoS2 and the Faradaic redox behavior of NCB. Furthermore, a hybrid SC is assembled with NCB/H-MoS2-50 and activated carbon (AC) electrodes (NCB/H-MoS2-50//AC), which operates in a potential window up to 1.7 V and delivers a high energy density of 76.8 W h kg−1 at a power density of 850 W kg−1. A distinguished cycling stability of 93.2% over 20,000 cycles is also obtained for NCB/H-MoS2-50//AC. These findings disclose the significant potential of NCB/H-MoS2-50 as a highly performed battery-type material of SCs.

Superconductivity in ZrB12 under High Pressure

Transition metal borides have emerged as pivotal players in various fields. In addition to their exceptional properties such as high hardness, a high melting point, and corrosion resistance, certain compounds exhibit remarkable characteristics including superconductivity, magnetism, electrical conductivity, and catalytic activity. Among these compounds, ZrB12 has garnered significant attention due to its unique physicochemical properties. However, previous research on ZrB12 has predominantly focused on its mechanical behavior while overlooking the electron-electron interactions of the superconducting state. In this paper, resistance characterization of ZrB12 under high-pressure conditions was conducted to further investigate its superconductivity. Our research findings indicate that ZrB12 maintains its superconductivity within a pressure range of 0 to 1.5 GPa and is classified as a type 2 superconductor. Additionally, the results confirm the anisotropic nature of ZrB12’s superconductivity. As the pressure increases, the superconducting transition temperature undergoes a gradual decrease. Remarkably, ZrB12 exhibits metallic behavior under pressures up to 31.4 GPa. The observed decline in superconductivity in ZrB12 can be ascribed to the intensified influence of Zr’s movement on phonon dispersion, ultimately leading to a reduction in carrier concentration.

Powder metallurgy processing of seven/eight component multi-phase (HfTiZr-Mn/Mo/W/Cr/Ta)B2 high entropy diboride ceramics

This study aims to show the possibility of synthesizing seven- and eight-component high entropy diboride (HEB) ceramics using high energy ball milling-assisted spark plasma sintering (SPS). Metal boride powders, synthesized in laboratory conditions from metal oxide-boron oxide-magnesium powder blends, were combined equimolarly as seven and eight components containing systems. Afterwards, hybridized powders were mechanically alloyed (MA) for 6 h and subjected to spark plasma sintering (SPS) at 2000 °C and under 30 MPa. Detailed phase analysis and physical, microstructural, and mechanical characterization of the samples were performed. ın the sintered products, the main phase belongs to the HEB, and also low amounts of Hf/Zr oxides and secondary phases (W or Ti-rich) occurred. The highest hardness was observed at the (HfTiZrMoWCrTa)B2 with ∼25 GPa, and the lowest hardness was seen at the (HfTiZrMnCrMoWTa)B2 with ∼17 GPa. Also, the highest wear resistance was calculated for the (HfTiZrMnCrMoTa)B2 as 6.05 × 10−7 mm3/Nm. Additionally, (HfTiZrMnMoWTa)B2 and (HfTiZrMnMoCrTa)B2 have the highest and lowest Archimedes’ densities, with 7.94 g/cm3 and 6.91 g/cm3, respectively.

Hydrogen Evolution Reactions of Hydrocarbons and Hydroborons Promoted by Superatomic Nbn- Clusters.

Hydrogen evolution reactions (HER) are crucial for producing renewable and ecological hydrogen energy. Here we report the finding that ethyl acetylene (C2H2), borane (B2H6), and benzene (C6H6) undergo drastic dehydrogenation reactions upon interaction with niobium cluster anions (Nbn-). This finding was enabled by our very sensitive and specialized mass spectrometer, which monitored the cluster ions and the resulting metal carbide and boride products in real time. Through mass spectrometry experiments and density functional theory computations, we delved into the varying reactivities of these common gas molecules with small Nbn- clusters and elucidated the underlying reaction mechanisms. These findings shed light on the HER mechanisms of hydrocarbon and hydroboron molecules on superatomic Nbn- clusters, furnishing valuable insights pertinent to the advancement of hydrogen energy resources.

Tailorable MBene aerogel with the lowest evaporation enthalpy for solar seawater desalination and wastewater purification

Growing global water scarcity has fueled the quest for sustainable and effective desalination solutions under lower energy requirements. However, it has a common strategy that has led to reducing the enthalpy of evaporation of water during solar-driven interfacial evaporation by dual-layer aerogels with effective mechanical robustness. Here, we introduce a novel class of 2D transition metal boride (MBene) integrated into the hydratable polymeric network of Polyvinyl alcohol/Chitosan/Polyurethane (MPCP) for an “all-in-one” solar evaporator. This dual-layer aerogel possesses both photothermal properties (for evaporating seawater) and reduced evaporation enthalpy (resulting in lower energy requirements). The MPCP aerogel gains broadband light absorption, and effective heat localization and exploits the polar groups on the polymer chains to interact with water molecules, resulting in reduced enthalpies of evaporation of 1132 J g−1 for water and 1245 J g−1 for seawater, which promotes excellent solar steam generation performance with a high evaporation rate of 2.83 kg/m2h under 1 kW m−2 solar intensity. The MBene aerogel has favorable endurance and versatility in effectively treating a wide range of polluted wastewater sources, such as organic dyes and heavy metal solutions, with high efficiency and exceptional longevity under real seawater tests over 20 consecutive days. This work could guide the development of MBenes for efficient solar-driven water evaporation and wastewater remediation.

Microstructure evolution and tribological properties over a wide temperature range of Ni-based composite coatings with Ti3AlC2 addition

Ni60A alloy powders doped with varying concentrations (0, 10 wt% and 20 wt%) of Ti3AlC2 MAX phase were coated on S31008 NiCr stainless steel substrate using atmosphere plasma spraying technique in this work. Comparative investigation was conducted to examine the effects of Ti3AlC2 additions on the microstructure evolution, microhardness, and wide temperature range (room temperature to 800 oC) tribological performance of the composite coatings. The findings demonstrated that the composite coatings were composed of γ-Ni, intermetallic hard metal borides, Ti3AlC2 and TiC phases, without any noticeable oxide phases. The 20 wt% Ti3AlC2 additions to the Ni60A alloy coating exhibited minimum imperfections in microstructure with a porosity drop of 65.8 %, and the highest microhardness which was enhanced by 64 % to 924 HV0.515. After introducing of Ti3AlC2, the coefficient of friction decreased and appeared to distinguish itself by remaining minimal and stable at low-medium temperatures compared with an increase of more than 70 % at high temperatures. Ni60A-10 wt% Ti3AlC2 coating resulted in the lowest friction coefficient of approximately 0.45 from room temperature to 400 oC and it peaked to 0.78 at 800 oC, reducing by 19.6 % and 6 % compared to non-composite coating, respectively. The wear resistance of the composite coating was considerably improved with the increment of Ti3AlC2, and the coating with 20 wt% Ti3AlC2 showed the most significant reduction in wear rate: 18.5 % at room temperature, 45.2 % at 200 oC, 37.2 % at 400 oC, 60 % at 600 oC, 90.8 % at 800 oC. The lubricate layered Ti3AlC2 phases and the tribo-oxide film predominate composed of derivative NiO, Cr2O3 Al2O3 and TiO2 played a critical role in antifriction and wear resistance. The wear mechanisms were accordingly conducted as abrasion and adhesion wear at low-medium temperature and transferred into tribo-oxidation wear at elevated temperature.

Insights into molecular interactions at organic-MBene heterointerfaces for efficient Zn-ion storage

The intercalation of organic molecules is a promising approach to modulate the structure of 2D transition metal borides (MBenes), aiming to enhance charge transport and improve electrochemical performance in energy storage applications. However, key questions remain regarding how organic molecules with diverse functionalities penetrate and align between the MBene layer, as well as the mechanism of charge redistribution during intercalation. Addressing these questions is crucial for guiding the design of Organic-MBene heterostructures. To this end, a comprehensive approach combining theoretical calculations and experimental analyses was employed to explore the self-assembly mechanisms of organic molecules featuring N, O, S and tertiary amine end groups on the MoB-MBene surface. Experimental characterizations confirm that the interaction between MoB and organic compounds depends on the end groups. First principles calculations demonstrate that organic molecules tend to adopt a flat configuration on the MoB surface during molecular assembly. Calculations also reveal that the binding and charge transfer processes from organic molecules to MoB are highly dependent on the specific end groups, consistent with experimental observations. Furthermore, the effect of combining organic molecules with MoB on battery performance was further discussed, offering new insights for advancing the research and development of MBenes in aqueous battery systems.

Theoretical prediction of two-dimensional metallic AM2B8 (AM = K, Rb, Cs) as anode materials for Na-ion batteries

The development of two-dimensional anode materials with superior performance is becoming a critical undertaking for the advancement of Na-ion battery technology. Using isoelectronic substitution strategies, we predicted three alkali metal borides AM2B8 (AM = K, Rb, Cs) based on the SrB8 monolayer. Ab initio molecular dynamics simulations and phonon dispersion relationship calculations demonstrated their stability. Using density functional theory, we predict the feasibility of these three new metal nanosheets as anodes for Na-ion batteries. The AM2B8 monolayer retains its metallicity after the insertion of Na ions, ensuring that the anode has good electrical conductivity. In addition, AM2B8 has a low diffusion barrier and open circuit voltage (K2B8 is 0.08 eV and 0.26 V) during charge/discharge. In the voltage range that inhibits dendrite growth, K2B8 can reach the maximum theoretical specific capacity (326 mAh/g). These results indicate that AM2B8, especially K2B8, is a promising anode material for Na-ion batteries.

Unlocking Enhanced Electrochemical Performance of MBene-MoB Through Controlled Aluminum Dissipation from MoAlB.

2D transition metal borides, known as MBenes, have attracted considerable attention due to their exceptional properties. This study explores the feasibility of aluminum (Al) etching from MoAlB using environmentally friendly and sustainable fluoride-free dilute acidic/alkaline solutions at room temperature, revealing its thermodynamic and kinetic viability. Furthermore, it is found that complete removal of Al can be achieved in dilute alkaline reagent under hydrothermal conditions, yielding pristine single/few-layered MBene-MoB for the first time, while acidic solutions result in ≈33% etching rates. XRD refinement, which tracks aluminum removal from 0% to 100%, reveals transient metastable phases of MoAl1-xB (x<0.5) in the initial etching stages, evolving into relatively stable pure Mo2AlB2 structures with 50% Al deficiency, serving as a precursor to MBenes. The subsequent loss of Al results in a 2D MBene-MoB structure. DFT calculations confirm excellent conductivity for MoAlB, MoAl1-xB (x=0-1), and MBene-MoB. Remarkably, MBene-MoB exhibits superior supercapacitor performance with a 4025.60mFcm-2/201.28Fg-1 capacitance. Simulations validate rapid electrolyte diffusion in layered MBene-MoB, contributing significantly to enhanced capacitance. Additionally, in the hydrogen evolution reaction (HER), MBene-MoB demonstrates superior catalytic activity compared to the precursor MoAlB and commercial MoB. Calculations suggest the potential for enhancing HER through surface modulation, considering its suboptimal hydrogen adsorption energy.

Attaining high-rate hydrogen evolution via SILAR deposited bimetallic nickel cobalt boride electrode: Exploring the influence of Ni to Co ratio

For the first time, a bimetallic Nickel Cobalt Boride (NCB) film with varying Ni to Co ratios was synthesized on stainless steel via the SILAR method. The NCB2 film (1:1 ratio) exhibited a mixed phase of metal boride and oxy-hydroxide with a highly porous, flaky-type morphology, while NCB1 (1:3 ratio) and NCB3 (3:1 ratio) showed only oxidized metal phases and agglomerated clusters. EDX confirmed the purity of the samples, and XPS indicated higher oxidation in NCB1 and NCB3 compared to NCB2. For HER, NCB2 showed the lowest overpotential (80 mV) compared to NCB1 (96 mV) and NCB3 (101 mV), and the smallest Tafel slope value (71 mV/dec). HER kinetics followed a Volmer-Heyrovsky mixed reaction path. NCB2 exhibited the highest Cdl value (16.55 mF/cm2) and the largest electrochemical active surface area (413.7 cm2), outperforming NCB1 (333.125 cm2) and NCB3 (205 cm2). At an overpotential of 100 mV, NCB2's TOF value was 8.23 s⁻1, higher than NCB1 (1.4 s⁻1) and NCB3 (1 s⁻1). For OER, NCB2 showed the highest Cdl value (106 mF/cm2) and ECSA value (2650 cm2). The Faradic efficiency of NCB2 was ∼98% after 190 h. Hydrogen evolution rates for NCB1, NCB2, and NCB3 as cathodes were 952 mL/h, 1022 mL/h, and 800.8 mL/h, respectively. In a prototype electrolyzer, NCB2 enhanced the hydrogen evolution rate by 30% in bifunctional mode to 1334.6 mL/h. After 100 h, performance declined by only 2.7% due to surface oxidation and phase changes. This achievement marks a milestone towards low-cost green hydrogen production, achieving the highest rate of hydrogen evolution as ever reported.

A preparation of niobium diboride (NbB2) via molten salt method: Impact of boron concentration on the structural and electrochemical performance

In this work, niobium diboride (NbB2) nanoparticles were successfully synthesized using a simple and facile molten salt method and examined as electrodes for supercapacitors. The synthesized nanoparticles were characterized using SEM, HRTEM, XRD, XPS, and BET techniques. Also, the electrochemical performance of various NbB2 nanoparticles depending on the various amorphous boron concentrations was systematically investigated using both a neutral (1 M Na2SO4) and a basic (6 M KOH) electrolyte. Electrochemical analysis revealed that the obtained sample denoted as the NbB2–8 exhibited the best electrochemical performance (159.6 F/g at 10 mV/s) in Na2SO4 electrolyte compared to that of the KOH electrolyte (69.6 F/g at 10 mV/s). Such a result can be owing to the size and mobility of ions in the electrolyte. Overall, this work could pave the way for other metal borides’ versatility and potential in energy storage.

Mechanistic Interrogation on Wound Healing and Scar Removing by the Mo4/3B2-x Nanoscaffold Revealed Regulated Amino Acid and Purine Metabolism.

Wound rehabilitation is invariably time-consuming, scar formation further weakens therapeutic efficacy, and detailed mechanisms at the molecular level remain unclear. In this work, a Mo4/3B2-x nanoscaffold was fabricated and utilized for wound healing and scar removing in a mice model, while metabolomics was used to study the metabolic reprogramming of metabolome during therapy at the molecular level. The results showed that transition metal borides, called Mo4/3B2-x nanoscaffolds, could mimic superoxide dismutase and glutathione peroxidase to eliminate excess reactive oxygen species (ROS) in the wound microenvironment. During the therapeutic process, the Mo4/3B2-x nanoscaffold could facilitate the regeneration of wounds and removal of scars by regulating the biosynthesis of collagen, fibers, and blood vessels at the pathological, imaging, and molecular levels. Subsequent metabolomics study revealed that the Mo4/3B2-x nanoscaffold effectively ameliorated metabolic disorders in both wound and scar microenvironments through regulating ROS-related pathways including the amino acid metabolic process (including glycine and serine metabolism and glutamate metabolism) and the purine metabolic process. This study is anticipated to illuminate the potential clinical application of the Mo4/3B2-x nanoscaffold as an effective therapeutic agent in traumatic diseases and provide insights into the development of analytical methodology for interrogating wound healing and scar removal-related metabolic mechanisms.

FenB2+2n (n = 1, 2), an intrinsic room temperature ferromagnetic MBene with significant magnetic performance enhancement achievable by carbon substitution

From spintronics to data storage technology, two-dimensional (2D) ferromagnetic materials show great promise for various applications. This work reports a series of stable ferromagnetic transition metal boride FenB2+2n (n = 1, 2), where robust long-range ferromagnetic exchange coupling and large perpendicular magnetic anisotropy energy (MAE) allow the ferromagnetic transition temperature (Tc) of the FenB2+2n monolayer to reach above room temperature. The metallic FenB2+2n exhibits n- and p-type Dirac transport in both spin channels with a high Fermi velocity. Furthermore, the application of biaxial compressive strain and electron doping can greatly increase the ferromagnetic coupling and MAE of FeB4 monolayers. On this basis, the FeB2C2 alloy with a high concentration of carbon substitution has been designed, which allows the nonvolatile integration of in-plane compressive strain and electron doping. As expected, this substitution doping resulted in a significant increase in the Tc and MAE of the system. Our findings provide perspectives for the study of 2D magnetic materials.

Electrophoretically Deposited TiB2 Coatings in NaF-AlF3 Melt for Corrosion Resistance in Liquid Zinc

Molten salt electrophoretic deposition is a novel method for preparing coatings of transition metal borides such as TiB2, which has emerged in recent years. To broaden the applications of transition metal boride coatings prepared by this method, this paper investigates the corrosion resistance of TiB2 coatings, produced through molten salt electrophoretic deposition, to liquid zinc. By applying a cell voltage of 1.2 V (corresponding to an electric field of 0.6 V/cm) for 1 h in molten NaF-AlF3, the nanoscale TiB2 particles migrated to the cathode and were deposited on the graphite substrate, forming a smooth and dense TiB2 coating with a thickness of 43 μm. Subsequently, after subjecting the TiB2-coated graphite to corrosion resistance tested in molten zinc for 120 h of continuous immersion, no cracks were observed on the surface or within the coating. The produced TiB2 coating demonstrated excellent corrosion resistance. These research results suggest that the fully dense TiB2 coating on the graphite substrate, produced through molten salt electrophoretic deposition, exhibits excellent corrosion resistance to liquid zinc.

Tuning Oxygen Evolving Catalytic Activity of a Precious Metal-Free Nickel Boride by a Cost-Effective Method

The production of hydrogen (H2) by electrochemical water splitting [Green Hydrogen (Green H2)], if driven by green electricity, has attracted considerable interest as an alternative sustainable energy carrier, e.g., in fuel cells for electricity or power and heat generation [1]. However, the lack of satisfactory and cheap electrocatalysts (ECs) to drive the vital electrochemical reactions of hydrogen evolution (HER) and oxygen evolution (OER) in water splitting is the biggest challenge for this technology.Currently, the most advanced electrocatalysts for the two half-reactions of water electrolysis (HER and OER) are noble metal-based materials [2]. Despite the excellent catalytic properties of these noble metal catalysts, their high cost, and scarcity make their commercial use both uneconomical and impractical in low temperature water electrolysis (LT-WE) systems at industrial scale for green H2 as a clean energy alternative to cheaper fossil fuels[3]. In addition to addressing this issue by the development of precious-material-based with a low-loading of precious metal elements, the development of desirable and high-efficiency electrocatalysts (ECs) based on earth-abundant metal elements materials is paramount. However, their catalytic activity is often limited by poor electron transfer, low conductivity, low stability, and small surface area of these materials. Thus, it is crucial to develop earth-abundant metal elements-based materials that are more cost-effective to reduce the high cost of active catalysts for water electrolysis. Although several low-cost materials have already been designed, the potential required for the practical application of water splitting is still very high compared to the theoretical potential (1.23 V), which means that much energy is consumed, which theoretically could be reduced. Due to their remarkable advanced charge transfer and durability for water oxidation in alkaline media, electrocatalysts derived from metal borides-based materials have received a lot of attention as new high-performance catalysts for water oxidation.[4] These properties stem from the multi-dimensional covalent bonding of the metalloid with the surrounding metal atoms.We present here an approach to tune the OER of transition metal borides (TMBs) using the cost-effective and less energy-consuming method that is nevertheless a highly efficient material for OER (Fig. 1). We have developed a low-cost, rational and easily scalable method to enhance the catalytic activity of nickel boride (Ni–B), which requires an annealing process to optimize the catalytic activity. However, this method may have limited applicability on a large scale as it requires a highly inert environment and high-temperature treatment of Ni–B catalysts. We also elucidate a structure-activity relationship using scale-bridging techniques such as TEM and electrochemical characterization. The developed based on non-noble electrocatalysts are prepared by a simple method of chemical reduction of transition metal elements with boron in aqueous solution. The production is a one-step process and the material does not require any further treatment, yet this material shows comparable activity to the state of the art (precious metal-based materials) for OER in alkaline solution at a selected current density. This improved catalytic performance is further corroborated by the microstructural investigations in the TEM. The nanoparticles obtained have an improved porous structure compared to Ni–B and thus provide more available sites for the surface reactions and hence for the catalytic performance of the material. Furthermore, it is shown that activation enables the morphological and structural changes, while some transition metal elements act as sacrificial elements to provide more accessible and stable sites for oxygen-forming centers. This paves the way for a better understanding of metal boride-derived electrocatalysts for water oxidation, a crucial chemical reaction in water electrolysis and other electrochemical energy technologies. Acknowledgements: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 945422. We acknowledge the use of the DFG-funded Micro-and Nanoanalytics Facility (MNaF) at the University of Siegen (INST 221/131-1).

A Literature Survey of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) are a new class of oxygen evolution reaction (OER) electrocatalysts, which have become a relevant topic for electrocatalytic energy conversion and storage research. This is because of their earth abundance, high electrical conductivity, and resultant high OER performance. Furthermore, some X-ide electrocatalysts demonstrate various degrees of oxidation resistance under OER potentials due to their differences in chemical composition, crystal structure, and morphology. Interestingly, there are three possible post-OER electrocatalyst models: a fully oxidized oxide/(oxy)hydroxide material, a partially oxidized core@shell structure, and an unoxidized material.1 In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Recently, several topical reviews have been published. However, typically these literature reviews have provided limited conclusions targeted at only certain X-ides. Additionally, certain reviews omit key points, especially regarding the “catalytically active species” in X-ide OER electrocatalysts.In this work, we provide a comprehensive summary of (i) the experimental parameters (e.g., substrates, electrocatalyst loading amounts, electrocatalyst shapes, geometric overpotentials, Tafel slopes, etc.) and (ii) the details of the electrochemical stability tests and following post analyses used in all the X-ide OER electrocatalyst publications from 2013 (the birth of this research area) to 2022.2 In particular, based on the reported post-OER analytical results, we attempt to exhaustively classify all the X-ide electrocatalysts into four groups: no oxidation, partial oxidation, full oxidation, and unknown, which is relevant to the nature of the “catalytically active species” in X-ide OER electrocatalysts. After investigating the simpler X-ide systems, transition metal-based polyanion compounds/composites are also surveyed. Finally, we introduce the reported novel and special analytical techniques employed for observing X-ide reconstruction (i.e., oxidation and other phase transformations) during OER testing, which can be useful in selecting the analytical technique of maximum utility for the researchers’ purpose. Additionally, for each material sub-group (e.g., borides, carbides, nitrides, phosphides, sulfides, selenides, and tellurides), we also point out further challenges to be addressed and propose further questions yet to be answered, which may provide clues pointing to future research tasks. References B. R. Wygant, K. Kawashima, and C. B. Mullins, ACS Energy Lett., 3, 2956–2966 (2018).K. Kawashima et al., Chem. Rev., 123, 12795–13208 (2023).

Synthesis, Characterization, and Magnetocaloric Properties of the Ternary Boride Fe2AlB2 for Caloric Applications.

The ternary transition metal boride Fe2AlB2 is a unique ferromagnetic "MAB" phase that demonstrates a sizable magnetocaloric effect near room temperature-a feature that renders this material suitable for magnetic heat pump devices (MHP), a promising alternative to conventional vapor compression technology. Here, we provide a comprehensive review of the material properties of Fe2AlB2 (magnetofunctional response, transport properties, and mechanical stability) and discuss alloy synthesis from the perspective of shaping these materials as porous active magnetic regenerators in MHPs. Salient aspects of the coupled magnetic and structural phase transitions are critically assessed to elucidate the fundamental origin of the functional response. The goal is to provide insight into strategies to tune the magnetofunctional response via elemental substitution and microstructure optimization. Finally, outstanding challenges that reduce the commercial viability of Fe2AlB2 are discussed, and opportunities for further developments in this field are identified.

Isothermal oxidation of bulk dense Fe2AlB2 and Mn2AlB2 phases in 700–1000 °C temperature range

Herein, the isothermal oxidation of Mn2AlB2 and Fe2AlB2 MAB phases in air was studied. When oxidized at 700 °C, the weight gain kinetics for Mn2AlB2 are sub-cubic up to 96 h as a result of the formation of a Mn2-xAlxO3 protective layer. Severe spallation of the oxides formed was observed at 800 °C and 900 °C, limiting its service temperature. The oxidation kinetics at 900 °C, for Fe2AlB2 become sub-parabolic beyond 60 h due to the formation of a passivating Αl4Β2Ο9 with excellent corner adherence. At both 800 °C and 1000 °C, however, the oxidation is rapid and severe. Therefore, both Mn2AlB2 and Fe2AlB2 may be used in practical application up to 700 °C and 900 °C, respectively. As far as we are aware, Fe2AlB2 is the second transition metal boride that is oxidation resistant at 900 °C; the first, MoAlB, is also a MAB phase.

Electronic modulation of MOF-derived CoxMnyB nanosheet arrays toward efficient bifunctional electrocatalysts for water splitting

The design of robust and efficient bifunctional electrocatalysts for total water splitting is of paramount importance for the advancement of sustainable energy conversion technologies. To fully exploit the electrocatalytic capabilities of transition metal borides, we integrate manganese-incorporated cobalt boride (CoxMnyB) nanoarrays derived from metal-organic frameworks (MOFs). CoxMnyB nanosheet arrays exhibit pronounced electronic modulation, indicating superior electrochemical behavior. CoxMnyB can served as a binder-free catalytic electrode, which exhibits bifunctional electrocatalytic activity of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). CoxMnyB demonstrates an overpotential ∼ 277 mV under 10 mA cm−2 and a Tafel slope of 71 mV dec-1 for HER. It also exhibits optimised OER characteristics, with a potential of 1.54 V at a current density of 10 mA cm−2 and the lowest Tafel slope of 62 mV dec-1. CoxMnyB catalysts emerge as promising candidates for bifunctional electrocatalysts in overall water splitting, delivering remarkable and enduring electrocatalytic functionalities. The intricate mechanisms governing the electrocatalytic performance of the CoxMnyB bifunctional catalyst are systematically discussed in relation to nanostructure, conductive behavior, and the covalent bonding nature of metal-metalloid borides. Density functional theory (DFT) calculations reveal a reduced hydrogen binding energy at the catalyst surface and a weakened energy barrier of OOH*. This study suggests a favourable and feasible pathway for deploying metal borides in high-efficiency electrocatalysis and energy storage applications.