Recent Advances in Metallic Glass Nanostructures: Synthesis Strategies and Electrocatalytic Applications

Recent advances in metallic glass nanostructures (MGNs) are reported, covering a wide array of synthesis strategies, computational discovery, and design solutions that provide insight into distinct electrocatalytic applications. A brief introduction to the development and unique features of MGNs with an overview of top‐down and bottom‐up synthesis strategies is presented. Specifically, the morphology and structural analysis of several examples applying MGNs as electrodes are highlighted. Subsequently, a comprehensive discussion of commonly employed kinetic parameters and their connection with the unique material structures of MGNs on individual electrocatalytic reactions is made, including the hydrogen evolution reaction, oxygen reduction reaction, and alcohol (methanol or ethanol) oxidation reaction. Finally, a summary of the challenges and perspective on the future research and development relevant to MGNs as electrocatalysts is provided.     

Water Dissociation Kinetic-Oriented Design of Nickel Sulfides via Tailored Dual Sites for Efficient Alkaline Hydrogen Evolution

The reaction kinetics of alkaline hydrogen evolution reactions (HER) is a trade-off between adsorption and desorption for intermediate species (H₂O, OH, and H_ads). However, due to the complicated correlation between the intermediates adsorption energy and electronic states, targeted regulating the adsorption energy at the atomic level is not comprehensive. Herein, nonmetals (B, N, O, and F) are used to modulate the adsorption energy and electronic structure of Ni₃S₄, and propose that H₂O and OH adsorption energy are correlate directly with d-band center (ε_d) of transition metal Ni, and H_ads adsorption energy has a linear dependence on p-band center (ε_p) of nonmetal S. Direct experimental evidence is offered that in all nonmetals doping samples, Tafel slope and exchange current density can be improved regularly with the ε_d and ε_p, and F-Ni₃S₄ shows the optimum activity with tiny overpotential 29 and 92 mV for harvesting current density 10 and 100 mA cm⁻², respectively. Furthermore, the micro-kinetics analysis and density functional theory calculations verify that F-doping can efficiently reduce the energy barrier of the Volmer step, eventually accelerating the HER kinetics. This work provides atomic-level insight into the structure-properties relationship, and opens an avenue for kinetic-oriented design of alkaline HER and beyond.     

Interfacial Engineering of Bifunctional Niobium (V)-Based Heterostructure Nanosheet Toward High Efficiency Lean-Electrolyte Lithium–Sulfur Full Batteries

High-efficiency lithium–sulfur (Li–S) batteries depend on an advanced electrode structure that can attain high sulfur utilization at lean-electrolyte conditions and minimum amount of lithium. Herein, a twinborn holey Nb₄N₅–Nb₂O₅ heterostructure is designed as a dual-functional host for both redox–kinetics–accelerated sulfur cathode and dendrite-inhibited lithium anode simultaneously for long-cycling and lean-electrolyte Li–S full batteries. Benefiting from the accelerative polysulfides anchoring–diffusion–converting efficiency of Nb₄N₅–Nb₂O₅, polysulfide-shutting is significantly alleviated. Meanwhile, the lithiophilic nature of holey Nb₄N₅–Nb₂O₅ is applied as an ion-redistributor for homogeneous Li-ion deposition. Taking advantage of these merits, the Li–S full batteries present excellent electrochemical properties, including a minimum capacity decay rate of 0.025% per cycle, and a high areal capacity of 5.0 mAh cm⁻² at sulfur loading of 6.9 mg cm⁻², corresponding to negative to positive capacity ratio of 2.4:1 and electrolyte to sulfur ratio of 5.1 µL mg⁻¹. Therefore, this work paves a new avenue for boosting high-performances Li–S batteries toward practical applications.     

Sub-2 nm Ultrathin and Robust 2D FeNi Layered Double Hydroxide Nanosheets Packed with 1D FeNi-MOFs for Enhanced Oxygen Evolution Electrocatalysis

Water oxidation is a critical process for electrochemical water splitting due to its inherent sluggish kinetics. In spite of the high catalytic activities of noble metal-based electrocatalysts for water oxidation, their high cost, rare reserves, and low stabilities drive researchers to exploit efficient but low-cost electrocatalysts. Ultrathin 2D nanomaterials are considered efficient electrocatalysts for oxygen evolution reaction (OER) in water splitting. Herein, a facile strategy is proposed to fabricate 2D FeNi layered double hydroxide (FeNi-LDH) nanosheets packed with the in situ produced 1D sword-like FeNi-MOFs by using FeNi-LDH as a semi-sacrificial template. In the composite, the thickness of the formed nanosheets is only 1.34 nm, much thinner than that of most previously reported 2D materials. The 1D porous sword-like MOF nanorods have a long length of around 1.3 µm. Due to the unique 2D/1D combined structure, the as-prepared FeNi LDH/MOF is directly used as electrocatalyst for the OER displays enhanced OER electrocatalytic performance with a low overpotential of 272 mV@100 mA cm^–2, a small Tafel slope of 34.1 mV dec^–1, high long-term durability. This work provides a new way to fabricate integrated ultrathin 2D nanosheets and MOFs as advanced catalysts for electrochemical energy conversion.     

Carbon Free and Noble Metal Free Ni2Mo6S8 Electrocatalyst for Selective Electrosynthesis of H2O2

Electrocatalytic two-electron reduction of oxygen is a promising method for producing sustainable H₂O₂ but lacks low-cost and selective electrocatalysts. Here, the Chevrel phase chalcogenide Ni₂Mo₆S₈ is presented as a novel active motif for reducing oxygen to H₂O₂ in an aqueous electrolyte. Although it has a low surface area, the Ni₂Mo₆S₈ catalyst exhibits exceptional activity for H₂O₂ synthesis with >90% H₂O₂ molar selectivity across a wide potential range. Chemical titration verified successful generation of H₂O₂ and confirmed rates as high as 90 mmol H₂O₂ g_cat⁻¹ h⁻¹. The outstanding activities are attributed to the ligand and ensemble effects of Ni that promote H₂O dissociation and proton-coupled reduction of O₂ to HOO*, and the spatial effect of the Chevrel phase structure that isolates Ni active sites to inhibit O O cleavage. The synergy of these effects delivers fast and selective production of H₂O₂ with high turn-over frequencies of ≈30 s⁻¹. In addition, the Ni₂Mo₆S₈ catalyst has a stable crystal structure that is resistive for oxidation and delivers good catalyst stability for continuous H₂O₂ production. The described Ni-Mo₆S₈ active motif can unlock new opportunities for designing Earth-abundant electrocatalysts to tune oxygen reduction for practical H₂O₂ production.     

Oxygen-Incorporated NiMoP Nanotube Arrays as Efficient Bifunctional Electrocatalysts For Urea-Assisted Energy-Saving Hydrogen Production in Alkaline Electrolyte

To couple hydrogen evolution reaction (HER) with urea oxidation reaction (UOR) is a promising approach to produce H₂ with reduced energy consumption. However, the development of a low-cost and high-performance bifunctional electrocatalyst toward HER and UOR is still a challenge. In this work, oxygen-incorporated nickel molybdenum phosphide nanotube arrays are synthesized on nickel foam (O-NiMoP/NF) via electrodeposition accompanied with in-situ template etching. Benefiting from the modulated electronic structure and the nanotube array architecture of O-NiMoP, the self-supporting O-NiMoP/NF electrodes demonstrate highly efficient bifunctional catalytic activity toward HER and UOR. Particularly, in the HER and UOR (HER||UOR) coupled system for H₂ production, a significantly reduced cell voltage of 1.55 V is obtained at the current density of 50 mA cm^–2, which is about 300 mV lower than that of the conventional water electrolysis. Density functional theory calculations reveal that the remarkable HER and UOR activities originated from the Ni sites with the modulated electronic environment induced by Mo, P and O atoms, which facilitate the water dissociation during HER and balance the adsorption/desorption of the intermediates during UOR. The development of Ni-based phosphides nanotube arrays as a bifunctional electrocatalyst in HER||OER system provides a new approach enabling energy-saving H₂ production.     

Iridium-Doped N-Rich Mesoporous Carbon Electrocatalyst with Synthetic Macrocycles as Carbon Source for Hydrogen Evolution Reaction

Utilizing supramolecular synthetic macrocycles with distinct porous structures and abundant functional groups as a precursor for metal-doped carbon electrocatalysts can endow the resulting materials with great potential in electrocatalysis. Herein, iridium-doped electrocatalysts (CBC-Ir), using a synthetic macrocycle named cucurbit[6]uril as the carbon source precursor, are designed and prepared. Interestingly, owing to the numerous N-containing backbone and unique porous structure from cucurbit[6]uril self-assembly, the newly designed catalysts CBC-Ir possess abundant N-doped and mesoporous structures without the need of additional N sources and templates. The catalysts exhibit superior catalytic performance toward the hydrogen evolution reaction with high Faradaic efficiency (91.5% and 92.7%), superior turnover frequency (2.1 and 0.69 H₂ s⁻¹) at the 50 mV overpotential, and only 17 and 33 mV overpotentials in acidic and alkaline conditions reaching the current density of 10 mA cm⁻², better than the commercial Pt/C (28 and 43 mV). This work not only expands the application of supramolecular macrocycles in the water splitting field but also provides a new approach for preparing robust electrocatalysts.     

碳化的MOF用于电催化还原二氧化碳制备乙烯和乙醇

电化学催化还原二氧化碳是一种有效的能源储存手段。探索具有高乙烯选择性和高产率的高效电催化剂是非常必要的,但仍然具有挑战性。通过对金属有机骨架（Cu-BTC）的简单碳化制备了多孔Cu-Cu₂O/C催化剂,用于高效且选择性地电催化CO₂还原为C₂₊产物。碳化的MOF表现出优异的还原CO₂为C₂₊的性能,在电位为-1.3 V（vs RHE）时,C₂₊的最大法拉第效率（FE）为47.8%,其部分电流密度为4.33 mA·cm^-2。研究表明,较低的碳化温度有助于保留Cu-MOF的形貌,抑制活性金属位点团聚,而多孔特性也能提升其电化学活性面积,进而提高其对CO₂电化学还原为C₂₊产物的性能。     

Porous Iron–Cobalt Alloy/Nitrogen‐Doped Carbon Cages Synthesized via Pyrolysis of Complex Metal–Organic Framework Hybrids for Oxygen Reduction

Efficient and stable nonprecious metal electrocatalysts for oxygen reduction are of great significance in some important electrochemical energy storage and conversion systems. As a unique class of porous hybrid materials, metal–organic frameworks (MOFs) and their composites are recently considered as promising precursors to derive advanced functional materials with controlled structures and compositions. Here, an “MOF‐in‐MOF hybrid” confined pyrolysis strategy is developed for the synthesis of porous Fe–Co alloy/N‐doped carbon cages. A unique “MOF‐in‐MOF hybrid” architecture constructed from a Zn‐based MOF core and a Co‐based MOF hybrid shell encapsulated with FeOOH nanorods is first prepared, followed by a pyrolysis process to obtain a cage‐shaped hybrid material consisting of Fe–Co alloy nanocrystallites evenly distributed inside a porous N‐doped carbon microshell. Of note, this strategy can be extended to synthesize many other multifunctional “nanosubstrate‐in‐MOF hybrid” core–shelled structures. Benefiting from the structural and compositional advantages, the as‐derived hybrid cages exhibit superior electrocatalytic performance for the oxygen reduction reaction in alkaline solution. The present approach may provide some insight in design and synthesis of complex MOF hybrid structures and their derived functional materials for energy storage and conversion applications.