Transient and general synthesis of high-density and ultrasmall nanoparticles on two-dimensional porous carbon via coordinated carbothermal shock

Supersaturated Doping-Induced Maximized Metal-Support Interaction for Highly Active and Durable Oxygen Evolution

Metal-support interaction (MSI) is pivotal and ubiquitously used in the development of next-generation catalysts, offering a pathway to enhance both catalytic activity and stability. However, owing to the lattice mismatch and poor solubility, traditional catalysts often exhibit a metal-on-support heterogeneous structure with limited interfaces and interaction and, consequently, a compromised enhancement of properties. Herein, we report a universal and tunable method for supersaturated doping of transition-metal carbides via strongly nonequilibrium carbothermal shock synthesis, characterized by rapid heating and swift quenching. Our results enable ∼20 at. % Ni2FeCo doping in Mo2C, significantly surpassing the thermodynamic equilibrium limit of <3 at. %. The supersaturation ensures more catalytically active NiFeCo doping and sufficient interaction with Mo2C, resulting in the maximized MSI (Max-MSI) effect. The Max-MSI enables outstanding activity and particularly stability in alkaline oxygen evolution reaction, showing an overpotential of 284 mV at 100 mA cm-2 and stable for 700 h, while individual Ni2FeCo and Mo2C only last less than 70 and 10 h (completely dissolved), respectively. In particular, the SD-Mo2C catalyst also exhibits excellent durability at 100 mA cm-2 for up to 400 h in 7 M KOH. Such a significantly improved stability is attributed to the supersaturated doping that led to each Mo atom strongly binding with adjacent heteroatoms, thus elevating the dissolution potential and corrosion resistance of Mo2C at a high current density. Additionally, the highly dispersed NiFeCo also facilitates the formation of dense oxyhydroxide coating during reconstruction, further protecting the integrated catalysts for durable operation. Furthermore, the synthesis has been successfully scaled up to fabricate large (16 cm2) electrodes and is adaptable to nickel foam substrates, indicating promising industrial applications. Our strategy allows the general and versatile production of various highly doped transition-metal carbides, such as Ni2FeCo-doped TiC, NbC, and W2C, thus unlocking the potential of maximized or adjustable MSI for diverse catalytic applications.

Achievements and Challenges in Surfactants-Assisted Synthesis of MOFs-Derived Transition Metal-Nitrogen-Carbon as a Highly Efficient Electrocatalyst for ORR, OER, and HER

Metal-organic frameworks (MOFs) are excellent precursors for preparing transition metal and nitrogen co-doped carbon catalysts, which have been widely utilized in the field of electrocatalysis since their initial development. However, the original MOFs derived catalysts have been greatly limited in their development and application due to their disadvantages such as metal atom aggregation, structural collapse, and narrow pore channels. Recently, surfactants-assisted MOFs derived catalysts have attracted much attention from researchers due to their advantages such as hierarchical porous structure, increased specific surface area, and many exposed active sites. This review mainly focuses on the synthesis methods of surfactants-assisted MOFs derived catalysts and comprehensively introduces the action of surfactants in MOFs derived materials and the structure-activity relationship between the catalysts and the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction performance. Apparently, the aims of this review not only introduce the status of surfactants-assisted MOFs derived catalysts in the field of electrocatalysis but also contribute to the rational design and synthesis of MOFs derived catalysts for fuel cells, metal-air cells, and electrolysis of water toward hydrogen production.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

Phase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non-equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six-electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec-1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Kaolinite-mediated synthesis of ultra-small silver nanoparticles with high antimicrobial activity

Ultra-small Ag nanoparticles (<5 nm) loaded on a kaolinite surface were successfully prepared in large batches by a dry-process, displaying excellent broad-spectrum antimicrobial ability and size-dependent activity. This Ag-loaded kaolinite (Ag@AT/K) inhibited the growth of pathogenic bacteria and accelerated wound healing in in vivo experiments on MRSA-infected wounds. This work provides a new strategy for the preparation of mineral-based nanoscale antibacterial materials.

In Situ, Rapid Synthesis of Carbon-Loaded High Density and Ultrasmall High Entropy Oxide Nanoparticles as Efficient Electrocatalysts

High entropy materials offer almost unlimited catalytic possibilities due to their variable composition, unique structure, and excellent electrocatalytic performance. However, due to the strong tendency of nanoparticles to coarsen and agglomerate, it is still a challenge to synthesize nanoparticles using simple methods to precisely control the morphology and size of the nanoparticles in large quantities, and their large-scale application is limited by high costs and low yields. Herein, a series of high-entropy oxides (HEOs) nanoparticles with high-density and ultrasmall size (<5 nm) loaded on carbon nanosheets with large quantities are prepared by Joule-heating treatment of gel precursors in a short period of time (≈60 s). Among them, the prepared (FeCoNiRuMn)3O4-x catalyst shows the best electrocatalytic activity for oxygen evolution reaction, with low overpotentials (230 mV @10 mA cm-2, 270 mV @100 mA cm-2), small Tafel slope (39.4 mV dec-1), and excellent stability without significant decay at 100 mA cm-2 after 100 h. The excellent performance of (FeCoNiRuMn)3O4-x can be attributed to the synergistic effect of multiple elements and the inherent structural stability of high entropy systems. This study provides a more comprehensive design idea for the preparation of efficient and stable high entropy catalysts.

Explosive Leidenfrost-Droplet-Mediated Synthesis of Monodispersed High-Entropy-Alloy Nanoparticles for Electrocatalysis

High-entropy-alloy nanoparticles (HEA NPs) exhibit promising potential in various catalytic applications, yet a robust synthesis strategy has been elusive. Here, we introduce a straightforward and universal method, involving the microexplosion of Leidenfrost droplets housing carbon black and metal salt precursors, to fabricate PtRhPdIrRu HEA NPs with a size of ∼2.3 nm. The accumulated pressure within the Leidenfrost droplet triggers an intense explosion within milliseconds, propelling the carbon support and metal salt rapidly into the hot solvent through explosive force. The exceptionally quick temperature rise ensures the coreduction of metal salts, and the dilute local concentration of metal ions limits the final size of the HEA NPs. Additionally, the explosion process can be fine-tuned by selecting different solvents, enabling the harvesting of diverse HEA NPs with superior electrocatalytic activity for alcohol electrooxidation and hydrogen electrocatalysis compared to commercial Pt (Pd) unitary catalysts.

Carbon Support Enhanced Mass Transfer and Metal-Support Interaction Promoted Activation for Low-Concentrated Nitric Oxide Electroreduction to Ammonia

The electrochemical NO reduction reaction (NORR) is a promising approach for both nitrogen cycle regulation and ammonia synthesis. Due to the relatively low concentration of the NO source and poor solubility of NO in solution, mass transfer limitation is a serious but easily overlooked issue. In this work, porous carbon-supported ultrafine Cu clusters grown on Cu nanowire arrays (defined as Cu@Cu/C NWAs) are prepared for low-concentration NORR. A high Faradaic efficiency (93.0%) and yield rate (1180.5 μg h-1 cm-2) of ammonia are realized on Cu@Cu/C NWAs at -0.1 V vs a reversible hydrogen electrode (RHE), which are far superior to those of Cu NWAs and other reported performances under similar conditions. The construction of a porous carbon support can effectively decrease the NO diffusion kinetics and promote NO coverage for subsequent highly effective conversion. Moreover, the favorable metal-support interaction between ultrafine Cu clusters and carbon support enhances the adsorption of NO and decreases the barrier for *HNO formation in comparison with that of pure Cu NWAs. Overall, the whole NORR can be fully strengthened on Cu@Cu/C NWAs at low NO concentrations.

High-entropy engineering with regulated defect structure and electron interaction tuning active sites for trifunctional electrocatalysis

High-entropy alloy nanoparticles (HEANs) possessing regulated defect structure and electron interaction exhibit a guideline for constructing multifunctional catalysts. However, the microstructure-activity relationship between active sites of HEANs for multifunctional electrocatalysts is rarely reported. In this work, HEANs distributed on multi-walled carbon nanotubes (HEAN/CNT) are prepared by Joule heating as an example to explain the mechanism of trifunctional electrocatalysis for oxygen reduction, oxygen evolution, and hydrogen evolution reaction. HEAN/CNT excels with unmatched stability, maintaining a 0.8V voltage window for 220 h in zinc-air batteries. Even after 20 h of water electrolysis, its performance remains undiminished, highlighting exceptional endurance and reliability. Moreover, the intrinsic characteristics of the defect structure and electron interaction for HEAN/CNT are investigated in detail. The electrocatalytic mechanism of trifunctional electrocatalysis of HEAN/CNT under different conditions is identified by in situ monitoring and theoretical calculation. Meanwhile, the electron interaction and adaptive regulation of active sites in the trifunctional electrocatalysis of HEANs were further verified by density functional theory. These findings could provide unique ideas for designing inexpensive multifunctional high-entropy electrocatalysts.

Ternary Heteroatomic Doping Induced Microenvironment Engineering of Low Fe-N4-Loaded Carbon Nanofibers for Bifunctional Oxygen Electrocatalysis

Fabricating highly efficient and long-life redox bifunctional electrocatalysts is vital for oxygen-related renewable energy devices. To boost the bifunctional catalytic activity of Fe-N-C single-atom catalysts, it is imperative to fine-tune the coordination microenvironment of the Fe sites to optimize the adsorption/desorption energies of intermediates during oxygen reduction/evolution reactions (ORR/OER) and simultaneously avoid the aggregation of atomically dispersed metal sites. Herein, a strategy is developed for fabricating a free-standing electrocatalyst with atomically dispersed Fe sites (≈0.89 wt.%) supported on N, F, and S ternary-doped hollow carbon nanofibers (FeN4 -NFS-CNF). Both experimental and theoretical findings suggest that the incorporation of ternary heteroatoms modifies the charge distribution of Fe active centers and enhances defect density, thereby optimizing the bifunctional catalytic activities. The efficient regulation isolated Fe centers come from the dual confinement of zeolitic imidazole framework-8 (ZIF-8) and polymerized ionic liquid (PIL), while the precise formation of distinct hierarchical three-dimensional porous structure maximizes the exposure of low-doping Fe active sites and enriched heteroatoms. FeN4 -NFS-CNF achieves remarkable electrocatalytic activity with a high ORR half-wave potential (0.90 V) and a low OER overpotential (270 mV) in alkaline electrolyte, revealing the benefit of optimizing the microenvironment of low-doping iron single atoms in directing bifunctional catalytic activity.

Sabatier Relations in Electrocatalysts Based on High-entropy Alloys with Wide-distributed d-band Centers for Li-O2 Batteries

Li-O2 battery (LOB) is a promising "beyond Li-ion" technology with ultrahigh theoretical energy density (3457 Wh kg-1 ), while currently impeded by the sluggish cathodic kinetics of the reversible gas-solid reaction between O2 and Li2 O2 . Despite many catalysts are developed for accelerating the conversion process, the lack of design guidance for achieving high performance makes catalysts exploring aleatory. The Sabatier principle is an acknowledged theory connecting the scaling relationship with heterogeneous catalytic activity, providing a tradeoff strategy for the topmost performance. Herein, a series of catalysts with wide-distributed d-band centers (i.e., wide range of adsorption strength) are elaborately constructed via high-entropy strategy, enabling an in-depth study of the Sabatier relations in electrocatalysts for LOBs. A volcano-type correlation of d-band center and catalytic activity emerges. Both theoretical and experimental results indicate that a moderate d-band center with appropriate adsorption strength propels the catalysts up to the top. As a demonstration of concept, the LOB using FeCoNiMnPtIr as catalyst provides an exceptional energy conversion efficiency of over 80 %, and works steadily for 2000 h with a high fixed specific capacity of 4000 mAh g-1 . This work certifies the applicability of Sabatier principle as a guidance for designing advanced heterogeneous catalysts assembled in LOBs.

Flash-Thermal Shock Synthesis of Single Atoms in Ambient Air

Single-atom catalysts feature interesting catalytic activity toward applications that rely on surface reactions such as electrochemical energy storage, catalysis, and gas sensors. However, conventional synthetic approaches for such catalysts require extended periods of high-temperature annealing in vacuum systems, limiting their throughput and increasing their production cost. Herein, we report an ultrafast flash-thermal shock (FTS)-induced annealing technique (temperature > 2850 °C, <10 ms duration, and ramping/cooling rates of ∼105 K/s) that operates in an ambient-air environment to prepare single-atom-stabilized N-doped graphene. Melamine is utilized as an N-doping source to provide thermodynamically favorable metal-nitrogen bonding sites, resulting in a uniform and high-density atomic distribution of single metal atoms. To demonstrate the practical utility of the single-atom-stabilized N-doped graphene produced by the FTS method, we showcased their chemiresistive gas sensing capabilities and electrocatalytic activities. Overall, the air-ambient, ultrafast, and versatile (e.g., Co, Ni, Pt, and Co-Ni dual metal) FTS method provides a general route for high-throughput, large area, and vacuum-free manufacturing of single-atom catalysts.

Sustainable zinc-air battery chemistry: advances, challenges and prospects

Sustainable zinc-air batteries (ZABs) are considered promising energy storage devices owing to their inherent safety, high energy density, wide operating temperature window, environmental friendliness, etc., showing great prospect for future large-scale applications. Thus, tremendous efforts have been devoted to addressing the critical challenges associated with sustainable ZABs, aiming to significantly improve their energy efficiency and prolong their operation lifespan. The growing interest in sustainable ZABs requires in-depth research on oxygen electrocatalysts, electrolytes, and Zn anodes, which have not been systematically reviewed to date. In this review, the fundamentals of ZABs, oxygen electrocatalysts for air cathodes, physicochemical properties of ZAB electrolytes, and issues and strategies for the stabilization of Zn anodes are systematically summarized from the perspective of fundamental characteristics and design principles. Meanwhile, significant advances in the in situ/operando characterization of ZABs are highlighted to provide insights into the reaction mechanism and dynamic evolution of the electrolyte|electrode interface. Finally, several critical thoughts and perspectives are provided regarding the challenges and opportunities for sustainable ZABs. Therefore, this review provides a thorough understanding of the advanced sustainable ZAB chemistry, hoping that this timely and comprehensive review can shed light on the upcoming research horizons of this prosperous area.

Sub-second ultrafast yet programmable wet-chemical synthesis

Wet-chemical synthesis via heating bulk solution is powerful to obtain nanomaterials. However, it still suffers from limited reaction rate, controllability, and massive consumption of energy/reactants, particularly for the synthesis on specific substrates. Herein, we present an innovative wet-interfacial Joule heating (WIJH) approach to synthesize various nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. In the WIJH, Joule heat generated by the graphene film (GF) is confined at the substrate-solution interface. Accompanied by instantaneous evaporation of the solvent, the temperature is steeply improved and the precursors are concentrated, thereby synergistically accelerating and controlling the nucleation and growth of nanomaterials on the substrate. WIJH leads to a record high crystallization rate of HKUST-1 (~1.97 μm s-1), an ultralow energy cost (9.55 × 10-6 kWh cm-2) and low precursor concentrations, which are up to 5 orders of magnitude faster, -6 and -2 orders of magnitude lower than traditional methods, respectively. Moreover, WIJH could handily customize the products' amount, size, and morphology via programming the electrified procedures. The as-prepared HKUST-1/GF enables the Joule-heating-controllable and low-energy-required capture and liberation towards CO2. This study opens up a new methodology towards the superefficient synthesis of nanomaterials and solvent-involved Joule heating.