Low-temperature liquid platinum catalyst

The interplay of shape and catalyst distribution in the yield of compressible flow microreactors

We develop a semi-analytical model for transport in structured catalytic microreactors, where both reactant and product are compressible fluids. Using lubrication and Fick-Jacobs approximations, we reduce the three-dimensional governing equations to an effective one-dimensional set of equations. Our model captures the effect of compressibility, corrugations in the shape of the reactor, and an inhomogeneous catalytic coating of the reactor walls. We show that in the weakly compressible limit (e.g., liquid-phase reactors), the distribution of catalyst does not influence the reactor yield, which we verify experimentally. Beyond this limit, we show that introducing inhomogeneities in the catalytic coating and corrugations to the reactor walls can improve the yield.

Surface-Enriched Room-Temperature Liquid Bismuth for Catalytic CO2 Reduction

Bismuth-based electrocatalysts are effective for carbon dioxide (CO2) reduction to formate. However, at room temperature, these materials are only available in solid state, which inevitably suffers from surface deactivation, declining current densities, and Faradaic efficiencies. Here, the formation of a liquid bismuth catalyst on the liquid gallium surface at ambient conditions is shown as its exceptional performance in the electrochemical reduction of CO2 (i.e., CO2RR). By doping a trace amount of bismuth (740 ppm atomic) in gallium liquid metal, a surface enrichment of bismuth by over 400 times (30 at%) in liquid state is obtained without atomic aggregation, achieving 98% Faradic efficiency for CO2 conversion to formate over 80 h. Ab initio molecular simulations and density functional theory calculations reveal that bismuth atoms in the liquid state are the most energetically favorable sites for the CO2RR intermediates, superior to solid Bi-sites, as well as joint GaBi-sites. This study opens an avenue for fabricating high-performing liquid-state metallic catalysts that cannot be reached by elementary metals under electrocatalytic conditions.

Electrochemical Nitrate-to-Ammonia Conversion Enabled by Carbon-Decoration of Ni─GaOOH Synthesized via Plasma-Assisted CO2 Reduction

The release of nitrates into the environment leads to contaminated soil and water that poses a health risk to humans and animals. Due to the transition to renewable energy-based technologies, an electrochemical approach is an emerging option that can selectively produce valuable ammonia from nitrate sources. However, traditional metal-based electrocatalysts often suffer from low nitrate adsorption that reduces NH3 production rates. Here, a Ni-GaOOH-C/Ga electrocatalyst for electrochemical nitrate conversion into NH3 is synthesized via a low energy atmospheric-pressure plasma process that reduces CO2 into highly dispersed activated carbon on dispersed Ni─GaOOH particles produced from a liquid metal Ga─Ni alloy precursor. Nitrate conversion rates of up to 26.3 µg h-1 mg-1 cat are achieved with good stability of up to 20 h. Critically, the presence of carbon centers is central to improved performance where both Ni─C and NiO─C interfaces act as NO3- adsorption and reduction centers during the reaction. Density functional theory (DFT) calculations indicate that the NiO─C and Ni─C reaction sites reduce the Gibbs free energy required for NO3- reduction to NH3 compared to NiO and Ni. Importantly, catalysts without carbon centers do not produce NH3, emphasizing the unique effects of incorporating carbon nanoparticles into the electrocatalyst.

Humidity-Responsive Liquid Metal Core-Shell Materials for Enduring Heat Retention and Insulation

High humidity in extremely cold weather can undermine the insulation capability of the clothing, imposing serious life risks. Current clothing insulation technologies have inherent deficiencies in terms of insulation efficiency and humidity adaptability. Here, humidity-stimulated self-heating clothing using aluminum core-liquid metal shell microparticles (Al@LM-MPs) as the filler is reported. Al@LM-MPs exhibit a distinctive capability to react to water molecules in the air to generate heat, exhibiting remarkable sensitivity across a broad temperature range. This ability leads to the creation of intelligent clothing capable of autonomously responding to extreme cold and wet weather conditions, providing both enduring heat retention and insulation capabilities.

The atomic intelligence of liquid metals

Liquid metals may deliver greener and more sustainable chemical reactions.

The Reconstruction of Pt(001) Surface and the Shell-Like Reconstruction of the Vicinal Pt(001) Surfaces Revealed by Neural Network Potential

In this work, a highly accurate neural network potential (NNP) is presented, named PtNNP, and the exploration of the reconstruction of the Pt(001) surface and its vicinal surfaces with it. Contrary to the most accepted understanding of the Pt(001) surface reconstruction, the study reveals that the main driving force behind Pt(001) quasi-hexagonal reconstruction is not the surface stress relaxation but the increased coordination number of the surface atoms resulting in stronger intralayer binding in the reconstructed surface layer. In agreement with experimental observations, the optimized supercell size of the reconstructed Pt(001) surface contains (5 × 20) unit cells. Surprisingly, the reconstruction of the vicinal Pt(001) surfaces leads to a smooth shell-like surface layer covering the whole surface and diminishing sharp step edges.

Structural Evolution of Liquid Metals and Alloys

Low-melting liquid metals are emerging as a new group of highly functional solvents due to their capability to dissolve and alloy various metals in their elemental state to form solutions as well as colloidal systems. Furthermore, these liquid metals can facilitate and catalyze multiple unique chemical reactions. Despite the intriguing science behind liquid metals and alloys, very little is known about their fundamental structures in the nanometric regime. To bridge this gap, this work employs small angle neutron scattering and molecular dynamics simulations, revealing that the most commonly used liquid metal solvents, EGaIn and Galinstan, are surprisingly structured with the formation of clusters ranging from 157 to 15.7 Å. Conversely, noneutectic liquid metal alloys of GaSn or GaIn at low solute concentrations of 1, 2, and 5 wt%, as well as pure Ga, do not exhibit these structures. Importantly, the eutectic alloys retain their structure even at elevated temperatures of 60 and 90 °C, highlighting that they are not just simple homogeneous fluids consisting of individual atoms. Understanding the complex soft structure of liquid alloys will assist in comprehending complex phenomena occurring within these fluids and contribute to deriving reaction mechanisms in the realm of synthesis and liquid metal-based catalysis.

Spontaneous Liquefaction of Solid Metal-Liquid Metal Interfaces in Colloidal Binary Alloys

Crystallization of alloys from a molten state is a fundamental process underpinning metallurgy. Here the direct imaging of an intermetallic precipitation reaction at equilibrium in a liquid-metal environment is demonstrated. It is shown that the outer layers of a solidified intermetallic are surprisingly unstable to the depths of several nanometers, fluctuating between a crystalline and a liquid state. This effect, referred to herein as crystal interface liquefaction, is observed at remarkably low temperatures and results in highly unstable crystal interfaces at temperatures exceeding 200 K below the bulk melting point of the solid. In general, any liquefaction process would occur at or close to the formal melting point of a solid, thus differentiating the observed liquefaction phenomenon from other processes such as surface pre-melting or conventional bulk melting. Crystal interface liquefaction is observed in a variety of binary alloy systems and as such, the findings may impact the understanding of crystallization and solidification processes in metallic systems and alloys more generally.

A facile cellulose finishing strategy through in-situ growth of sliver-doped manganese dioxide assisted by amine-quinone for improving indoor living quality

Nowadays, various harmful indoor pollutants especially including bacteria and residual formaldehyde (HCHO) seriously threaten human health and reduce the quality of public life. Herein, a universal substrate-independence finishing approach for efficiently solving these hybrid indoor threats is demonstrated, in which amine-quinone network (AQN) was employed as reduction agent to guide in-situ growth of Ag@MnO2 particles, and also acted as an adhesion interlayer to firmly anchor nanoparticles onto diverse textiles, especially for cotton fabrics. In contrast with traditional hydrothermal or calcine methods, the highly reactive AQN ensures the efficient generation of functional nanoparticles under mild conditions without any additional catalysts. During the AQN-guided reduction, the doping of Ag atoms onto cellulose fiber surface optimized the crystallinity and oxygen vacancy of MnO2, providing cotton efficient antibacterial efficiency over 90 % after 30 min of contact, companying with encouraging UV-shielding and indoor HCHO purification properties. Besides, even after 30 cycles of standard washing, the Ag@MnO2-decorated textiles can effectively degrade HCHO while well-maintaining their inherent properties. In summary, the presented AQN-mediated strategy of efficiently guiding the deposition of functional particles on fibers has broad application prospects in the green and sustainable functionalization of textiles.

Activation of Ga Liquid Catalyst with Continuously Exposed Active Sites for Electrocatalytic C-N Coupling

Environmentally friendly electrocatalytic coupling of CO2 and N2 for urea synthesis is a promising strategy. However, it is still facing problems such as low yield as well as low stability. Here, a new carbon-coated liquid alloy catalyst, Ga79Cu11Mo10@C is designed for efficient electrochemical urea synthesis by activating Ga active sites. During the N2 and CO2 co-reduction process, the yield of urea reaches 28.25 mmol h-1 g-1, which is the highest yield reported so far under the same conditions, the Faraday efficiency (FE) is also as high as 60.6 % at -0.4 V vs. RHE. In addition, the catalyst shows excellent stability under 100 h of testing. Comprehensive analyses showed that sequential exposure of a high density of active sites promoted the adsorption and activation of N2 and CO2 for efficient coupling reactions. This coupling reaction occurs through a thermodynamic spontaneous reaction between *N=N* and CO to form a C-N bond. The deformability of the liquid state facilitates catalyst recovery and enhances stability and resistance to poisoning. Moreover, the introduction of Cu and Mo stimulates the Ga active sites, which successfully synthesises the *NCON* intermediate. The reaction energy barrier of the third proton-coupled electron transfer process rate-determining step (RDS) *NHCONH→*NHCONH2 was lowered, ensuring the efficient synthesis of urea.

Gallium-based liquid metals as reaction media for nanomaterials synthesis

Gallium-based liquid metals (LMs) and their alloys have gained prominence in the realm of flexible and stretchable electronics. Recent advances have expanded the interest to explore the electron-rich core and interface of LMs to synthesize various nanomaterials, where Ga-based LMs serve as versatile reaction media. In this paper, we delve into the latest developments within this burgeoning field. Our discussion begins by elucidating the unique attributes of LMs that render them suitable as reaction media, including their high metal solubility, low standard reduction potential, self-limiting oxidation and ultra-smooth and "layer" surface. We then provide a comprehensive categorized summary of utilizing these features to fabricate a variety of nanomaterials, including pure metallic materials (metal alloys, metal crystals, porous metals, high-entropy alloys and metallic single atoms), metal-inorganic compounds (2D metal oxides, 2D metallic inorganic compounds and 2D graphitic materials), as well as metal-organic composites (metal-organic frameworks). This paper concludes by discussing the current challenges in this field and exploring potential future directions. The versatility and unique properties of Ga-based LMs are poised to play a pivotal role in the future of nanomaterial science, paving the way for more efficient, sustainable, and innovative technological solutions.

Liquid metals for boosting stability of zeolite catalysts in the conversion of methanol to hydrocarbons

Methanol-to-hydrocarbons (MTH) process has been considered one of the most practical approaches for producing value-added products from methanol. However, the commonly used zeolite catalysts suffer from rapid deactivation due to coke deposition and require regular regeneration treatments. We demonstrate that low-melting-point metals, such as Ga, can effectively promote more stable methanol conversion in the MTH process by slowing coke deposition and facilitating the desorption of carbonaceous species from the zeolite. The ZSM-5 zeolite physically mixed with liquid gallium exhibited an enhanced lifetime in the MTH reaction, which increased by a factor of up to ~14 as compared to the parent ZSM-5. These results suggest an alternative route to the design and preparation of deactivation-resistant zeolite catalysts.

Liquid Metal as Energy Conversion Sensitizers: Materials and Applications

Energy can exist in nature in a wide range of forms. Energy conversion refers to the process in which energy is converted from one form to another, and this process will be greatly enhanced by energy conversion sensitizers. Recently, an emerging class of new materials, namely liquid metals (LMs), shows excellent prospects as highly versatile materials. Notably, in terms of energy delivery and conversion, LMs functional materials are chemical responsive, heat-responsive, photo-responsive, magnetic-responsive, microwave-responsive, and medical imaging responsive. All these intrinsic virtues enabled promising applications in energy conversion, which means LMs can act as energy sensitizers for enhancing energy conversion and transport. Herein, first the unique properties of the light, heat, magnetic and microwave converting capacity of gallium-based LMs materials are summarized. Then platforms and applications of LM-based energy conversion sensitizers are highlighted. Finally, some of the potential applications and opportunities of LMs are prospected as energy conversion sensitizers in the future, as well as unresolved challenges. Collectively, it is believed that this review provides a clear perspective for LMs mediated energy conversion, and this topic will help deepen knowledge of the physical chemistry properties of LMs functional materials.

Dynamic configurations of metallic atoms in the liquid state for selective propylene synthesis

The use of liquid gallium as a solvent for catalytic reactions has enabled access to well-dispersed metal atoms configurations, leading to unique catalytic phenomena, including activation of neighbouring liquid atoms and mobility-induced activity enhancement. To gain mechanistic insights into liquid metal catalysts, here we introduce a GaSn0.029Ni0.023 liquid alloy for selective propylene synthesis from decane. Owing to their mobility, dispersed atoms in a Ga matrix generate configurations where interfacial Sn and Ni atoms allow for critical alignments of reactants and intermediates. Computational modelling, corroborated by experimental analyses, suggests a particular reaction mechanism by which Sn protrudes from the interface and an adjacent Ni, below the interfacial layer, aligns precisely with a decane molecule, facilitating propylene production. We then apply this reaction pathway to canola oil, attaining a propylene selectivity of ~94.5%. Our results offer a mechanistic interpretation of liquid metal catalysts with an eye to potential practical applications of this technology.

Dynamic sampling of liquid metal structures for theoretical studies on catalysis

Liquid metals have recently emerged as promising catalysts that can outcompete their solid counterparts for many reactions. Although theoretical modelling is extensively used to improve solid-state catalysts, there is currently no way to capture the interactions of adsorbates with a dynamic liquid metal. We propose a new approach based on ab initio molecular dynamics sampling of an adsorbate on a liquid catalyst. Using this approach, we describe time-resolved structures for formate adsorbed on liquid Ga-In, and for all intermediates in the methanol oxidation pathway on Ga-Pt. This yields a range of accessible adsorption energies that take into account the at-temperature motion of the liquid metal. We find that a previously proposed pathway for methanol oxidation on Ga-Pt results in unstable intermediates on a dynamic liquid surface, and propose that H desorption must occur during the path. The results showcase a more accurate way to treat liquid metal catalysts in this emerging field.

Liquid Metal Combinatorics toward Materials Discovery

Liquid metals and their derivatives provide several opportunities for fundamental and practical exploration worldwide. However, the increasing number of studies and shortage of desirable materials to fulfill different needs also pose serious challenges. Herein, to address this issue, a generalized theoretical frame that is termed as "Liquid Metal Combinatorics" (LMC) is systematically presented, and summarizes promising candidate technical routes toward new generation material discovery. The major categories of LMC are defined, and eight representative methods for manufacturing advanced materials are outlined. It is illustrated that abundant targeted materials can be efficiently designed and fabricated via LMC through deep physical combinations, chemical reactions, or both among the main bodies of liquid metals, surface chemicals, precipitated ions, and other materials. This represents a large class of powerful, reliable, and modular methods for innovating general materials. The achieved combinatorial materials not only maintained the typical characteristics of liquid metals but also displayed distinct tenability. Furthermore, the fabrication strategies, wide extensibility, and pivotal applications of LMC are classified. Finally, by interpreting the developmental trends in the area, a perspective on the LMC is provided, which warrants its promising future for society.

Metal Alloys-Structured Electrocatalysts: Metal-Metal Interactions, Coordination Microenvironments, and Structural Property-Reactivity Relationships

Metal alloys-structured electrocatalysts (MAECs) have made essential contributions to accelerating the practical applications of electrocatalytic devices in renewable energy systems. However, due to the complex atomic structures, varied electronic states, and abundant supports, precisely decoding the metal-metal interactions and structure-activity relationships of MAECs still confronts great challenges, which is critical to direct the future engineering and optimization of MAECs. Here, this timely review comprehensively summarizes the latest advances in creating the MAECs, including the metal-metal interactions, coordination microenvironments, and structure-activity relationships. First, the fundamental classification, design, characterization, and structural reconstruction of MAECs are outlined. Then, the electrocatalytic merits and modulation strategies of recent breakthroughs for noble and non-noble metal-structured MAECs are thoroughly discussed, such as solid solution alloys, intermetallic alloys, and single-atom alloys. Particularly, unique insights into the bond interactions, theoretical understanding, and operando techniques for mechanism disclosure are given. Thereafter, the current states of diverse MAECs with a unique focus on structural property-reactivity relationships, reaction pathways, and performance comparisons are discussed. Finally, the future challenges and perspectives for MAECs are systematically discussed. It is believed that this comprehensive review can offer a substantial impact on stimulating the widespread utilization of metal alloys-structured materials in electrocatalysis.

Voltage-Driven Chemical Reactions Enable the Synthesis of Tunable Liquid Ga-Metal Nanoparticles

Nanosized particles of liquid metals are emerging materials that hold promise for applications spanning from microelectronics to catalysis. Yet, knowledge of their chemical reactivity is largely unknown. Here, we study the reactivity of liquid Ga and Cu nanoparticles under the application of a cathodic voltage. We discover that the applied voltage and the spatial proximity of these two particle precursors dictate the reaction outcome. In particular, we find that a gradual voltage ramp is crucial to reduce the native oxide skin of gallium and enable reactive wetting between the Ga and Cu nanoparticles; instead, a voltage step causes dewetting between the two. We determine that the use of liquid Ga/Cu nanodimer precursors, which consist of an oxide-covered Ga domain interfaced with a metallic Cu domain, provides a more uniform mixing and results in more homogeneous reaction products compared to a physical mixture of Ga and Cu NPs. Having learned this, we obtain CuGa2 alloys or solid@liquid CuGa2@Ga core@shell nanoparticles by tuning the stoichiometry of Ga and Cu in the nanodimer precursors. These products reveal an interesting complementarity of thermal and voltage-driven syntheses to expand the compositional range of bimetallic NPs. Finally, we extend the voltage-driven synthesis to the combination of Ga with other elements (Ag, Sn, Co, and W). By rationalizing the impact of the native skin reduction rate, the wetting properties, and the chemical reactivity between Ga and other metals on the results of such voltage-driven chemical manipulation, we define the criteria to predict the outcome of this reaction and set the ground for future studies targeting various applications for multielement nanomaterials based on liquid Ga.

Emerging Liquid Metal Catalysts

Catalysts serve pivotal roles in facilitating the development of sustainable energy systems on a global scale. Liquid metal usually refers to metal that is liquid below 330 °C, also known as low melting point metal. Liquid metal has emerged as an intriguing catalyst due to its commendable electrical conductivity, favorable fluidity, solubility in metals, phase transition capabilities, and modifiable oxide surface, thereby presenting a plethora of prospects for diverse catalytic reactions. In this Perspective, we elucidate the four primary merits of liquid metal catalysts: resistance to coking, the ability to tune elemental composition, the potential for structural transformation, and the capacity to inhibit coalescence. In light of this, a comprehensive summary is presented on the research advancements pertaining to liquid metal in methane pyrolysis, alkane dehydrogenation, carbon dioxide reduction, alcohol oxidation, and various other catalytic reactions. Finally, the challenges and prospects of liquid metal catalysts are elucidated.

Activated platinum in gallium-based room-temperature liquid metals for enhanced reduction reactions

Room-temperature gallium-based liquid metals (LMs) have recently attracted significant attention worldwide for application in catalysis because of their unique combination of fluidic and catalytic properties. Platinum loading in LMs is expected to enhance the catalytic performance of various reaction systems. However, Pt-loaded methods for Ga-based LMs have not yet been sufficiently developed to improve the catalytic performance and Pt utilization efficiency. In this study, a novel method for the fabrication of Pt-incorporated LMs using Pt sputter deposition (Pt(dep)-LMs) was developed. The Pt(dep)-LMs contained well-dispersed Pt flakes with diameters of 0.89 ± 0.6 μm. The catalytic activity of the Pt(dep)-LM with a Pt loading of ∼0.7 wt% was investigated using model reactions such as methylene blue (MB) reduction and hydrogen production in an acidic aqueous solution. The Pt(dep)-LMs showed a higher MB reduction rate (three times) and hydrogen production (three times) than the LM loaded with conventional Pt black (∼0.7 wt%). In contrast to the Pt(dep)-LMs, solid-based Ga with a Pt loading of ∼0.7 wt% did not catalyze the reactions. These results demonstrate that Pt activation occurred in the Pt(dep)-LMs fabricated by Pt sputtering, and that the fluidic properties of the LMs enhanced the catalytic reduction reactions. Thus, these findings highlight the superior performance of the Pt deposition method and the advantages of using Pt-LM-based catalysts.

Catalytic Alkyne Semihydrogenation with Polyhydride Ni/Ga Clusters

The bimetallic, decanuclear Ni3 Ga7 -cluster of the formula [Ni3 (GaTMP)3 (μ2 -GaTMP)3 (μ3 -GaTMP)] (1, TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2. Low-temperature 2D NMR experiments at -80 °C show that 2 consist of a mixture of a di- (2Di ), tetra- (2Tetra ) and hexahydride species (2Hexa ). The structures of 2Di and 2Tetra are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis.

Recent advancements in non-enzymatic electrochemical sensor development for the detection of organophosphorus pesticides in food and environment

Organophosphorus Pesticides (OPPs) are among the extensively used pesticides throughout the world to boost agricultural production. However, persistent residues of these toxic pesticides in various vegetables, fruits, and drinking water poses detrimental health effects. Consequently, the rapid monitoring of these harmful chemicals through simple and cost-effective methods has become crucial. In such an instance, electrochemical methods offer simple, rapid, sensitive, reproducible, and affordable detection pathways. To overcome the limitations associated with electrochemical enzymatic sensors, non-enzymatic sensors have emerged as promising and simpler alternatives. The non-enzymatic sensors have demonstrated superior activity, reaching detection limit up to femto (10-15) molar concentration in recent years, leveraging higher selectivity obtained through the molecularly imprinted polymers, synergistic effects between carbonaceous nanomaterials and metals, metal oxide alloys, and other alternative approaches. Herein, this review paper provides an overview of the recent advancements in the development of non-enzymatic electrochemical sensors for the detection of commonly used OPPs, such as Chlorpyrifos (CHL), Diazinon (DZN), Malathion (MTN), Methyl parathion (MP) and Fenthion (FEN). The design method of the electrodes, electrode functioning mechanism, and their analytical performance metrics, such as limit of detection, sensitivity, selectivity, and linearity range, were reviewed and compared. Furthermore, the existing challenges within this rapidly growing field were discussed along with their potential solutions which will facilitate the fabrication of advanced and sustainable non-enzymatic sensors in the future.

Ternary NiMo-Bi liquid alloy catalyst for efficient hydrogen production from methane pyrolysis

Methane pyrolysis (MP) is a potential technology for CO2-free hydrogen production that generates only solid carbon by-products. However, developing a highly efficient catalyst for stable methane pyrolysis at a moderate temperature has been challenging. We present a new and highly efficient catalyst created by modifying a Ni-Bi liquid alloy with the addition of Mo to produce a ternary NiMo-Bi liquid alloy catalyst (LAC). This catalyst exhibited a considerably low activation energy of 81.2 kilojoules per mole, which enabled MP at temperatures between 450 and 800 Celsius and a hydrogen generation efficiency of 4.05 ml per gram of nickel per minute. At 800 Celsius, the catalyst exhibited 100% H2 selectivity and 120 hours of stability.

Ga-Pt supported catalytically active liquid metal solutions (SCALMS) prepared by ultrasonication - influence of synthesis conditions on n-heptane dehydrogenation performance

Supported catalytically active liquid metal solution (SCALMS) materials represent a recently developed class of heterogeneous catalysts, where the catalytic reaction takes place at the highly dynamic interface of supported liquid alloys. Ga nuggets were dispersed into nano-droplets in propan-2-ol using ultrasonication followed by the addition of Pt in a galvanic displacement reaction - either directly into the Ga/propan-2-ol dispersion (in situ) or consecutively onto the supported Ga droplets (ex situ). The in situ galvanic displacement reaction between Ga and Pt was studied in three different reaction media, namely propan-2-ol, water, and 20 vol% water containing propan-2-ol. TEM investigations reveal that the Ga-Pt reaction in propan-2-ol resulted in the formation of Pt aggregates on top of Ga nano-droplets. In the water/propan-2-ol mixture, the desired incorporation of Pt into the Ga matrix was achieved. The ex situ prepared Ga-Pt SCALMS were tested in n-heptane dehydrogenation. Ga-Pt SCALMS synthesized in pure alcoholic solution showed equal dehydrogenation and cracking activity. Ga-Pt SCALMS prepared in pure water, in contrast, showed mainly cracking activity due to oxidation of Ga droplets. The Ga-Pt SCALMS material prepared in water/propan-2-ol resulted in high activity, n-heptene selectivity of 63%, and only low cracking tendency. This can be attributed to the supported liquid Ga-Pt alloy where Pt atoms are present in the liquid Ga matrix at the highly dynamic catalytic interface.

Dry liquid metals stabilized by silica particles: Synthesis and application in photothermoelectric power generation

HYPOTHESIS

Gallium-based room-temperature liquid metals (LMs) have unique physicochemical properties; however, their high surface tension, low flowability, and high corrosiveness to other materials limit their advanced processing (including precise shaping) and application. Consequently, LM-rich free-flowing powders, named "dry LMs" that offer the inherent advantages of dry powders, should play a critical role in expanding the application scope of LMs.

EXPERIMENTS

A general method of preparing silica-nanoparticle-stabilized LMs in the form of LM-rich powders (>95 wt% LM) is developed.

FINDINGS

Dry LMs can be simply prepared by mixing LMs with silica nanoparticles in a planetary centrifugal mixer in the absence of solvents. As a sustainable dry-process route alternative to wet-process routes, this ecofriendly and simple method of dry LM fabrication has several advantages, e.g., high throughput, scalability, and low toxicity owing to the lack of organic dispersion agents and milling media. Moreover, the unique photothermal properties of dry LMs are used for photothermal electric power generation. Thus, dry LMs not only pave the way for the use of LMs in powder form but also provide a new opportunity for expanding their application scope in energy conversion systems.

Constructing liquid metal/metal-organic framework nanohybrids with strong sonochemical energy storage performance for enhanced pollutants removal

With endogenous redox systems and multiple enzymes, the storage and utilization of external energy is general in living cells, especially through photo/ultrasonic synthesis/catalysis due to in-situ generation of abundant reactive oxygen species (ROS). However, in artificial systems, because of extreme cavitation surroundings, ultrashort lifetime and increased diffusion distance, sonochemical energy is rapidly dissipated via electron-hole pairs recombination and ROS termination. Here, we integrate zeolitic imidazolate framework-90 (ZIF-90) and liquid metal (LM) with opposite charges by convenient sonosynthesis, and the resultant nanohybrid (LMND@ZIF-90) can efficiently capture sonogenerated holes and electrons, and thus suppress electron-hole pairs recombination. Unexpectedly, LMND@ZIF-90 can store the ultrasonic energy for over ten days and exhibit acid-responsive release to trigger persistent generation of various ROS including superoxide (O₂•^-), hydroxyl radicals (•OH), and singlet oxygen (¹O₂), presenting significantly faster dye degradation rate (short to seconds) than previously reported sonocatalysts. Moreover, unique properties of gallium could additionally facilitate heavy metals removal through galvanic replacement and alloying. In summary, the LM/MOF nanohybrid constructed here demonstrates strong capacity for storing sonochemical energy as long-lived ROS, enabling enhanced water decontamination without energy input.

Adaptable graphitic C6N6-based copper single-atom catalyst for intelligent biosensing

Self-adaptability is highly envisioned for artificial devices such as robots with chemical noses. For this goal, seeking catalysts with multiple and modulable reaction pathways is promising but generally hampered by inconsistent reaction conditions and negative internal interferences. Herein, we report an adaptable graphitic C₆N₆-based copper single-atom catalyst. It drives the basic oxidation of peroxidase substrates by a bound copper-oxo pathway, and undertakes a second gain reaction triggered by light via a free hydroxyl radical pathway. Such multiformity of reactive oxygen-related intermediates for the same oxidation reaction makes the reaction conditions capable to be the same. Moreover, the unique topological structure of Cu_SAC₆N₆ along with the specialized donor-π-acceptor linker promotes intramolecular charge separation and migration, thus inhibiting negative interferences of the above two reaction pathways. As a result, a sound basic activity and a superb gain of up to 3.6 times under household lights are observed, superior to that of the controls, including peroxidase-like catalysts, photocatalysts, or their mixtures. Cu_SAC₆N₆ is further applied to a glucose biosensor, which can intelligently switch sensitivity and linear detection range in vitro.

Incorporating Fe, Co co-doped graphene with PDI supermolecular for promoted photocatalytic activity: A story of electron transfer

Iron-cobalt dual single-atom anchoring on nitrogen-doped graphene (Fe_xCo_y-NG) improves the efficiency of migration and separation of photo-generated carriers. In this work, the perylene diimide (PDI) is self-assembled on the Fe_xCo_y-NG to form the Fe_xCo_y-NG/PDI composites by π-π interaction, which is reported for the first time. The bisphenol A (BPA) degradation of optimized 20% Fe_0.2Co_0.8-NG/PDI are nearly 100%, and the degradation rate is 1.5 and 12.7 times that of the self-assembled PDI and commercial-grade PDI. The high degradation performance by Fe_xCo_y-NG/PDI are mainly due to: (i) regulating the proportion of Fe-Co dual active sites content, so that it can achieve the synergistic interaction to facilitate the transfer of electrons in the catalytic reaction. (ii) PDI is uniformly dispersed by adding the Fe_xCo_y-NG, which increases the specific surface area of composites to adsorb more pollutants. Free radical trapping experiments and electron spin-resonance spectroscopy characterization confirmed that the O₂^-, OH, ¹O₂ and h⁺ are the main reactive species (RSs) for BPA degradation. Under the attack of RSs, BPA completes the processes of hydroxylation, demethylation, aromatization, ring-opening, and finally complete mineralization into CO₂ and H₂O. These results revealed that Fe_0.2Co_0.8-NG/PDI photocatalysts may be efficiently applied for the remediation of phenol contaminated natural waters.

Bimetallic Sites for Catalysis: From Binuclear Metal Sites to Bimetallic Nanoclusters and Nanoparticles

Heterogeneous bimetallic catalysts have broad applications in industrial processes, but achieving a fundamental understanding on the nature of the active sites in bimetallic catalysts at the atomic and molecular level is very challenging due to the structural complexity of the bimetallic catalysts. Comparing the structural features and the catalytic performances of different bimetallic entities will favor the formation of a unified understanding of the structure-reactivity relationships in heterogeneous bimetallic catalysts and thereby facilitate the upgrading of the current bimetallic catalysts. In this review, we will discuss the geometric and electronic structures of three representative types of bimetallic catalysts (bimetallic binuclear sites, bimetallic nanoclusters, and nanoparticles) and then summarize the synthesis methodologies and characterization techniques for different bimetallic entities, with emphasis on the recent progress made in the past decade. The catalytic applications of supported bimetallic binuclear sites, bimetallic nanoclusters, and nanoparticles for a series of important reactions are discussed. Finally, we will discuss the future research directions of catalysis based on supported bimetallic catalysts and, more generally, the prospective developments of heterogeneous catalysis in both fundamental research and practical applications.

Atomically Thick Oxide Overcoating Stimulates Low-Temperature Reactive Metal-Support Interactions for Enhanced Catalysis

Reactive metal-support interactions (RMSIs) induce the formation of bimetallic alloys and offer an effective way to tune the electronic and geometric properties of metal sites for advanced catalysis. However, RMSIs often require high-temperature reductions (>500 °C), which significantly limits the tuning of bimetallic compositional varieties. Here, we report that an atomically thick Ga₂O₃ coating of Pd nanoparticles enables the initiation of RMSIs at a much lower temperature of ∼250 °C. State-of-the-art microscopic and in situ spectroscopic studies disclose that low-temperature RMSIs initiate the formation of rarely reported Ga-rich PdGa alloy phases, distinct from the Pd₂Ga phase formed in traditional Pd/Ga₂O₃ catalysts after high-temperature reduction. In the CO₂ hydrogenation reaction, the Ga-rich alloy phases impressively boost the formation of methanol and dimethyl ether ∼5 times higher than that of Pd/Ga₂O₃. In situ infrared spectroscopy reveals that the Ga-rich phases greatly favor formate formation as well as its subsequent hydrogenation, thus leading to high productivity.

Dynamic Activation of Ga Sites by Pt Dopant in Low-Temperature Liquid-Metal Catalysts

Liquid GaPt catalysts with Pt concentrations as low as 1×10^-4  atomic % have recently been identified as highly active for the oxidation of methanol and pyrogallol under mild reaction conditions. However, almost nothing is known about how liquid state catalysts support these significant improvements in activity. Here, ab initio molecular dynamics simulations are employed to examine GaPt catalysts in isolation and interacting with adsorbates. We find that persistent geometric features can exist in the liquid state, given the correct environment. We postulate that the Pt dopant may not be limited to direct involvement in catalysis of reactions, but rather that its presence can also enable Ga atoms to become catalytically active.

Diblock Copolymer Stabilized Liquid Metal Nanoparticles: Particle Settling Behavior and Application to 3D Printing

Eutectic gallium indium (EGaIn) is a liquid metal with promising applications due to its favorable thermal and electrical conductivity, low viscosity, and metallic nature. For applications, including imaging, catalysis, and nanomedicine, stable EGaIn particles with submicron diameters are required. However, the low viscosity and high density of EGaIn have typically precluded the formation of stable submicron particles due to rapid EGaIn droplet coalescence. In this work, we show that poly(acrylic acid)-block-poly(N,N'-dimethylacrylamide) copolymers are able to effectively stabilize EGaIn nanodroplets formed upon ultrasonication, where the poly(acrylic acid) block anchors the polymer to the EGaIn surface and the poly(N,N'-dimethylacrylamide) block provides colloidal stability to the particles in solution. Although the high density of EGaIn causes rapid particle settling, the behavior is predictable, which allows the average particle size to be controlled through centrifugation. We demonstrate that stable EGaIn particles with sizes on the order of 50-100 nm and narrow particle size distributions can be easily obtained using this method and further used in photopolymer resins to prepare 3D printed EGaIn-polymer hybrid materials. The predictable sizes and high stability of these EGaIn nanoparticles should allow further applications in soft-electronics, nanomedicine, catalysis, and other nanotechnology.

Liquid Metal as Bioinspired and Unusual Modulator in Bioorthogonal Catalysis for Tumor Inhibition Therapy

Bioorthogonal catalysis mediated by Pd-based transition metal catalysts has sparked increasing interest in combating diseases. However, the catalytic and therapeutic efficiency of current Pd⁰ catalysts is unsatisfactory. Herein, inspired by the concept that ligands around metal sites could enable enzymes to catalyze astonishing reactions by changing their electronic environment, a LM-Pd catalyst with liquid metal (LM) as an unusual modulator has been designed to realize efficient bioorthogonal catalysis for tumor inhibition. The LM matrix can serve as a "ligand" to afford an electron-rich environment to stabilize the active Pd⁰ and promote nucleophilic turnover of the π-allylpalladium species to accelerate the uncaging process. Besides, the photothermal properties of LM can lead to the enhanced removal of tumor cells by photo-enhanced catalysis and photothermal effect. We believe that our work will broaden the application of LM and motivate the design of bioinspired bioorthogonal catalysts.

Liesegang Phenomenon of Liquid Metals on Au Film

Room temperature liquid metals (LM) such as gallium (Ga) own the potential to react with specific materials which would incubate new application categories. Here, diverse self-organized ring patterns due to nonequilibrium reaction-diffusion and spreading-limitation of Ga-based LM clusters on gold (Au) film are reported, among which diffusion is the controlling step and the self-limiting oxide layer plays the role of kinetic barrier. Such phenomena, classically known as the Liesegang rings, mainly occur in electrolyte media. Unlike existing systems, the present periodic crystallization mechanism enables highly symmetric spatiotemporal periodic Liesegang rings on a smaller scale under ambient conditions. Typically, the Ga-Au and eutectic gallium-indium alloy (EGaIn)-Au reaction-diffusion-spreading systems are constructed, obtaining the revert type and hybrid type concentric Liesegang patterns, respectively. The competitive patterning behavior of the intermediate phase products AuGa₂ and AuIn₂ in hybrid Liesegang patterns is further analyzed by altering the initial Ga/In mass ratio, first-principles calculations, and molecular dynamic simulations. When the mass ratio of In in GaIn alloy exceeds 15%, it will preferentially react with Au. The discovery of LM Liesegang phenomenon is expected to be a flashpoint for self-organized reaction-diffusion systems and offers promising rules for diverse areas such as materials synthesis and the jewelry design industry.

Structural and electronic changes in Ga-In and Ga-Sn alloys on melting

The melting behaviour of surface slabs of Ga-In and Ga-Sn is studied using periodic density functional theory and ab initio molecular dynamics. Analysis of the structure and electronics of the solid and liquid phases gives insight into the properties of these alloys, and why they may act as promising CO₂ reduction catalysts. We report melting points for slabs of hexa-layer Ga-In (386 K) and Ga-Sn (349 K) that are substantially lower than the pure hexa-layer Ga system (433 K), and attribute the difference to the degree to which the dopant (In or Sn) disrupts the layered Ga network. In molecular dynamics trajectories of the liquid structures, we find that dopant tends to migrate from the centre of the slab towards the surface and accumulate there. Bader charge calculations reveal that the surface dopant atoms have increased positive charge, and density of states analyses suggest the liquid alloys maintain metallic electronic behaviour. Thus, surface In and Sn may provide good binding sites for intermediates in CO₂ reduction. This work contributes to our understanding of the properties of liquid metal systems, and provides a foundation for modelling catalysis on these materials.

Concentration dependent alloying behaviour of liquid GaAu

Liquid GaAu systems provide the possibility of developing dynamic and self-healing materials for a variety of applications, including catalysis. GaAu systems provide both dynamic capability by being liquid at just above room temperature, as a result of the Ga, and likely catalytic activity, resulting from the Au. While the formation of a Ga₂Au intermetallic is known, the behaviours that result from lower Au concentrations within a liquid Ga solvent are hitherto unknown. Here, ab initio molecular dynamics are used to understand how different low concentrations of Au operate within a liquid Ga solvent. We determine that Au concentrations of between 15% Au wt and 25% Au wt will give rise to the highest abundance of stabilised single Au atoms.

A self-healing electrocatalytic system via electrohydrodynamics induced evolution in liquid metal

Catalytic deterioration during electrocatalytic processes is inevitable for conventional composite electrodes, which are prepared by depositing catalysts onto a rigid current collector. In contrast, metals that are liquid at near room temperature, liquid metals (LMs), are potential electrodes that are uniquely flexible and maneuverable, and whose fluidity may allow them to be more adaptive than rigid substrates. Here we demonstrate a self-healing electrocatalytic system for CO₂ electroreduction using bismuth-containing Ga-based LM electrodes. Bi₂O₃ dispersed in the LM matrix experiences a series of electrohydrodynamic-induced structural changes when exposed to a tunable potential and finally transforms into catalytic bismuth, whose morphology can be controlled by the applied potential. The electrohydrodynamically-induced evolved electrode shows considerable electrocatalytic activity for CO₂ reduction to formate. After deterioration of the electrocatalytic performance, the catalyst can be healed via simple mechanical stirring followed by in situ regeneration by applying a reducing potential. With this procedure, the electrode's original structure and catalytic activity are both recovered.

Catalysis of Alloys: Classification, Principles, and Design for a Variety of Materials and Reactions

Alloying has long been used as a promising methodology to improve the catalytic performance of metallic materials. In recent years, the field of alloy catalysis has made remarkable progress with the emergence of a variety of novel alloy materials and their functions. Therefore, a comprehensive disciplinary framework for catalytic chemistry of alloys that provides a cross-sectional understanding of the broad research field is in high demand. In this review, we provide a comprehensive classification of various alloy materials based on metallurgy, thermodynamics, and inorganic chemistry and summarize the roles of alloying in catalysis and its principles with a brief introduction of the historical background of this research field. Furthermore, we explain how each type of alloy can be used as a catalyst material and how to design a functional catalyst for the target reaction by introducing representative case studies. This review includes two approaches, namely, from materials and reactions, to provide a better understanding of the catalytic chemistry of alloys. Our review offers a perspective on this research field and can be used encyclopedically according to the readers' individual interests.

Non-wettable/wettable coatings floating on liquid metal marbles for anti-combination, reversible conductivity transformation and magnetic motion in solution

Novel non-wetted/wetted floatable polyethylene/Cu and porous-Ni/Cu (P-Ni/Cu) coatings have been designed and fabricated for anti-combination of gallium-based liquid metal alloy (LM) marbles in solutions. Both coated LM pairs show strong anti-combination resistances even under a large extrusion ratio. Additionally, both coatings also show strong bonding forces with LMs and are floatable on the surfaces of LMs. Driven by electric or magnetic fields, floatable polyethylene/Cu or P-Ni/Cu coatings on LM surfaces are guided by these external fields, and then restore the original arrangement by the surface tension of the LMs and buoyancy of the coatings themselves after removing external fields, by which these coated LM marble or LM marble pair exhibit the revisable conductivity transitions and magnetic driven motion applications. This work should present a new way for the clustering and functional application of LMs in solutions.