Laser solid-phase synthesis of single-atom catalysts

Rapid synthesis of metastable materials for electrocatalysis

Metastable materials are considered promising electrocatalysts for clean energy conversions by virtue of their structural flexibility and tunable electronic properties. However, the exploration and synthesis of metastable electrocatalysts via traditional equilibrium methods face challenges because of the requirements of high energy and precise structural control. In this regard, the rapid synthesis method (RSM), with high energy efficiency and ultra-fast heating/cooling rates, enables the production of metastable materials under non-equilibrium conditions. However, the relationship between RSM and the properties of metastable electrocatalysts remains largely unexplored. In this review, we systematically examine the unique benefits of various RSM techniques and the mechanisms governing the formation of metastable materials. Based on these insights, we establish a framework, linking RSM with the electrocatalytic performance of metastable materials. Finally, we outline the future directions of this emerging field and highlight the importance of high-throughput approaches for the autonomous screening and synthesis of optimal electrocatalysts. This review aims to provide an in-depth understanding of metastable electrocatalysts, opening up new avenues for both fundamental research and practical applications in electrocatalysis.

Pulsed laser synthesis of free-standing Pt single atoms in an ice block for enhancing photocatalytic hydrogen evolution of g-C3N4

This study reports an innovative synthesis method of a Pt/g-C3N4 single atom catalyst for enhancing photocatalytic hydrogen evolution. The method involves the synthesis of free-standing Pt single atoms within an H2PtCl6 ice block using a pulsed laser reduction process, followed by transferring them onto few-layer g-C3N4 through electrostatic adsorption at low temperature. This approach eliminates the need for high-energy lasers and porous support materials during laser solid-phase synthesis. The photocatalytic activities of Pt/g-C3N4 synthesized under various laser conditions are evaluated to optimize the synthesis parameters. The optimal Pt/g-C3N4 catalyst demonstrates a significantly higher photocatalytic hydrogen evolution capability (320 μmol h-1), 129 times that of pure g-C3N4 (2.2 μmol h-1). This work expands the laser-solid phase synthesis method, offering a promising route for the production of single atom catalysts with simple operation, clear synthetic pathways, low cost, and environmental friendliness.

Single-atom nanozymes for enhanced electrochemical biosensing: A review

Enzyme-based electrochemical biosensors have broad and significant applications in biomedical, environmental monitoring, and food safety fields. However, the application of natural enzymes is limited due to issues such as poor stability, complex preparation, and high cost. Single-atom nanozymes (SAzymes), with their unique catalytic properties and efficient enzyme-like activities, present a promising alternative in the field of electrochemical biosensing. Compared to traditional enzymes, SAzyme offer enhanced stability and controllability, making them particularly effective in complex detection environments. This work presents the first systematic review of the progress made since 2018 in the use of SAzymes as alternatives to natural enzymes in electrochemical biosensors, and presents the latest advancements in this area. The review begins with a discussion of various enzyme-like activities of single-atom materials, including peroxidase (POD)-like, oxidase (OXD)-like, catalase (CAT)-like, and superoxide dismutase (SOD)-like activities. It then explores the advantages of SAzymes in improving the performance of electrochemical biosensors from multiple perspectives. The review also summarizes the applications of SAzyme-based electrochemical sensors for reactive oxygen species (ROS), metabolites, neurotransmitters, and other analytes, highlighting specific examples to elucidate underlying catalytic mechanisms and understand fundamental structure-performance relationships. In the final section, the challenges faced by SAzyme-based electrochemical biosensing are discussed, along with potential solutions.

Ultrafast Synthesis of Single-Atom Catalysts for Electrocatalytic Applications

A recent development in catalytic research, single-atom catalysts (SACs) are one of the most significant categories of catalytic materials. During preparation, individual atoms migrate and agglomerate due to the high surface free energy. The rapid thermal shock strategy addresses this challenge by employing instantaneous high-temperature pulses to synthesize SACs, while minimizing heating duration to prevent metal aggregation and substrate degradation, thereby preserving atomic-level dispersion. The resultant SACs exhibit exceptional catalytic activity, remarkable selectivity, and long-term stability, which have attracted extensive attention in electrocatalysis. In this paper, cutting-edge ultrafast synthesis techniques such as Joule heating, microwave radiation, pulsed discharge, and arc discharge are comprehensively analyzed. Their ability is emphasized to achieve uniform dispersion of separated metal atoms and optimize the catalytic activity for electrocatalytic applications. A systematic summary of SACs synthesized by these rapid methods is provided, with particular emphasis on their implementation in carbon dioxide reduction reaction (CO2RR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) systems. The review provides an in-depth discussion on the rapid synthesis strategy for development trend, remaining challenges, and the application prospects in electrocatalysis.

Laser-Induced Solid-Phase Strategy to Synthesize Single-Atomic Lithiophilic Sites Enabled Dendrite-Free Lithium Deposition on Graphene Matrix

The introduction of metal Single-atom (SA) to construct lithium-philic active sites shows the ability to guide uniform lithium deposition and improve the stability of lithium hosts. Nevertheless, the development of facile and expedient methods for synthesizing SA remains a considerable challenge. Herein, The SA metal loaded on graphene (Bi@LrGO) is designed by laser-induced solid-phase strategy. The bismuth salts simultaneously decompose under the high local temperature and in the reductive atmosphere induced by laser to form SA metal. Simultaneously, graphene oxide (GO) nanosheets absorb photon energy to be reduced/graphitized into graphene, which serves as anchoring sites for Bismuth Sing-atom (Bi SA) immobilization. The SA metals, supported on the graphene not only provide sufficient lithiophilic sites but also significantly increase the adsorption energy (-2.11 eV) with lithium atoms, promote the uniform nucleation and deposition of lithium, and inhibit the growth of lithium dendrites. Additionally, the layered structure of the graphene film adapts to the volume change during the repeated lithium plating/stripping process. Therefore, the symmetrical battery-based Li deposited on Bi@LrGO (Bi@LrGO@Li) achieves an ultra-long stable cycle life of ≈2400 h at 1 mA cm-2. In particular, a full cell with LiFePO4 cathode provides a good capacity retention of 81.2% at 4 C after 600 cycles.

Laser Irradiation Induced Electronic Structure Modulation of the Palladium-Based Nanosheets for Efficient Electrocatalysts

Palladium nanosheets (Pd NSs) are widely used as electrocatalysts due to their high atomic utilization efficiency, and long-term stability. Here, the electronic structure modulation of the Pd NSs is realized by a femtosecond laser irradiation strategy. Experimental results indicate that laser irradiation induces the variation in the atomic structures and the macrostrain effects in the Pd NSs. The electronic structure of Pd NSs is modulated by laser irradiation through the balancing between Au-Pd charge transfer and the macros-strain effects. Finite element analysis (FEA) indicates that the lattice of the nanostructures undergoes fast heating and cooling during laser irradiation. The structural evolution mechanism is disclosed by a combined FEA and molecule dynamics (MD) simulation. These results coincide well with the experimental results. The L-AuPd NSs exhibit excellent mass activity and specific activity of 7.44 A mg-1 Pd and 18.70 mA cm-2 toward ethanol oxidation reaction (EOR), 4.3 and 4.4 times higher than the commercial Pd/C. The 2500-cycle accelerated durability (ADT) test confirms the outstanding catalytic stability of the L-AuPd NSs. Density functional theory (DFT) calculations reveal the catalytic mechanism. This unique strategy provides a new pathway to design the ultrathin nanosheet-based materials with excellent performance.

Materials Containing Single-, Di-, Tri-, and Multi-Metal Atoms Bonded to C, N, S, P, B, and O Species as Advanced Catalysts for Energy, Sensor, and Biomedical Applications

Modifying the coordination or local environments of single-, di-, tri-, and multi-metal atom (SMA/DMA/TMA/MMA)-based materials is one of the best strategies for increasing the catalytic activities, selectivity, and long-term durability of these materials. Advanced sheet materials supported by metal atom-based materials have become a critical topic in the fields of renewable energy conversion systems, storage devices, sensors, and biomedicine owing to the maximum atom utilization efficiency, precisely located metal centers, specific electron configurations, unique reactivity, and precise chemical tunability. Several sheet materials offer excellent support for metal atom-based materials and are attractive for applications in energy, sensors, and medical research, such as in oxygen reduction, oxygen production, hydrogen generation, fuel production, selective chemical detection, and enzymatic reactions. The strong metal-metal and metal-carbon with metal-heteroatom (i.e., N, S, P, B, and O) bonds stabilize and optimize the electronic structures of the metal atoms due to strong interfacial interactions, yielding excellent catalytic activities. These materials provide excellent models for understanding the fundamental problems with multistep chemical reactions. This review summarizes the substrate structure-activity relationship of metal atom-based materials with different active sites based on experimental and theoretical data. Additionally, the new synthesis procedures, physicochemical characterizations, and energy and biomedical applications are discussed. Finally, the remaining challenges in developing efficient SMA/DMA/TMA/MMA-based materials are presented.

Electron Redistribution in Iridium-Iron Dual-Metal-Atom Active Sites Enables Synergistic Enhancement for H2O2 Decomposition

Developing efficient heterogeneous H2O2 decomposition catalysts under neutral conditions is of great importance in many fields such as clinical therapy, sewage treatment, and semiconductor manufacturing but still suffers from low intrinsic activity and ambiguous mechanism understanding. Herein, we constructed activated carbon supported with an Ir-Fe dual-metal-atom active sites catalyst (IrFe-AC) by using a facile method based on a pulsed laser. The electron redistribution in Ir-Fe dual-metal-atom active sites leads to the formation of double reductive metal active sites, which can strengthen the metal-H2O2 interaction and boost the H2O2 decomposition performance of Ir-Fe dual-metal-atom active sites. Ir-Fe dual-metal-atom active sites show a high second-order reaction rate constant of 3.53 × 106 M-1·min-1, which is ∼106 times higher than that of Fe3O4. IrFe-AC is effective in removing excess intracellular reactive oxygen species, protecting DNA, and reducing inflammation under oxidative stress, indicating its therapeutic potential against oxidative stress-related diseases. This study could advance the mechanism understanding of H2O2 decomposition by heterogeneous catalysts and provide guidance for the rational design of high-performance catalysts for H2O2 decomposition.

Laser Synthesis of Nonprecious Metal-Based Single-Atom Catalysts for Oxygen Reduction Reaction

Development of nonprecious metal-based single-atom catalysts (SACs) has provided opportunities to substitute Pt group metals and offer maximum atom utilization and unique coordination environments. Among these catalysts, Fe-N-C catalysts with atomically dispersed Fe-N4 active sites have emerged as some of the most promising oxygen reduction reaction (ORR) catalysts. However, furnace synthesis of Fe-N-C catalysts with carbon substrate derived from metal-organic framework (MOF) involves a high-temperature procedure, in which nitrogen from the carbonized MOF tends to be removed, subsequently leading to a low density of active sites. In this work, we developed a rapid and simple solid-state route to fabricate SACs through laser-induced thermal activation (LITA) of carbonized zeolitic imidazolate framework-8 (ZIF-8) adsorbed with Fe precursors. The results demonstrate that the laser process effectively avoids the loss of nitrogen in the nitrogen-doped carbon substrate and achieves a loading of Fe single atoms of 2.3 wt %, in comparison with that of 1.2 wt % from the conventional furnace treatment. The Fe-N-C catalyst synthesized in the study presents a half-wave potential of 0.91 V for ORR in alkaline media, which is higher than that of commercial Pt/C (0.87 V). When used as a cathode catalyst in zinc-air batteries (ZABs), the battery exhibits excellent electrochemical performance. This work also demonstrates the versatility of the technique through the successful synthesis of Co-N-C and Ni-N-C single atoms on nitrogen-doped carbon substrates.

Noble-Metal Nanoparticle-Embedded Silicon Nanogratings via Single-Step Laser-Induced Periodic Surface Structuring

Here, we show that direct femtosecond laser nanostructuring of monocrystalline Si wafers in aqueous solutions containing noble-metal precursors (such as palladium dichloride, potassium hexachloroplatinate, and silver nitrate) allows for the creation of nanogratings decorated with mono- (Pd, Pt, and Ag) and bimetallic (Pd-Pt) nanoparticles (NPs). Multi-pulse femtosecond-laser exposure was found to drive periodically modulated ablation of the Si surface, while simultaneous thermal-induced reduction of the metal-containing acids and salts causes local surface morphology decoration with functional noble metal NPs. The orientation of the formed Si nanogratings with their nano-trenches decorated with noble-metal NPs can be controlled by the polarization direction of the incident laser beam, which was justified, for both linearly polarized Gaussian and radially (azimuthally) polarized vector beams. The produced hybrid NP-decorated Si nanogratings with a radially varying nano-trench orientation demonstrated anisotropic antireflection performance, as well as photocatalytic activity, probed by SERS tracing of the paraaminothiophenol-to-dimercaptoazobenzene transformation. The developed single-step maskless procedure of liquid-phase Si surface nanostructuring that proceeds simultaneously with the localized reduction of noble-metal precursors allows for the formation of hybrid Si nanogratings with controllable amounts of mono- and bimetallic NPs, paving the way toward applications in heterogeneous catalysis, optical detection, light harvesting, and sensing.

Ultrafast materials synthesis and manufacturing techniques for emerging energy and environmental applications

Energy and environmental issues have attracted increasing attention globally, where sustainability and low-carbon emissions are seriously considered and widely accepted by government officials. In response to this situation, the development of renewable energy and environmental technologies is urgently needed to complement the usage of traditional fossil fuels. While a big part of advancement in these technologies relies on materials innovations, new materials discovery is limited by sluggish conventional materials synthesis methods, greatly hindering the advancement of related technologies. To address this issue, this review introduces and comprehensively summarizes emerging ultrafast materials synthesis methods that could synthesize materials in times as short as nanoseconds, significantly improving research efficiency. We discuss the unique advantages of these methods, followed by how they benefit individual applications for renewable energy and the environment. We also highlight the scalability of ultrafast manufacturing towards their potential industrial utilization. Finally, we provide our perspectives on challenges and opportunities for the future development of ultrafast synthesis and manufacturing technologies. We anticipate that fertile opportunities exist not only for energy and the environment but also for many other applications.

Atomic-Level Pt Electrocatalyst Synthesized via Iced Photochemical Method for Hydrogen Evolution Reaction with High Efficiency

In heterogeneous catalysis, metal particle morphology and size can influence markedly the activity. It is of great significance to rationally design and control the synthesis of Pt at the atomic level to demonstrate the structure-activity relationship toward electrocatalysis. Herein, a powerful strategy is reported to synthesize graphene-supported platinum-based electrocatalyst, that is, nanocatalysts with controllable size can be prepared by iced photochemical method, including single atoms (Pt-SA@HG), nanoclusters (Pt-Clu@HG), and nanocrystalline (Pt-Nc@HG). The Pt-SA@HG exhibits unexpected electrocatalytic hydrogen evolution reaction (HER) performances with 13 mV overpotential at 10 mA cm^-2 current densities which surpass Pt-Clu@HG and Pt-Nc@HG. The in situ X-ray absorption fine structure spectroscopy (XAFS) and density functional theory (DFT) calculations determine the Pt-C₃ active site is linchpin to the excellent HER performance of Pt-SA@HG. Compared with the traditional Pt-N_x coordination structure, the pure carbon coordinated Pt-C₃ site is more favorable for HER. This work opens up a new way to adjust the metal particle size and catalytic performance of graphene at a multiscale level.

Single Atom Catalysts for Selective Methane Oxidation to Oxygenates

Direct conversion of methane (CH₄) to C_1-2 liquid oxygenates is a captivating approach to lock carbons in transportable value-added chemicals, while reducing global warming. Existing approaches utilizing the transformation of CH₄ to liquid fuel via tandemized steam methane reforming and the Fischer-Tropsch synthesis are energy and capital intensive. Chemocatalytic partial oxidation of methane remains challenging due to the negligible electron affinity, poor C-H bond polarizability, and high activation energy barrier. Transition-metal and stoichiometric catalysts utilizing harsh oxidants and reaction conditions perform poorly with randomized product distribution. Paradoxically, the catalysts which are active enough to break C-H also promote overoxidation, resulting in CO₂ generation and reduced carbon balance. Developing catalysts which can break C-H bonds of methane to selectively make useful chemicals at mild conditions is vital to commercialization. Single atom catalysts (SACs) with specifically coordinated metal centers on active support have displayed intrigued reactivity and selectivity for methane oxidation. SACs can significantly reduce the activation energy due to induced electrostatic polarization of the C-H bond to facilitate the accelerated reaction rate at the low reaction temperature. The distinct metal-support interaction can stabilize the intermediate and prevent the overoxidation of the reaction products. The present review accounts for recent progress in the field of SACs for the selective oxidation of CH₄ to C_1-2 oxygenates. The chemical nature of catalytic sites, effects of metal-support interaction, and stabilization of intermediate species on catalysts to minimize overoxidation are thoroughly discussed with a forward-looking perspective to improve the catalytic performance.

Optical Modification of 2D Materials: Methods and Applications

2D materials are under extensive research due to their remarkable properties suitable for various optoelectronic, photonic, and biological applications, yet their conventional fabrication methods are typically harsh and cost-ineffective. Optical modification is demonstrated as an effective and scalable method for accurate and local in situ engineering and patterning of 2D materials in ambient conditions. This review focuses on the state of the art of optical modification of 2D materials and their applications. Perspectives for future developments in this field are also discussed, including novel laser tools, new optical modification strategies, and their emerging applications in quantum technologies and biotechnologies.