Anchoring zero valence single atoms of nickel and iron on graphdiyne for hydrogen evolution

Single-atom Fe anchored graphdiyne for high-efficiency nitrate-to-ammonia conversion under ambient conditions

The electrocatalytic conversion of wastewater nitrate (NO3-) to ammonia (NH3) under industrial-grade current densities at ambient conditions presents a sustainable alternative to the energy-intensive Haber-Bosch process, yet remains fundamentally challenging. Here, a highly efficient NO3- to NH3 electrocatalyst with single Fe atoms dispersed on graphdiyne (GDY) is constructed through an in situ growth method. Experimental analysis demonstrates the formation of high-density atomic active sites on GDY, ensuring the high intrinsic activity of the electrocatalyst. Besides, the newly formed sp-C-Fe chemical bonds bridged GDY and Fe atoms providing a well-defined channel for selectively and efficiently transferring electrons from the active sites to the reactants/key intermediates, allowing for selective NO3- activation and efficient protonation. This atomic-scale electronic modulation enables exceptional nitrate reduction performance, achieving record-high faradaic efficiency (45.48%) and ammonia yield (202.34 μmol h-1 cm-2) while maintaining operational stability.

Controlled Synthesis of Dy/Cu Bimetallic Atoms for Efficient Artificial Photosynthesis

The birth of metal atom catalysts marked a new historical stage in the field of catalysis, allowing scientists to better understand the science of catalysis at the atomic level. On the basis of anchoring independent metal atoms, bimetal dysprosium-copper atoms are successfully anchored on graphdiyne (DyCu/GDY). Dy and Cu metal atoms are selectively anchored in triangular holes of GDY and stabilized by non-integer charge transfer and the confined space effect between the metals and GDY. The dynamic charge-transfer equilibrium caused by the inherent non-integer charge transfer between GDY and metal atoms produces sustained high activity, inducing a redistribution of surface charge. This result shows that the non-integer charge transfer strongly promotes the adsorption activation of CO2 and the desorption of the reaction intermediates, realizing the unpredictable selectivity and activity of CO2 conversion in the process of artificial photosynthesis, where the selectivity and yield of CO are 98% and 279 µmol gcat. -1 h-1, respectively.

Modulating the electronic structure of graphdiyne-based nanomaterials for engineering nano-bio interfaces in biomedical applications

Graphdiyne (GDY), a two-dimensional (2D) carbon allotrope featuring a unique electronic structure, has attracted considerable attention due to its outstanding properties and potential applications in various fields, particularly in biomedicine due to its exceptional surface area, tunable electronic structure, and biocompatibility. Although promising, this field is still in the proof-of-concept stage due to incomplete understanding of the effects of structural regulation, particularly electronic structure, of GDY-based nanomaterials on their nano-bio interfaces, which seriously hinders the research of GDY-based nanomaterials in the biomedical field. To provide a comprehensive understanding of the relationship between electronic structures and nano-bio interfaces, this review focuses on the modulation of the electronic structure of GDY-based nanomaterials and its implications for engineering nano-bio interfaces for biomedical applications. Firstly, we delve into the intrinsic electronic properties of GDY, including its bandgap tunability and high carrier mobility, which are critical for its functionality in biomedical applications. We then discuss strategies for modulating these properties through oxidation, nonmetallic doping, covalent modification, and metal loading, aiming to optimize the electronic structure of GDY-based nanomaterials for superior performance in specific biomedical contexts, such as biomedical imaging, surface and interface catalysis, free radical scavenging, and drug delivery. Furthermore, we provide an overview of the methodologies for the investigation of these electronic properties, including theoretical simulation, characterization techniques, and real-time analysis of electron transfer at the nano-bio interfaces, highlighting their roles in advancing our understanding and guiding the design of novel GDY-based materials. Finally, this review provides an outlook on future research directions aimed at further optimizing the design of GDY-based nanomaterials and nano-bio interfaces, emphasizing the need for interdisciplinary collaboration to overcome current challenges and to fully realize the potential of GDY-based nanomaterials in biomedical applications. These principles are anticipated to facilitate the future development and clinical translation of precise, safe, and effective nanomedicines with intelligent theranostic features.

Unravelling Species-Specific Loading Effects on Oxygen Reduction Activity of Heteronuclear Single Atom Catalysts

Toward high-density single atom catalysts (SACs), the interaction between neighboring SACs and the induced non-linear loading effect become crucial for their intrinsic catalytic performance. Despite recent investigations on homonuclear SACs, understanding such effect in heteronuclear SACs remains limited. Using Fe and Co SACs co-supported on the nitrogen-doped graphene as a model system, the loading effect on the site-specific activity of heteronuclear SACs toward oxygen reduction reaction (ORR) is here reported by density functional theory calculations. The Fe site exhibits an oscillatory decrease in activity with the loading. In contrast, the Co site has a volcano-like activity with the optimum performance achieved at ≈16.8 wt.% (average inter-site distance: ≈7 Å). At the ultra-high loading of 38.4 wt.% (inter-site distance: ≈4 Å), the Co site is the only ORR active site, whereas Fe sites turn into spectators. This distinct loading-dependent activity between the Fe and Co sites can be ascribed to their difference in the binding capability with the substrate and the dxz and dyz orbitals' occupation. These findings highlight the importance of the loading effect in heteronuclear SACs, which could be useful for the development of high-performance heteronuclear and high-entropy SACs toward various catalytic reactions in the high-loading regime.

Rational Synthesis of Isomeric Graphdiyne Frameworks toward Single-Ruthenium Catalysts and High-Performance Nitrogen Reduction

Graphdiynes (GDYs), synthesized via direct coupling of arylacetylenes, have attracted great attention due to their unique electronic properties and structural diversity, typically forming 2D layered frameworks. However, crystalline GDY-like frameworks with 3D topology remain challenging to synthesize. Here, the study reports two highly crystalline, isomeric GDY-like frameworks with ThSi2 topology, constructed from 2,2'-binaphthalene and 6,6'-biazulene-based monomers. The azulene-based framework, due to its large dipole moment, exhibits a narrow bandgap of 1.15 eV, significantly lower than its naphthalene counterpart (2.33 eV). As ruthenium (Ru) single-atom supports, these frameworks enable strong Ru-diyne interactions, achieving an ammonia yield rate of 188.7 ± 1.6 µg h-1 mgcat -1 and a Faradaic efficiency of 37.4 ± 0.6%. Such bicontinuous channels and tunable electronic structures offer electrocatalysis field new opportunities. Moreover, the azulene-based framework, featuring a higher highest occupied molecular orbital  and lower lowest unoccupied molecular orbital  energy level, ensures superior electron mobility. These 3D crystalline frameworks introduce a new covalent organic framework (COF) family with diyne linkages and pure carbon skeletons, broadening the scope of COF materials. Their well-defined structures provide an ideal platform for tuning optoelectronic properties, enabling fundamental studies on structure-property relationships and opening new opportunities for catalytic and electronic applications.

Interfacial Atom Rearrangement Drives Potential-Adaptive Electrocatalytic Olefin Hydrogenation

Dynamic rearrangement of metal atoms at heterointerfaces by chemical bond conversion drives high efficiency electrocatalytic processes, which is a new concept in the field of electrocatalysis and a new discovery to directly improve catalytic activity. It is of great significance to explore transformative catalytic systems that directly control the interfacial structure and function of atomic composition. As an emerging 2D carbon allotrope featuring unique sp-sp2 co-hybridization, graphdiyne (GDY) offers unprecedented advantages for heterointerface engineering. In particular, the uneven surface charge distribution of GDY, high distribution of active sites and customizable electronic structures provide unprecedented opportunities for the development of a new generation of catalytic systems. Here, we report a new idea to directly control the cooperative growth and drive metal atomic rearrangement on the interface of GDY/NiPd/GDY. The results of atomic-resolution electron microscopy characterization revealed two unique interfacial phenomena: i) GDY-induced massive dislocation formation within NiPd nanoalloys and ii) rearrangement of surface metal atoms from (111) to (200) facets. Detailed spectroscopic analysis further demonstrated the composition-dependent evolution of elemental valence states and stoichiometric ratios. This atomic-level restructuring establishes a charge-redistribution network featuring non-integer charge transfer, which improves the overall conductivity and intrinsic activity. What is even more encouraging is that this electrocatalytic olefin hydrogenation is carried out in an aqueous solution. The GDY/NiPd/GDY heterostructure achieves exceptional activity (turnover frequency: 6.8 s-1), stability (>5 cycles), and chemo-selectivity (-100%), which is superior to traditional catalysts.

Lactate-Modulating Nanozyme-Mediated Mitochondrial Respiration Block for Tumor Immunosuppression Remodeling

Abnormal lactate metabolism in tumor cells leads to immune escape in the tumor microenvironment. Intervening in specific lactate metabolic pathways while blocking downstream pyruvate influx holds great promise for overcoming conventional lactate-targeted therapy limitations such as short half-life, insufficient lactate consumption, and pathological microenvironment elasticity. Herein, a nanocatalytic medicine based on carbondoping engineered copper nitride enzyme (Cu3N-C NE) with enhanced lactate oxidase (LOX) activity was carefully designed. Computational results revealed that the introduction of C favors activation of the hydroxyalkyl C-H bond in lactate by the polarization of adjacent hydroxyl groups, correspondingly facilitating the abstraction of hydrogen atoms from the desired α-C-H and α-C-O-H groups in lactate via the hydrogen atom-transfer (HAT) process. The Cu3N-C NEs could downregulate lactate levels in tumor cells for robust remodeling of the immunosuppressive microenvironment and further block as-generated pyruvate to influx into the mitochondrial respiration, achieving lactate homeostasis reprogramming. Our study provides a proof-of-concept design of next-generation lactate-modulation nanomedicine via heteroatom-doping and evolution with the additional potential to expedite the industrial production of lactate to pyruvate.

B/N modified GDY as a rare base 2D sensor: a first-principles study

Detecting DNA rare bases is essential for diagnosing genetic disorders and cancers. However, their low abundance and high structural similarity make selective and sensitive detection challenging. The two-dimensional functionalized carbon material graphdiyne (GDY) holds great promise for enhancing sensor performance due to its excellent electronic properties, biocompatibility, and ease of functionalization. This study employs density functional theory (DFT) to investigate the adsorption behavior of rare bases on GDY and R-GDY (R = B/N) surfaces. Essential factors, including adsorption energy, bandgap, charge transfer, and density of states, are systematically analyzed. Additionally, critical sensor performance metrics, such as deposition time, sensitivity, and selectivity are predicted, providing valuable insights into the potential applications of these materials. The results indicate that while pure GDY can specifically recognize 5-hydroxymethylcytosine, its sensitivity is limited. In contrast, R-GDY stably adsorbs rare bases via π-π interactions, exhibiting good reversibility and moderate charge transfer, which significantly enhance its sensitivity. R-GDY effectively distinguishes between rare bases based on translocation time, making it ideal for the development of efficient and reusable electrochemical biosensors, thus providing a reliable approach for clinical diagnostics.

Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions

Atomic site catalysts (ASCs) have recently gained prominence for their potential in the electrochemical hydrogen evolution reaction (HER) due to their exceptional activity, selectivity, and stability. ASCs with individual atoms dispersed on a support material, offer expanded surface areas and increased mass efficiency. This is because each atom in these catalysts serves as an active site, which enhances their catalytic activity. This review is focused on providing a detailed analysis of ASCs in the context of the HER. It will delve into their properties, types, and performance to provide a comprehensive understanding of their role in electrochemical HER processes. The introduction part underscores HER's significance in transitioning to sustainable energy sources and emphasizes the need for innovative catalysts like ASCs. The fundamentals of the HER section emphasizes the importance of understanding the HER and highlights the key role that catalysts play in HER. The review also explores the properties of ASCs with a specific emphasis on their atomic structure and categorizes the types based on their composition and structure. Within each category of ASCs, the review discusses their potential as catalysts for the HER. The performance section focuses on a thorough evaluation of ASCs in terms of their activity, selectivity, and stability in HER. The performance section assesses ASCs in terms of activity, selectivity, and stability, delving into reaction mechanisms via experimental and theoretical approaches, including density functional theory (DFT) studies. The review concludes by addressing ASC-related challenges in HER and proposing future research directions, aiming to inspire further innovation in sustainable catalysts for electrochemical HER.

In-situ adsorption-coupled-oxidation enabled mercury vapor capture over sp-hybridized graphdiyne

Developing efficient and sustainable carbon sorbent for mercury vapor (Hg0) capture is significant to public health and ecosystem protection. Here we show a carbon material, namely graphdiyne with accessible sp-hybridized carbons (HsGDY), that can serve as an effective "trap" to anchor Hg atoms by strong electron-metal-support interaction, leading to the in-situ adsorption-coupled-oxidation of Hg. The adsorption process is benefited from the large hexagonal pore structure of HsGDY. The oxidation process is driven by the surface charge heterogeneity of HsGDY which can itself induce the adsorbed Hg atoms to lose electrons and present a partially oxidized state. Its good adaptability and excellent regeneration performance greatly broaden the applicability of HsGDY in diverse scenarios such as flue gas treatment and mercury-related personal protection. Our work demonstrates a sp-hybridized carbon material for mercury vapor capture which could contribute to sustainability of mercury pollution industries and provide guide for functional carbon material design.

Graphdiyne and its heteroatom-doped derivatives for Li-ion/metal batteries

Graphdiyne (GDY), which is composed of benzene rings and acetylene linkage units, is a new allotrope of carbon material. In particular, the large triangular pores of GDY, with a diameter of 5.4 Å, theoretically predict a higher lithium embedding density than traditional graphite anodes, making it a promising candidate for energy storage materials in lithium-ion (Li-ion) batteries. GDY is primarily synthesized via a cross-coupling reaction of hexaethynylbenzene (HEB). Under similar preparation conditions, the cross-coupling reaction of aryne precursors, other than HEB, yields many GDY heteroatom-doped derivatives. This introduces numerous heteroatomic defects as well as electrochemically active sites, potentially enhancing electrochemical performance. Recent advancements have focused on utilizing GDY and its heteroatom-doped derivatives as electrode materials or composite materials in Li-ion/metal batteries. This review systematically summarizes the strategies developed for GDY and its heteroatom-doped derivatives. Notably, recent research on the effects of morphology and chemical/electronic structure on performance, particularly new conceptual mechanisms in Li-ion/metal batteries, including self-expanding Li-ion transport channels and a capture/pore filling-intercalation hybrid mechanism, is briefly described. The results presented herein highlight the significant potential of GDY and its heteroatom-doped derivatives for energy storage applications and inspire further development.

A Highly Conjugated Nickel(II)-Acetylide Framework for Efficient Photocatalytic Carbon Dioxide Reduction

The incorporation of transition-metal single atoms as molecular functional entities into the skeleton of graphdiyne (GDY) to construct novel two-dimensional (2D) metal-acetylide frameworks, known as metalated graphynes (MGYs), is a promising strategy for developing efficient catalysts, which can combine the tunable charge transfer of GDY frameworks, the catalytic activity of metal and the precise distribution of single metallic centers. Herein, four highly conjugated MGY photocatalysts based on NiII, PdII, PtII, and HgII were synthesized for the first time using the 'bottom-up' strategy through the use of M-C bonds (-C≡C-M-C≡C-). Remarkably, the NiII-based graphyne (TEPY-Ni-GY) exhibited the highest CO generation rate of 18.3 mmol g-1 h-1 and a selectivity of 98.8 %. This superior performance is attributed to the synergistic effects of pyrenyl and -C≡C-Ni(PBu3)2-C≡C- moieties. The pyrenyl block functions as an intramolecular π-conjugation channel, facilitating kinetically favorable electron transfer, while the -C≡C-Ni(PBu3)2-C≡C- moiety serves as the catalytic site that enhances CO2 adsorption and activation, thereby suppressing competitive hydrogen evolution. This study provides a new perspective on MGY-based photocatalysts for developing highly active and low-cost catalysts for CO2 reduction.

Boosting Enzyme-Like Activity Through Controlled Coordination of Metal Single-Atoms in Rhombic Cavity of Graphyne

The coordination number of metal single-atoms, being an important factor, should be precisely controlled as it affects both activity and specificity. Herein, the introduction of nitrogen into the para position of benzene in graphyne (2N-GY) is proposed as a carrier for anchoring metal single-atoms onto pyrazine nitrogen. These atoms are then coordinated to the center of the rhombic cavity, ensuring precisely controlled coordination numbers. Inspired by natural enzymes, a series of transition metal single-atom nanozymes (SANs) are constructed utilizing 2N-GY. Both theory calculations and experiments demonstrated that the incorporation of metal single-atoms of Fe, Mn, and Mo effectively augmented the enzyme-like activity, with Mo/GY exhibiting the highest peroxidase -like activity. Based on the differing activities of M/GY (M = Fe, Mn, Mo) and the varying abilities of sulfhydryl groups in biothiols to occupy metal active sites, sensing arrays for the high-throughput identification of six biothiols are constructed. After combining the fingerprint feature responses of biothiols and SANs with machine learning algorithms, the efficient distinction of the six biothiols is achieved. This study introduces a novel pathway for designing and synthesizing SANs that mimic natural enzymes.

The Accurate Synthesis of a Multiscale Metallic Interface on Graphdiyne

The accurate construction of composite material systems containing graphdiyne (GDY) and other metallic materials has promoted the formation of innovative structures and practical applications in the fields of energy, catalysis, optoelectronics, and biomedicine. To fulfill the practical requirements, the precise formation of multiscale interfaces over a wide range, from single atoms to nanostructures, plays an important role in the optimization of the structural design and properties. The intrinsic correlations between the structure, synthesis process, characteristic properties, and device performance are systematically investigated. This review outlines the current research achievements regarding the controlled formation of multiscale metallic interfaces on GDY. Synthetic strategies for interface regulation, as well as the correlation between the structure and performance, are presented. Furthermore, innovative research ideas for the design and synthesis of functional metal-based materials loaded onto GDY-based substances are also provided, demonstrating the promising application potential of GDY-based materials.

Two-Dimensional Tantalum Carbo-Selenide for Hydrogen Evolution

Herein, we report the synthesis of two-dimensional Ta2Se2C (2D-Ta2Se2C) nanosheets using electrochemical lithiation in multilayer Ta2Se2C followed by sonication in deionized water. Multilayer Ta2Se2C was obtained via solid-state synthesis of FexTa2Se2C followed by chemical etching of Fe. 2D-Ta2Se2C exhibited promising electrocatalytic activity for the hydrogen evolution reaction from water compared to multilayer Ta2Se2C and 2D-TaSe2. 2D-Ta2Se2C showed an overpotential at 10 mA·cm-2 (η10) of 264 mV, a Tafel slope of 91 mV·dec-1, and an electrochemically active surface area of 17.61 mECSA2·gcatalyst-1. The high performance could be attributed to the large surface area of single sheets which hence maximizes the number of exposed catalytic sites and increased density of vacancies, observed with transmission electron microscopy, during synthesis and processing.

The Interfacial Interpenetration Effect for Controlled Reaction Stability of Palladium Catalysts

Tailoring well-defined interfacial structures of heterogeneous metal catalysts has become an effective strategy for identifying the interface relationships and facilitating the reactions involving multiple intermediates. Here, a particle-particle heterostructure catalyst consisting of Pd and copper oxide nanoparticles is designed to achieve high-performance alkaline methanol oxidation electrocatalysis. The strong coupling particle-particle heterostructure catalyst induced a unique interfacial interpenetration effect to improve the interfacial charge redistribution and regulate the d-band structure for optimizing the adsorption of CO intermediates on the catalyst. The resulting catalyst shows impressive mass activity (4.0 A mgPd-1) and current density (215.8 mA cm-2) for the methanol oxidation reaction (MOR) in alkaline media, which is 80.0 and 154.1 times higher than 10% Pd/C. The catalyst also exhibited outstanding stability for the MOR without obvious mass activity decay after 30,000 cycles. Experimental results and theoretical simulation (DFT) studies show that the chemical bond of the Cu-O-Pd interface can be regulated by the Pd penetration effect, greatly improving the activity and stability of the MOR. The present work exhibits the superiority of the metal particle-metal oxide heterostructure interface toward the rational design of advanced electrocatalysts.

Biology-Based Synthesis of Nickel Single Atoms on the Surface of Geobacter sulfurreducens as an Efficient Electrocatalyst for Alkaline Water Electrolysis

Single-atom metal catalysts are promising electrocatalysts for water electrolysis. Nickel-based electrocatalysts have shown attractive application prospects for water electrolysis. However, synthesizing stable Ni single atoms using chemical and physical approaches remains a practical challenge. Here, a facile and precise method for synthesizing stable nickel single atoms on the surface of Geobacter sulfurreducens using a microbial-mediated extracellular electron transfer (EET) process is demonstrated. It is shown that G. sulfurreducens can effectively anchor nickel single atoms on their surface. X-ray absorption near-edge structure and Fourier-transformed extended X-ray absorption fine structure spectroscopy confirm that the nickel single atom is coordinated to nitrogen in the cytochromes. The as-synthesized nickel single atoms on G. sulfurreducens exhibit excellent bifunctional catalytic properties for alkaline water electrolysis with low overpotential (η) to achieve current density (10 mA cm-2) for both hydrogen evolution reactions (η = 80 mV) and oxygen evolution reaction (η = 330 mV) with minimal catalyst loading of 0.0015 mg Ni cm-2. The nickel single-atom catalyst shows long-term stability at a constant electrode potential. This synthesis method based on the EET capability of electroactive bacteria provides a simple and scalable approach for producing low-cost and highly efficient nonnoble transition metal single-atom catalysts for practical applications.

High catalytic activity and abundant active sites in M2C12 monolayer for nitrogen reduction reaction

Developing highly efficient single-atom catalysts (SACs) for the nitrogen reduction reaction (NRR) to ammonia production has garnered significant attention in the scientific community. However, achieving high activity and selectivity remains challenging due to the lack of innate activity in most existing catalysts or insufficient active site density. This study delves into the potential of M2C12 materials (M = Cr, Ir, Mn, Mo, Os, Re, Rh, Ru, W, Fe, Cu, and Ti) with high transition metal coverage as SACs for NRR using first-principles calculations. Among these materials, Os2C12 exhibited superior catalytic activity for NRR, with a low overpotential of 0.39 V and an Os coverage of up to 72.53 wt%. To further boost its catalytic activity, a nonmetal (NM) atom doping (NM = B, N, O, and S) and C vacancy modification were explored in Os2C12. It is found that the introduction of O enables exceptional catalytic activity, selectivity, and stability, with an even lower overpotential of 0.07 V. Incorporating the O atom disrupted the charge balance of its coordinating C atoms, effectively increasing the positive charge density of the Os-d-orbit-related electronic structure. This promoted strong d-π* coupling between Os and N2H, enhancing N2H adsorption and facilitating NRR processes. This comprehensive study provides valuable insights into NRR catalyst design for sustainable ammonia production and offers a reference for exploring alternative materials in other catalytic reactions.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at -10 mA cm-2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

Improved high-current-density hydrogen evolution reaction kinetics on single-atom Co embedded in an order pore-structured nitrogen assembly carbon support

Single-atom catalysis is a subcategory of heterogeneous catalysis with well-defined active sites. Numerous endeavors have been devoted to developing single-atom catalysts for industrially applicable catalysis, including the hydrogen evolution reaction (HER). High-current-density electrolyzers have been pursued for single-atom catalysts to increase active-site density and enhance mass transfer. Here, we reasoned that a single-atom metal embedded in nitrogen assembly carbon (NAC) catalysts with high single-atom density, large surface area, and ordered mesoporosity, could fulfil an industrially applicable HER. Among several different single-atom catalysts, the HER overpotential with the best performing Co-NAC reached a current density of 200 mA cm-2 at 310 mV, which is relevant to industrially applicable current density. Density functional theory (DFT) calculations suggested feasible hydrogen binding on single-atom Co resulted in the promising HER activity over Co-NAC. The best-performing Co-NAC showed robust performance under alkaline conditions at a current density of 50 mA cm-2 for 20 h in an H-cell and at a current density of 150 mA cm-2 for 100 h in a flow cell.

Single and dual-atom catalysts towards electrosynthesis of ammonia and urea: a review

Ammonia and urea represent two important chemicals that have contributed to the rapid development of humanity. However, their industrial production requires harsh conditions, consuming excessive energy and resulting in significant greenhouse gas emission. Therefore, there is growing interest in the electrocatalytic synthesis of ammonia and urea as it can be carried out under ambient conditions. Recently, atomic catalysts (ACs) have gained increased attention for their superior catalytic properties, being able to outperform their micro and nano counterparts. This review examines the advantages and disadvantages of ACs and summarises the advancement of ACs in the electrocatalytic synthesis of ammonia and urea. The focus is on two types of AC - single-atom catalysts (SACs) and diatom catalysts (DACs). SACs offer various advantages, including the 100% atom utilization that allows for low material mass loading, suppression of competitive reactions such as hydrogen evolution reaction (HER), and alternative reaction pathways allowing for efficient synthesis of ammonia and urea. DACs inherit these advantages, possessing further benefits of synergistic effects between the two catalytic centers at close proximity, particularly matching the NN bond for N2 reduction and boosting C-N coupling for urea synthesis. DACs also possess the ability to break the linear scaling relation of adsorption energy of reactants and intermediates, allowing for tuning of intermediate adsorption energies. Finally, possible future research directions using ACs are proposed.

Single Atom Catalysts Based on Earth-Abundant Metals for Energy-Related Applications

Anthropogenic activities related to population growth, economic development, technological advances, and changes in lifestyle and climate patterns result in a continuous increase in energy consumption. At the same time, the rare metal elements frequently deployed as catalysts in energy related processes are not only costly in view of their low natural abundance, but their availability is often further limited due to geopolitical reasons. Thus, electrochemical energy storage and conversion with earth-abundant metals, mainly in the form of single-atom catalysts (SACs), are highly relevant and timely technologies. In this review the application of earth-abundant SACs in electrochemical energy storage and electrocatalytic conversion of chemicals to fuels or products with high energy content is discussed. The oxygen reduction reaction is also appraised, which is primarily harnessed in fuel cell technologies and metal-air batteries. The coordination, active sites, and mechanistic aspects of transition metal SACs are analyzed for two-electron and four-electron reaction pathways. Further, the electrochemical water splitting with SACs toward green hydrogen fuel is discussed in terms of not only hydrogen evolution reaction but also oxygen evolution reaction. Similarly, the production of ammonia as a clean fuel via electrocatalytic nitrogen reduction reaction is portrayed, highlighting the potential of earth-abundant single metal species.

Synthesis of Hexabenzocoronene-Cored Graphdiyne Nanosheets through Dehydrogenative Coupling on Au(111) Surface

Thermally-induced dehydrogenative coupling of polyphenylenes on metal surfaces is an important technique to synthesize π ${\pi }$ -conjugated carbon nanostructures with atomic precision. However, this protocol has rarely been utilized to fabricate structurally defined carbon nanosheets composed of sp- and sp2-hybridized carbon atoms. Here, we present the synthesis of butadiyne-linked hexabenzocoronenes (HBCs) on Au(111) surfaces as core-expanded graphdiynes. The reaction started from hexa(4-ethylphenyl)benzene, which undergoes dehydrogenation toward hexa(4-vinylphenyl)benzene, followed by planarization to hexabenzocoronene, coupling between the vinyl groups, and further dehydrogenation. In addition to butadiyne linkages, benzene groups were also found as another type of linker. The reaction sequences were monitored by scanning tunneling microscopy and bond-resolved non-contact atomic force microscopy, which disclose the structures of intermediates and final products. In combination with density functional theory simulations, the key steps from ethyl substituents to butadiyne and benzene linkers were elucidated. This is a new on-surface synthesis of core-expanded graphdiynes with unprecedented electronic properties.

Graphdiyne as an emerging sensor platform: Principles, synthesis and application

BACKGROUND

Graphdiyne (GDY) is a kind of carbon material, which has highly delocalized π-conjugated system and feasible green synthesis. Nowadays, the use of GDY substrate as a sensing platform has become a new research hotspot and is rapidly developing. However, its application as a sensor is still relatively overlook compared to other fields.

AIM OF REVIEW

This study is for the purpose of making researchers have a complete comprehensive understanding of GDY and its associated sensing platforms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This study introduces the structure, unique characteristics, and synthesis progress of GDY material. Moreover, the article systematically summarizes the improvement of GDY-based sensors in life, health and environmental detection. It also discusses the opportunities and challenges of designing high-performance GDY-based sensing platforms with the assistance of machine learning and theoretical calculate. It has essential scientific and practical meaning for accelerating the development of sensing platforms which base on GDY, triggering unknown phenomena and knowledge of material research, and initiating unlimited space for scientific innovation.

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Recent Advances on Two-Dimensional Nanomaterials Supported Single-Atom for Hydrogen Evolution Electrocatalysts

Water electrolysis has been recognized as a promising technology that can convert renewable energy into hydrogen for storage and utilization. The superior activity and low cost of catalysis are key factors in promoting the industrialization of water electrolysis. Single-atom catalysts (SACs) have attracted attention due to their ultra-high atomic utilization, clear structure, and highest hydrogen evolution reaction (HER) performance. In addition, the performance and stability of single-atom (SA) substrates are crucial, and various two-dimensional (2D) nanomaterial supports have become promising foundations for SA due to their unique exposed surfaces, diverse elemental compositions, and flexible electronic structures, to drive single atoms to reach performance limits. The SA supported by 2D nanomaterials exhibits various electronic interactions and synergistic effects, all of which need to be comprehensively summarized. This article aims to organize and discuss the progress of 2D nanomaterial single-atom supports in enhancing HER, including common and widely used synthesis methods, advanced characterization techniques, different types of 2D supports, and the correlation between structural hydrogen evolution performance. Finally, the latest understanding of 2D nanomaterial supports was proposed.

Performance of Nitrogen-Doped Carbon Nanoparticles Carrying FeNiCu as Bifunctional Electrocatalyst for Rechargeable Zinc-Air Battery

Catalysts for zinc-air batteries (ZABs) must be stable over long-term charging-discharging cycles and exhibit bifunctional catalytic activity. In this study, by doping nitrogen-doped carbon (NC) materials with three metal atoms (Fe, Ni, and Cu), a single-atom-distributed FeNiCu-NC bifunctional catalyst is prepared. The catalyst includes Fe(Ni-doped)-N4 for the oxygen evolution reaction (OER), Fe(Cu-doped)-N4 for the oxygen reduction reaction (ORR), and the NiCu-NC catalytic structure for the oxygen reduction reaction (ORR) in the nitrogen-doped carbon nanoparticles. This single-atom distribution catalyst structure enhances the bifunctional catalytic activity. If a trimetallic single-atom catalyst is designed, it will surpass the typical bimetallic single-atom catcalyst. FeNiCu-NC exhibits outstanding performance as an electrocatalyst, with a half-wave potential (E1/2) of 0.876 V versus RHE, overpotential (Ej = 10) of 253 mV versus RHE at 10 mA cm-2, and a small potential gap (ΔE = 0.61 V). As the anode in a ZAB, FeNiCu-NC can undergo continuous charge-discharged cycles for 575 h without significant attenuation. This study presents a new method for achieving high-performance, low-cost ZABs via trimetallic single-atom doping.

Sulfonic Acid-Functionalized Graphdiyne for Effective Li-S Battery Separators

Lithium-sulfur (Li-S) batteries enable a promising high-energy-storage system while facing practical challenges regarding lithium dendrites and lithium polysulfides (LiPSs) shuttling. Herein, a fascinating SO3H-functionalized graphdiyne (SOGDY) was developed by grafting SO3H onto GDY to modify the separator in Li-S batteries. It realizes structure-retained material transformation, that is, SOGDY retains the crystalline all-carbon network and uniform subnanopores from the initial GDY. The abundant SO3H and uniform pores create a rapid Li+ transport relay station, benefit rapid Li+ transport and even lithium deposition, and prevent lithium dendrite growth. The spatial obstruction and strong polar adsorption sites from SO3H effectively inhibit LiPS shuttling. Additionally, SOGDY establishes a fast electron-transfer pathway to facilitate the LiPS conversion. The SOGDY/PP separator exhibited steady cycling at 1 mA cm-2 over 3500 h in the Li∥Li symmetric battery and achieved outstanding low-temperature and high-rate performance in the Li-S battery with a high initial specific capacity of 804.5 mA h g-1 and a final capacity of 504.9 mA h g-1 after 500 cycles at 3 C and -10 °C. This work demonstrates that introducing a stable all-carbon network and uniform functionalized nanopores is an effective strategy to modify the Li-S battery separator.

Growing highly ordered Pt and Mn bimetallic single atomic layers over graphdiyne

Controlling the precise growth of atoms is necessary to achieve manipulation of atomic composition and atomic position, regulation of electronic structure, and an understanding of reactions at the atomic level. Herein, we report a facile method for ordered anchoring of zero-valent platinum and manganese atoms with single-atom thickness on graphdiyne under mild conditions. Due to strong and incomplete charge transfer between graphdiyne and metal atoms, the formation of metal clusters and nanoparticles can be inhibited. The size, composition and structure of the bimetallic nanoplates are precisely controlled by the natural structure-limiting effect of graphdiyne. Experimental characterization clearly demonstrates such a fine control process. Electrochemical measurements show that the active site of platinum-manganese interface on graphdiyne guarantees the high catalytic activity and selectivity (~100%) for alkene-to-diol conversion. This work lays a solid foundation for obtaining high-performance nanomaterials by the atomic engineering of active site.

Confined Growth of Highly Ordered Metal Atomic Arrays for Seawater Oxidation

Metal atom catalysts have been among the most important research objects due to their specific physical and chemical properties. However, precise control of the anchoring of metal atoms is still challenging to achieve. Cobalt and iridium atomic arrays formed sequentially ordered stable arrays in graphdiyne (GDY) triangular cavities depending on their intrinsic chemical properties and interactions. The success of this method was attributed to multifunctional integration of GDY, enabling selective growth from one to several atoms and various atomic densities. The bimetallic atom arrays show several advantages resulting from reducibility of acetylene bonds, space limiting effect, incomplete charge transfer between GDY and metal atoms, and sp-C hybridized triple bond skeleton. This well-designed system exhibits unprecedented oxygen evolution reaction (OER) performance with a mass activity of 2.6 A mgcat. -1 at a low overpotential of 300 mV, which is 216.6 times higher than the state-of-the-art IrO2 catalyst, and long-term stability.

Ozone decomposition on transition-metal-atom anchored graphdiyne: Insights from computation and experiment

Transition-metal-atom anchored graphdiynes (TM@GDY, TM = Mn, Fe, Co, Ni and Cu) have already been synthesized and found applications in hydrogen evolution, nitrogen fixation and etc. By means of first-principle predictions and test experiments, we propose here that Fe@GDY and Co@GDY are efficient catalysts for the sustainable conversion of O3 to O2. These two catalysts can spontaneously chemisorb O3 with zero reaction barrier and have low O3 conversion barriers (0.31 eV and 0.19 eV, respectively). The O3 decomposition experiment in a continuous flow membrane reactor and electron paramagnetic resonance results verify that Fe@GDY and Co@GDY are efficient catalysts under humid conditions. Raman spectra prove the formation of the key Fe-O/Co-O and FeOO and CoOO intermediates. The hydrophobic nature of graphdiyne and the strongest chemisorption of O3 among tested ambient gases, make Fe@GDY and Co@GDY ideal catalysts under both dry and humid conditions. These findings would stimulate future explorations on metal anchored GDY-based catalysts for applications of toxic gas decomposition or fixation.

Direct conversion of CO2 to CH4 on Pd/graphdiyne single-crystalline

A major impediment to the development of the efficient use of artificial photosynthesis is the lack of highly selective and efficient photocatalysts toward the conversion of CO2 by sunlight energy at room temperature and ambient pressure. After many years of hard work, we finally completed the synthesis of graphdiyne-based palladium quantum dot catalysts containing high-density metal atom steps for selective artificial photosynthesis. The well-designed interface structure of the catalyst is composed of electron-donor and acceptor groups, resulting in the obvious incomplete charge-transfer phenomenon between graphdiyne and plasmonic metal nanostructures on the interface. These intrinsic characteristics are the origin of the high performance of the catalyst. Studies on its mechanism reveal that the synergism between 'hot electron' from local surface plasmon resonance and rapid photogenerated carrier separation at the ohmic contact interface accelerates the multi-electron reaction kinetics. The catalyst can selectively synthesize CH4 directly from CO2 and H2O with selectivity of near 100% at room temperature and pressure, and exhibits transformative performance, with an average CH4 yield of 26.2 μmol g-1 h-1 and remarkable long-term stability.

Two-Dimensional MXene-Based Electrocatalysts: Challenges and Opportunities

MXene, regarded as cutting-edge two-dimensional (2D) materials, have been widely explored in various applications due to their remarkable flexibility, high specific surface area, good mechanical strength, and interesting electrical conductivity. Recently, 2D MXene has served as a ideal platform for the design and development of electrocatalysts with high activity, selectivity, and stability. This review article provides a detailed description of the structural engineering of MXene-based electrocatalysts and summarizes the uses of 2D MXene in hydrogen evolution reactions, nitrogen reduction reactions, oxygen evolution reactions, oxygen reduction reactions, and methanol/ethanol oxidation. Then, key issues and prospects for 2D MXene as a next-generation platform in fundamental research and real-world electrocatalysis applications are discussed. Emphasis will be given to material design and enhancement techniques. Finally, future research directions are suggested to improve the efficiency of MXene-based electrocatalysts.

The Surface/Interface Modulation of Platinum Group Metal (PGM)-Free Catalysts for VOCs and CO Catalytic Oxidation

Effective management of volatile organic compounds (VOCs) and carbon monoxide (CO) is critical to human health and the ecological environment. Catalytic oxidation is one of the most promising technologies for achieving efficient VOCs and CO emission control. Platinum group metal (PGM)-free catalysts are recently receiving sustainable attention in catalyzing VOCs and CO removal due to their low cost, superior catalytic activity, and excellent stability, but PGM-free catalysts face challenges in low-temperature catalytic efficiency. In this mini-review, starting with discussing the catalytic mechanism of VOCs and CO oxidation, we summarize the surface/interface modulation strategies of PGM-free catalysts to promote oxygen and VOCs/CO molecule activation for enhanced low-temperature oxidation activity, including oxygen vacancy engineering, heteroatom doping, surface acidity modification, and active interface construction. We highlight the currently remaining challenges and prospects of advanced PGM-free catalyst development for highly efficient VOCs and CO emission control in practical applications.

Bridging Nickel-MOF and Copper Single Atoms/Clusters with H-Substituted Graphdiyne for the Tandem Catalysis of Nitrate to Ammonia

Interfacial engineering of synergistic catalysts is one of the keys to achieving multiple proton-coupled electron transfer processes in nitrate-to-ammonia conversion. Herein, by joining ultrathin nickel-based metal-organic framework (denoted Ni-MOF) nanosheets with few-layered hydrogen-substituted graphdiyne-supported copper single atoms and clusters (denoted HsGDY@Cu), a tandem catalyst of Ni-MOFs@HsGDY@Cu with dual-active interfaces was developed for the concerted catalysis of nitrate-to-ammonia. In such a system, the sandwiched HsGDY layer could serve as a bridge to connect the coordinated unsaturated Ni2+ sites with Cu single atoms/clusters in a limited range of 0 to 3.6 nm. From Ni2+ to Cu, via the hydrogen spillover process, the hydrogen radicals (H⋅) generated at the unsaturated Ni2+ sites could migrate across HsGDY to the Cu sites to participate in the transformation of *HNO3 to NH3. From Cu to Ni2+, bypassing the higher reaction energy for *HNO3 formation on the Ni2+ sites, the NO2 - detached from the Cu sites could diffuse onto the unsaturated Ni2+ sites to form NH3 as well. The combined results make this hybrid a tandem catalyst with dual active sites for the catalysis of nitrate-to-ammonia conversion with improved Faradaic efficiency at lower overpotentials.

Island-Like Heterogeneous Interface Generating Tandem Toroidal Built-In Electric Field for Efficient Potassium Ions Diffusion

For large-size potassium accommodation, heterostructure usually suffers severe delamination and exfoliation at the interfaces due to different volume expansion of two-phase during charge/discharge process, resulting in the deconstruction of heterostructures and shortened lifespan of batteries. Here, an innovative strategy is proposed through constructing a microscopic heterostructure system containing copper quantum dots (Cu QDs) highly dispersed in the triphenyl-substituted triazine graphdiyne (TPTG) substrates (TPTG@CuQDs) to solve this problem. The copper quantum dots are uniformly anchored on TPTG substrates, generating a myriad of island-like heterogeneous structures, together with tandem toroidal built-in electric field (BIEF) between every micro heterointerface. The island-like heterostructure endows both benefits of exposed contact interface and robust architecture. Generated tandem toroidal BIEF provides efficient transport pathways with lower energy barriers, reducing the diffusion resistance and facilitating the reaction kinetics of potassium ions. When used as anode, the TPTG@CuQDs exhibit highly reversible capacity and low-capacity degradation (≈0.01% over 5560 cycles at 1 A g-1). Moreover, the TPTG@CuQDs-based full cell delivers an outstanding reversible capacity of ≈110 mAh g-1 over 800 cycles at 1 A g-1. This quantum-scale heterointerface construction strategy offers a new approach toward stable heterostructure design for the application of metal ion batteries.

Mesoporous Electrocatalysts with p-n Heterojunctions for Efficient Electroreduction of CO2 and N2 to Urea

The electrocatalytic synthesis of high-value-added urea by activating N2 and CO2 is a green synthesis technology that has achieved carbon neutrality. However, the chemical adsorption and C-N coupling ability of N2 and CO2 on the surface of the catalyst are generally poor, greatly limiting the improvement of electrocatalytic activity and selectivity in electrocatalytic urea synthesis. Herein, novel hierarchical mesoporous CeO2/Co3O4 heterostructures are fabricated, and at an ultralow applied voltage of -0.2 V, the urea yield rate reaches 5.81 mmol g-1 h-1, with a corresponding Faraday efficiency of 30.05%. The hierarchical mesoporous material effectively reduces the mass transfer resistance of reactants and intermediates, making it easier for them to access active centers. The emerging space-charge regions at the heterointerface generate local electrophilic and nucleophilic regions, facilitating CO2 targeted adsorption in the electrophilic region and activation to produce *CO intermediates and N2 targeted adsorption in the nucleophilic region and activation to generate *N ═ N* intermediates. Then, the electrons in the σ orbitals of *N ═ N* intermediates can be easily accepted by the empty eg orbitals of Co3+ in CeO2/Co3O4, which presents a low-spin state (LS: t2g6eg0). Subsequently, *CO couples with *N ═ N* to produce the key intermediate *NCON*. Interestingly, it was discovered through in situ Raman spectroscopy that the CeO2/Co3O4 catalyst has a reversible spinel structure before and after the electrocatalytic reaction, which is due to the surface reconstruction of the catalyst during the electrocatalytic reaction process, producing amorphous active cobalt oxides, which is beneficial for improving electrocatalytic activity.

Theoretical Prediction Leads to Synthesize GDY Supported InOx Quantum Dots for CO2 Reduction

The preparation of formic acid by direct reduction of carbon dioxide is an important basis for the future chemical industry and is of great significance. Due to the serious shortage of highly active and selective electrocatalysts leading to the development of direct reduction of carbon dioxide is limited. Herein the target catalysts with high CO2RR activity and selectivity were identified by integrating DFT calculations and high-throughput screening and by using graphdiyne (GDY) supported metal oxides quantum dots (QDs) as the ideal model. It is theoretically predicted that GDY supported indium oxide QDs (i.e., InOx/GDY) is a new heterostructure electrocatalyst candidate with optimal CO2RR performance. The interfacial electronic strong interactions effectively regulate the surface charge distribution of QDs and affect the adsorption/desorption behavior of HCOO* intermediate during CO2RR to achieve highly efficient CO2 conversion. Based on the predicted composition and structure, we synthesized the advanced catalytic system, and demonstrates superior CO2-to-HCOOH conversion performance. The study presents an effective strategy for rational design of highly efficient heterostructure electrocatalysts to promote green chemical production.

Properties, Synthesis and Emerging Applications of Graphdiyne: A Journey Through Recent Advancements

Graphdiyne (GDY) is a new variant of nano-carbon material with excellent chemical, physical and electronic properties. It has attracted wide attention from researchers and industrialists for its extensive role in the fields of optics, electronics, bio-medics and energy. The unique arrangement of sp-sp2 carbon atoms, linear acetylenic linkages, uniform pores and highly conjugated structure offer numerous potentials for further exploration of GDY materials. However, since the material is at its infancy, not much understanding is available regarding its properties, growth mechanism and future applications. Therefore, in this review, readers are guided through a brief discussion on GDY's properties, different synthesis procedures with a special focus on surface functionalization and a list of applications for GDY. The review also critically analyses the advantages and disadvantages of each synthesis route and emphasizes the future scope of the material.

Elevated temperature-driven coordinative reconstruction of an unsaturated single-Ni-atom structure with low valency on a polymer-derived matrix for the electrolytic oxygen evolution reaction

A high-temperature pyrolysis-controlled coordination reconstruction resulted in a single-Ni-atom structure with a Ni-Nx-C structural unit (x = N atom coordinated to Ni). Pyrolysis of Ni-phen@ZIF-8-RF at 700 °C resulted in NiNP-NC-700 with predominantly Ni nanoparticles. Upon elevating the pyrolysis temperature from 700 to 900 °C, a coordination reconstruction offers Ni-Nx atomic sites in NiSA-NC-900. A combined investigation with X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and soft X-ray L3-edge spectroscopy suggests the stabilization of low-valent Niδ+ (0 < δ < 2) in the Ni-N-C structural units. The oxygen evolution reaction (OER) is a key process during water splitting in fuel cells. However, OER is a thermodynamically uphill reaction with multi-step proton-coupled electron transfer and sluggish kinetics, due to which there is a need for a catalyst that can lower the OER overpotentials. The adsorption energy of a multi-step reaction on a single metal atom with coordination unsaturation tunes the adsorption of each oxygenated intermediate. The promising OER activity of the NiSA-NC-900/NF anode on nickel foam was followed by the overall water splitting (OWS) using using NiSA-NC-900/NF as anode and Pt coil as the cathodic counterpart, wherein a cell potential of 1.75 V at 10 mA cm-2 was achieved. The cell potential recorded with Pt(-)/(+)NiSA-NC-900/NF was much lower than that obtained for other cells, i.e., Pt(-)/NF and NF(-)/(+)NF, which enhances the potentials of low-valent NiSAs for insightful understanding of the OER. At a constant applied potential of 1.61 V (vs. RHE) for 12 h, an small increase in current for initial 0.6 h followed by a constant current depicts the fair stability of catalyst for 12 h. Our results offer an insightful angle into the OER with a coordinatively reconstructed single-Ni-atom structure at lower valency (<+2).

Self-Organized Gradually Single-Atom-Layer of Metal Osmium for an Unprecedented Hydrogen Production from Seawater

Atomic thick two-dimensional (2D) materials with exciting physical, chemical, and electronic properties are gaining increasing attention in next-generation science and technology, showing great promise in catalysis and energy science. However, the precise design and synthesis of efficient catalytic systems based on such materials still face many difficulties, especially in how to control the preparation of structurally determined, highly active, atomic-scale distribution of material systems. Here, we report that a highly active zerovalent osmium single-atom-layer with a thickness of single atom size has been successfully and controllably self-organized on the surface of 2D graphdiyne (GDY) material. Detailed characterizations showed that the incomplete charge transfer effect between the Os atoms and GDY not only stabilized the catalytic system but also improved the intrinsic activity, making the Gibbs free energy reach the best and resulting in remarkable performance with a small overpotential of 49 mV at 500 mA cm-2, large specific j0 of 18.6 mA cm-2, and turnover frequency of 3.89 H2 s-1 at 50 mV. In addition, the formation of sp-C-Os bonds guarantees the high long-term stability of 800 h at a large current density of 500 mA cm-2 in alkaline simulated seawater.

Is Fe the Most Active Site for Fe/N-Doped Graphdiyne?

We performed a systematic study on the activity of pristine, Fe-doped, N-doped, and Fe/N-codoped graphdiyne (GDY) for oxygen reduction reactions (ORRs). We found that the pristine GDY has a high overpotential because of the weak binding of the intermediates. The sp-hybridized N-doped GDY enhances the binding of the intermediates at the adjacent sp-hybridized C site, which greatly enhances its ORR activities with a low overpotential of 0.45 V. On the other hand, on Fe-doped GDY, the binding of the intermediates at the Fe site and its neighboring C sites becomes too strong, while the C site at the second nearest acetylene chain becomes the most active site with an overpotential of 0.43 V. In the case of Fe and N codoping, Fe and the C sites near Fe and N still bind the intermediates too strongly, and the most active site is located at the C with an optimal distance. The binding energy of OH* is an activity descriptor for Fe- and/or N-doped GDY. Based on the machine learning analysis of ΔG(OH*), both the properties of the active center (electronic and geometric properties) and its environment, especially the latter, play important roles in determining its activity. The scaling relation analysis and volcano plot suggest that Fe and N doping enhance the binding of the intermediates to different extents, and the C atom, which is bonded neither to N nor to Fe atom, with an optimal binding strength, becomes the most active site.

Exploring the synergistic effect of palladium nanoparticles and highly dispersed transition metals on carbon nitride/super-activated carbon composites for boosting electrocatalytic activity

In the present work, multifunctional electrocatalysts formed by palladium nanoparticles (Pd NPs) loaded on Fe or Cu-containing composite supports, based on carbon nitride (C3N4) and super-activated carbon with a high porosity development (SBET 3180 m2/g, VDR 1.57 cm3/g, and VT 1.65 cm3/g), were synthesised. The presence of Fe or Cu sites favoured the formation of Pd NPs with small average particle size and a very narrow size distribution, which agreed with Density Functional Theory (DFT) calculations showing that the interaction of Pd clusters with C3N4 flakes is weaker than with Cu- or Fe-C3N4 sites. The electroactivity was also dependent on the composition and, as suggested by preliminary DFT calculations, the Pd-Cu catalyst showed lower overpotential for hydrogen evolution reaction (HER) while bifunctional oxygen reduction reaction/ oxygen evolution reaction (ORR/OER) behaviour was superior in Pd-Fe sample. The Pd-Fe electrocatalyst was studied in a zinc-air battery (ZAB) for 10 h, showing a performance similar to a commercial Pt/C + RuO2 catalyst with a high content of precious metal. This study demonstrates the synergistic effect between Pd species and transition metals and shows that transition metals anchored on C3N4-based composite materials promote the electroactivity of Pd NPs in HER, ORR and OER due to the interaction between both species.

Surface atom knockout for the active site exposure of alloy catalyst

The fine regulation of catalysts by the atomic-level removal of inactive atoms can promote the active site exposure for performance enhancement, whereas suffering from the difficulty in controllably removing atoms using current micro/nano-scale material fabrication technologies. Here, we developed a surface atom knockout method to promote the active site exposure in an alloy catalyst. Taking Cu3Pd alloy as an example, it refers to assemble a battery using Cu3Pd and Zn as cathode and anode, the charge process of which proceeds at about 1.1 V, equal to the theoretical potential difference between Cu2+/Cu and Zn2+/Zn, suggesting the electricity-driven dissolution of Cu atoms. The precise knockout of Cu atoms is confirmed by the linear relationship between the amount of the removed Cu atoms and the battery cumulative specific capacity, which is attributed to the inherent atom-electron-capacity correspondence. We observed the surface atom knockout process at different stages and studied the evolution of the chemical environment. The alloy catalyst achieves a higher current density for oxygen reduction reaction compared to the original alloy and Pt/C. This work provides an atomic fabrication method for material synthesis and regulation toward the wide applications in catalysis, energy, and others.

Graphdiyne/metal oxide hybrid materials for efficient energy and environmental catalysis

Graphdiyne (GDY)-based materials, owing to their unique structure and tunable electronic properties, exhibit great potential in the fields of catalysis, energy, environmental science, and beyond. In particular, GDY/metal oxide hybrid materials (GDY/MOs) have attracted extensive attention in energy and environmental catalysis. The interaction between GDY and metal oxides can increase the number of intrinsic active sites, facilitate charge transfer, and regulate the adsorption and desorption of intermediate species. In this review, we summarize the structure, synthesis, advanced characterization, small molecule activation mechanism and applications of GDY/MOs in energy conversion and environmental remediation. The intrinsic structure-activity relationship and corresponding reaction mechanism are highlighted. In particular, the activation mechanisms of reactant molecules (H2O, O2, N2, etc.) on GDY/MOs are systemically discussed. Finally, we outline some new perspectives of opportunities and challenges in developing GDY/MOs for efficient energy and environmental catalysis.

Direct solar energy conversion on zinc-air battery

A concept of solar energy convertible zinc-air battery (SZAB) is demonstrated through rational design of an electrode coupled with multifunction. The multifunctional electrode is fabricated using nitrogen-substituted graphdiyne (N-GDY) with large π-conjugated carbonous network, which can work as photoresponsive bifunctional electrocatalyst, enabling a sunlight-promoted process through efficient injection of photoelectrons into the conduction band of N-GDY. SZAB enables direct conversion and storage of solar energy during the charging process. Such a battery exhibits a lowered charge voltage under illumination, corresponding to a high energy efficiency of 90.4% and electric energy saving of 30.3%. The battery can display a power conversion efficiency as high as 1.02%. Density functional theory calculations reveal that the photopromoted oxygen evolution reaction kinetics originates from the transition from the alkyne bonds to double bonds caused by the transfer of excited electrons, which changes the position of highest occupied molecular orbital and lowest unoccupied molecular orbital, thus greatly promoting the formation of intermediates to the conversion process. Our findings provide conceptual and experimental confirmation that batteries are charged directly from solar energy without the external solar cells, providing a way to manufacture future energy devices.

Surface Engineered Single-atom Systems for Energy Conversion

Single-atom catalysts (SACs) are demonstrated to show exceptional reactivity and selectivity in catalytic reactions by effectively utilizing metal species, making them a favorable choice among the different active materials for energy conversion. However, SACs are still in the early stages of energy conversion, and problems like agglomeration and low energy conversion efficiency are hampering their practical applications. Substantial research focus on support modifications, which are vital for SAC reactivity and stability due to the intimate relationship between metal atoms and support. In this review, a category of supports and a variety of surface engineering strategies employed in SA systems are summarized, including surface site engineering (heteroatom doping, vacancy introducing, surface groups grafting, and coordination tunning) and surface structure engineering (size/morphology control, cocatalyst deposition, facet engineering, and crystallinity control). Also, the merits of support surface engineering in single-atom systems are systematically introduced. Highlights are the comprehensive summary and discussions on the utilization of surface-engineered SACs in diversified energy conversion applications including photocatalysis, electrocatalysis, thermocatalysis, and energy conversion devices. At the end of this review, the potential and obstacles of using surface-engineered SACs in the field of energy conversion are discussed. This review aims to guide the rational design and manipulation of SACs for target-specific applications by capitalizing on the characteristic benefits of support surface engineering.

Microcrystalline Nanofiber Electrode with Adaptive Intrinsic Structure and Microscopic Interface

A strategy of microcrystalline aggregation is proposed to fabricate energy storage electrode with outstanding capacity and stability. Carbon-rich electrode (BDTG) functionalized with benzo[1,2-b:4,5-b']dithiophene units and butadiyne segments are prepared. The linear conjugate chains pack as microcrystalline nanofibers on nanoscale, which further aggregates to form a porous interpenetrating network. The microcrystalline aggregation feature of BDTG exhibit stable structure during long cycling test, revealing the following advantage in structure and property. The stretchable butadiyne linker facilitates reversible adsorption and desorption of Li with the aid of adjacent sulfur heteroatom. The alkyne-alkene transition exhibits intrinsic structural stability of microcrystalline region in BDTG electrodes. Meanwhile, alkynyl groups and sulfur heteroatoms on the surface of BDTG nanofibers participate in the formation of microscopic interface, providing a stable interfacial contact between BDTG electrodes and adjacent electrolyte. As a proof-of-concept, BDTG-based electrode shows high capacity (1430 mAh g-1 at 50 mA g-1) and excellent cycle performance (8000 cycles under 5 A g-1) in half-cell of lithium-ion batteries, and a reversible capacity of 120 mAh g-1 is obtained under the current density of 2 C in full-cell. This work shows microcrystalline aggregation is beneficial to realize adaptive intrinsic structure and interface contact during the charge-discharge process.

Fabrication of Zn-Air Battery with High Output Capacity Under Ultra-Large Current

Zn-air battery (ZAB) is advocated as a more viable option in the new-energy technology. However, the limited-output capacity at a high current density impedes the driving range in power batteries substantially. Here, a novel heterojunction-based graphdiyne (GDY) and Ag29Cu7 alloy quantum dots (Ag29Cu7 QDs/GDY) for constructing a high-performance aqueous ZAB are fabricated. The as-fabricated ZAB achieves discharge at up to 100 mA cm-2 (the highest value ever reported) along with a remarkable output specific capacity of 786.2 mAh g-1 Zn, which is mainly benefitted from the binary-synergistic effect toward a stable triple-phase interface for air electrode induced by the Ag29Cu7 QDs and GDY in harsh base, together with the decreasing reaction energy barrier and polarization. The results outperform the superior reports discharging at low current and will bring breakthrough progress toward the practical applications of ZAB on large power supply facilities.

Construction of n-type homogeneous to improve interfacial carrier transfer for enhanced photoelectrocatalytic hydrolysis

Photoelectrocatalyzed hydrogen production plays an important role in the path to carbon neutrality. The construction of heterojunctions provides an ideal example of an oxygen precipitation reaction. In this work, the performance of the n-n type heterojunction CeBTC@FeBTC/NIF in the photoelectronically coupled catalytic oxygen evolution reaction (OER) reaction is presented. The efficient transfer of carriers between components enhances the catalytic activity. Besides, the construction of heterojunctions optimizes the energy level structure and increases the absorption of light, and the microstructure forms holes with a blackbody effect that also enhances light absorption. Consequently, CeBTC@FeBTC/NIF has excellent photoelectric coupling catalytic properties and requires an overpotential of only 300 mV to drive a current density of 100 mA cm-2 under illumination. More importantly, the n-n heterojunction was found to be effective in enhancing charge and photogenerated electron migration by examining the carrier density of each component and carrier diffusion at the interface.