Including Hydrogen Evolution Reaction Research Articles

Recent progress in the synthesis and electrocatalytic application of MXene‐based metal phosphide composites

AbstractIn the domain of novel catalyst design and application, metal phosphides have attracted widespread interest due to their unique electronic structure and potential catalytic activity. Various types of supports that can effectively anchor metal phosphides have been reported, among which MXene have received significant attention due to their two‐dimensional (2D) structure, adjustable composition, and composite variability. This work mainly aims to elucidate the preparation of novel MXene carriers and their unique roles in loading metal phosphides and participating in catalytic reactions. We will clarify the preparation strategy of MXene, the interaction between metal phosphides and MXene carriers, to explain the stabilization of metal phosphide active sites and the rational adjustment of electronic structure. In addition, we will comprehensively summarize recent research progress of MXene‐based metal phosphide composites, with particular emphasis on advancements in the synergistic effect of heterostructures. Regarding applications, we review the utilization of MXene‐based metal phosphide composites in electrocatalysis, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). Finally, some fundamental challenges and prospects for the efficient electrocatalysis of MXene‐based metal phosphide composites are introduced.

Inorganic-organic hybrid heterogeneous membrane for zinc protective layers in high-performance aqueous zinc ion batteries

Aqueous zinc-ion Batteries (AZIBs) suffer from stability and performance limitations due to challenges related to the zinc (Zn) metal anode, including hydrogen evolution reaction (HER), metal corrosion, and Zn dendrite formation. To mitigate these issues, researchers are developing innovative coatings and protective layers for Zn anodes, focusing on enhancing ion conductivity, electrochemical inertness, mechanical strength, and processability. Hybrid organic-inorganic heterostructure coating materials with silver nanowires (Ag NWs) encapsulated with Polypyrrole (Ag/PPy) have shown promise in addressing these challenges. The Zn anode coated with Ag/PPy layers and paired with an α-MnO2 cathode, achieved an impressive initial capacity of 302 mAh/g at a current density of 0.5 A/g. Remarkably, it retained a substantial capacity of 283 mAh/g after 300 cycles at a current density of 0.5 A/g, demonstrating a 94 % capacity retention rate. Moreover, the symmetry cell using this anode maintains stable Zn deposition/stripping overpotentials even at a high current density (a rate of 10C) for over 175 h. These findings highlight the potential of Ag/PPy coatings as a viable approach for enhancing the surface chemistry and physical properties of the Zn metal anode, paving the way for a wider use of AZIBs.

Sulfur-Phosphorus Doped Metal Composites As Superior Catalyst for Electrolytic Hydrogen Production in Real Seawater

In the face of the increasingly severe global energy crisis and challenges posed by climate change, promoting energy transition has become an international consensus. Among various renewable energy sources, hydrogen is considered an ideal energy carrier due to its clean and efficient characteristics. The electrolysis of seawater for hydrogen production has garnered widespread attention for its ability to fully utilize abundant seawater resources and the advantage of zero carbon dioxide emissions. However, achieving efficient, stable, and economically viable hydrogen production in seawater still faces many challenges, with catalyst design and optimization being recognized as key issues.Firstly, NiFe-LDH was synthesized using a simple one-pot solvothermal method. Subsequently, phosphorization, sulfurization, and sulfur-phosphorus co-doping were conducted to obtain samples namely NiFe-P, NiFe-S and NiFe-SP, respectively. Various electrochemical tests, including hydrogen evolution reaction (HER), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly performed in simulated seawater to evaluate the electrochemical performance of the synthesized catalysts. The overall seawater splitting reaction was conducted with the same catalysts for both anode and cathode sides.After comparing the electrochemical activity of four different catalysts, it was found that NiFe-SP performs superior HER activity in alkaline simulated seawater. NiFe-SP required merely -0.143 V to deliver 100 mA cm-2 current density, which was 95 mV lower than NiFe-LDH to achieve the same current density. In EIS tests, NiFe-SP exhibited a smaller charge transfer resistance than NiFe-LDH, and NiFe-SP had the largest double-layer capacitance (Cdl) value in ECSA measurements, indicating that NiFe-SP possessed and lowest reaction resistance and the maximum electrochemically active surface area.X-ray Diffraction (XRD) and Raman spectroscopy analyses indicate that the catalyst, after sulfur-phosphorus doping, does not exhibit a pure-phase LDH structure but transforms into a heterogeneous structure of Ni3S2 and FeS2. Scanning Electron Microscopy (SEM) observations suggest that sulfur-phosphorus co-doping causes the original spherical structure of NiFe-LDH to aggregate, with the appearance of some lamellar structures on the surface. Energy Dispersive Spectroscopy (EDS) also confirms the successful doping of sulfur and phosphorus elements into NiFe-LDH, with uniform distribution on the material's surface.Finally, the catalyst underwent a 2000-hours continuous stability test at a constant current of 100 mA cm-² in real seawater. The results indicate that the potential of NiFe-SP increased by only 5%, demonstrating that the doping of sulfur and phosphorus not only reduces the catalytic overpotential but also significantly sustains potential retention. This suggests that the metal composite structure obtained after sulfur-phosphorus co-doping is well-formed and stable. The systematic electrochemical tests and stability evaluation in this study highlights the potential of sulfur-phosphorus co-doped metal composite NiFe-SP as an efficient and stable catalyst for real seawater electrolysis. This not only contributes to a deeper understanding of the fundamental principles governing catalyst behavior but also opens new possibilities for the practical application of hydrogen production technology. Figure 1

Well‐defined nanostructures of high entropy alloys for electrocatalysis

AbstractHigh‐entropy alloys (HEAs) have attracted significant attention for electrocatalytic energy conversion by virtue of their promisingly high efficiency, stability, and low cost. Recently, encouraging progress has been made in tuning the structure and composition of HEAs used in electrolyzers and fuel cells. However, the understanding on the synthetic methods and the structure‐property‐performance relationship of well‐defined HEAs nanostructures is still inadequate. To gain insight into the future research directions on HEAs for electrocatalysis, in this paper, the synthetic methods commonly used to obtain well‐defined HEAs nanostructures (0D nanoparticles, 1D nanowires, 2D nanosheets/nanoplates, 3D nanoporous structures, and other three‐dimensional morphologies) are first summarized. Then, the authors discuss the application of well‐defined HEAs nanostructures in several typical electrocatalytic reactions, including hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, alcohol oxidation reaction, carbon dioxide reduction reaction, nitrogen reduction reaction, and formic acid oxidation reaction. Finally, a practical perspective on the future research directions on well‐defined HEAs nanostructured electrocatalysts is provided.

Synergistic modulation of hydrogen bond network reconstruction and pH buffering of electrolyte enables highly reversible Zn anode

Utilizing aqueous electrolytes offers zinc-ion batteries (ZIBs) with inherent safety, high ionic conductivity, and power density, which is promising for energy storage applications. While the H2O-induced problems including hydrogen evolution reaction (HER) and the accumulation of by-products hinder the electrochemical performance of ZIBs. Herein, proline is used as an electrolyte additive to solve the above issues. Density functional theory (DFT) calculation and experimental results confirm that abundant hydrogen bonds (HBs) are formed between proline and H2O, disrupting the original HB network to inhibit HER kinetics. Meanwhile, as an amphoteric compound, proline neutralizes the OH− generated by HER, preventing it to react with Zn2+ and SO42− to form insulating by-products. Consequently, the Zn||Zn symmetric cell reaches the cycle life of 5500 h at 1.0 mA cm−2, 1.0 mAh cm−2, and 660 h at 10 mA cm−2, 5.0 mAh cm−2. When matching with the VO2 cathode, the Zn||VO2 cell achieves a capacity retention of 68.25 % at 5.0 A g−1 after 6694 cycles. This work provides a novel perspective integrating the regulation of the HB network and pH buffer chemistry to develop advanced aqueous electrolytes.

Research progress of amorphous catalysts in the field of electrocatalysis

Amorphous materials feature unique structures and physicochemical properties, resulting in their synthesis and applications becoming a dynamic and fascinating new research direction. The high specific surface area, abundant active sites, and good electron transport properties endow amorphous materials with excellent electrocatalytic properties, thus appealing to increasing attention. Based on this, the summary of the current research status of amorphous catalysts in the field of electrocatalysis is urgent and important. In this review, the research progress of amorphous catalysts in electrocatalysis is systematically introduced, focusing on the classification, synthesis methods, modification strategies, characterizations, and electrocatalytic application (including hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction). Finally, this review proposes the prospects and challenges for the future development of high-active and high-selectivity amorphous electrocatalysts.

Optimal Molecular Configuration of Electrolyte Additives Enabling Stabilization of Zinc Anodes

AbstractFor the development of electrolyte additives as an effective strategy to improve the performance of zinc‐ion batteries (ZIBs), most researchers focus on the functional groups but overlook the crucial molecular configuration. Herein, six stereoisomers of 2,3,4,5‐tetrahydroxyvaleraldehyde with identical groups but various spatial arrangements are studied as the electrolyte additive in ZIBs. Based on the experimental analysis and theoretical calculations, the adsorption with Zn (002) plane is found to be an important dominant for the stereoisomer to enhance the Zn anode performance. Among these stereoisomers, D‐Arabinose with preferential and strongest chemisorption effect modifies the anode/electrolyte interface most effectively, leading to the highest stability and reversibility of the Zn anode. The adsorbed D‐Arabinose shows multifunctional effects at the interface, which not only regulates the Zn2+ solvation structure and reconfigures the hydrogen bond framework, but also facilitates uniform Zn2+ deposition by promoting 3D Zn2+ diffusion and homogenizing the electric field. Therefore, with the D‐Arabinose additive in ZnSO4 electrolyte, the undesired Zn dendrite growth and side reactions including hydrogen evolution reaction, corrosion, and passivation are significantly limited during the Zn plating/stripping processes. This work proposes a new insight toward the optimal molecular configuration of additive designing for electrolyte engineering in stable ZIBs.

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.

Advances and challenges in MXene-based electrocatalysts: unlocking the potential for sustainable energy conversion.

MXenes, a novel class of two-dimensional materials, have garnered significant attention for their promising electrocatalytic properties in various energy conversion applications such as water splitting, fuel cells, metal-air batteries, and nitrogen reduction reactions. Their excellent electrical conductivity, high specific surface area, and versatile surface chemistry enable exceptional catalytic performance. This review highlights recent advancements in the design and application strategies of MXenes as electrocatalysts, focusing on key reactions including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and nitrogen reduction reaction (NRR). We discuss the tunability of MXenes' layered structures and surface properties through surface modification, MXene lattice substitution, defect and morphology engineering, and heterostructure construction. Despite the considerable progress, MXenes face challenges such as restacking during catalysis, stability issues, and difficulties in large-scale production. Addressing these challenges through innovative engineering approaches and advancing industrial synthesis techniques is crucial for the broader application of MXene-based materials. Our review underscores the potential of MXenes in transforming electrocatalytic processes and highlights future research directions to optimize their catalytic efficiency and stability.

Chiral Quantum Materials: When Chemistry Meets Physics.

Chirality is a fundamental property of nature with relevance in biochemistry and physics, particularly in the field of catalysis. Understanding the mechanisms underlying chirality transfer is crucial for advancing the knowledge of chiral-related catalysis. Chiral quantum materials with intriguing chirality-dependent electronic properties, such as spin-orbital coupling (SOC) and exotic spin/orbital angular momentum (SAM/OAM), open novel avenues for linking solid-state topologies with chiral catalysis. In this review, the growth of topological homochiral crystals (THCs) is described, and their applications in heterogeneous catalysis, including hydrogen evolution reaction (HER), oxygen electrocatalysis, and asymmetric catalysis are summarized. A possible link between chirality-dependent electronic properties and heterogeneous catalysis is discussed. Finally, existing challenges in this field are highlighted, and a brief outlook on the impact of THCs on the overarching chemical-physical research is presented.

Predictable Local Polarization inside Electrodes By Three-Dimensional Multi-Scale Model in Flow Batteries

Redox flow batteries (RFBs) are regarded as one of the most promising grid-scale energy storage technologies, which can improve the applicability of wind and solar energy by leveling their fluctuating power output. In RFBs, the gas side reactions including hydrogen evolution reaction and oxygen evolution reaction reduce the efficiency and capacity of the batteries and the gas produced may even cause safety problems. Even if the voltage is controlled in practical applications to restrict the gas side reactions, it is still inevitable due to flow dead zones or insufficient reactants locally inside the electrode. Gas side reactions are usually caused by too high local overpotential, i.e., local over polarization. Therefore, in this work, we propose a multi-scale model that allows the rapid prediction of local polarization to limit and manage the gas side reactions. The multi-scale model contains a deep neural network, a pore network model, and a three-dimensional continuum model with the advantages of both accuracy and extensibility. By learning from the sample data provided by the cell-scale model and the pore-scale model, the deep neural network can quickly predict the local polarization under different operating conditions and give the distribution map of the entire electrode. Compared with conventional models, multi-scale models can take into account the geometry of electrode fibers and are suitable for electrode design and modification. Due to the calculation superiority of the pore network model, the multi-scale model can realize three-dimensional local polarization prediction, which enables a more accurate analysis of the internal uniformity of the electrode. Through the developed model, we explore the effects of the interdigitated flow field, flow rate, initial concentration and voltage on local polarization. It is shown that the multi-scale model can accurately predict local polarization. However, the promotion of flow rate cannot completely eliminate the occurrence of local over polarization.

Acetamide-Caprolactam Deep Eutectic Solvent-Based Electrolyte for Stable Zn-Metal Batteries.

Aqueous Zn-ion batteries (AZIBs) are promising for grid-scale energy storage. However, conventional AZIBs face challenges including hydrogen evolution reaction (HER), leading to high local pH, and by-product formation on the anode. Hereby the hydrogen bonds in the aqueous electrolyte are reconstructed by using a deep eutectic co-solvent (DES) made of acetamide (H-bond donor) and caprolactam (H-bond acceptor), which effectively suppresses the reactivity of water and broadens the electrochemical voltage stability window. The coordination between Zn2+ and acetamide-caprolactam in DES-based electrolytes produces a unique solvation structure that promotes the preferential growth of Zn crystals along the (002) plane. This will inhibit the formation of Zn dendrites and ensure the uniform deposition of Zn-ions on the anode surface. In addition, it is found that this DES-based electrolyte can form a protective membrane on the anode surface, reducing the risks of Zn corrosion. Compared to conventional electrolytes, the DES-based electrolyte shows a long-term stable plating/stripping performance with a significantly improved Coulombic efficiency from 78.18% to 98.37%. It is further demonstrated that a Zn||VS2 full-cell with the DES-based electrolyte exhibits enhanced stability after 500 cycles with 85.4% capacity retention at 0.5Ag-1 .

Enabling Highly-Reversible Aqueous Zn-Ion Batteries via 4-Hydroxybenzoic Acid Sodium Salt Electrolyte Additive.

Due to the intrinsic safety and cost effectiveness, aqueous Zn-ion batteries (AZIBs) are considered a promising candidate for future energy storage systems. However, the widespread implementation of AZIBs faces significant obstacles due to various undesirable side reactions, including hydrogen evolution reaction (HER), corrosion, and uncontrolled dendrite growth at the anodes. Here, 4-hydroxybenzoic acid sodium salt (PHB) is employed in the ZnSO4 electrolyte to enable highly-reversible zinc anodes. PHB has a greater tendency to bind with the Zn surface, resulting in increased steric effects within the electrolyte. As a result, it hinders the direct interaction between anode and water while facilitating the uniform plating of Zn2+ . Zn/Zn batteries with PHB additives realized more than 1600 h stable cycling life under 1 mA cm-2 and 1 mAh cm-2 . Moreover, Zn/Cu batteries with PHB additives achieved a reversible plating/stripping process for over 500 cycles with high average CE of 98.6 %. In addition, the assembled Zn/NH4 V4 O10 batteries with PHB additive yielded 80.5 mAh g-1 after 1000 cycles at 10 A g-1 . The inexpensive and effective application of PHB as an electrolyte additive has the potential to significantly enhance the stability and dependability of ZIBs.

NiFe LDH/MoS2/Ni3S2 p-n/Mott-Schottky heterojunction for efficient hydrogen generation coupled with electrochemical oxidation of organic molecules

Urea and organic molecules assisted electrochemical water splitting is a promising strategy to realize energy-saving hydrogen production and simultaneous treatment of wastewater containing urea and organic pollutants. It is an effective approach to develop advanced electrocatalysts being of excellent catalytic performance by constructing a metal-semiconductor or semiconductor-semiconductor heterogeneous interface to regulate the electronic structure, thus forming the highly catalytic sites. Herein, we prepared a NiFe LDH/MoS2/Ni3S2 ternary heterojunction as a bifunctional catalyst on nickel foam (NiFe LDH/MoS2/Ni3S2/NF) via constructing Schottky interface and p-n heterojunction interface. In view of the built-in electric field between the heterogeneous interfaces, the electron transfer in interfaces is accelerated, and the adsorption of OH- and the dissociation of urea are also promoted, which results in excellent electrocatalytic performance including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), urea oxidation reaction (UOR) and ethanol oxidation reaction (ETOR). At 50 mA cm−2, the voltages of HER, OER, UOR and ETOR are −0.100, 1.511, 1.410, 1.427 V vs. RHE, respectively, better than the most of reported electrocatalysts. In two-electrode electrolytic cells using NiFe LDH/MoS2/Ni3S2/NF as cathode and anode catalysts, this material also exhibits the outstanding catalytic performance in electrolytes of 1.0 M KOH, 1.0 M KOH containing 0.5 M urea and 1.0 M KOH containing 0.5 M lactic acid. This research provides a feasible approach for constructing advanced electrocatalysts by combining the different metal-based compounds to form the heterojunction with highly catalytic sites, thus realizing the aim of acquiring hydrogen energy and simultaneous treatment of urea wastewater and other organic pollutants.

Progress on Two-Dimensional Transitional Metal Dichalcogenides Alloy Materials: Growth, Characterisation, and Optoelectronic Applications.

Two-dimensional (2D) transitional metal dichalcogenides (TMDs) have garnered remarkable attention in electronics, optoelectronics, and hydrogen precipitation catalysis due to their exceptional physicochemical properties. Their utilisation in optoelectronic devices is especially notable for overcoming graphene's zero-band gap limitation. Moreover, TMDs offer advantages such as direct band gap transitions, high carrier mobility, and efficient switching ratios. Achieving precise adjustments to the electronic properties and band gap of 2D semiconductor materials is crucial for enhancing their capabilities. Researchers have explored the creation of 2D alloy phases through heteroatom doping, a strategy employed to fine-tune the band structure of these materials. Current research on 2D alloy materials encompasses diverse aspects like synthesis methods, catalytic reactions, energy band modulation, high-voltage phase transitions, and potential applications in electronics and optoelectronics. This paper comprehensively analyses 2D TMD alloy materials, covering their growth, preparation, optoelectronic properties, and various applications including hydrogen evolution reaction catalysis, field-effect transistors, lithium-sulphur battery catalysts, and lasers. The growth process and characterisation techniques are introduced, followed by a summary of the optoelectronic properties of these materials.

Toward rational design of dual-metal-site single atom electrocatalysts for hydrogen and oxygen evolution reactions

Dual-metal-site catalysts (DMSCs) have emerged as a frontier in the field of heterogeneous catalysis due to they can improve the original structure catalytic performances of water splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, the effective DMSCs for HER and OER is still lacking due to their limited activity and complex electronic interactions of metal sites. Here, the HER and OER activities of 12 DMSCs and 6 single-metal-site catalysts (SMSCs) are investigated by density functional theory (DFT) calculations. It is found that N4-coordinated DMSCs and SMSCs exhibit better OER performance than that with N3-coordinated structures, in which Fe/Co-N4-a-Fe-Gr and Co/Ni-N4-a-Ni have the best OER and HER performances, with the corresponding ηOER and ΔGH* are 0.32 V and −0.02 eV, respectively. In addition, strong linear relationships are found between ΔG*O and ΔG*OH, ΔG*OOH and ΔG*OH (correlation coefficient, R2 almost equal to 1). There is a significant volcanic curve and a strong linear relationship between the metal-loaded d-band center (εd) and ηOER, εd and ΔG*OH in N4-coordinated DMSCs, respectively. The dynamics simulations results indicated that most of DMSCs are dynamically stable at reaction temperature.

Ru anchored on Co(OH)2 nanowire arrays as highly effective electrocatalyst for full water splitting

With the development of hydrogen energy, it is necessary to develop a cost-effective catalyst for electrochemical water splitting including hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER). Co-based composites are regarded as good catalysts toward OER, but weak H adsorption abilities lead to bad HER activities. Herein, Ru anchored on Co(OH)2 nanowire arrays (Ru/Co(OH)2 NWAs) as bifunctional catalysts for alkaline water splitting, are fabricated by hydrothermal process and subsequent immersion method. Ru/Co(OH)2 NWAs catalyst exhibits excellent activity for HER and OER, owing to strong electronic interaction of Ru participant and Co(OH)2 NWAs. To catalyze 10 mA cm−2 current density for HER and OER, Ru/Co(OH)2 NWAs catalyst only needs the overpotentials of 96 and 186 mV, respectively. An alkali electrolyzer assembled by bifunctional Ru/Co(OH)2 NWAs catalyst delivers 100 mA cm−2 at a cell voltage of 1.76 V, even superior than the couples of Pt/C and RuO2 electrodes (1.88 V).

Transition metal carbide‐based photocatalysts for artificial photosynthesis

AbstractTransition metal carbides, including both MXene and non‐MXene metal carbides, have enjoyed a soaring reputation in recent years. Benefitting from their intriguing physical and chemical characteristics, they shine in multifarious research fields and currently, they have emerged as promising nanomaterials for photocatalysis in energy and environmental science. Herein, based on the recent theoretical research and experimental studies, a systematic and comprehensive review of the expeditious advances of metal carbides and their nano‐architectures in the flourishing arena of photocatalysis is presented. The fundamental mechanism involved in photocatalysis with metal carbides serving as semiconductors or cocatalysts is thoroughly discussed. Besides, we highlight the main synthetic strategies of MXene and non‐MXene metal carbides and unravel the structural properties of the as‐obtained metal carbides via different fabrication routes to establish and elucidate their intriguing role in ameliorating photocatalytic activity. Moreover, the state‐of‐the‐art advancements of metal carbides in diverse photocatalytic applications, including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, and carbon dioxide reduction reaction, are summarized. In particular, insights into the structure–activity relationship of metal carbide in photocatalysis are elucidated. Finally, this review concludes with the ongoing challenges and perspectives on the future directions of metal carbides in the realm of photocatalysis.

Tuning the surface electronic structure of WS2 with Zn- and Cu-phthalocyanine for improved hydrogen evolution reaction: Experimental and DFT investigation

WS2 nanosheets have been successfully demonstrated to be promising materials for several important catalytic reactions including Hydrogen Evolution Reaction (HER) and Oxygen Reduction Reactions (ORR) either standalone or by functionalizing and as composites. Tungsten disulfide (WS2) is known to exist in two phases: 2H semiconducting and 1 T conducting. The 2H phase is commonly obtained by simple exfoliation of bulk WS2. Due to the semiconducting nature of the 2H phase, catalytic activity towards HER is very feeble compared to its 1 T counterpart. In this work, we have enhanced the activity of 2H WS2 nanosheets by interfacial modification through metal phthalocyanine (Pc) molecule (Cu-Pc and Zn-Pc) functionalization. We observe that the HER activity shows significant enhancement with the functionalization, with Zn-Pc showing better performance than the Cu-Pc. This functionalization creates an electronically coupled inorganic–organic heterostructure which shows improved response to HER. The WS2 functionalized nanosheets were studied in-depth with X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HRTEM) analyses. Electrochemical studies like linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) demonstrates that the heterostructures deliver enhanced charge transfer kinetics. The Zn-Pc functionalized nanosheets display an overpotential of 233 mV for attaining a current density of 10 mA.cm-2 and the overpotential decreased to 165 mV after cycling due to the surface reconstruction, when the stability was assessed with chronoamperometry. Density Functional Theory (DFT) studies reveal that the charge transfer due to the adsorption of Zn-Pc onto WS2 nanosheets is comparatively better than that of Cu-Pc. This work recounts that by simple metal phthalocyanine functionalization, charge transfer characteristics of WS2 can be markedly improved, thereby signifying the importance of interface modification in two-dimensional (2D) heterostructures.

Ambient Electrosynthesis toward Single-Atom Sites for Electrocatalytic Green Hydrogen Cycling.

With the ultimate atomic utilization, well-defined configuration of active sites and unique electronic properties, catalysts with single-atom sites (SASs) exhibit appealing performance for electrocatalytic green hydrogen generation from water splitting and further utilization via hydrogen-oxygen fuel cells, such that a vast majority of synthetic strategies toward SAS-based catalysts (SASCs) are exploited. In particular, room-temperature electrosynthesis under atmospheric pressure offers a novel, safe, and effective route to access SASs. Herein, the recent progress in ambient electrosynthesis toward SASs for electrocatalytic sustainable hydrogen generation and utilization, and future opportunities are discussed. A systematic summary is started on three kinds of ambient electrochemically synthetic routes for SASs, including electrochemical etching (ECE), direct electrodeposition (DED), and electrochemical leaching-redeposition (ELR), associated with advanced characterization techniques. Next, their electrocatalytic applications for hydrogen energy conversion including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, and oxygen reduction reaction are reviewed. Finally, a brief conclusion and remarkson future challenges regarding further development of ambient electrosynthesis of high-performance and cost-effective SASCs for many other electrocatalytic applications are presented.