Advanced Ultrathin RuPdM (M = Ni, Co, Fe) Nanosheets Electrocatalyst Boosts Hydrogen Evolution

Rapid Surface Reconstruction of Amorphous-Crystalline NiO for Industrial-Scale Electrocatalytic PET Upcycling

The conversion of plastic waste into valuable chemicals through innovative and selective nano-catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial-grade current densities is limited. Herein, we develop a self-supported amorphous-crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen fuel. The catalyst achieves an industrial current density of over 1 A cm-2 at 1.5 V vs. RHE, with an 80 % Faradaic efficiency and a formate production rate of 7.16 mmol cm-2 h-1. In situ Raman spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous-crystalline NiO into γ-NiOOH at the amorphous-crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is challenging to achieve for fully crystalline NiO. A techno-economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $582 per ton. This work presents a cost-effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Decoding the Hume-Rothery Rule in a Bifunctional Tetra-metallic Alloy for Alkaline Water Electrolysis

The 90-year-old Hume-Rothery rule was adapted to design an outstanding bifunctional tetra-metallic alloy electrocatalyst for water electrolysis. Following the radius mismatch principles, Fe (131 pm) and Ni (124 pm) are selectively incorporated at the Pd (139 pm) site of Mo0.30Pd0.70 nanosheets. Analogously, Cu (132 pm) alloys with only Pd, while Ag (145 pm) alloys with both Pd and Mo (154 pm). The face-centered cubic Mo0.30Pd0.35Ni0.23Fe0.12 nanosheets with 10-12 atomic layers, featuring in-plane compressive strain along the {111} basal plane, show 1/3 (422) reflection from local hexagonal symmetry. The more electronegative Pd attracts electron density from Ni/Fe in Mo0.30Pd0.35Ni0.23Fe0.12, synergistically boosting the mass activities for hydrogen and oxygen evolution reactions to 89 ± 5 and 38.6 ± 3.1 A g-1 at ±400 mV versus RHE, respectively. Full water electrolysis continues for ≥550 h, requiring cell voltages of 1.51 and 1.63 V at 10 and 100 mA cm-2, delivering 45 mL h-1 green H2.

Entropy Engineering of 2D Materials

Entropy, a measure of disorder or uncertainty in the thermodynamics system, has been widely used to confer desirable functions to alloys and ceramics. The incorporation of three or more principal elements into a single sublattice increases the entropy to medium and high levels, imparting these materials a mélange of advanced mechanical and catalytic properties. In particular, when scaling down the dimensionality of crystals from bulk to the 2D space, the interplay between entropy stabilization and quantum confinement offers enticing opportunities for exploring new fundamental science and applications, since the structural ordering, phase stability, and local electronic states of these distorted 2D materials get significantly reshaped. During the last few years, the large family of high-entropy 2D materials is rapidly expanding to host MXenes, hydrotalcites, chalcogenides, metal-organic frameworks (MOFs), and many other uncharted members. Here, the recent advances in this dynamic field are reviewed, elucidating the influence of entropy on the fundamental properties and underlying elementary mechanisms of 2D materials. In particular, their structure-property relationships resulting from theoretical predictions and experimental findings are discussed. Furthermore, an outlook on the key challenges and opportunities of such an emerging field of 2D materials is also provided.

A catalyst family of high-entropy alloy atomic layers with square atomic arrangements comprising iron- and platinum-group metals

We report a catalyst family of high-entropy alloy (HEA) atomic layers having three elements from iron-group metals (IGMs) and two elements from platinum-group metals (PGMs). Ten distinct quinary compositions of IGM-PGM-HEA with precisely controlled square atomic arrangements are used to explore their impact on hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). The PtRuFeCoNi atomic layers perform enhanced catalytic activity and durability toward HER and HOR when benchmarked against the other IGM-PGM-HEA and commercial Pt/C catalysts. Operando synchrotron x-ray absorption spectroscopy and density functional theory simulations confirm the cocktail effect arising from the multielement composition. This effect optimizes hydrogen-adsorption free energy and contributes to the remarkable catalytic activity observed in PtRuFeCoNi. In situ electron microscopy captures the phase transformation of metastable PtRuFeCoNi during the annealing process. They transform from random atomic mixing (25°C), to ordered L10 (300°C) and L12 (400°C) intermetallic, and finally phase-separated states (500°C).

Phase Electronic Structure Tuning via Pt, P-Doped Ni4Mo-Implanted Ti4O7 for Highly Efficient Water Splitting and Mg/Seawater Batteries

Fine-tuning nanoscale structures, morphologies, and electronic states are crucial for creating efficient water-splitting electrocatalysts. In this study, a method for electronic structure engineering to enhance overall water splitting in a corrosion-resistant electrocatalyst matrix by integrating Pt, P dual-doped Ni4Mo electrocatalysts onto a Ti4O7 nanorod grown on carbon cloth (Pt, P-Ni4Mo-Ti4O7/CC) is introduced. By optimizing platinum and phosphorus concentrations to 1.18% and 2.42%, respectively, low overpotentials are achieved remarkably: 24 mV at 10 mA cm-2 for the hydrogen evolution reaction and 290 mV at 20 mA cm-2 for the oxygen evolution reaction in 1.0 m KOH. These values approach or surpass those of benchmark Pt-C and IrO2 catalysts. Additionally, the Pt, P-Ni4Mo-Ti4O7/CC bifunctional electrocatalyst displays low cell potentials across various mediums, maintaining excellent current retention (96% stability after 40 h in mimic seawater at 20 mA cm-2) and demonstrating strong corrosion resistance and suitability for seawater  electrolysis. As a cathode in magnesium/seawater batteries, it achieves a power density of 7.2 mW cm-2 and maintains stability for 100 h. Density functional theory simulations confirm that P, Pt doping-assisted electronic structure modifications augment electrical conductivity and active sites in the hybrid electrocatalysts.

Bimetallic Nanoalloy Catalysts for Green Energy Production: Advances in Synthesis Routes and Characterization Techniques

Bimetallic Nanoalloy catalysts have diverse uses in clean energy, sensing, catalysis, biomedicine, and energy storage, with some supported and unsupported catalysts. Conventional synthetic methods for producing bimetallic alloy nanoparticles often produce unalloyed and bulky particles that do not exhibit desired characteristics. Alloys, when prepared with advanced nanoscale methods, give higher surface area, activity, and selectivity than individual metals due to changes in their electronic properties and reduced size. This review demonstrates the synthesis methods and principles to produce and characterize highly dispersed, well-alloyed bimetallic nanoalloy particles in relatively simple, effective, and generalized approaches and the overall existence of conventional synthetic methods with modifications to prepare bimetallic alloy catalysts. The basic concepts and mechanistic understanding are represented with purposely selected examples. Herein, the enthralling properties with widespread applications of nanoalloy catalysts in heterogeneous catalysis are also presented, especially for Hydrogen Evolution Reaction (HER), Oxidation Reduction Reaction (ORR), Oxygen Evolution Reaction (OER), and alcohol oxidation with a particular focus on Pt and Pd-based bimetallic nanoalloys and their numerous fields of applications. The high entropy alloy is described as a complicated subject with an emphasis on laser-based green synthesis of nanoparticles and, in conclusion, the forecasts and contemporary challenges for the controlled synthesis of nanoalloys are addressed.

Dealloying-Induced Zeolite-like Metal Framework of AB2 Laves Phase Intermetallic Electrocatalysts

Exploring an efficient and robust electrocatalyst for hydrogen evolution reaction (HER) at high pH and temperature holds the key to the industrial application of alkaline water electrolysis (AWE). Herein, we design an open tunnel structure by dealloying a series of Laves phase intermetallics, i.e., MCo2 and MRu0.25Co1.75 (M = Sc and Zr). The dealloying process can induce a zeolite-like metal framework for ScCo2 and ScRu0.25Co1.75 by stripping Sc metal from the center of a tunnel structure. This structural engineering significantly lowers their overpotentials at a current density of 500 mA/cm2 (η500) ca. 80 mV in 1.0 M KOH. Through a simple process, ScRu0.25Co1.75 can be easily decorated on a carbon cloth substrate and only requires 132 mV to reach 500 mA/cm2. More importantly it can maintain activity over 1000 h in industrial conditions (6.0 M KOH at 333 K), showing its potential for practical industrial applications.

Atomic vacancies-engineered ultrathin trimetallic nanozyme with anti-inflammation and antitumor performances for intestinal disease treatment

Colitis-associated colorectal cancer, which represents a highly aggressive subtypes of colorectal cancer, requires concurrent antitumor and anti-inflammation therapies in clinic. Herein, we successfully engineered Ru38Pd34Ni28 ultrathin trimetallic nanosheets (TMNSs) by introducing diverse transition metal atoms into the structure of RuPd nanosheets. Density functional theory (DFT) calculations reveal that the elaborate introduction of transition metal Ru and Ni facilitates the formation of Ru-O and Ni-O bonds on the surface of TMNSs for efficient reactive oxygen species (ROS) and reactive nitrogen species (RNS) scavenging, respectively. Moreover, the engineered abundant atomic vacancies on their surface conspicuously improve the performance in eliminating reactive oxygen and nitrogen species (RONS). The designed TMNSs act as a multi-metallic nanocatalyst with RONS elimination performance for chronic colitis treatment by relieving inflammation, as well as photothermal conversion capability for colon cancer therapy by inducing hyperthermia effect. Profiting from the excellent RONS scavenging activities, TMNSs can down-regulate the expression levels of the pro-inflammatory factors, thereby leading to prominent therapeutic efficacy against dextran sulfate sodium-induced colitis. Benefiting from the high photothermal performance, TMNSs cause significant suppression of CT-26 tumors without obvious recurrence. This work provides a distinct paradigm to design multi-metallic nanozymes for colon disease treatment by elaborate introduction of transition metal atoms and engineering of atomic vacancies.

Nanoarchitectonics of Metallene Materials for Electrocatalysis

Controlling the synthesis of metal nanostructures is one approach for catalyst engineering and performance optimization in electrocatalysis. As an emerging class of unconventional electrocatalysts, two-dimensional (2D) metallene electrocatalysts with ultrathin sheet-like morphology have gained ever-growing attention and exhibited superior performance in electrocatalysis owing to their distinctive properties originating from structural anisotropy, rich surface chemistry, and efficient mass diffusion capability. Many significant advances in synthetic methods and electrocatalytic applications for 2D metallenes have been obtained in recent years. Therefore, an in-depth review summarizing the progress in developing 2D metallenes for electrochemical applications is highly needed. Unlike most reported reviews on the 2D metallenes, this review starts by introducing the preparation of 2D metallenes based on the classification of the metals (e.g., noble metals, and non-noble metals) instead of synthetic methods. Some typical strategies for preparing each kind of metal are enumerated in detail. Then, the utilization of 2D metallenes in electrocatalytic applications, especially in the electrocatalytic conversion reactions, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, fuel oxidation reaction, CO₂ reduction reaction, and N₂ reduction reaction, are comprehensively discussed. Finally, current challenges and opportunities for future research on metallenes in electrochemical energy conversion are proposed.

Modulate the metallic Sb state on ultrathin PdSb-based nanosheets for efficient formic acid electrooxidation

Incorporation of oxophilic metals into Pd-based nanostructures has shown great potential in small molecule electrooxidation owing to their superior anti-poisoning capability. However, engineering the electronic structure of oxophilic dopants in Pd-based catalysts remains challenging and their impact on electrooxidation reactions is rarely demonstrated. Herein, we have developed a method for synthesizing PdSb-based nanosheets, enabling the incorporation of the Sb element in a predominantly metallic state despite its high oxophilic nature. Moreover, the Pd₉₀Sb₇W₃ nanosheet serves as an efficient electrocatalyst for the formic acid oxidation reaction (FAOR), and the underlying promotion mechanism is investigated. Among the as-prepared PdSb-based nanosheets, the Pd₉₀Sb₇W₃ nanosheet exhibits a remarkable 69.03% metallic state of Sb, surpassing the values observed for the Pd₈₆Sb₁₂W₂ (33.01%) and Pd₈₃Sb₁₄W₃ (25.41%) nanosheets. X-ray photoelectron spectroscopy (XPS) and CO stripping experiments confirm that the Sb metallic state contributes the synergistic effect of their electronic and oxophilic effect, thus leading to an effective electrooxidation removal of CO and significantly enhanced FAOR electrocatalytic activity (1.47 A mg^-1; 2.32 mA cm^-1) compared with the oxidated state of Sb. This work highlights the importance of modulating the chemical valence state of oxophilic metals to enhance electrocatalytic performance, offering valuable insights for the design of high-performance electrocatalysts for electrooxidation of small molecules.

Optimization Methods of Tungsten Oxide-Based Nanostructures as Electrocatalysts for Water Splitting

Electrocatalytic water splitting, as a sustainable, pollution-free and convenient method of hydrogen production, has attracted the attention of researchers. However, due to the high reaction barrier and slow four-electron transfer process, it is necessary to develop and design efficient electrocatalysts to promote electron transfer and improve reaction kinetics. Tungsten oxide-based nanomaterials have received extensive attention due to their great potential in energy-related and environmental catalysis. To maximize the catalytic efficiency of catalysts in practical applications, it is essential to further understand the structure-property relationship of tungsten oxide-based nanomaterials by controlling the surface/interface structure. In this review, recent methods to enhance the catalytic activities of tungsten oxide-based nanomaterials are reviewed, which are classified into four strategies: morphology regulation, phase control, defect engineering, and heterostructure construction. The structure-property relationship of tungsten oxide-based nanomaterials affected by various strategies is discussed with examples. Finally, the development prospects and challenges in tungsten oxide-based nanomaterials are discussed in the conclusion. We believe that this review provides guidance for researchers to develop more promising electrocatalysts for water splitting.

Ru-Ni Alloy Nanoparticles Loaded on N-Doped Amphiphilic Mesoporous Hollow Carbon@silica Spheres as Catalyst for the Hydrogenation of α-Pinene to cis-Pinane

N-doped mesoporous carbon spheres (NHMC@mSiO₂ ) encapsulated in silica shells were prepared by emulsion polymerization and domain-limited carbonization using ethylenediamine as the nitrogen source, and Ru-Ni alloy catalysts were prepared for the hydrogenation of α-pinene in the aqueous phase. The internal cavities of this nanomaterial are lipophilic, enhancing mass transfer and enrichment of the reactants, and the hydrophilic silica shell enhances the dispersion of the catalyst in water. N-doping allows more catalytically active metal particles to be anchored to the amphiphilic carrier, enhancing its catalytic activity and stability. In addition, a synergistic effect between Ru and Ni significantly enhances the catalytic activity. The factors influencing the hydrogenation of α-pinene were investigated, and the optimum reaction conditions were determined to be as follows: 100 °C, 1.0 MPa H₂ , 3 h. The high stability and recyclability of the Ru-Ni alloy catalyst were demonstrated through cycling experiments.

Recent development and challenges in fuel cells and water electrolyzer reactions: an overview

Water electrolysis is the most promising method for the production of large scalable hydrogen (H2), which can fulfill the global energy demand of modern society. H2-based fuel cell transportation has been operating with zero greenhouse emission to improve both indoor and outdoor air quality, in addition to the development of economically viable sustainable green energy for widespread electrochemical applications. Many countries have been eagerly focusing on the development of renewable as well as H2-based energy storage infrastructure to fulfill their growing energy demands and sustainable goals. This review article mainly discusses the development of different kinds of fuel cell electrocatalysts, and their application in H2 production through various processes (chemical, refining, and electrochemical). The fuel cell parameters such as redox properties, cost-effectiveness, ecofriendlyness, conductivity, and better electrode stability have also been highlighted. In particular, a detailed discussion has been carried out with sufficient insights into the sustainable development of future green energy economy.

Ordered micropattern arrays fabricated by lung-derived dECM hydrogels for chemotherapeutic drug screening

AIMS

This study aims to evaluate ECM-coated micropattern arrays derived from decellularization of native porcine lungs as a novel three-dimensional cell culture platform.

METHODS

ECM derived from decellularization of native porcine lungs was exploited to prepare hydrogels. Then, dECM-coated micropattern arrays were fabricated at four different diameters (50, 100, 150 and 200 ​μm) using polydimethylsiloxane (PDMS). Two lung cancer cell lines, A549 and H1299, were tested on a dECM-coated micropattern array as a novel culture platform for cell adhesion, distribution, proliferation, viability, phenotype expression, and drug screening to evaluate the cytotoxicity of paclitaxel, doxorubicin and cisplatin.

RESULTS

The ECM derived from decellularization of native porcine lungs supported cell adhesion, distribution, viability and proliferation better than collagen I and Matrigel as the coated matrix on the surface. Moreover, the optimal diameter of the micropattern arrays was 100-150 ​μm, as determined by measuring the morphology, viability, proliferation and phenotype of the cancer cell spheroids. Cell spheroids of A549 and H1299 on dECM-coated micropattern arrays showed chemoresistance to anticancer drugs compared to that of the monolayer. The different distributions of HIF-1α, MCL-1 (in the center) and Ki-67 and MRP2 (in the periphery) of the spheroids demonstrated the good establishment of basal-lateral polarity and explained the chemoresistance phenomenon of spheroids.

CONCLUSIONS

This novel three-dimensional cell culture platform is stable and reliable for anticancer drug testing. Drug screening in dECM-coated micropattern arrays provides a powerful alternative to existing methods for drug testing and metabolic profiling in the drug discovery process.

Porous PdWM (M = Nb, Mo and Ta) Trimetallene for High C1 Selectivity in Alkaline Ethanol Oxidation Reaction

Direct ethanol fuel cells are among the most efficient and environmentally friendly energy-conversion devices and have been widely focused. The ethanol oxidation reaction (EOR) is a multielectron process with slow kinetics. The large amount of by-product generated by incomplete oxidation greatly reduces the efficiency of energy conversion through the EOR. In this study, a novel type of trimetallene called porous PdWM (M = Nb, Mo and Ta) is synthesized by a facile method. The mass activity (15.6 A mgPd -1 ) and C1 selectivity (55.5%) of Pd50 W27 Nb23 /C trimetallene, obtained after optimizing the compositions and proportions of porous PdWM, outperform those of commercial Pt/C (1.3 A mgPt -1 , 5.9%), Pd/C (5.0 A mgPd -1 , 7.2%), and Pd97 W3 /C bimetallene (9.5 A mgPd -1 , 14.1%). The mechanism by which Pd50 W27 Nb23 /C enhances the EOR performance is evaluated by in situ Fourier transform infrared spectroscopy and density functional theory calculations. It is found that W and Nb enhance the adsorption of CH3 CH2 OH and oxophilic high-valence Nb accelerates the subsequent oxidation of CO and CHx species. Moreover, Nb promotes the cleavage of CC bonds and increases the C1 selectivity. Pd60 W28 Mo12 /C and Pd64 W27 Ta9 /C trimetallene synthesized by the same method also exhibit excellent EOR performance.

One-pot synthesis of core@shell PdAuPt nanodendrite@Pd nanosheets for boosted visible light-driven methanol electrooxidation

Herein, we developed a one-pot, surfactant-free approach to obtain a PdPtAu@Pd core@shell catalyst for the photocatalytic methanol oxidation reaction. By virtue of its dimensions, conjunction architecture and robust core@shell construction, 0D@2D PdPtAu@Pd exhibited a superior catalytic performance, with a mass activity 2.3- and 6.7-times higher than that of Pt/C and Pd/C catalysts, respectively.

Facile Synthesis of PdCuRu Porous Nanoplates as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Medium

Ru is a key component of electrocatalysts for hydrogen evolution reaction (HER), especially in alkaline media. However, the catalytic activity and durability of Ru-based HER electrocatalysts are still far from satisfactory. Here we report a solvothermal approach for the synthesis of PdCuRu porous nanoplates with different Ru compositions by using Pd nanoplates as the seeds. The PdCuRu porous nanoplates were formed through underpotential deposition (UPD) of Cu on Pd, followed by alloying Cu with Pd through interdiffusion and galvanic replacement between Cu atoms and Ru precursor simultaneously. When evaluated as HER electrocatalysts, the PdCuRu porous nanoplates exhibited excellent catalytic activity and durability. Of them, the Pd24Cu29Ru47/C achieved the lowest overpotential (40.7 mV) and smallest Tafel slope (37.5 mV dec−1) in an alkaline solution (much better than commercial Pt/C). In addition, the Pd24Cu29Ru47/C only lost 17% of its current density during a stability test for 10 h, while commercial Pt/C had a 59.5% drop under the same conditions. We believe that the electron coupling between three metals, unique porous structure, and strong capability of Ru for water dissociation are responsible for such an enhancement in HER performance.

Promoting the Phosphidation Process using an Oxygen Vacancy Precursor for Efficient Hydrogen Evolution Reaction

Based on previous works, most of the transition metal phosphides (TMPs) were directly prepared by decomposing NaH₂ PO₂ with the precursors at high temperatures, which resulted in different degrees of phosphidation in the final product. Therefore, it is necessary to design an innovative approach to enhance the degree of phosphidation in the material using crystal defects. Here, oxygen-vacancy iron oxide/iron foam (Ov-Fe₂ O₃ /IF) was firstly prepared by generating oxygen vacancy in situ in an iron foam through heating in vacuum conditions. Subsequently, FeP/IF was formed by phosphating Ov-Fe₂ O₃ /IF. Under the effects of oxygen vacancies, oxygen-vacancy iron oxide could be completely phosphatized to produce more active sites on the surface of the material. This, in turn, could result in a catalyst with exceptional hydrogen evolution activity. Thus, the successful fabrication of FeP/IF demonstrated in this work provides an effective and feasible way for the preparation of other high-efficiency catalysts.

ZIF-67-derived N-enriched porous carbon doped with Co, Fe and CoS for electrocatalytic hydrogen evolution reaction

Hybrid composites based on transition metal-doped materials exhibit excellent performance and stability as electrocatalysts for the hydrogen evolution reaction (HER). Thus, they could easily replace HER catalysts based on noble metals. To demonstrate this, we fabricated Co, Fe, and CoS doped N-enriched porous carbon materials (CoFeS/NC) using a simple, straightforward and quick method (involving absorption, pyrolysis and sulfidation steps), which used ZIF-67 metal-organic framework (MOF) material as a precursor. The fabricated CoFeS/NC showed excellent HER performance and long-term stability: it achieved a low potential (equal to 176 mV) at 10 mA cm^-2 current density and a small Tafel slope (equal to 67.8 mV dec^-1) in 1.0 KOH. Such outstanding HER performance was attributed to the synergistic effect of the CoFeS/NC components, including unique mesoporosity. All these properties ensured the presence of numerous active sites and high conductivity provided by the carbon matrix. The excellent CoFeS/NC electrocatalytic activity makes it a promising material for H₂ production on an industrial scale. Our work demonstrated a simple way of its preparation, which could be applied to other material groups.

Recent progress in water-splitting electrocatalysis mediated by 2D noble metal materials

Two-dimensional (2D) nanostructures have enabled noble-metal-based nanomaterials to be promising electrocatalysts toward overall water splitting due to their inherent structural advantages, including a high specific surface active area, numerous low-coordinated atoms, and a high density of defects and edges. Moreover, it is also disclosed that the electronic effect and strain effect within 2D nanostructures also benefit the further promotion of the electrocatalytic performance. In this review, we have focused on the recent progress in the fabrication of advanced electrocatalysts based on 2D noble-metal-based nanomaterials toward water splitting electrocatalysis. First, fundamental descriptions about water-splitting mechanisms, some promising engineering strategies, and major challenges in electrochemical water splitting are given. Then, the structural merits of 2D nanostructures for water splitting electrocatalysis are also highlighted, including abundant surface active sites, lattice distortion, abundant surface defects, electronic effects, and strain effects. Additionally, some representative water-splitting electrocatalysts have been discussed in detail to highlight the superiorities of 2D noble-metal-based nanomaterials for electrochemical water splitting. Finally, the underlying challenges and future opportunities for the fabrication of more advanced electrocatalysts for water splitting are also highlighted. We hope that this review article provides guidance for the fabrication of more efficient electrocatalysts for boosting industrial hydrogen production via water splitting.

Supramolecular Anchoring Strategy for Facile Production of Ruthenium Nanoparticles Embedded in N-Doped Mesoporous Carbon Nanospheres for Efficient Hydrogen Generation

Because of the favorable mass transport and increased available active sites, the rational design and preparation of porous carbon structures are essential but still challenging. Herein, a novel and facile supramolecular anchoring strategy was developed to achieve the embedding of ruthenium (Ru) nanoparticles in N-doped mesoporous carbon nanospheres through pyrolyzing the precursor formed by coordination assembly between metal ions and zinc gluconate (G(Zn)). Featuring rich hydroxyl groups, the G(Zn) can effectively chelate Ru³⁺ via metal-oxygen bonds to form 3D supramolecular nanospheres, and meanwhile, mesopores in carbon nanospheres were expanded after subsequent pyrolysis thanks to the volatilization of zincic species at high temperature. As a demonstration, the best-performing catalyst displayed extraordinary activity for the hydrogen evolution reaction (HER) with a small overpotential of 43 mV versus reversible hydrogen electrode (vs RHE) at 10 mA/cm² and a Tafel slope of 39 mV/dec, which was superior to that of commercial Pt/C in alkaline medium. Theoretical calculations revealed that the catalytic activity was significantly promoted by the strong electronic coupling between Ru nanoparticles and N-doped porous carbon, which increased the electron transfer capability and facilitated the adsorption and dissociation of H₂O to realize an efficient HER.

High Valence M-Incorporated PdCu Nanoparticles (M = Ir, Rh, Ru) for Water Electrolysis in Alkaline Solution

The high-valence metal catalysts show extraordinary talent in various electrochemical reactions. However, there is no facile method to synthesize high-valence noble metal-based materials. Herein, we synthesized the different high valence noble metal M-incorporated PdCu nanoparticles (M = Ir, Ru, Rh) by the assistant of Fe³⁺ and exhibit excellent performance for water electrolysis. In 0.1 M KOH, the OER and HER mass activities of Ir₁₆-PdCu/C were 50.5 and 16.5 times as much as PdCu/C, and achieved a current density of 10 mA cm^-2 at 1.63 V when worked for overall water splitting. DFT calculation revealed that the incorporating of high valence Ir could optimize the binding energy of the intermediate products, and promote the evolution of oxygen and hydrogen. Ex situ XPS shows that the huge amount of oxidized Ir (V) formed in OER could promote the formation of O-O bonds.

Electronic Modulation of Non-van der Waals 2D Electrocatalysts for Efficient Energy Conversion

The exploration of efficient electrocatalysts for energy conversion is important for green energy development. Owing to their high surface areas and unusual electronic structure, 2D electrocatalysts have attracted increasing interest. Among them, non-van der Waals (non-vdW) 2D materials with numerous chemical bonds in all three dimensions and novel chemical and electronic properties beyond those of vdW 2D materials have been studied increasingly over the past decades. Herein, the progress of non-vdW 2D electrocatalysts is critically reviewed, with a special emphasis on electronic structure modulation. Strategies for heteroatom doping, vacancy engineering, pore creation, alloying, and heterostructure engineering are analyzed for tuning electronic structures and achieving intrinsically enhanced electrocatalytic performances. Lastly, a roadmap for the future development of non-vdW 2D electrocatalysts is provided from material, mechanism, and performance viewpoints.

Solvent-free microwave synthesis of ultra-small Ru-Mo2C@CNT with strong metal-support interaction for industrial hydrogen evolution

Exploring a simple, fast, solvent-free synthetic method for large-scale preparation of cheap, highly active electrocatalysts for industrial hydrogen evolution reaction is one of the most promising work today. In this work, a simple, fast and solvent-free microwave pyrolysis method is used to synthesize ultra-small (3.5 nm) Ru-Mo₂C@CNT catalyst with heterogeneous structure and strong metal-support interaction in one step. The Ru-Mo₂C@CNT catalyst only exhibits an overpotential of 15 mV at a current density of 10 mA cm⁻², and exhibits a large turnover frequency value up to 21.9 s⁻¹ under an overpotential of 100 mV in 1.0 M KOH. In addition, this catalyst can reach high current densities of 500 mA cm⁻² and 1000 mA cm⁻² at low overpotentials of 56 mV and 78 mV respectively, and it displays high stability of 1000 h. This work provides a feasible way for the reasonable design of other large-scale production catalysts.

While H₂ could be a renewable fuel, the large-scale preparation of cheap, active electrocatalysts for large-scale production remains a challenge. Here, authors use a rapid, solvent-free microwave pyrolysis method to synthesize nanostructured catalysts for large-scale industrial H₂ production.

Atomically Dispersed Reactive Centers for Electrocatalytic CO2 Reduction and Water Splitting

Developing electrocatalytic energy conversion technologies for replacing the traditional energy source is highly expected to resolve the fossil fuel exhaustion and related environmental problems. Exploring stable and high-efficiency electrocatalysts is of vital importance for the promotion of these technologies. Single-atom catalysts (SACs), with atomically distributed active sites on supports, perform as emerging materials in catalysis and present promising prospects for a wide range of applications. The rationally designed near-range coordination environment, long-range electronic interaction and microenvironment of the coordination sphere cast huge influence on the reaction mechanism and related catalytic performance of SACs. In the current Review, some recent developments of atomically dispersed reactive centers for electrocatalytic CO2 reduction and water splitting are well summarized. The catalytic mechanism and the underlying structure-activity relationship are elaborated based on the recent progresses of various operando investigations. Finally, by highlighting the challenges and prospects for the development of single-atom catalysis, we hope to shed some light on the future research of SACs for the electrocatalytic energy conversion.

Facet-controlled palladium nanocrystalline for enhanced nitrate reduction towards ammonia

Electrochemical nitrate reduction reaction (NO₃^-RR) is considered an appealing way for producing ammonia (NH₃) under ambient conditions and solving environmental problems caused by nitrate, whereas the lack of adequate catalysts hampers the development of NO₃^-RR. Here, we firstly demonstrate that the Pd nanocrystalline with a well-desired facet can act as a highly efficient NO₃^-RR electrocatalyst for ambient ammonia synthesis. Pd (1 1 1) exhibits excellent activity and selectivity in reducing NO₃^- to NH₄⁺ with a Faradaic efficiency of 79.91% and an NH₄⁺ production of 0.5485 mmol h^-1 cm^-2 (2.74 mmol h^-1 mg^-1) in 0.1 M Na₂SO₄ (containing 0.1 M NO₃^-), which is 1.4 times higher than Pd (1 0 0) and 1.9 times higher than Pd (1 1 0), respectively. Density functional theory (DFT) calculation reveals that the superior NO₃^-RR activity of Pd (1 1 1) originates from its optimized activity of NO₃^- adsorption, smaller free energy change of the rate-limiting step (*NH₃ to NH₃), and poorer hydrogen evolution reaction activity (HER, competitive reaction). This work not only highlights the potentials of Pd-based nanocatalysts for NO₃^-RR but also provides new insight for the applications in NO₃^-RR of other facet-orientation nanomaterials.

Mesoporous RhRu Nanosponges with Enhanced Water Dissociation toward Efficient Alkaline Hydrogen Evolution

Lowering the energy barrier of water dissociation is critical to achieving highly efficient hydrogen evolution in alkaline conditions. Herein, we reported mesoporous RhRu nanosponges with enhanced water dissociation behavior as a new class of high-performance electrocatalysts for alkaline hydrogen evolution reaction (HER). The obtained nanosponges have a binary alloy structure (fcc) and a highly porous structure with high surface area. Our RhRu catalyst displayed an outstanding HER activity with an overpotential of 25 mV at 10 mA cm^-2 and a Tafel slope of 47.5 mV dec^-1 in 1.0 M KOH, which significantly outperformed that of commercial Pt/C catalyst and was even comparable to the classic Pt/metal (hydro)oxide catalysts. Density functional theory (DFT) calculations disclosed that charge redistribution on the RhRu alloy surface enabled tuning of the Ru d-band center and then promoted the adsorption and dissociation of water molecules. Based on the experimental results and theoretical modeling, a bifunctional mechanism contributed to the remarkable alkaline HER activity on the RhRu catalyst surface.

A New ternary organometallic Pd(ii)/Fe(iii)/Ru(iii) self-assembly monolayer: the essential ensemble synergistic for improving catalytic activity

The synergistic catalytic effect in a hetero-trimetallic catalytic monolayer is one of the intriguing topics because the additive effects of the second or third component play an important role in improving the activity. In this paper, a new Schiff-base organometallic nanosheet containing Pd/Fe/Ru immobilized on graphene oxide (GO@H-Pd/Fe/Ru) was prepared and characterized. The catalytic performance of GO@H-Pd/Fe/Ru and synergistic effect were systematically investigated. GO@H-Pd/Fe/Ru was found to be an efficient catalyst with higher turnover frequency (TOF) (26 892 h-1) and stability with recyclability of at least 10 times in the Suzuki-Miyaura coupling reaction. The deactivation mechanism was caused by the aggregation of the active species, loss of the active species, the changes of the organometallic complex, and active sites covered by adsorbed elements during the catalytic process. GO@H-Pd/Fe/Ru was a heterogeneous catalyst, as confirmed by kinetic studies with in situ FT-IR, thermal filtration tests and poisoning tests. The real active center containing Pd, Ru and Fe arranged as Fe(iii)-Ru(iii)-Pd(ii)-Fe(iii) was proposed. Although Ru(iii) and Fe(iii) were shown to be less active or inactive, the addition of Fe and Ru could effectively improve the entire activity by their ''indirect'' function, in which Fe or Ru made Pd more negative and more stable. The ensemble synergistic effect between metals, the ligand and support was described as a process in which the electron was transferred from GOvia ligand to Ru, and then to Pd or from Fe to Pd to make Pd more negative, promoting the oxidation addition with aryl halide. Also, the vicinity of Ru around Pd as the promoter adsorbed aryl boronic acid, which facilitates its synergism to react with the oxidation intermediate to the trans-metallic intermediate.

Ultrasmall PdPtCo trimetallic nanorings with enriched low-coordinated edge sites and optimized compositions for effective oxygen reduction electrocatalysis

Ultrasmall two-dimensional Pd₅₅Pt₁₈Co₂₇ trimetallic alloy nanorings with enriched low-coordinated edge sites exhibit greatly enhanced ORR electrocatalytic activity.

Computational Screening toward Hydrogen Evolution Reaction by the Introduction of Point Defects at the Edges of Group IVA Monochalcogenides: A First-Principles Study

Exploring materials with high hydrogen evolution reaction (HER) performance is of importance for the development of clean hydrogen energy, and the defects on the surfaces of catalysts are essential. In this work, we evaluate the HER performance among group IVA monochalcogenides MXs (M = Ge/Sn, X = S/Se) with M/X point defects on the edges. Compared with basal planes and bare edges, the GeS edge with Ge vacancy (ΔG_H* = 0.016 eV), GeSe edge with Se vacancy (ΔG_H* = 0.073 eV), and SnSe edge with Sn vacancy (ΔG_H* = -0.037 eV) hold the best HER performances, which are comparable to or even better than the value for Pt (-0.07 eV). Furthermore, the relationships between ΔG_H* and p-band centers of considered models are summarized. The stability of proposed electrocatalysts are analyzed by vacancy-formation energy and strain engineering. In summary, the HER performance of MXs is greatly improved by introduction of point defects at the edges, which is promising for their use as electrocatalysts for the conversion and storage of energy in the future.

IrCo alloy nanoparticles supported on N-doped carbon for hydrogen evolution electrocatalysis in acidic and alkaline electrolytes

Designing efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) is of great importance to advance water splitting technology towards practical applications. Herein, we report the preparation of IrCo nanoparticles supported on nitrogen-doped carbon (IrCo/NC) as a HER electrocatalyst in acidic and alkaline electrolytes. The IrCo/NC composite is obtained by pyrolyzing an Ir-doped Co(OH)2 precursor on g-C3N4, and is endowed with N-doped carbon and uniform IrCo alloy nanoparticles via a crystal confinement resulting from the Ir-doping into the Co(OH)2 layer. Electrocatalytic analysis shows that the IrCo/NC electrode requires low overpotentials of 32 mV at 10 mA cm-2 in 0.5 M H2SO4 and 33 mV in 1 M KOH, which are superior to those of the Co/NC and IrCo alloys that are free of Ir-doping or N-doped carbon. The results provide a strategy for designing and preparing active noble-transition bimetallic alloy electrocatalysts as efficient HER catalysts.