Unprotected and interconnected Ru0 nano-chain networks: advantages of unprotected surfaces in catalysis and electrocatalysis

RuZn NPs with electroactivity and oxidase-like property for dual-mode anti-cancer drug monitoring

6-mercaptopurine (6-MP) as the effective anti-cancer drug was used for the treatment of Crohn's disease and acute lymphoblastic leukaemia, but the response to maintenance therapy was variable with individual differences. In order to control the dosage and decrease the side effects of 6-MP, a sensitive and stable assay was urgently needed for 6-MP monitoring. Herein, RuZn NPs with electrochemical oxidation property and oxidase-like activity was proposed for dual-mode 6-MP monitoring. Burr-like RuZn NPs were prepared and explored to not only exhibit an electrochemical oxidation signal at 0.78 V, but also displayed excellent oxidase-like performances. RuZn NPs were utilized for the dual-mode monitoring of 6-MP, attributing to the formation of Ru-SH covalent bonding. The colorimetric method showed good linearity from 10 μM to 5 mM with the limit of detection (LOD) of 300 nM, while the electrochemical method provided a higher sensitivity with the LOD of 37 nM in range from 100 nM to 200 μM. This work provided a new way for the fabrication of dual-functional nanotags with electroactivity and oxidase-like property, and opened a dual-mode approach for the 6-MP detection applications with complementary and satisfactory results.

Crystal-Phase Engineering in Heterogeneous Catalysis

The performance of a chemical reaction is critically dependent on the electronic and/or geometric structures of a material in heterogeneous catalysis. Over the past century, the Sabatier principle has already provided a conceptual framework for optimal catalyst design by adjusting the electronic structure of the catalytic material via a change in composition. Beyond composition, it is essential to recognize that the geometric atomic structures of a catalyst, encompassing terraces, edges, steps, kinks, and corners, have a substantial impact on the activity and selectivity of a chemical reaction. Crystal-phase engineering has the capacity to bring about substantial alterations in the electronic and geometric configurations of a catalyst, enabling control over coordination numbers, morphological features, and the arrangement of surface atoms. Modulating the crystallographic phase is therefore an important strategy for improving the stability, activity, and selectivity of catalytic materials. Nonetheless, a complete understanding of how the performance depends on the crystal phase of a catalyst remains elusive, primarily due to the absence of a molecular-level view of active sites across various crystal phases. In this review, we primarily focus on assessing the dependence of catalytic performance on crystal phases to elucidate the challenges and complexities inherent in heterogeneous catalysis, ultimately aiming for improved catalyst design.

Cobalt Ferrite Surface-Modified Carbon Nanotube Fibers as an Efficient and Flexible Electrode for Overall Electrochemical Water Splitting Reactions

One of the most practical and environmentally friendly ways to deal with the energy crises and global warming is to produce hydrogen as clean fuel by splitting water. The central obstacle for electrochemical water splitting is the use of expensive metal-based catalysts. For electrocatalytic hydrogen production, it is essential to fabricate an efficient catalyst for the counterpart oxygen evolution reaction (OER), which is a four-electron-transfer sluggish process. Here in this study, we have successfully fabricated cobalt-based ferrite nanoparticles over the surface of carbon nanotube fiber (CNTF) that was utilized as flexible anode materials for the OER and overall electrochemical water splitting reactions. Scanning electron microscopy images with elemental mapping showed the growth of nanoparticles over CNTF, while electrochemical characterization exhibited excellent electrocatalytic performance. Linear sweep voltammetry revealed the reduced overpotential value (260 mV@η10mAcm-2) with a small Tafel slope of 149 mV dec-1. Boosted electrochemical double layer capacitance (0.87 mF cm-2) for the modified electrode also reflects the higher surface area as compared to pristine CNTF (Cdl = 0.022 mF cm-2). Charge transfer resistance for the surface-modified CNTF showed the lower diameter in the Nyquist plot and was consequently associated with the better Faradaic process at the electrode/electrolyte interface. Overall, the as-fabricated electrode could be a promising alternative for the efficient electrochemical water splitting reaction as compared to expensive metal-based electrocatalysts.

Superhydrophilic and Superaerophobic Ru-Loaded NiCo Bimetallic Hydroxide Achieves Efficient Hydrogen Evolution over All pH Ranges

Realizing an effective, binder-free, and super-wetting electrocatalyst for the hydrogen evolution reaction (HER) at full pH is essential for the creation of clean hydrogen. In this study, the Ru-loaded NiCo bimetallic hydroxide (Ru@NiCo-BH) catalyst was prepared by spontaneous redox reaction. The chemical interaction between Ru NPs and NiCo-BH by the Ru-O-M (M=Ni, Co) interface bond, the electron-rich Ru active site, and the multi-channel nickel foam carrier make the superhydrophilic and superaerophobic surface advantageous for mass transfer in the HER process. Therefore, Ru@NiCo-BH has remarkable HER activity, with low overpotential of 29, 68 and 80 mV, a 10 mA cm-2 current density can be obtained in alkaline, neutral and acidic electrolytes respectively. This work provides a reference for the rational development of universal electrocatalysts for hydrogen evolution in the all pH ranges through simple design strategies.

Promoting water formation in sulphate-functionalized Ru for efficient hydrogen oxidation reaction under alkaline electrolytes

Improving the sluggish kinetics of the hydrogen oxidation reaction (HOR) under alkaline electrolytes plays a significant role in the practical application of alkaline polymer electrolyte fuel cells (APEFCs). Here we report a sulphate functionalized Ru catalyst (Ru-SO₄) that exhibits remarkable electrocatalytic performance and stability toward alkaline HOR, with a mass activity of 1182.2 mA mg_PGM^-1, which is four-times higher than that of the pristine Ru catalyst. Theoretical calculations and experimental studies including in situ electrochemical impedance spectroscopy and in situ Raman spectroscopy demonstrate that the charge redistribution on the interface of Ru through sulphate functionalization could lead to optimized adsorption energies of hydrogen and hydroxide, together with facilitated H₂ transfer through the inter Helmholtz plane and precisely tailored interfacial water molecules, contributing to a decreased energy barrier of the water formation step and enhanced HOR performance under alkaline electrolytes.

Unraveling CoNiP-CoP2 3D-on-1D Hybrid Nanoarchitecture for Long-Lasting Electrochemical Hybrid Cells and Oxygen Evolution Reaction

Evolving cost-effective transition metal phosphides (TMPs) using general approaches for energy storage is pivotal but challenging. Besides, the absence of noble metals and high electrocatalytic activity of TMPs allow their applicability as catalysts in oxygen evolution reaction (OER). Herein, CoNiP-CoP₂ (CNP-CP) composite is in situ deposited on carbon fabric by a one-step hydrothermal technique. The CNP-CP reveals hybrid nanoarchitecture (3D-on-1D HNA), i.e., cashew fruit-like nanostructures and nanocones. The CNP-CP HNA electrode delivers higher areal capacity (82.8 μAh cm^-2 ) than the other electrodes. Furthermore, a hybrid cell assembled with CNP-CP HNA shows maximum energy and power densities of 31 μWh cm^-2 and 10.9 mW cm^-2 , respectively. Exclusively, the hybrid cell demonstrates remarkable durability over 30 000 cycles. In situ/operando X-ray absorption near-edge structure analysis confirms the reversible changes in valency of Co and Ni elements in CNP-CP material during real-time electrochemical reactions.  Besides, a quasi-solid-state device unveils its practicability by powering electronic components. Meanwhile, the CNP-CP HNA verifies its higher OER activity than the other catalysts by revealing lower overpotential (230 mV). Also, it exhibits relatively small Tafel slope (38 mV dec^-1 ) and stable OER activity over 24 h. This preparation strategy may initiate the design of advanced TMP-based materials for multifunctional applications.

Cyclized Polyacrylonitrile as a Promising Support for Single Atom Metal Catalyst with Synergistic Active Site

Metal single atom catalysts (SAC) have been successfully used in heterogeneous catalysis but developing a scalable and economic support for SAC is still a great challenge. Here, cyclized polyacrylonitrile (CPAN) is proposed as a promising support for single atom metal catalysts. CPAN can be easily prepared from cheap industrial product polyacrylonitrile (PAN), which has excellent processability. A series of SAC on CPAN (M/CPAN, M = Ag, Cu, Ru) are designed and the catalytic activities of the as synthesized M/CPAN are investigated by the model reduction reaction of p-nitrophenol (4-NP). M/CPAN presents excellent catalytic performance with high stability and theoretical calculations elucidate that Ag/CPAN synergistically catalyze 4-NP reduction following the Langmuir-Hinshelwood (L-H) mechanism with 4-NP preferentially adsorbing at the Ag sites and H adsorbing at the bridge C sites. These results, for the first time, reveal that the single atom on CPAN can catalyze 4-NP reduction efficiently. This methodology provides a convenient route for the preparation of a variety of SAC, and this strategy is readily scalable and holds great potential in catalytic applications.

Metallic Gold-Incorporated Ni(OH)2 for Enhanced Water Oxidation in an Alkaline Medium: A Simple Wet-Chemical Approach

The development of a highly efficient electrocatalyst for the oxygen evolution reaction (OER) with a lower overpotential and high intrinsic activity is highly challenging owing to its sluggish kinetic behavior. As an alternative to the state-of-the-art OER catalyst, recently, transition-metal-based hydroxide materials have been shown to play important roles for the same. Owing to the high earth abundance of various Ni-based hydroxide and its derivatives, these are known to be highly studied materials for the OER. Herein, we report a simple wet-chemical synthesis of metallic gold-incorporated (by varying the concentration of Au³⁺ ions) Ni(OH)₂ nanosheets as an active and stable electrocatalyst for the OER in 1 M KOH medium. The Au-Ni(OH)₂ (2) catalyst demanded a low overpotential of 288 mV to attain a geometric current density of 10 mA/cm² with a lower Tafel value of 55 mV/dec compared to bare Ni(OH)₂ with a lower mass loading of only 0.1 mg/cm². Tafel slope analysis reveals that the incorporation of metallic gold on the hydroxide surfaces could alter the mechanistic pathways of the overall OER reaction. It has been proposed that the incorporation of metallic gold over the Ni(OH)₂ surfaces led to a change in the electronic structure of the electroactive nickel sites (Jahn-Teller distortion), which favors the OER by electronic aspects.

RuCu Cage/Alloy Nanoparticles with Controllable Electroactivity for Specific Electroanalysis Applications

Electrochemical nanotags with controllable and multiresponse electroactivity have a great capacity for overcoming the drawbacks of limited target monitoring and inaccurate detection results for electrochemical sensors. In this contribution, double electro-oxidative Ru and Cu metals were integrated into RuCu nanostructures for the generation of dual electro-oxidative signals. A facial approach was proposed for the controllable fabrication of RuCu cage nanoparticles (NPs) and RuCu alloy NPs by simply adjusting the pH value of the reaction system. RuCu cage NPs and RuCu alloy NPs demonstrated inherent different electro-oxidative responses owing to the remarkable distinction of structures with different metal valences. RuCu cage NPs showed a single electro-oxidization peak at 0.84 V, assigned to the exposure of more Ru⁰ electroactive sites on the hollow cage structures. RuCu alloy NPs illustrated dual electro-oxidization peak at 0.84 and -0.16 V, attributing to the presence of Ru⁰ and Cu⁺ electroactive sites on the alloy structures, respectively. RuCu cage NPs and RuCu alloy NPs served as specific electroactive tags, achieving the selective monitoring of Na₂S and ratiometric electrochemical detection of xanthine in monosodium glutamate, respectively. The limits of detection were as low as 27 pM for Na₂S and 70 nM for xanthine. The rational design of multimetal nanostructures holds enormous potential for the generation of multiresponse electroactivity with the impetus for exploring the capacity of specific electrochemical sensing.

Advanced Transition Metal-Based OER Electrocatalysts: Current Status, Opportunities, and Challenges

Oxygen evolution reaction (OER) is an important half-reaction involved in many electrochemical applications, such as water splitting and rechargeable metal-air batteries. However, the sluggish kinetics of its four-electron transfer process becomes a bottleneck to the performance enhancement. Thus, rational design of electrocatalysts for OER based on thorough understanding of mechanisms and structure-activity relationship is of vital significance. This review begins with the introduction of OER mechanisms which include conventional adsorbate evolution mechanism and lattice-oxygen-mediated mechanism. The reaction pathways and related intermediates are discussed in detail, and several descriptors which greatly assist in catalyst screen and optimization are summarized. Some important parameters suggested as measurement criteria for OER are also mentioned and discussed. Then, recent developments and breakthroughs in experimental achievements on transition metal-based OER electrocatalysts are reviewed to reveal the novel design principles. Finally, some perspectives and future directions are proposed for further catalytic performance enhancement and deeper understanding of catalyst design. It is believed that iterative improvements based on the understanding of mechanisms and fundamental design principles are essential to realize the applications of efficient transition metal-based OER electrocatalysts for electrochemical energy storage and conversion technologies.

Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Media

Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.

Rational Design of Single-Atom Site Electrocatalysts: From Theoretical Understandings to Practical Applications

Atomically dispersed metal-based electrocatalysts have attracted increasing attention due to their nearly 100% atomic utilization and excellent catalytic performance. However, current fundamental comprehension and summaries to reveal the underlying relationship between single-atom site electrocatalysts (SACs) and corresponding catalytic application are rarely reported. Herein, the fundamental understandings and intrinsic mechanisms underlying SACs and corresponding electrocatalytic applications are systemically summarized. Different preparation strategies are presented to reveal the synthetic strategies with engineering the well-defined SACs on the basis of theoretical principle (size effect, metal-support interactions, electronic structure effect, and coordination environment effect). Then, an overview of the electrocatalytic applications is presented, including oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, oxidation of small organic molecules, carbon dioxide reduction reaction, and nitrogen reduction reaction. The underlying structure-performance relationship between SACs and electrocatalytic reactions is also discussed in depth to expound the enhancement mechanisms. Finally, a summary is provided and a perspective supplied to demonstrate the current challenges and opportunities for rational designing, synthesizing, and modulating the advanced SACs toward electrocatalytic reactions.

DNA-Modified Cobalt Tungsten Oxide Hydroxide Hydrate Nanochains as an Effective Electrocatalyst with Amplified CO Tolerance during Methanol Oxidation

Direct methanol fuel cell technology implementation mainly depends on the development of non-platinum catalysts with good CO tolerance. Among the widely studied transition-metal catalysts, cobalt oxide with distinctively higher catalytic efficiency is highly desirable. Here, we have evolved a simple method of synthesizing cobalt tungsten oxide hydroxide hydrate nanowires with DNA (CTOOH/DNA) and without incorporating DNA (CTOOH) by microwave irradiation and subsequently employed them as electrocatalysts for methanol oxidation. Following this, we examined the influence of incorporating DNA into CTOOH by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The enhanced electrochemical surface area of CTOOH offered readily available electroactive sites and resulted in a higher oxidation current at a lower onset potential for methanol oxidation. On the other hand, CTOOH/DNA exhibited improved CO tolerance and it was evident from the chronoamperometric studies. Herein, we noticed only a 2.5 and 1.8% drop at CTOOH- and CTOOH/DNA-modified electrodes, respectively, after 30 min. Overall, from the results, it was evident that the presence of DNA in CTOOH played an important role in the rapid removal of adsorbed intermediates and regenerated active catalyst centers possibly by creating high density surface defects around the nanochains than bare CTOOH.

In-situ cellulose-framework templates mediated monodispersed silver nanoparticles via facile UV-light photocatalytic activity for anti-microbial functionalization

Cellulose is well known as a biocompatible material or natural reducing material. In this study, As an eco-friendly and facile method, we prepared monodispersed silver nanoparticles (AgNPs) in cellulose-framework through photocatalytic reaction. and we fabricated electrospun fiber scaffolds with excellent antibacterial properties and biocompatibility. UV-irradiation causes the electrical change of the cellulose-framework, thereby converting Ag ions into Ag particles. We applied a three-electrode system to confirm the phenomenon. Through STEM and EDS, it was found that the synthesized AgNPs were monodisperse in the nanofibers, and antibacterial activity was confirmed using gram-negative and gram-positive bacteria. In addition, it was suggested that the gradual release of simvastatin contained in the nanofibers and excellent mineralization would be easy to apply to bone regeneration. Therefore, the manufactured composite electrospun fiber mat can be used not only in biomedical fields but also in various applications that need to prevent the accumulation of microorganisms.

Intervening Bismuth Tungstate with DNA Chain Assemblies: A Perception toward Feedstock Conversion via Photoelectrocatalytic Water Splitting

An advanced approach with DNA-mediated bismuth tungstate (Bi₂WO₆) one-dimensional (1-D) nanochain assemblies for hydrogen production with 5-fold enhanced photoelectrochemical (PEC) water splitting reaction is presented. The creation of new surface states upon DNA modification mediates the electron transfer in a facile manner for a better PEC process. The UV-Vis-DRS analysis results a red shift in the optical absorption phenomenon with the interference of DNA modification on Bi₂WO₆, and, thus, the band gap was tuned from 3.05 eV to 2.71 eV. The applied bias photon-to-current efficiency (ABPE) was calculated and shows a maximum for the Bi₂WO₆@DNA-2 (25.22 × 10^-4%), compared to pristine Bi₂WO₆ (7.76 × 10^-4%). Furthermore, the idea of practical utility of produced hydrogen from PEC is established for the first time with photocatalytic feedstock conversion to platform chemicals using cinnamaldehyde, 2-hydroxy-1-phenylethanone, and 2-(3-methoxyphenoxy)-1-phenylethanone in large scale by hydrogenation and/or hydrogenolysis reactions under eco-friendly green conditions with external hydrogen pressure in an aqueous mixture. Also, the recyclability experiment delivered good yields, which further confirm the robustness of the developed catalyst.

Designing transition-metal-boride-based electrocatalysts for applications in electrochemical water splitting

Investigating renewable and clean energy materials as alternatives to fossil fuels can be foreseen as a potential solution to the global problems of energy shortages and environmental pollution. Recently, transition metal boride (TMB)-based materials have emerged as the rising star as efficient electrocatalysts for hydrogen evolution reaction (HER) and/or oxygen evolution reaction (OER). In this review, an overview of the most recent developments in the use of TMB-based materials as electrocatalysts for HER/OER or overall water splitting has been presented. Initially, we provide a comprehensive introduction of the fundamentals of electrochemical water splitting. Then, the synthesis approaches of TMB materials are summarized and compared. Emphasis is put on the various strategies for further improving the electrocatalytic performance of TMBs. Finally, challenges and future perspectives for TMBs in water-splitting applications are proposed.

Ultrafine α-CoOOH Nanorods Activated with Iron for Exceptional Oxygen Evolution Reaction

Two-dimensional oxyhydroxide materials are proved to be a potential candidate for oxygen evolution reaction (OER). Robust, efficient, and cost-effective electrocatalysts are critical to overcome the sluggish kinetics and high overpotential of OERs. Herein, a simple co-precipitation method followed by solvothermal treatment is used to synthesize Fe-doped α-CoOOH at higher pH under optimum conditions for OER. The α-Fe_0.24Co_0.76OOH/NF illustrates superior OER electrocatalytic performance and requires an overpotential of only 280 mV to produce a current density of 50 mA cm^-2 with excellent stability. The detailed analysis reveals that the exceptional OER performance originates from thin nanorods and partially due to the replacement of Fe in α-CoOOH. This work illustrates the presence of interlayer chloride ions through energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.

Synthesis of 3-alkenylindoles through regioselective C-H alkenylation of indoles by a ruthenium nanocatalyst

3-Alkenylindoles are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron-withdrawing and electron-donating groups on the indole moiety. Additionally, a "robustness screen" has also been employed to demonstrate the tolerance of several functional groups relevant to medicinal chemistry. With respect to the Ru nanocatalyst, it has been demonstrated that it is recoverable and recyclable up to four cycles. Also, the catalyst acts through a heterogeneous mechanism, which has been proven by various techniques, such as ICPMS and three-phase tests. The nature of the Ru nanocatalyst surface has also been thoroughly examined by various techniques, and it has been found that the oxides on the surface are responsible for the high catalytic efficiency of the Ru nanocatalyst.

Rational Design of Multisite Trielement Ru-Ni-Fe Alloy Nanocatalysts with Efficient and Durable Catalytic Hydrogenation Performances

The co-decomposition of non-noble metals into Ru nanoparticles (NPs) would provide multiple active centers as well as synergistically alter the reaction pathway, enhancing the catalytic hydrogenation performance. Herein, a facile route for synthesizing trielement Ru-Ni-Fe alloy NPs was proposed. The catalytic hydrogenation performance of NPs was measured using p-nitrophenol as a model. The synergistic effect of these three elements (Ru, Ni, and Fe) and synergistic catalysis of multiple crystal faces greatly improved the catalytic hydrogenation performance of Ru₄₄Ni₂₈Fe₂₈ alloy NPs. Ru with more vacant orbitals showed a strong coordination with BH₄^- for the generation of active H species. Ni played a major role in transporting electrons and active H species, increasing the accessibility of catalytically active sites. Fe could cooperate with BH₄^- to produce active H species and promote electrons transfer. Ru₄₄Ni₂₈Fe₂₈ alloy NPs could be reused and applied for the fabrication of films at the oil-water (ethyl acetate-water) interface. The densely packed Ru₄₄Ni₂₈Fe₂₈ NP films were good Raman substrates for monitoring the complete conversion of 4-nitrothiophenol into 4-aminothiophenol. The rational design of Ru₄₄Ni₂₈Fe₂₈ will broaden the application range of Ru-based catalysts and provide new insights into the rational design of other multisite alloy catalysts.

Ruthenium Trichloride Catalyst in Water: Ru Colloids versus Ru Dimer Characterization Investigations

An easy-to-prepare ruthenium catalyst obtained from ruthenium(III) trichloride in water demonstrates efficient performances in the oxidation of several cycloalkanes with high selectivity toward the ketone. In this work, several physicochemical techniques were used to demonstrate the real nature of the ruthenium salt still unknown in water and to define the active species for this Csp³-H bond functionalization. From transmission electron microscopy analyses corroborated by SAXS analyses, spherical nanoobjects were observed with an average diameter of 1.75 nm, thus being in favor of the formation of reduced species. However, further investigations, based on X-ray scattering and absorption analyses, showed no evidence of the presence of a metallic Ru-Ru bond, proof of zerovalent nanoparticles, but the existence of Ru-O and Ru-Cl bonds, and thus the formation of a water-soluble complex. The EXAFS (extended X-ray absorption fine structure) spectra revealed the presence of an oxygen-bridged diruthenium complex [Ru(OH) _xCl_{3- x}]₂(μ-O) with a high oxidation state in agreement with catalytic results. This study constitutes a significant advance to determine the true nature of the RuCl₃·3H₂O salt in water and proves once again the invasive nature of the electron beam in microscopy experiments, routinely used in nanochemistry.

Ruthenium Supported on Ionically Cross-linked Chitosan-Carrageenan Hybrid MnFe2O4 Catalysts for 4-Nitrophenol Reduction

Herein, we report a facile procedure to synthesize the hybrid magnetic catalyst (Ru@CS-CR@Mn) using ruthenium (Ru) supported on ionically cross-linked chitosan-carrageenan (CS-CR) and manganese ferrite (MnFe2O4) nanoparticles with excellent catalytic activity. The ionic gelation of CS-CR is acting as a protecting layer to promote the encapsulation of MnFe2O4 and Ru nanoparticles by electrostatic interactions. The presence of an active metal and a CS-CR layer on the as-prepared Ru@CS-CR@Mn catalyst was well determined by a series of physicochemical analyses. Subsequently, the catalytic performances of the Ru@CS-CR@Mn catalysts were further examined in the 4-nitrophenol (4-NP) reduction reaction in the presence of sodium borohydride (reducing agent) at ambient temperature. The Ru@CS-CR@Mn catalyst performed excellent catalytic activity in the 4-NP reduction, with a turnover frequency (TOF) values of 925 h−1 and rate constant (k) of 0.078 s−1. It is worth to mentioning that the Ru@CS-CR@Mn catalyst can be recycled and reused up to at least ten consecutive cycles in the 4-NP reduction with consistency in catalytic performance. The Ru@CS-CR@Mn catalyst is particularly attractive as a catalyst due to its superior catalytic activity and superparamagnetic properties for easy separation. We foresee this catalyst having high potential to be extended in a wide range of chemistry applications.

The Chemical Properties of Hydrogen Atoms Adsorbed on M0 -Nanoparticles Suspended in Aqueous Solutions: The Case of Ag0 -NPs and Au0 -NPs Reduced by BD4. Angew Chem Int Ed Engl 2018;57:16525-16528. [PMID: 30320944 DOI: 10.1002/anie.201809302]

The nature of H-atoms adsorbed on M⁰ -nanoparticles is of major importance in many catalyzed reduction processes. Using isotope labeling, we determined that hydrogen evolution from transient {(M⁰ -NP)-H_n }^n- proceeds mainly via the Heyrovsky mechanism when n is large (i.e., the hydrogens behave as hydrides) but mainly via the Tafel mechanism when n is small (i.e., the hydrogens behave as atoms). Additionally, the relative contributions of the two mechanisms differ considerably for M=Au and Ag. The results are analogous to those recently reported for the M⁰ -NP-catalyzed de-halogenation processes.

Simple Preparation of Porous Carbon-Supported Ruthenium: Propitious Catalytic Activity in the Reduction of Ferrocyanate(III) and a Cationic Dye

The present study involves the synthesis, characterization, and catalytic application of ruthenium nanoparticles (Ru NPs) supported on plastic-derived carbons (PDCs) synthesized from plastic wastes (soft drink bottles) as an alternative carbon source. PDCs have been further activated with CO₂ and characterized by various analytical techniques. The catalytic activity of Ru@PDC for the reduction of potassium hexacyanoferrate(III), (K₃[Fe(CN)₆]), and new fuchsin (NF) dye by NaBH₄ was performed under mild conditions. The PDCs had spherical morphology with an average size of 0.5 μm, and the Ru NP (5 ± 0.2 nm) loading (4.01 wt %) into the PDC provided high catalytic performance for catalytic reduction of ferrocyanate(III) and NF dye. This catalyst can be recycled more than six times with only a minor loss of its catalytic activity. In addition, the stability and reusability of the Ru@PDC catalyst are also discussed.

Cobalt Phosphide Composite Encapsulated within N,P-Doped Carbon Nanotubes for Synergistic Oxygen Evolution

Exploring highly efficient and stable oxygen evolution reaction (OER) electrocatalysts such as transition-metal phosphides (TMPs) is critical to advancing renewable hydrogen fuel. TMP nanostructures typically involving binary or ternary TMPs tuned by cation or anion doping are suggested to be promising low-cost and durable OER catalysts. Herein, the preparation of CoP/CoP₂ composite nanoparticles encapsulated within N,P-doped carbon nanotubes (CoP/CoP₂ @NPCNTs) is demonstrated as a synergistic electrocatalyst for OER via the calcination of a CoAl-layered double hydroxide/melamine mixture and subsequent phosphorization. Facile visualization by scanning electron microscopy in conjunction with electron backscatter diffraction demonstrates the encapsulation of the CoP/CoP₂ nanoparticles within the N,P-codoped CNTs. Electrocatalytic evaluation shows that the composite electrode requires a low overpotential of 300 mV for the OER at 10 mA cm^-2 in a 1.0 m KOH solution and, in particular, exhibits an excellent long-term durability of ≈100 h, which is superior to that of the state-of-the-art RuO₂ electrocatalyst. Density functional theory calculations reveal that the synergistic effect of CoP and CoP₂ can enhance the electrocatalytic performance. In addition, molecular dynamics simulations demonstrate that the generated O₂ molecules can readily diffuse out of the CNTs. Both the effects give rise to the observed OER enhancement.

Cobalt phosphide/carbon dots composite as an efficient electrocatalyst for oxygen evolution reaction

The oxygen evolution reaction (OER) is a promising energy conversion system, which has been studied a lot in recent years. However, owing to the high overpotential and sluggish kinetics of the OER, an efficient electrocatalyst is necessary to lower the overpotential and accelerate the reaction. In this paper, we report a cobalt phosphide (CoP)/carbon dots (CDs) composite as an electrocatalyst for the OER for the first time. A facile two-step method was used to synthesize the CoP/CDs composite and the concentration of CDs in the composite was further regulated. The experimental results show that when the amount of CDs in the composite is 6 mg (28.79 wt%C), the obtained CoP/CDs composite exhibits optimal electrocatalytic activity (with an overpotential of 400 mV in 1 M KOH at a current density of 10 mA cm-2) and high stability towards the OER. The good electrocatalytic activity of the composite is attributed to the small size of CoP and CDs and rapid electron transfer of CDs.

Green-fabrication of gold nanomaterials using Staphylococcus warneri from Sundarbans estuary: an effective recyclable nanocatalyst for degrading nitro aromatic pollutants

Microbial synthesis of gold nanoparticles (GNPs) has attracted considerable attention in recent times due to their exceptional capability for the bioremediation of industrial wastes and also for the treatment of wastewater. A bacterial strain Staphylococcus warneri, isolated from the estuarine mangroves of Sundarbans region produced highly stable GNPs by reducing hydrogen auric chloride (HAucl₄) salt using intracellular protein extract. The nanoparticles were characterized utilizing ultraviolet-visible spectrophotometry, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and surface enhanced Raman scattering. Highly dispersed, spherically shaped GNPs varied around 15-25 nm in size and were highly crystalline with face-centered cubic structures. Recyclable catalytic activity of as-synthesized GNPs was evidenced by complete degradation of nitro aromatic pollutants like 2-nitroaniline, 4-nitroaniline, 2-nitrophenol and 4-nitrophenol. Our GNPs show excellent and efficient catalytic activity with significantly high rate constant (10^-1 order) and high turnover frequency (10³ order) in recyclable manner up to three times. To our knowledge, this is the first report of Staphylococcus warneri in the production of gold nanoparticles. This green technology for bioremediation of toxic nitro aromatic pollutants is safe and economically beneficial to challenge the development and sustainability issue.

Low-cost palladium decorated on m-aminophenol-formaldehyde-derived porous carbon spheres for the enhanced catalytic reduction of organic dyes

A novel method for the synthesis of recyclable Pd@PCS catalyst was applied for the reduction of CV, EY, and SY.