Metal-substrate Interaction Research Articles

CoFe2O4 Nanoparticles on Bio-Based Polymer Derived Nitrogen Doped Carbon as Bifunctional Electrocatalyst for Li-Air Battery

Lithium-air batteries (LABs) are gaining attention as a promising energy storage solution. Their theoretical energy density of 3,505 Whkg−1 exceeds that of conventional lithium-ion batteries (500–800 Whkg−1). The commercial viability and widespread adoption of lithium-air batteries face challenges such as poor cycling stability, limited lifespan, and unresolved side reactions. In this study, we synthesized spinel CoFe2O4-decorated on bio-based poly(2,5-benzimidazole) derived N-doped carbon for electrocatalysts. Notably, strong metal-substrate interaction (SMSI) was observed through various characterizations. The bifunctional electrocatalytic activity and stability toward oxygen reduction reaction and oxygen evolution reaction were significantly enhanced by the SMSI, The LAB demonstrated a high discharge capacity of 18,356 mAhg−1 at a current density of 200 mAg−1, maintaining a remarkable discharge capacity of 1,000 mAhg−1 even at a high current density of 400 mAg−1 for 200 cycles. CoFe2O4-decorated on bio-derived ABPBI holds promise as a practical air-breathing electrode for high-capacity rechargeable LABs.

Catalytic cracking of oleic acid to generate aviation kerosene using platinum–modified ZSM–5 nanosheets

AbstractBACKGROUNDA series of Pt@NZSM–5 and Pt/NZSM–5 nanosheets having different Si/Al ratios were prepared via an in situ synthesis and impregnation method, respectively, using C22H45–N+(CH3)2–C6H12–N+(CH3)2–C6H13 (C22–6–6) as the template agent. The oleic acid decarboxylation reaction was carried out using these materials under CO2 atmosphere and the oleic acid cracking mechanism was inferred from the product distribution of the C8‐C17 alkanes.RESULTSThe Pt@NZSM–5 and Pt/NZSM–5 was found to comprise thinner nanosheets and exhibited strong metal–substrate interactions. Pt@NZSM–5 nanosheets with a Si/Al molar ratio of 100 had thicknesses of only 8–9 nm along with a mesopore/micropore capacity ratio of 2.7, an acid content of 11 cm3/g STP and a high Pt0/PtOx ratio.CONCLUSIONThe Pt@NZSM‐5 and Pt/NZSM‐5 nanosheets had an interconnected hierarchical system and a large number of metal active sites that facilitated the decarboxylation of oleic acid. The Pt@NZSM–5 nanosheets demonstrated excellent catalytic activity during the cracking of oleic acid under a CO2 atmosphere, giving a yield of C8–C17 alkanes as high as 83.8% after 5 h at 320 °C. These Pt@NZSM–5 nanosheets also showed greater stability than the Pt/NZSM–5 specimens. © 2024 Society of Chemical Industry (SCI).

Platinum Nanoparticles Bonded with Carbon Nanotubes for High-Performance Ampere-Level All-Water Splitting.

Platinum nanoparticles loaded on a nitrogen-doped carbon nanotubes exhibit a brilliant hydrogen evolution reaction (HER) in an alkaline solution, but their bifunctional hydrogen and oxygen evolution reaction (OER) has not been reported due to the lack of a strong Pt-C bond. In this work, platinum nanoparticles bonded in carbon nanotubes (Pt-NPs-bonded@CNT) with strong Pt-C bonds are designed toward ultralow overpotential water splitting ability in alkaline solution. Benefit from the strong interaction between platinum and high conductivity carbon nanotube substrates through the Pt-C bond also the platinum nanoparticles bonded in carbon nanotube can provide more stable active sites, as a result, the Pt-NPs-bonded@CNT exhibits excellent hydrogen evolution in acid and alkaline solution with ultralow overpotential of 0.19 and 0.23 V to reach 1000 mA cm-2, respectively. Besides, it shows superior oxygen evolution electrocatalysis in alkaline solution with a low overpotential of 1.69 V at 1000 mA cm-2. Furthermore, it also exhibits high stability over 110 h against the evolution of oxygen and hydrogen at 1000 mA cm-2. This strategy paves the way to the high performance of bifunctional electrocatalytic reaction with extraordinary stability originating from optimized electron density of metal active sites due to strong metal-substrate interaction.

Equilibrium structure and shape of Ag and Pt nanoparticles grown on silica surfaces: From experimental investigations to the determination of a metal-silica potential.

A combination of experimental and numerical investigations on metallic silver and platinum nanoparticles deposited on silica substrates is presented, with a focus on metal-substrate interactions. Experimentally, the nanoparticles, obtained by ultra-high vacuum atom deposition, are characterized by grazing-incidence small-angle x-ray scattering and high resolution transmission electronic microscopy to determine their structure and morphology and, in particular, their aspect ratio (height/diameter), which quantifies the metal-substrate interaction, from the as-grown to equilibrium state. Numerically, the interactions between the metal and the silica species are modeled with the Lennard-Jones (12, 6) potential, with two parameters for each metal and silica species. The geometric parameters were found in the literature, while the energetic parameters were determined from our experimental measurements of the aspect ratio. The parameters are as follows: σAg-O = 0.278nm, σAg-Si = 0.329nm, ɛAg-O = 75meV, and ɛAg-Si = 13meV for Ag-silica and σPt-O = 0.273nm, σPt-Si = 0.324nm, ɛPt-O = 110meV, and ɛPt-Si = 18 meV for Pt-silica. The proposed Ag-silica potential reproduces quantitatively the unexpected experimental observation of the variation of the aspect ratio for Ag nanoparticles larger than 5nm, which has been interpreted as a consequence of the silica roughness. The nanoparticle orientation, structure, and disorder are also considered. This metal-silica potential for Ag and Pt should be helpful for further studies on pure metals as well as their alloys.

Dual-Atom Co/Ni Electrocatalyst Anchored at the Surface-Modified Ti3C2Tx MXene Enables Efficient Hydrogen and Oxygen Evolution Reactions.

Dual-atom catalytic sites on conductive substrates offer a promising opportunity for accelerating the kinetics of multistep hydrogen and oxygen evolution reactions (HER and OER, respectively). Using MXenes as substrates is a promising strategy for depositing those dual-atom electrocatalysts, if the efficient surface anchoring strategy ensuring metal-substrate interactions and sufficient mass loading is established. We introduce a surface-modification strategy of MXene substrates by preadsorbing L-tryptophan molecules, which enabled attachment of dual-atom Co/Ni electrocatalyst at the surface of Ti3C2Tx by forming N-Co/Ni-O bonds, with mass loading reaching as high as 5.6 wt %. The electron delocalization resulting from terminated O atoms on MXene substrates, N atoms in L-tryptophan anchoring moieties, and catalytic metal atoms Co and Ni provides an optimal adsorption strength of intermediates and boosts the HER and OER kinetics, thereby notably promoting the intrinsic activity of the electrocatalyst. CoNi-Ti3C2Tx electrocatalyst displayed HER and OER overpotentials of 31 and 241 mV at 10 mA cm-2, respectively. Importantly, the CoNi-Ti3C2Tx electrocatalyst also exhibited high operational stability for both OER and HER over 100 h at an industrially relevant current density of 500 mA cm-2. Our study provided guidance for constructing dual-atom active metal sites on MXene substrates to synergistically enhance the electrochemical efficiency and stability of the energy conversion and storage systems.

Effective Photocatalytic Ethanol Reforming into High-Value-Added Multicarbon Compound Coupled with H2 Production Over Pt-S3 Sites at PtSA-ZnIn2S4 Interface.

Selective photocatalytic production of high-value acetaldehyde concurrently with H2 from bioethanol is an appealing approach to meet the urgent environment and energy issues. However, the difficult ethanol dehydrogenation and insufficient active sites for proton reduction within the catalysts, and the long spatial distance between these two sites always restrict their catalytic activity. Here, guided by the strong metal-substrate interaction effect, an atomic-level catalyst design strategy to construct Pt-S3 single atom on ZnIn2S4 nanosheets (PtSA-ZIS) is demonstrated. As active center with optimized H adsorption energy to facilitate H2 evolution reaction, the unique Pt single atom also donates electrons to its neighboring S atoms with electron-enriched sites formed to activate the O─H bond in *CH3CHOH and promote the desorption of *CH3CHO. Thus, the synergy between Pt single atom and ZIS together will reduce the energy barrier for the ethanol oxidization to acetaldehyde, and also narrow the spatial distance for proton mass transfer. These features enable PtSA-ZIS photocatalyst to produce acetaldehyde with a selectivity of ≈100%, which will spontaneously transform into 1,1-diethoxyethane via acetalization to avoid volatilization. Meanwhile, a remarkable H2 evolution rate (184.4µmolh-1) is achieved with a high apparent quantum efficiency of 10.50% at 400nm.

Theory-guided design of electron-deficient ruthenium cluster for ampere-level current density electrochemical hydrogen evolution

Ru-based materials have regarded as ideal alternatives to Pt-based catalysts for hydrogen evolution reaction (HER), however, strong adsorption of H intermediate for Ru-based catalysts results in an unsatisfactory HER activity. Herein, we perform a high-throughput computational screening of different Ru clusters that supported on a carbon substrate embedded with various non-precious metals by comparing their structure stability and adsorption energy of H intermediate. Guided by the computational predictions, a unique 3D catalyst of Ru cluster with a size of < 2 nm anchored on spherical carbon shell confining Ni particles (Ru/Ni@C) is developed. Owing to the strong metal-substrate interaction and optimized electronic structure, Ru/Ni@C exhibits an outstanding HER performance with an ultra-low overpotential of 309 mV at 1.0 A cm−2, outperformed commercial Pt/C and Ru/C catalysts. Experimental observations and theoretical calculations demonstrate the efficient electron transfer from anchored Ru cluster to core Ni particles via carbon layer, which leads to the formation of electron-deficient Ru site, beneficial to adjust the ability of H adsorption and eventually promotes the whole HER process.

In Situ Spectroscopy and Microscopy Insights into the CO Oxidation Mechanism on Au/CeO2(111)

In this work, we prepared and investigated in ultra-high vacuum (UHV) two stoichiometric CeO2(111) surfaces containing low and high amounts of step edges decorated with 0.05 ML of gold using synchrotron-radiation photoelectron spectroscopy (SRPES) and scanning tunneling microscopy (STM). The UHV study helped to solve the still unresolved puzzle on how the one-monolayer-high ceria step edges affect the metal-substrate interaction between Au and the CeO2(111) surface. It was found that the concentration of ionic Au+ species on the ceria surface increases with increasing number of ceria step edges and is not correlated with the concentration of Ce3+ ions that are supposed to form on the surface after its interaction with gold nanoparticles. We associated this with an additional channel of Au+ formation on the surface of CeO2(111) related to the interaction of Au atoms with various peroxo oxygen species formed at the ceria step edges during the film growth. The study of CO oxidation on the highly stepped Au/CeO2(111) model sample was performed by combining near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS), UHV-STM, and near-ambient-pressure STM (NAP-STM). This powerful combination provided comprehensive information on the processes occurring on the Au/CeO2(111) surface during the interaction with CO, O2, and CO + O2 (1:1) mixture at conditions close to the real working conditions of CO oxidation. It was found that the system demonstrates high stability in CO. However, the surface undergoes substantial chemical and morphological changes as the O2 is added to the reaction cell. Already at 300 K, gold nanoparticles begin to grow using a mechanism that involves the disintegration of small gold nanoparticles in favor of the large ones. With increasing temperature, the model catalyst quickly transforms into a system of primarily large Au particles that contains no ionic gold species.

Identifying the roles of Ru single atoms and nanoclusters for energy-efficient hydrogen production assisted by electrocatalytic hydrazine oxidation

With a much lower thermodynamic reaction potential, the hydrazine oxidation reaction (HzOR) can be employed as an alternative of water oxidation reaction to integrate with the cathodic hydrogen evolution reaction (HER), accomplishing an energy-efficient H2 production. The realization of this necessitates the development of the excellent bifunctional electrocatalysts for both HER and HzOR. Herein, a common Ru complex was applied to prepare a Ru/porous N-doped carbon composite (Ru/PNC) simultaneously containing abundant Ru single atoms (SAs) and ultrafine Ru nanoclusters (1.7 nm). Firstly, the new Ru/PNC catalysts containing both metal-metal as well as metal-substrate interactions display superb HER and HzOR activities in alkaline and neutral electrolytes, both greatly surpassing the sole Ru nanoparticles or Ru SAs sample. The controlled experiments and theoretical studies unravel water dissociation and H ad-desorption occurs on Ru SAs and nanoclusters, respectively, involving the proton transfer between them during the HER process, while HzOR is mainly proceeded on Ru SAs sites. Secondly, the alkaline overall hydrazine splitting with Ru/PNC only demands a voltage of 0.19 V to achieve 100 mA cm−2, demonstrating the huge energy-saving advantage compared with conventional water splitting. Additionally, the hydrogen generation can be readily operated with the hydrazine fuel cell and commercial solar cell with the appreciable H2 production rate of 32.7 and 27.1 mL cm−2 h−1, respectively.

Electrocatalysis in Li–O2 battery over single-atom catalyst based on g-C3N4 substrate

The development of Li–O2 battery is severely hindered by the sluggish reaction kinetics of the oxygen electrode. Herein, we perform a first-principles study of single transition metal atom supported on g-C3N4 substrate (TM/g-C3N4) as potential single-atom catalyst (SAC) in Li–O2 batteries. Combined electronic analysis and thermodynamic calculations, the electrocatalytic mechanism of TM/g-C3N4 SACs in Li–O2 batteries is elucidated. Due to strong metal-substrate interactions, the TM atom is durably anchored at the unsaturated pyridine N site in the holey g-C3N4 substrate, thereby enabling long cycling stability of the oxygen electrode. Among the fifteen candidates studied, Ru/g-C3N4 SAC exhibits the lowest discharge and charge overpotentials. This behavior can be attributed to the synergistic effect of the moveable d electrons of Ru and electron-rich N coordinators, which results in significant interfacial charges, metallic electrical conductivity, and large spin magnetic moments of the RuN2 active center. This study provides in-depth atomic and electronic insights into the catalytic mechanism of TM/g-C3N4 SACs in Li-O2 batteries.

Fe-N-C Boosts the Stability of Supported Platinum Nanoparticles for Fuel Cells.

The poor durability of Pt-based nanoparticles dispersed on carbon black is the challenge for the application of long-life polymer electrolyte fuel cells. Recent work suggests that Fe- and N-codoped carbon (Fe-N-C) might be a better support than conventional high-surface-area carbon. In this work, we find that the electrochemical surface area retention of Pt/Fe-N-C is much better than that of commercial Pt/C during potential cycling in both acidic and basic media. In situ inductively coupled plasma mass spectrometry studies indicate that the Pt dissolution rate of Pt/Fe-N-C is 3 times smaller than that of Pt/C during cycling. Density functional theory calculations further illustrate that the Fe-N-C substrate can provide strong and stable support to the Pt nanoparticles and alleviate the oxide formation by adjusting the electronic structure. The strong metal-substrate interaction, together with a lower metal dissolution rate and highly stable support, may be the reason for the significantly enhanced stability of Pt/Fe-N-C. This finding highlights the importance of carbon support selection to achieve a more durable Pt-based electrocatalyst for fuel cells.

Isolated transition metal nanoparticles anchored on N-doped carbon nanotubes as scalable bifunctional electrocatalysts for efficient Zn–air batteries

Accelerating the sluggish anode reaction in a Zn–air battery can improve its energy efficiency, but the large-scale development of this battery is hindered by the lack of bifunctional catalysts. Herein, we designed a one-step carbonization strategy for synthesizing monodispersed Co nanoparticles supported on N-doped carbon nanotube (Co/CNT), which shows excellent bifunctional electrocatalytic performance with long-term durability for oxygen reduction reaction/oxygen evolution reaction. The formation of carbon substrates from the carbonization of nitrogenous organic molecules are benefit to capture more Co nanoparticles though strong metal–substrate interaction, then construct high-density effective active sites of the Lewis base for accelerating the electrocatalytic reaction process. To verify its superior performance, a rechargeable Zn–air battery with a Co/CNT air electrode was subsequently constructed. The battery exhibits an open-circuit voltage of 1.41 V and a specific discharge capacity of 835.2 mAh/gZn, which can be continuously charged and discharged with good cycle stability. Our study provides a new strategy for developing various practical carbon-based non-noble metallic bifunctional electrocatalysts with promising performance in electrocatalysis and batteries to achieve the target of carbon neutrality.

A Borane Lewis Acid in the Secondary Coordination Sphere of a Ni(II) Imido Imparts Distinct C-H Activation Selectivity.

Two borane-functionalized bidentate phosphine ligands that vary in tether length have been prepared to examine cooperative metal-substrate interactions. Ni(0) complexes react with aryl azides at low temperatures to form structurally unusual κ2-(N,N)-N3Ar adducts. Warming these adducts affords products of N2 extrusion and in one case, a Ni-imido compound that is capped by the appended borane. Reactions with 1-azidoadamantane (AdN3) provide a distinct outcome, where a proposed nickel imido intermediate activates the sp2 C-H bonds of arenes, even in the presence of benzylic C-H sites. Combined experimental and computational mechanistic studies demonstrate that the unique reactivity is a consequence of Lewis-acid-induced polarization of the Ni-NR bond, potentially providing a synthetic strategy for chemoselective reaction engineering.

Study of Cu, Co and Ru Nanoclusters on MoS2 to Predict Thin Film Morphology

Interfaces of 2D materials with metals are of interest for a large variety of applications, including sensors, batteries, catalysis, electronics, and semi-conductor devices. Transition metal dichalcogenides (TMDs) and specifically MoS2 are some of the most widely studied 2D materials. A detailed understanding of the interactions of metals with 2D TMDs can give useful insights into possible applications for metal-TMD systems. However, the literature focuses mainly on comparing trends in single atom adsorption and studying nanoparticles on MoS2 monolayers.In this work we aim to increase the understanding of metal-MoS2 interactions and metal nucleation on TMDs. We use density functional theory (DFT) to study the adsorption of small metal clusters with up to four atoms on MoS2 monolayers. Insights gained from this work allow us to understand the initial nucleation of metal thin films on TMDs as well as predict the likely morphology of the thin film as it grows.The metals studied are Cu, Co and Ru, which are chosen for their range of applications, particularly in electronics. Metal-substrate interactions, preferred adsorption modes and stable nanocluster geometries are presented on pristine MoS2 and in the presence of the readily formed sulfur vacancy. The strength of interaction between the metals and MoS2 is in the order Co > Ru > Cu. Metal-substrate interactions are localised to the adsorption site; however we find that both Ru and Co can induce formation of sulfur vacancies through the formation of the corresponding metal sulfide.

Boron-doping effect on the enhanced hydrogen storage of titanium-decorated porous graphene: A first-principles study

The exploitation of solid hydrogen storage materials is an important part of the large-scale application of hydrogen energy. However, Metal agglomeration is one of the main reasons that restrict the hydrogen storage performance of carbon-based hydrogen storage materials. Herein, we develop Ti-decorated boron doped porous graphene as a novel hydrogen storage material based on first-principles calculations. The geometry and electronic structure of Ti-decorated porous graphene with and without boron doped are calculated. Doping boron in porous graphene (PG) can significantly increase the metal-substrate interaction and prevents the formation of Ti-metal clusters. The Ti atom-decorated boron-doped porous graphene (Ti–B/PG) system can stably adsorb sixteen hydrogen molecules with a gravimetric hydrogen uptake of 8.58 wt%. The thermodynamic calculations prove a high usable capacity of the material, at the adsorbing and desorbing conditions of 25 °C, 30 atm and 100 °C, 3 atm. The excellent hydrogen capacity, good recyclability, and desirable desorption capacity of Ti–B/PG make it a very prospective material for hydrogen storage.

Structure and Stability of Small Metal Clusters on Stoichiometric and Defective 2D MoS2

Layered materials, such as MoS2, are of great interest to the research community due to their wide range of potential applications. They are of particular interest as supports for low dimensional metal catalysts, as well as for use in the electronics industry as ultra-thin diffusion barriers in semi-conductor device interconnects.Thus, understanding the interaction between a variety of metal structures and the MoS2 monolayer is of great importance. In previous studies the focus has been largely on the strength of the interaction between a single atom or a nanoparticle of a wide variety of metals, which creates a significant knowledge gap in thin film nucleation on 2D materials. To begin addressing this deficit, we present a density functional theory (DFT) study of the adsorption of small metal structures, with up to four atoms, on a monolayer of MoS2. The metals of interest are Cu, Co and Ru, chosen for their relevance in electronics applications. We show how the metal-substrate interaction changes depending on the particular metal, as well as the mode of adsorption and overall nanocluster structure. Further, we show the effect that the presence of a sulphur vacancy in the monolayer has on the metal-substrate interaction, as this is a commonly observed defect.The strength of interaction between the metals and MoS2 is in the order Co > Ru > Cu. The effect of adsorption on MoS2 is localised to the metal cluster, however depending on the particular structure, some distortions of the MoS2 lattice can be observed upon adsorption of Ru.

Effect of Functional Substrate on the Electrocatalytic Oxygen Evolution Reaction Activity of IrO2 Nanoparticles

Water electrolysis (WE) using proton exchange membrane water electrolyser (PEMWE) stands as one of the cleanest methods to produce hydrogen from water which is the greener alternative that can replace fossil fuels. Oxygen evolution reaction (OER) that happens at its anode is both thermodynamically and kinetically demanding. IrO2 is the only known catalyst that can be used in acidic conditions but its high overpotential ~330 mV and cost preclude its future use.In the past, several attempts have been made to tune the catalytic activity, durability and overpotential by changing the morphology and electronic structure. The high surface area nanostructures could achieve decent activity but the overpotential and durability are still at stake. The high surface area nanostructures could achieve decent activity but the overpotential and durability are still at stake. Norskov1 et al., showed a linear relation between metal oxide d band centre and binding energies to O (intermediates) to the surface (ΔEO) which play a key role in determining the overpotential of the system. Hence, tuning of electronic structure by doping with other metals like Ru, Ni, Co, Pb, Y, Se, Sn, Sr2 etc or with fluorine3 was found to be trending in recent years. But, the leaching of alloying metals (durability) and precise tuning of electronic structure are not achieved. Recently our group has come up with a novel strategy of tuning the electronic structure of IrO2 nanoparticles (nps) by (a) using electrochemically stable carbon and doped carbon substrates4,5 (b) very strong metal substrate interaction and (c) changing the electronic structure of IrO2. By using 10 at% nitrogen doped graphene, overpotential was reduced to 260-270 mV with very high durability. There is always a limit for heteroatom doping using conventional ways. Further very less works on precise tuning of electronic structure and anchoring of IrO2 nanoparticles to substrate gives a scope of research.In this regard conducting polymers as substrates with coordination sites for anchoring the nanoparticles and tuning the electronic structure was explored in this study. An electropolymerizable monomer bearing α-diimine and thienyle groups was prepared by condensation between acenaphthequinone and 2 equivalents of aminothiophene. Electropolymerization technique was utilized to prepare polythiophene (PTh) on TiO2 nanotube (PTh-TNT) array as substrate. Further, the α-diimine moiety was utilized to prepare polythiophene-Ir metal complex. Ir metal complex centers could act as the nucleation sites for the growth of IrO2 nanoparticles due to which the electronic interaction with IrO2 and the diimine ligand will be still active. This interaction may lead to alter the electronic states of IrO2 like that of Ir in the complex at the same time will anchor the IrO2 nanoparticles strongly that results in high activity and durability during OER. For comparison TNT-PTh-IrO2 material without prior complexation was also prepared. Shift in the electron structure was characterized by X-ray photoelectron spectroscopy. The shift of binding energy (BE) of Ir 4f peak of TNT-PTh-IrO2 (with complex) to a lower BE compared to TNT-PTh-IrO2 (without complex) was a clear indication for increased electron cloud on IrO2. This shift of electron cloud will modulate the bond length of intermediate ions and help in their easy mass transfer leading to higher activity. Electrocatalytic OER activity was studied by linear-sweep voltammetry (LSV) technique in 3 electrode system in 1 M H2SO4. The effect of anchoring through coordination showed twice the activity compared to IrO2 on polythiophene without anchoring (Figure 1). Further a clear reduction in overpotential was also observed. When compared with TNT-IrO2, TNT-PTh-IrO2 with complexation showed at least 10 times higher current density. Further, preliminary chronopotentiometry showed no change in the over potential at 10 mAcm2 for 5 h. Thus, utilization of strong coordination of α-diimine in the polythiophene structure was key in modifying the electronic structure and anchoring resulting very high OER activity in acidic environment.Acknowledgement: We thank financial support by JSPS, KAKENHI, grant number 19K15674.

Ionic Liquid Mediated Decoration of Pt Nanoparticles on Graphene and Its Electrocatalytic Characteristics

In most of the conventional ionic liquid (IL) or poly-ionic liquid (PIL) mediated Pt carbon catalyst preparations, IL or PIL are covalently linked to the carbon involving complex reaction procedures. IL or PIL acts as the interface between Pt and carbon which increases the internal resistance of the material resulting in high overpotentials for electrocatalysis. In this regard we present a novel methodology to ionically tag IL to graphene that can easily be removed during the chemical reduction procedure for Pt decoration. We successfully prepared platinum nanparticles decorated on ionic liquid treated graphene (Pt-TMIm-rGO) material using a simple and scalable preparation method and systematically characterized. To understand the electrocatalytic efficiency of the material prepared, oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) characterization were studied and benchmarked with commercial counterparts. X-ray photoelectron spectroscopy results revealed a modulation of d-band centre of Pt and strong metal substrate interaction that reduced the over potential and increased durability. Pt-TMIm-rGO showed very high mass activity, low over potential compared to its counterparts in both ORR and MOR catalytic reactions. Pt-TMIm-rGO showed a high mass activity of ∼346 A g−1 at 0.9 V vs RHE in the case of ORR and 195.2 mA g−1 in case of MOR at 0.86 V vs RHE.

S-Block chemistry in weakly coordinating solvents.

Alkaline earth metal catalysis has been a growing field in recent years. To enhance reactivity and to understand the metal-substrate interactions in more detail, reactions are increasingly carried out in weakly coordinating solvents. This article gives an overview over the two main approaches to facilitate this, which are either through the employment of highly dipolar haloaryls as solvents, or by increasing the solubility of the ligand systems. The resulting coordination modes and reactivities are presented together with the synthetic strategies. Additionally, the latest results of group 1 complex chemistry in aliphatic solvents are illustrated and future challenges are highlighted.

Interface study of thermally driven chemical kinetics involved in Ti/Si3N4 based metal-substrate assembly by X-ray photoelectron spectroscopy

Diffusion mediated interaction in metal-substrate assembly during high temperatureannealing leads to possible formation of new composite materials. Here, sputtered grown Ti films on Si3N4/Sisubstrate has been reported to produce titanium nitride and silicide based binary composites while undergoing high vacuum annealing process at temperatures 650 °C andabove. Diffusion of thermally decomposed Si and N atoms from Si3N4 and their subsequent chemical reaction with Ti have been probed by X-ray photo electron spectroscopy. For annealing at 800 °C and above, most of the Si atoms show preferences to stay in elemental form rather than developing silicide phase with Ti. Whereas atlower annealing temperature, silicide becomes the dominant phase for decomposed Si atoms. However, N atoms react promptly with Ti and form TiN which appears as the majority phase for each of the studied annealing temperature. Further, the nitride andsilicide phases across the films have been compared quantitatively for various annealing temperature and the maximum silicide formation is observed for the sample annealed at 780 °C. Finally, the thermally anchored metal-substrate interaction mechanism can be exploited to fabricate disordered superconducting TiNfilms where TiSi2 and Si can be used to tune the level of disorder by altering the annealing temperature.