Atomic Ratio Research Articles

Tuning Flame Spray Pyrolysis for Variation of the Crystallite Size in Cu/ZnO/ZrO2 and its Influence on the Performance in CO2‐to‐Methanol Synthesis

AbstractCO2 hydrogenation to methanol (MeOH) is a key transformation in the Power‐to‐liquid concept, which aims to store energy in chemical energy carriers and chemicals. Cu/ZnO/ZrO2 (CZZ) shows great promise due to its enhanced stability in the presence of water, a critical by‐product when utilizing CO2‐based feedstocks. The structure‐sensitivity of this reaction, especially for particle sizes below 10 nm and in three‐component systems, remains highly debated. Herein, we systematically prepared a series of CZZ catalysts by flame spray pyrolysis (FSP) to vary the crystallite size and to study its effect on methanol synthesis in this three‐component system. FSP enabled us to maintain a fixed Cu/Zn/Zr ratio close to the commercial composition (61/29/10 atomic ratio), while varying the precursor feed rate. This resulted in variation in the crystallinity. The characterization by X‐ray diffraction and electron microscopy revealed an increase in crystallite size with rising feed rate for Cu and t‐ZrO2, whereas ZnO remained mostly unaffected. The testing of the materials in methanol synthesis uncovered an increase in performance, higher space time yield and MeOH selectivity, with decreasing crystallite size for two (Cu, t‐ZrO2) of its three components. The increased selectivity with smaller sizes might be attributed to an increase in interfacial sites.

Visible-Light-Stimulated Optoelectronic Neuromorphic Transistor Based on Indium-Gallium-Zinc Oxide via Bi2Te3 Light Absorption Layer.

To emulate a visual perception system, a bismuth telluride (Bi2Te3)/indium-gallium-zinc oxide (IGZO) heterostructure is introduced for optoelectronic neuromorphic transistors (ONTs). Amorphous IGZO is applied as a channel layer to exhibit low off-current, high mobility, and persistent photoconductivity, enabling light-stimulated neuromorphic characteristics. The atomic ratio of In/Ga/Zn was 9.4:9.8:5.2. For a light absorption layer, Bi2Te3 is applied due to a small bandgap, high photoresponse, and carrier concentration. However, conventional optoelectronic devices using Bi2Te3 exhibit insufficient performance owing to their excessive conductivity. To resolve the constraint, the oxidation of Bi2Te3 is performed to suppress its electrical conductivity. Finally, the IGZO ONT with a Bi2Te3 layer exhibits optoelectronic characteristics under visible-light irradiation. Under red-light irradiation having a light intensity of 5 mW mm-2, it exhibits enhanced optoelectronic characteristics including photoresponsivity, photosensitivity, and detectivity from 19.6 to 3.46 × 102 A/W, 4.95 to 1.46 × 108, and 1.45 × 107 to 2.13 × 1012 Jones compared to that without a Bi2Te3 layer, respectively. To confirm reproducibility and uniformity, we fabricated and compared the optoelectronic characteristics of 5 samples from batch to batch. Regarding optoelectronic neuromorphic characteristics, the ONT exhibits short- and long-term memory and a highly linear relationship between peak synaptic current and pulse number under red-light pulses. The paired-pulse facilitation index was 208%. To confirm the applicability of artificial visual perception, a 6 × 6 ONT array demonstrates long-term memory characteristic successfully after red-light irradiation with a Y-shaped pattern. In view of stability and reliability, we conducted three potentiation processes and compared the peak synaptic currents of each potentiation process.

Synergistic enhancement of Co doped Ni/NiOx nanofilms for catalytic hydrolysis towards ammonia borane

Transition metal catalysts exhibit a potential application for the hydrolytic dehydrogenation of ammonia borane (AB). The regulation of active sites through heterogeneous metal doping have been acknowledged as an efficient technology. Herein, Co-doped Ni/NiO nanofilms (Ni/NiCoOx-Y, Y is Co/(Co + Ni) atom ratio) were synthesized on an ionic liquid (IL)/water interface, in which Co atoms are uniformly doped in the basal NiO crystal lattice in the form of Co ions. The Ni/NiCoOx-Y catalysts exhibit a “volcanic” relationship between the catalytic activities for AB hydrolysis and Co-doped content. The optimized Ni/NiCoOx-20 nanofilms exhibit observably enhanced catalytic activity for AB hydrolysis, completely producing H2 within 4 min with a turnover frequency of 12.93 molH2·molmetal−1·min−1 and a low activation energy of 39.57 kJ mol−1. Moreover, Co doping can effectively enhance the stability of Ni-based nanofilms. The incorporation of Co ions into Ni/NiO crystal lattice slightly increases Ni electron density or Ni lattice expansion. Thus “electronic effect” strengthens the adsorption of H2O/intermediates and further beneficially accelerate combination of AB and H2O molecules, contributing to the improved catalytic activity. Meantime, the strong interaction of Co–Ni atoms can utilize the synergistic enhancement effect.

Anthropogenic actinides in seawater and biota from the west coast of Sweden

The assessment of the origin of the anthropogenic contamination in marine regions impacted by other sources than global fallout is a challenge. This is the case of the west coast of Sweden, influenced by the liquid effluents released by the European Nuclear Reprocessing Plants through North Sea currents and by Baltic Sea local and regional sources, among others. This work focused on the study of anthropogenic actinides (236U, 237Np and 239,240Pu) in seawater and biota from a region close to Gothenburg where radioactive wastes with an unknown composition were dumped in 1964. To this aim, a radiochemical procedure for the sequential extraction of U, Np and Pu from biota samples and the subsequent analysis of 236U, 237Np, 239Pu and 240Pu by Accelerator Mass Spectrometry was developed. The method was validated through the study of two reference materials provided by the International Atomic Energy Agency (IAEA): IAEA-446 (Baltic Sea seaweed) and IAEA-437 (Mediterranean Sea mussels). The 233U/236U atom ratio was also studied in the seawater samples. The obtained results indicate that the North Sea currents and global fallout are the major sources for 236U, 237Np and 239,240Pu to the studied area, without clear evidence of other local sources. Complementary, information on the Concentrations Factors (CF) in biota was obtained, for which the available information is very scarce. For seaweed, CF values of (4.07 ± 0.90)·103, 61 ± 22 and 76 ± 16 have been obtained for Pu, Np and U, respectively. Lower CF values of (3.37 ± 0.78)·102, 34 ± 10 and 15.9 ± 3.4 for Pu, Np and U, respectively, have been obtained for mussels.

Sustainable stabilization/solidification of electroplating sludge using a low-carbon ternary cementitious binder

Electroplating sludge (ES), due to its high dosages of heavy metals (HMs), is classified as hazardous waste, presenting risks to both health and environment. Stabilization/solidification (S/S) technology is extensively applied in ES treatment. This study designs a low-carbon ternary cementitious binder, limestone calcined clay cement (LC3), for S/S treatment of ES and investigates the immobilization mechanism of HMs in the crystalline products and calcium alumino-silicate hydrate (C-A-S-H) within LC3. Results show that CrO42- and Cd2+ are primarily stabilized in aluminate crystalline products by replacing SO42- and Ca2+ in the double-layered plate structure, respectively. The remaining CrO42- is captured by the (SiOOH)2AlCa⁺ groups in C-A-S-H generated from substitution of aluminum tetrahedra to bridging silicon tetrahedra. For positively charged Cd2+, it is mainly stabilized through ion exchange with Ca2+ on the C-A-S-H chains. The pozzolanic reaction of calcined clay increases the Al/Ca and Si/Ca atomic ratios in C-A-S-H, enhancing the immobilization efficiency of C-A-S-H to CrO42- and Cd2+. The synergistic effect of calcined clay and limestone, along with the dissolution of aluminosilicates in calcined clay, changes the structure and composition of hydration products, facilitating the chemical binding of CrO42- and Cd2+ by aluminate products. Moreover, the extra hydration products generated by the pozzolanic reaction and the formation of numerous carboaluminate phases strengthen the physical encapsulation performance to HMs. Regarding actual S/S performance, multi-scale evaluation results show that the designed LC3 binder achieves sustainable S/S of ES with high strength, low carbon emission, low cost, and low energy consumption.

Bucket effect of Cobalt Nanoparticles and Single Atoms in Nitroarenes Transfer Hydrogenation

Synergetic metal nanoparticles (NPs) and single atoms hold significant potential in reactions that require activating multiple substrate molecules. However, due to the differences in adsorption, activation and kinetics among distinct substrates during the multistep reaction process, the synergy and matching relationship between metal NPs and single atoms remain unclear. In this work, we synthesized a series of Co1-NP/CNT@CN-X dual-site catalysts with tunable molar ratios (X%) of Co single atoms to total Co species through a coordination site regulation (CSR) strategy and investigated the bucket effect of the dual active sites in the transfer hydrogenation of nitro compounds. Density functional theory calculations reveal that active hydrogen generation from ammonia borane hydrolysis primarily occurs at the surface of Co NPs, while nitroarenes hydrogenation predominantly takes place at Co single atoms, which is consistent with experimental findings. The optimized Co1-NP/CNT@CN-7.6 maintains high selectivity for nitro hydrogenation (> 99.9%) and exhibits conversion (99.9%) nearly 3.7 times that of the original Co1-NP/CNT@CN-1.6 catalyst (27%), achieved by overcoming the bucket effect between Co NPs and single atoms. This work not only elucidates the synergistic mechanisms of dual sites in transfer hydrogenation, but also establishes that optimizing matching effect is an effective approach to significantly enhance their catalytic performance.

Dynamic hydrogen bubble template electrodeposition of a self-supported Co-P electrocatalyst for efficient alkaline oxygen evolution reaction

The development of efficient, inexpensive, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) represents a significant challenge for the large-scale production of hydrogen. The primary obstacle to the advancement of OER is the necessity for a considerably higher overpotential than the theoretical oxygen evolution potential, due to the sluggish kinetics of the electron transfer reaction, which involves a large amount of thermodynamic energy. In this article, amorphous and cauliflower-like Co-P electrocatalysts were in situ grown on nickel foam by dynamic hydrogen bubble template (DHBT) electrodeposition method. The Co-P electrocatalyst with Co/P ratio optimal presented excellent electrocatalytic activities with a low overpotential of 239 mV for OER at 10 mA·cm−2 and long-term stability in 1.0 M KOH. The outstanding OER performance of the catalyst is mainly attributed the synergistic effect of amorphous and cauliflower-like structure, superhydrophilicity surface, and the electronic regulation by adjusting the atomic ratio of Co to P. This research will bring fresh ideas and strategies for developing novel simple, affordable, and efficient electrocatalysts to boost OER kinetics.

Influence of gaseous dielectrics on the wettability of Al-6061 alloy using dry μ-electrical discharge milling

Superhydrophobic surfaces are essential for applications such as self-cleaning and corrosion resistance. This study explores the fabrication of superhydrophobic surfaces on Al-6061 alloy using dry micro electrical discharge milling (μEDM milling) and investigates the effects of gaseous dielectrics on wettability under atmospheric conditions. Surfaces machined in an oxygen environment showed a surface area roughness (Sa) of 4.68 μm, 73.3 % higher than those machined in argon, attributed to enhanced metal oxide formation. Energy Dispersive X-ray Analysis (EDAX) indicated a significantly elevated O/Al atomic ratio of 0.80 for oxygen-machined samples, which was 73.9 % greater than argon-machined samples, suggesting the presence of hydrophilic compounds such as AlO(OH) and Al2O3. Additionally, X-ray Photoelectron Spectroscopy (XPS) revealed that Al2O3 peaks on oxygen-machined surfaces were broadened and shifted to higher binding energies, correlating with decreased contact angles and increased surface hydrophilicity. These results suggest that using oxygen as a dielectric in theelectrical discharge machining (EDM) process promotes oxide layer formation, resulting in hydrophilic characteristics, while machining in argon encourages organic adsorption and greater hydrophobicity. The findings of this research provide insights that can inform future efforts to tailor surface properties for advancements in aerospace, automotive, and biomedical engineering applications.

Grain refinement for indium zinc oxide ceramic targets by praseodymium doped induced blocked boundary migration

How to refine the grain has been a difficult problem in the preparation of high-performance ceramic targets. In this work, the doping-induced grain refinement strategy was proposed, indium zinc oxide doped with different concentrations of Pr (Pr-doped IZO, PrIZO) targets were obtained by optimizing the sintering time and holding temperature. Effects of Pr doping content on the density, phase microevolution, grain size and resistivity during the densification process as well as the kinetics of the grain growth and the mechanism of grain refinement of PrIZO targets were investigated in detail. The results demonstrated that PrIZO targets with the atomic ratios of Pr:In:Zn=0.01-0.03:1:1 all exhibited the excellent performance with high densification (>99.10%) and mere average grain size (<3.0 μm) at low sintering temperature of 1350 °C. Additionally, XRD and EDS analysis indicated that PrIZO targets were composed of In2O3 and Zn3In2O6 with slight PrInO3, which formed by the limited solid solubility of Pr element. Combined with theoretical calculations, it inferred that the mechanism of grain refinement was attributed to the solute transformation and fine PrInO3 distributed at the grain boundaries of In2O3 phases, which produced the drag effect of grain boundary migration, then hindering the further growth of grains.

Hydrogenation Reaction Mechanisms on Ni-Doped MoS2 Catalysts: A Density Functional Theory Study of Sulfur Edge Engineering and Coregulated Electronic Effects.

Precise modulation of local interatomic interactions affecting the electronic structure is an important method to control the catalytic activity and reaction pathways. In this study, we focused on the hydrogenation reaction of naphthalene and employed density functional theory calculations to investigate the specific influence of electronic effects triggered by the coregulation of Ni and sulfur edge engineering on the hydrogenation performance of Ni-doped MoS2 at different edge sulfur coverages (Ni-MoS2-X-θs). Our findings reveal that the interaction between Ni and S in the catalyst matrix material modifies the local electronic structure surrounding the sulfur atoms in the active site. Notably, Ni doping facilitates significant electron transfer, altering the charge and the electronic states at the catalyst edge. This, in turn, affects the adsorption capacity and reactivity of the catalyst, thereby reducing the energy barrier of the hydrogenation reaction. Furthermore, we paid particular attention to the modulation of catalytic activity and reaction pathways under the Eley-Rideal (E-R) mechanism. Interestingly, the sulfur coverage exhibited a nonlinear relationship with the adsorption and activation properties of the probe molecule. Typically, changes in the Mo edge sulfur coverage probability of Ni-MoS2-X-θs have a greater impact on the activation properties. Through comprehensive studies, we demonstrated that both compositional and structural factors must be considered when tailoring the catalytic performance. Importantly, adjusting the ratio of marginal sulfur atoms to metal atoms to 1:1 can effectively enhance the catalytic activity. This study provides valuable insights into the electronic effects regulating the hydrogenation reaction activity of MoS2-based catalysts. It also opens the way for the rational design of novel hydrogenation catalysts, offering a new strategy for optimizing the catalytic performance.

FeCoNi-Based Alloy Coatings as Low Overpotential Electrocatalysts for Alkaline Water Electrolysis.

Developing efficient, stable and low-cost electrocatalysts is a viable approach to solve the current energy crisis. It is found that increasing the surface area of the electrodes can effectively promote the electrocatalytic efficiency. Herein, the atmospheric plasma spraying (APS) technology was used to prepare FeCoNi-Ni3C alloy coating by adding Ni3C powder to FeCoNi powder with an equal molar ratio. After mechanical mixing, the atomic ratios of Ni3C in the powder are 25 %, 50 %, and 75 %, respectively. The results prove that the pores on the surface of the coating have increased after Ni3C doping, which can provide more active sites in the electrocatalytic process to promote the electrocatalytic reaction. By controlling the proportion of Ni3C, the porosity of the coating surface can be effectively regulated. The results suggested that in 1.0 M KOH electrolyte and 10 mA cm-2, the FeCoNi coating shows an overpotential of 191 and 277 mV for HER and OER, respectively, the HER overpotential of 50 at % Ni3C FeCoNi-Ni3C coating is 105 mV, and the OER overpotential is 212 mV. It is worth noting that the 50 at % Ni3C FeCoNi-Ni3C coating has a low Tafel slope of 45.78 mV dec-1 (HER) and 44 mV dec-1 (OER). Meanwhile, the attenuation of the overpotential of the 50 at % Ni3C FeCoNi-Ni3C coating after the stability test is almost negligible, indicating that the prepared catalyst has excellent electrocatalytic stability. Furthermore, the 50 at.% Ni3C FeCoNi-Ni3C coating catalyst has a low potential of 1.664 V at 10 mA cm-2 in a water-splitting system. This work provids a new idea for designing inexpensive electrocatalysts.

How Ir–Rh Alloys Improve Electrochemical Ammonia Oxidation Activity Studied by Density Functional Theory

AbstractThe electrochemical ammonia oxidation reaction (AOR) has applications in hydrogen storage and ammonia waste remediation. Using density functional theory, we investigate the mechanism of AOR on Ir, Rh, and their alloys at varied atomic ratios (, , and ) toward (g), (aq), and (aq) formation. This work introduces a method for computational alloy design by considering both electronic energy and configurational entropy. The structures considered are selective to (g) formation and all favored *N–N coupling. An alloy was found to reduce the theoretical onset potential for (g) formation relative to pure Ir while not exhibiting a downhill coupling step corresponding to catalyst poisoning by *N as shown for pure Rh, consistent with previous experimental work. The formation of (aq) and (aq) demand significantly higher potentials, typically limited by the final hydroxylation step before desorption.

Resistive switching and artificial synapses performance of co-evaporated Cs3Cu2I5 films

Perovskite memristors have garnered significant interest for their potential simulating artificial synapses; however, the presence of the toxic lead-based perovskites has hindered advancements in this field. In this work, a nontoxic, thickness-controllable Cs3Cu2I5 perovskite functional layer is synthesized through a dual-source vapor deposition for the Ag/Cs3Cu2I5/ITO memristor. The co-evaporation method shows advantages of various element, controllable atomic ratio and thickness, free impurity, and continuously uniform film. This device demonstrates an operating voltage of 1.2 V, a low power consumption of 0.013 W, a retention time exceeding 104 s, and an endurance of over 400 cycles. The synaptic behavior is emulated using the memristor, focusing on phenomena such as short-term potentiation and depression, paired-pulse facilitation, and spike-time-dependent plasticity. The migration of Na+ and Cl− ions, which occurs between the synaptic cleft and the postsynaptic membrane in biological synapses, is analogously represented by the movement of Ag+ ions between functional layer and the bottom electrode of the memristor. This process is further analyzed using the Hodgkin–Huxley neuron model. The Cs3Cu2I5-based memristor shows considerable promise for applications in storage systems and artificial synapses.

Effect of Mn/P atomic ratio on the microstructure and properties of Cu-Mn-P alloy

In this study, Cu-Mn-P alloys with Mn/P atomic ratios ranging from 1 to 3 were designed based on computational phase diagrams. The microstructures of these alloys were systematically investigated using a combination of TEM, EPMA, EBSD, and XRD. The results indicate that the alloy with a Mn/P atomic ratio of 2 exhibits optimal comprehensive properties. A simple thermomechanical treatment involving solution treatment followed by 70 % cold rolling and aging at 400°C for 6 hours resulted in a hardness of 186.8 HV, a tensile strength of 577 MPa, a yield strength of 548 MPa, and an electrical conductivity of 63.5 % IACS. Alloys with Mn/P ratios below 2 showed a reduced density of precipitates, leading to diminished precipitation hardening, while higher ratios resulted in increased manganese content in the solid solution, causing lattice distortions and reduced conductivity. TEM analysis confirmed that the precipitated phase was rod-shaped hexagonal Mn2P, which grew along the (100) plane of the matrix and maintained a coherent interface with the matrix. This research provides insights for the future development of high-performance quaternary Cu-Mn-X-P alloys.

High stability cubic perovskite Sr0.9Y0.1Co1-xFexO3-δ oxygen evolution by phase control and electrochemical reconstruction

Transition metal oxides are considered ideal electrocatalyst materials due to their low cost and high intrinsic activity. Among them, SrCoO3-δ has received increasing attention due to its multi-phase structure and tunable electronic properties, though its OER reaction kinetics and catalysis stability are unsatisfactory. Herein, based on a simple one-step solid-state reaction method, we use a small amount of rare earth Y ions (10 %) to transform H-SCO2.52 from a hexagonal structure to a stable cubic perovskite Sr0.9Y0.1CoO3−δ. While broadening the atomic ratio of Co and Fe in the B-site under the cubic perovskite Sr0.9Y0.1Co1-xFexO3−δ (x = 0–1), the relationship between the B-site electronic state, oxygen vacancies, and OER performance has been explored. Sr0.9Y0.1Co0.2Fe0.8O3−δ with a high concentration of oxygen vacancies, exhibits the lowest overpotential of 277 mV and maintains stability at 10 mA cm−2 for 88 h. The valence states of Fe and Co atoms in SYC0.2F0.8 O are optimized (Fe2+∼50.81 %, Co2+∼19.39 %), and the oxygen evolution activity is enhanced by electrochemical reconfiguration to form high-valence Fe and Co ions. Selective leaching of Sr ions via electrochemical surface reconstruction activates FeOOH and CoOOH amorphous layer active sites on the catalyst surface, significantly enhancing reaction kinetics.

Improving electrocatalytic OER activity of perovskites through insertion of ternary B-site metals

Anion exchange membrane water electrolysers (AEMWEs) demonstrate promise for efficient and cost-effective hydrogen production. However, the sluggish kinetics of the oxygen evolution reaction (OER) hinder their deployment, requiring the development of cheap and efficient electrocatalysts. In this work, lanthanum nickelate-based perovskites have been prepared via sol-gel synthesis and modified with ternary Co and Mn B-site metals, increasing their catalytic activity. X-ray diffraction (XRD) data indicates that a rhombohedral crystal structure has been achieved, with strain increasing as the percentage of ternary metal increases. The best performing cobalt-doped material, with a Ni:Fe:Co atomic ratio of 6:2:2, displayed a Tafel slope of 38.4 mV dec−1, with an OER overpotential of 348 mV at 10 mA cm−2, while the best performing manganese-doped material had a Ni:Fe:Mn atomic ratio of 8:1.5:0.5 and achieved 10 mA cm−2 at an OER overpotential of 361 mV and a Tafel slope of 42.7 mV dec−1. Electrochemical surface area (ECSA) calculations and particle size analysis suggest that the surface area and physical structure of the materials is not the most influential factor in determining catalytic activity; rather, electronic structure appears to play a defining role. XPS analysis has shown that both Co- and Mn-doped catalysts with an average Fe oxidation state around 2.5 and average Ni oxidation state around 2.4 demonstrate the best performance, likely due to an increased number of oxygen vacancies, which are necessary for achieving charge neutrality within the perovskite structure. Furthermore, ternary metal insertion results in a negative shift in the Ni2+ binding energy, facilitating electrochemical oxidation of Ni(II) to Ni(III), which is an essential prerequisite to the OER.

Microstructure transformation and mechanical properties of Co68AlxFe24.7-xV4.8Cr2.5 high-entropy alloys with dual-phase structures

Here, we designed Co68AlxFe24.7-xV4.8Cr2.5 (x = 16.5,17 and 18 at.%) high-entropy alloys (HEAs) by adjusting the atomic ratio of Fe and Al elements and successfully prepared a series of eutectic or near-eutectic HEAs by direct casting method. All designed HEAs exhibit a dual-phase eutectic or near-eutectic structure containing FCC and B2 phases. As the Al content increases from 16.5 to 18 at.%, the microstructure of the designed HEAs evolves from eutectic structure to hypereutectic structure. Among the studied HEAs, Co68Al16.5Fe8.2V4.8Cr2.5 HEA with eutectic structure exhibits an excellent strength-plastic combination, i.e., the yield strength of 761 MPa, the ultimate compressive strength of 2178 MPa and the fracture strain of 21.9 %, respectively. Such an excellent mechanical performance is mainly attributed to dislocation strengthening and interface strengthening. Furthermore, the stable K-S orientation relationship between FCC and B2 phases endows this HEA with remarkable strength-ductility combination. The design strategy in this work can provide new ideas for the development of high-performance dual-phase HEAs.

Improving the Chemical Utilization Efficiency of Pd Hydrodechlorination Catalysts through Hydrogen-Spillover Empowered Synergy between Pd and TiNiN Support.

The sustainable and affordable environmental application of Pd catalysis needs further improvement of Pd mass activity. Besides the well-recognized importance of physical utilization efficiency─the ratio of surface atoms forming reactant-accessible reactive sites─a lesser-known fact is that the congestion of these reactive sites, which we term as the chemical utilization efficiency, also influences the mass activity. Herein, by leveraging the 100% physical utilization efficiency of a fully exposed Pd cluster (Pdn) and the hydrogenation activity of TiNiN, we developed Pdn/TiNiN as a high physical and chemical utilization efficiency catalyst. During the catalytic hydrodechlorination of 4-chlorophenol and the subsequent hydrogenation of phenol, Pdn focuses on H2 dissociation and C-Cl cleavage, while TiNiN facilitates the subsequent hydrogenation of phenol into less toxic cyclohexanone via H-spillover. This synergy results in a 20-40-fold increase in the hydrodechlorination rate. The enhanced chemical utilization efficiency of Pd informs the design of Pdn/TiNiN microspheres for the conversion of halogenated organics from pharmaceutical wastewater and the design of a fixed-bed reactor to transfer trace amounts of 4-CP from river water. Ultimately, this approach decentralizes the use of Pd in environmental catalysis and reduction processes.

Controlled Formation of Silicon-Vacancy Centers in High-Pressure Nanodiamonds Produced from an "Adamantane + Detonation Nanodiamond" Mixture.

Despite progress in the high-pressure synthesis of nanodiamonds from hydrocarbons, the problem of controlled formation of fluorescent impurity centers in them still remains unresolved. In our work, we explore the potential of a new precursor composition, a mixture of adamantane with detonation nanodiamond, both in the synthesis of nanodiamonds and in the controlled formation of negatively charged silicon-vacancy centers in such nanodiamonds. Using different adamantane/detonation nanodiamond weight ratios, a series of samples was synthesized at a pressure of 7.5 GPa in the temperature range of 1200-1500 °C. It was found that temperature around 1350 °C, is optimal for the high-yield synthesis of nanodiamonds <50 nm in size. For the first time, controlled formation of negatively charged silicon-vacancy centers in such small nanodiamonds was demonstrated by varying the atomic ratios of silicon/carbon in the precursor in the range of 0.01-1%.

Glucose electrooxidation on carbon supported NiAu electrocatalysts

NiAu/C nanomaterials are synthesised using a wet chemistry method with targeted Au atomic ratios of 10 %, 20 % and 30 %. Physicochemical characterisations indicate that the materials have mean compositions close to the nominal ones but ca. 20 at% Au richer in average than expected (Au ratios of 13.6 at%, 23.1 at% and 35.9 at%, respectively). The NiAu/C materials are composed of Au-rich spherical-like Janus particles of several tenths nm and of a phase of very small Ni-rich nanoparticles and Ni(OH2) clusters. The electrochemical measurements in a 0.1 M NaOH/0.1 M glucose electrolyte indicate that the NiAu20/C catalyst is the most active for the glucose oxidation reaction, leading to a mass activity at +0.6 V vs RHE >1.5 times higher than that with a pure Au/C catalyst, although the Au content is almost 5 times lower. The chronoamperometry measurements for 900 s at +0.6 V vs RHE confirm the activity gain with the NiAu20/C catalyst. The electrolysis measurement at a cell voltage of + 0.6 V for 6 h shows that the NiAu20/C catalyst is selective towards the production of gluconic acid, with a faradaic efficiency higher than 100 %, indicating the occurrence of a 1-electron reaction with anodic hydrogen coproduction. At +0.8 V, the faradaic efficiency is lower than 100 %, indicating the formation of other products than gluconic acid, but at a very low extent (not detectable by HPLC) guarantying a very high selectivity towards gluconic acid.