Activity Of Catalysts Research Articles

High‐Entropy Ag‐Ru‐based Electrocatalysts with Dual‐Active‐Center for Highly Stable Ultra‐Low‐Temperature Zinc‐Air Batteries

The development of advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for rechargeable zinc‐air batteries (ZABs). Herein, a unique dual active center alloying strategy is proposed to achieve the efficient bifunctional oxygen catalysis, and the high entropy effect is further exploited to modulate the structure and performance of the catalysts. The MOF‐assisted pyrolysis‐replacement‐alloying method was employed to construct the CoCuFeAgRu high‐entropy alloy (HEA), which are uniformly anchored in porous nitrogen‐doped carbon nanosheets. Notably, the obtained HEA catalyst exhibits excellent catalytic performance for both ORR and OER, and a peak power density of 136. 53 mW cm‐2 and an energy density of 987.9 mAh gZn‐1, surpassing the most of the previously reported bifunctional oxygen electrocatalysts. Moreover, the assembled flexible rechargeable ZAB enables excellent performance even at the ultralow temperature of ‐40°C, with an energy density of 601.6 mAh gZn‐1 and remarkable cycling stability up to 1,650 hours. Combined experimental and theoretical calculation results reveal that the excellent bifunctional catalytic activity of the HEA catalyst originated from the synergistic effect of the Ag and Ru dual active centers, and the optimization of the electronic structure by alloying effect.

First-Principles Calculations and Machine Learning of Hydrogen Evolution Reaction Activity of Nonmetallic Doped β-Mo2C Support Pt Single-Atom Catalysts.

The most widely used catalyst for the hydrogen evolution reaction (HER) is Pt, but the high cost and low abundance of Pt need to be urgently addressed. Single-atom catalysts (SACs) have been an effective means of improving the utilization of Pt atoms. In this work, we used a nonmetal (NM = B, N, O, F, Si, P, S, Cl, As, Se, Br, Te, and I) doped β-Mo2C (100) C-termination surface as the support, with Pt atoms dispersed on the support surface to construct Pt@NM-Mo2C. Using density functional theory (DFT) calculations, we selected catalysts with excellent HER activity. Among 117 candidate catalysts, 49 catalysts exhibited ideal catalytic performance with Gibbs free energy of hydrogen intermediate (H*) adsorption (ΔGH*) values less than 0.2 eV. The ΔGH* values of 16 catalysts were even lower than that of Pt (ΔGH* ≈ 0.09 eV), with PtI@N2/4-a-Mo2C demonstrating the best performance (ΔGH* = -0.01 eV). Combined with electronic structure analysis, we could understand the impact of charge transfer between Pt and the underlying NM atoms on the strength of the Pt-H bond, thereby promoting HER activity. Using machine learning (ML), we identified that the primary influencing factors of the HER catalytic activity in the Pt@NM-Mo2C system were the Bader charge transfer of Pt (NePt), the d-band center of Pt (εdPt), and the atomic radius of NM (RNM), with NePt having the greatest impact on the HER catalytic activity.

Metal-organic framework-derived silver/copper-oxide catalyst for boosting the productivity of carbon dioxide electrocatalysis to ethylene

Electrochemical reduction of CO2 into valuable multi-carbon (C2) chemicals holds promise for mitigating CO2 emissions and enabling artificial carbon cycling. However, achieving high selectivity remains challenging due to the limited activity and active sites of CC coupling catalysts. Herein, we report an Ag-modified Cu-oxide catalyst (CuO/Ag@C) derived from metal-organic frameworks (MOF), capable of efficiently converting CO2 to C2H4. The MOF-derived porous carbon confines the size of metal nanoparticles, ensuring sufficient exposure of active sites. Remarkably, the CuO/Ag@C catalyst achieves an impressive Faradaic efficiency of 48.6% for C2H4 at −0.7 V vs. RHE, demonstrating excellent stability. Both experimental results and theoretical calculations indicate that Ag sites promote the production of CO, enhancing the coverage of *CO on Cu sites. Furthermore, the reconfiguration of charge density at the Cu-Ag interface optimizes the electronic states of the reaction sites, reducing the formation energy of the key intermediate *OCCHO, thereby favoring C2H4 production effectively. This work provides insight into structurally rational catalyst design for highly active and selective multiphase catalysts.

Insight and comprehensive study of Ni-based catalysts supported on various metal oxides for CO2 methanation

In this study, nickel supported on various metal oxides were prepared by simple impregnation and the performance for CO2 methanation was tested. The oxide supports were all prepared by thermal decomposition of metal salts to provide comparable oxide properties such as surface area. Among the investigated oxides, nickel supported on CeO2 and Y2O3 showed the highest CO2 conversion of 90% at 320 °C with highest CH4 selectivity of 99%. The order of catalyst activity (XCO2@320°C) was reported: Ni/CeO2 ~ Ni/Y2O3 > > Ni/La2O3 > Ni/ZrO2 > Ni/Al2O3 > Ni/MgO > Ni/CaO > > Ni/MnO. The physicochemical properties of the catalysts were analyzed by TEM, BET, XRD, ICP, H2-TPR, CO2-TPD, H2 chemisorption, TGA, Raman, and XPS. From the characterization results, the catalyst activity was independent to specific surface area of catalyst and crystallite size of Ni. The amount of oxygen vacancies and weak-to-medium basic sites exhibited major roles for enhancing catalyst activity. The CeO2 and Y2O3 as reducible oxide supports not only provided abundant oxygen vacancies / basic sites, but also promoted Ni dispersion with appropriate interaction between metal and support, resulting in higher reducibility at low temperature. The reduction of catalyst at high temperature can significantly improve the performance of Ni supported on non-reducible MgO. However, the Ni/CeO2 and Ni/Y2O3 reduced at high temperature suffered from coalescence of CeO2 and Y2O3, though Ni crystallite sizes are well preserved from sintering.

Boosting the bifunctional catalytic activity of Co3O4 on silver and nickel substrates for the alkaline oxygen evolution and reduction reactions

Developing an efficient bifunctional catalyst for oxygen reduction (ORR) and evolution reactions (OER) is a crucial step for the wide commercialization of alkaline water electrolyzers. However, a proper assessment and comparison of various catalysts is still challenging due to the different catalyst substrates and loadings. In this work, Co3O4 spinel nanoparticles (NPs) were investigated as a bifunctional catalyst at different substrates of glassy carbon or Ag bulk substrate or Ni particles and with different loadings. For Co3O4 (800 µg cm-2)/Ag electrode, not only the overpotential for ORR was 50 mV lower than the bare Ag electrode, but also the OER overpotential was 40 mV lower than the sole Co3O4. Besides, less than 1% peroxide intermediate was detected during ORR using the rotating ring disc electrode (RRDE) method, suggesting a 4-electron O2 reduction. Tafel slopes of 70 and 60 mV dec‑1 at Co3O4/Ag were obtained for ORR and OER, respectively. The improved bifunctional activity could be attributed to a synergistic effect between Co3O4 and the Ag support. For the loading effect, it is revealed that the number of accessible sites of Ag surface decreases with increasing the Co3O4 loading, as evaluated from lead-underpotential deposition measurements. Interestingly, after running ORR/OER cycles, the surface area increased by 4–6 times. This surface roughening was also confirmed by SEM and EDX. The study was extended to Co3O4+Ni mixed catalyst to validate the effect of the support on this induced synergism. Hence, this work provides a simple route for designing potential effective catalytic interfaces and contributes to unravelling the influence of the substrate and loading on the catalyst activity for water electrolyzers.

A New Powerful Magnetic Dark Catalyst Based on rGO/Fe3O4/CdSe Nanocomposite for Ultrafast Degradation of Methylene Blue Dye.

In the present study, Rgo/Fe3O4/CdSe as a dark catalyst material was synthesized by a refluxing method. The synthesized magnetic nanocomposites were studied by various analyses such as Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), Raman, Zeta and vibrating sample magnetometer (VSM). Characterization of structural analysis showed that the nanocomposites were successfully synthesized. The absorption spectrum was used to determine the dark catalyst activity of rGO/Fe3O4/CdSe nanocomposite. Analysis of the absorption spectrum showed that the prepared nanocomposites degrade the MB organic dye completely (100%) after 2min of stirring in the dark, also experimenting with different pH showed that the best performance for the degradation of MB occurs in neutral and alkaline media. The Raman spectrum analysis showed that the Fe3O4/CdSe quantum dots (QDs) were correctly incorporated on the reduced graphene oxide (rGO) nanosheets. Zeta potential analysis showed that rGO/Fe3O4/CdSe has a large amount of negative charge on its surface and the surface charge increased by about 16 mV compared to the Fe3O4/CdSe compound. BET and BJH techniques were used to determine the effective surface area and pore size diameter, BET results to determine the effective surface area showed that by adding graphene to the compound, the specific surface area increased from 42.877 m2g-1 to 54.1896 m2g-1. The radical scavenger experiment showed that electrons play an essential role in the degradation process. VSM analysis showed that the prepared nanocomposites have excellent superparamagnetic behavior, this advantage enables the easy collection of nanocatalysts by magnets from wastewater after dye degradation.

Grain boundary engineering for efficient and durable electrocatalysis

Grain boundaries in noble metal catalysts have been identified as critical sites for enhancing catalytic activity in electrochemical reactions such as the oxygen reduction reaction. However, conventional methods to modify grain boundary density often alter particle size, shape, and morphology, obscuring the specific role of grain boundaries in catalytic performance. This study addresses these challenges by employing gold nanoparticle assemblies to control grain boundary density through the manipulation of nanoparticle collision frequency during synthesis. We demonstrate a direct correlation between increased grain boundary density and enhanced two-electron oxygen reduction reaction activity, achieving a significant improvement in both specific and mass activity. Additionally, the gold nanoparticle assemblies with high grain boundary density exhibit remarkable electrochemical stability, attributed to boron segregation at the grain boundaries, which prevents structural degradation. This work provides a promising strategy for optimizing the activity, selectivity, and stability of noble metal catalysts through precise grain boundary engineering.

Engineering medium-entropy alloy nanoparticle nanotubes for efficient oxygen reduction

Fuel cells, as promising energy conversion devices, realize the direct conversion of hydrogen fuel chemical energy into electrical energy. The kinetics of cathodic oxygen reduction reaction (ORR) is slow and plays a decisive role in the output efficiency of fuel cells. Platinum catalysts have been commercialized, but their high cost, relatively low catalytic activity and poor cycling durability limit the development of fuel cells. The introduction of non-platinum components is an effective strategy to minimize the cost and maximize the activity. In this study, PtPdCu medium entropy alloy nanoparticle nanotubes (PtPdCu MEANPTs) that demonstrate high catalytic activity and long durability are presented. Combined with density functional theory calculations, the introduction of Pd and Cu modulates surface electronic structure and optimizes the oxygen adsorption energy, thus enhancing the catalytic activity. The 0D/1D hybrid structure exposes more surface sites and inhibits particle maturation. The atomic migration and rearrangement are emerged during the initial stage of potential cycling process, induing a palladium-rich outer layer and preventing the oxidation of platinum atoms. The best-performing Pt24Pd28Cu48 MEANPTs deliver the impressive ORR activity (1.42 A/mgPt at 0.9 V vs. RHE, which is 6.17 times that of commercial Pt/C) and durability (retaining 2.87 times the initial activity of benchmark catalyst after 30,000 potential cycles). Theoretical calculations have confirmed the regulation of alloying on the surface oxygen affinity and revealed the true active sites on the catalyst surface. This work explores the research direction of platinum-based multi-element catalysts with low platinum content and high catalytic activity.

Role of Structural and Compositional Changes of Cu2O Nanocubes in Nitrate Electroreduction to Ammonia.

Nitrate electroreduction reaction (NO3RR) to ammonia (NH3) still faces fundamental and technological challenges. While Cu-based catalysts have been widely explored, their activity and stability relationship are still not fully understood. Here, we systematically monitored the dynamic alterations in the chemical and morphological characteristics of Cu2O nanocubes (NCs) during NO3RR in an alkaline electrolyte. In 1 h of electrolysis from -0.10 to -0.60 V vs RHE, the electrocatalyst achieved the maximum NH3 faradaic efficiency (FE) and yield rate at -0.3 V (94% and 149 μmol h-1 cm-2, respectively). Similar efficiency could be found at a lower overpotential (-0.20 V vs RHE) in long-term electrolysis. At -0.20 V vs RHE, the catalyst FE increased from 73% in the first 2 h to ∼90% in 10 h of electrolysis. Electron microscopy revealed the loss of the cubic shape with the formation of sintered domains. In situ Raman, X-ray diffraction (XRD), and in situ Cu K-edge X-ray absorption near-edge spectroscopy (XANES) indicated the reduction of Cu2O to oxide-derived Cu0 (OD-Cu). Nevertheless, a remaining Cu2O phase was noticed after 1 h of electrolysis at -0.3 V vs RHE. This observation indicates that the activity and selectivity of the initially well-defined Cu2O NCs are not solely dependent on the initial structure. Instead, it underscores the emergence of an OD-Cu-rich surface, evolving from near-surface to underlying layers over time and playing a crucial role in the reaction pathways. By employing online differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared spectroscopy (FTIR), we experimentally probed the presence of key intermediates (NO and NH2OH) and byproducts of NO3RR (N2 and N2H x ) for NH3 formation. These results show a complex relationship between activity and stability of the nanostructured Cu2O oxide catalyst for NO3RR.

Controlled synthesis of the M doped (M = Fe, Cu, Zn, Mn)-Co4S3/Ni3S2 catalyst with high electrocatalytic performance for hydrogen evolution reaction in seawater and urea

Electrolysis of seawater is a promising method for producing hydrogen, but sluggish reaction kinetics and electrolyte containing corrosive ions limit its development. In this work, a series of M doped (M = Fe, Cu, Zn, Mn)-Co4S3/Ni3S2 catalyst has been prepared on Ni foam by hydrothermal method with excellent seawater and urea splitting performance. The unique 3D porous structure provides a large number of active sites for the catalyst, which has strong catalytic activity. Fe-Co4S3/Ni3S2 electrode showed excellent hydrogen evolution reaction (HER) catalytic activity in 1 M KOH + seawater and 1 M KOH + 0.5 M urea, driving a current density of 10 mA cm−2 at a low overpotential of 81 and 66 mV. In addition, Fe-Co4S3/Ni3S2 electrode also shows strong stability in 15 h stability test. The results show that although the impurity ions in seawater affect the activity of catalyst, the corrosion resistance of catalyst also improves the catalytic activity and stability. Density functional theory calculations show that this Fe-Co4S material exhibits the optimal Gibbs free energy of hydrogen, the introduction of this Ni3S2 material enhances the electrical conductivity of the material, and the synergistic catalysis of the two materials promotes the optimal hydrogen production performance of the Fe-Co4S3/Ni3S2 material. This work provides a novel understanding for the research of catalysts used in the electrolysis of seawater and urea.

Bifunctional catalytic activity of anion-doped LaSrCoO4 for oxygen reduction and evolution reactions.

Here, we synthesized Co-based, anion-incorporated‍ ‌R‌u‌d‌d‌l‌e‌s-d‌e‌n‌-‌Popper perovskite electrocatalysts (LaSrCoO4-x X y ) and compared their catalytic performances in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The ORR mechanism with the newly synthesized F-doped LaSrCoO4 catalyst was dominated by a four-electron process, and the number of electrons involved in the reaction increased compared with that for LaSrCoO4. The OER activity of the hydride-doped LaSrCoO4 catalyst was the highest among the LaSrCoO4 system catalysts. Density functional theory calculations revealed that there is a correlation between the Co 3d unoccupied orbital band centre and the OER activity. The addition of anions and substitution of metal sites improved the ORR and OER activities of the catalysts. Our findings confirmed that the addition of heteroatom anions can improve the activity of perovskite-type electrocatalysts, promoting their application in various fields.

Synthesis of low-entangled UHMWiPP using Hf-pyridyl amido catalyst activated by trityl tetrakis (pentafluorophenyl) borate

Recently we demonstrated that low entangled ultra-high molecular weight isotactic polypropylene having molecular weight up to 2.4 million g/mol can be synthesized using a Hf-pyridyl amido catalyst activated by dimethylanilinium tetrakis (pentafluorophenyl)borate. Herein, we used an aprotic borate (trityl tetrakis(pentafluorophenyl)borate) to activate a Hf-pyridyl amido catalyst leading to a fast and ease catalyst activation even at lower temperatures, thus yielding exceptionally high molecular weight (up to 7.7 million g/mol) having improved tacticity (mmmm up to 98.5 %) and peak melting temperature (up to 165 °C). Thus synthesized polymers show extremely slow equilibration process by rheological characterization, indicating the low entangled state. These polymers can be processed in solid-state, without melting, into uniaxial drawn tapes having high tensile strength (1.46 N/tex) and tensile modulus (33 N/tex). The superior mechanical properties enable the tapes to be used as reinforcing material for commercial polypropylene grades, opening the possibilities of making one-component easy-to-recycle composites.

Cellulose pyrolysis via liquid metal catalysis

Liquid metals are largely unexplored as catalytic media for biomass conversion. Unlike conventional solid-state catalysts which are prone to deactivation, liquid metals, i.e., low-melting metals operated above their melting point, can show resilience against coking, high thermal conductivity, and enhanced liquid-solid contact between catalyst and biomass feedstocks. This promise motivated the present investigation of liquid metals as catalysts for cellulose pyrolysis. Bismuth, tin, and indium were selected as liquid metal candidates, and their impact on cellulose devolatilization kinetics is studied via thermogravimetric analysis. The results indicate that all three metals show catalytic activity, with bismuth catalyzing volatiles formation, while indium and tin enhance char formation. Quantitative analysis of liquid product reveals that bismuth is selective to dehydration and functional rearrangement reactions, leading to anhydro sugars and functionalized furans formation. In contrast, indium and tin are selective towards dehydration, fragmentation reactions, and Diels Alder chemistry, leading to formation of C2-C4 fragments and aromatic compounds, as further confirmed via infrared spectroscopic analysis of the obtained chars. Finally, the Sn and Bi liquid metals’ stability against deactivation via coking is examined against conventional solid-state zeolite catalyst through multiple cellulose pyrolysis runs in the thermogravimetric analyzer (TGA) with the same batch of catalyst. While ZSM-5 zeolite catalyst's activity and selectivity declined and approached non-catalytic sand results (both the TGA curve and the liquid product distribution) within the first few runs, both Sn and Bi fairly maintained their robustness against coking for the conducted durability runs. Overall, the results show significant promise for this new class of catalysts for biomass pyrolysis.

Efficient one-pot tandem C-C formation reaction catalyzed by a multi-functionalized polyacrylonitrile fiber catalyst

A simple and straightforward method has been proposed in this work to construct a multi-functionalized polyacrylonitrile fiber catalyst containing carboxylic acid, tertiary amine, and quaternary ammonium salt to enable series one-pot C-C bond formation in water. The fiber catalyst was prepared from polyacrylonitrile fiber using a two-step method and characterized using various detection techniques. Furthermore, the activity of multi-functional synergistic catalysts can be controlled by adjusting the ratio of acid and base. It is noteworthy that the polyacrylonitrile fiber catalyst with an acid-base ratio of 3:1 (PANF-ABNCl3/1) exhibited superior catalytic activity and high yield in a variety of C-C generation reactions. Additionally, the PANF-ABNCl3/1 catalyst demonstrated exceptional recyclability (at least 10 times) and performed well in scale-up (7.4g, 96%) and continuous flow experiments (can be used continuously for 7 × 24h) using kettle and tubular fixed bed reactor respectively. These findings suggest that the PANF-ABNCl3/1 catalyst holds promise for industrialization.

Iron phosphides nanoparticles strongly coupled to N-doped carbon for high-efficiency oxygen reduction and evolution

Constructing composite structures is an effective strategy for tailoring the electronic configuration and balances the adsorption/desorption capability of oxygen-containing intermediates for obtaining high-performance bifunctional catalysts. Herein, an in-situ pyrolysis strategy was used to construct Fe2P nanoparticles supported on N-doped carbon (Fe2P/NC) catalyst. The DFT indicated that the catalytic activity of the as-prepared catalyst is significantly increased by the strong electronic interaction between the Fe2P nanoparticles and the nitrogen-doped carbon, which endows the catalyst with fast electron transfer capability and optimizes the free energy between the catalyst and the adsorbed intermediate, as well as the d-band center of the material. The as-synthesized Fe2P/NC has a low potential gap ΔE (ΔE = Ej=10 – E1/2) of ca. 0.75 V, a specific capacity as high as 833 mAh·gZn-1 and cycling stability for 1320 cycles at the current density of 10 mA·cm−2. Such a synthesis strategy provides an effective route to realizing applications for portable electronic Zn-air battery-related devices.

Hydrogenation of CO2 to light olefins over Ga2O3-ZIF-8 tandem catalyst

Tandem catalysts composed of metal oxides and zeolites have demonstrated significant potential for the hydrogenation of CO2 to light olefins. However, their development is hindered by the competing reverse water–gas shift reaction and carbon accumulation on the zeolite surface. To address these challenges, we developed a series of innovative tandem catalysts by substituting conventional zeolites with ZIF-8. Our research primarily focused on examining the effects of metal species and content, as well as the particle size of ZIF-8, on catalytic performance. Notably, we achieved a CO2 conversion of 20.2 % and a light olefins selectivity of 73.6 % using a catalyst with 20 % Ga2O3 content and a ZIF-8 particle size of 100 nm at a reaction temperature of 340 °C and pressure of 3.0 MPa. In order to improve the stability of the catalyst, ZIF-8 was modified with La to improve its thermal stability. A CO2 conversion of 23.5 % and a light olefins selectivity of 66.5 % were maintained after 50 h of continuous reaction. While the catalytic activity of La-modified catalysts is slightly lower than that of unmodified ones, their superior stability makes them more suitable for thermal catalytic hydrogenation of CO2. Various characterizations and theoretical calculations revealed that La modification not only enhanced the thermal stability of catalyst but also improved its adsorption and activation capabilities for the reacting gases. Furthermore, the reaction mechanism of CO2 hydrogenation to light olefins was investigated by in-situ diffuse reflectance Fourier transform infrared spectroscopy. This study provides a technical foundation for designing efficient catalysts based on metal–organic frameworks in the field of carbon dioxide thermal catalytic conversion.

Study on the effect and mechanism of support structure and characteristic on Ag-based catalysts for low-temperature selective catalytic oxidation of ammonia

Herein, the influence of support type and properties on the catalytic activity and selectivity of Ag-based NH3-SCO catalyst was studied through the evaluation of NH3-SCO performance, the physicochemical characterization of H2-TPR, NH3-TPD, N2 isothermal adsorption–desorption, XPR and XPS, and the mechanism study of 1H MAS NMR, In-situ DRIFTS and DFT calculations. Ag/nano-TiO2, Ag/Al2O3, and Ag/MnO2 all showed better NH3-SCO activity because of more abundant Brønsted and Lewis acid sites of Al2O3 and TiO2 and more actual Ag loading amount due to the larger specific surface area and suitable surface chemistry. The N2 selectivity of Ag/nano-TiO2 is significantly better, which may be due to the highly dispersed Ag species and the abundant Brønsted acid sites with higher N2 selectivity. The mechanism study showed that the terminal hydroxyl was the preferred consumption target of Ag species, and this consumption promoted the effective dispersion and stable anchoring of Ag on the TiO2 surface.

First principles insights into the electronic and magnetic properties of [formula omitted] doped with VIII-group transition metal single atom

Inspired by the unprecedented surface chemical reaction activity of single-atom catalysts (SAC), this research presents a theoretical study on the doping of SnO2(110) surface with transition metal group VIII atoms (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt). Using density functional theory (DFT), the formation energy, electronic structure, charge transfer, and magnetic moments of the SnO2(110) system before and after doping were investigated. The formation energies of the different doped systems vary depending on the doping position. The doping of transition metal (TM) atoms can induce produces both charge transfer and magnetic moment. The charge transfer is largest in the Pd-doped system, with + 0.68 e at the position of the penta-coordinated Sn atom (Sn5c position) and + 0.67 e at the position of the hexa-coordinated Sn atom (Sn6c position), while the Co-doped system exhibits the smallest charge transfer of + 0.19 e (Sn6c position). Fe, Co, Ni, Ru and Os atoms introduce magnetic moments, with the Fe-doped system (Sn5c position) having the highest magnetic moments of 2.91 μB. In the SnO2(110) surface system doped with TM atoms, there are varying degrees of orbital overlap between the TM atoms and their surrounding O atoms. This theoretical work provides valuable insights into the physical properties of metal oxide based single-atom catalysts.

Ab initio calculations of high-entropy clusters for oxygen reduction and evolution as well as CO2 reduction reactions

This study introduces a design concept for a high-entropy cluster (HEC) comprising of Fe, Co, Ni, Cu, and Rh metals supported on nitrogen-doped graphene. Five different configurations including CoNiCuRh@FeN4, FeNiCuRh@CoN4, FeCoCuRh@NiN4, FeCoNiRh@CuN4, as well as; FeCoNiCu@RhN4 with the mixing entropy change of ΔSmix = 0.14 meV/K were considered. The positive dissociation potential and negative formation energy suggested the electrochemical and thermodynamic stabilities of these materials. According to density functional theory (DFT + U) calculations, the CoNiCuRh@FeN4 catalyst led to the overpotentials of 0.37 VRHE, 0.37 VRHE, and 0.24 VRHE for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and CO2 reduction reaction (CO2RR) towards CO production, respectively. It was determined that, FeN4 acted as an active site, while CoNiCuRh-HEC behaved as the modulator. Also, FeNiCuRh@CoN4 catalyst led to the CO2RR overpotential of 0.35 VRHE towards CH3OH formation where CoN4 acted as the active site, and FeNiCuRh-HEC species acted as the modulator surpassing the activity of single-atom catalysts (SAC). Moreover, the density of states (DOS) and charge transfer analyses suggested that, the presence of a high-entropy cluster may enhance the charge transfer and stabilize the reaction intermediates, toward selective methanol formation. Therefore, a DFT-based strategy to design a high-entropy cluster was developed through electrochemistry and beyond.

One-pot synthesis of Ir subnanosized clusters supported on MWW nanosheets as effective catalysts for C-C bond hydrogenolysis

The rational design synthesis of metal catalysts with high dispersion and ordered structure is a challenging subject in materials chemistry and heterogeneous catalysis. In this study, we report one-pot synthesis of Ir subnanosized particles supported on MWW nanosheets and their application in hydrogenolysis of decalin. Here, it has been found that C-C bond cleavage occurs via a synergistic carbocation and carbene mechanism on Ir-containing catalysts, and via carbocation in the case of solid acids. The combination of optimal acidic and metallic site characteristics in the subnanosized Ir supported on MWW nanosheets Pill_Ir-ZN_150 sample contributes to the high activity of the final catalysts. We expect that these Ir catalytic systems will open up more opportunities for hydrogenolysis of naphthenics to high-value products.