Selective Catalysts Research Articles

Mesoporous silica gel doped with terbium, cerium and modified with silver as an efficient and selective catalyst for hydrogenation of unsaturated hydrocarbons

Mesoporous silica gel doped with terbium, cerium and modified with silver as an efficient and selective catalyst for hydrogenation of unsaturated hydrocarbons

Unravelling the Effect of Crystal Facet of Derived-Copper Catalysts on the Electroreduction of Carbon Dioxide under Unified Mass Transport Condition.

Altering the physical structure and chemical property of copper, i.e., particle size, surface morphology, composition or crystal facet, has been demonstrated to be effective in steering the selectivity of products in electrochemical reduction of carbon dioxide. However, these modifications generally result in the change of active surface area, leading to differences in the geometric current density and local pH, which are also demonstrated to be the key factors for observed selectivity change. In this work, we deconvolute the effect of mass transport and local pH from the effect of crystal facet by investigating five copper-based catalysts with identical roughness factors for electrochemical reduction of carbon dioxide in an H-cell. Interestingly, CuO-derived catalyst stands out as the best catalyst for C-C coupling. At -1.07 V vs. RHE, the faradaic efficiency of C2+ product reaches 44.3%, with a partial current density of -10.8 mA cm-2. Electrochemical adsorption of *OH reveals that the C2+ product selectivity of derived-copper catalysts correlates positively with the ratio of Cu(100)/Cu(110) of five catalysts. Additionally, in situ Raman spectroscopy reveals that the percentage of low-frequency band linear CO (LFB-CO), which is attributed to the adsorbed *CO on Cu(100) facet, increases with the C-C coupling efficiency.

Coherent NiS2@SnS2nanosheet for accelerating electrocatalytic nitrate reduction to ammonia.

The development of an effective and selective catalyst is the key to improving the multi-electron transfer nitrate reduction reaction (NO3-RR) to ammonia. Here, we synthesized a coherent NiS2@SnS2nanosheet catalyst loaded on carbon cloth via one-step solvothermal method. Experimental data reveals that the integration of NiS2and SnS2can enhance the NO3-RR performance in terms of high NH3yield rate of 408.2μg h-1cm-2and Faradaic efficiency of 89.61%, as well as satisfying cycling and long-time stability.

CO2-assisted Controllable Synthesis of PdNi Nanoalloys for Highly Selective Hydrogenation of Biomass-derived 5-Hydroxymethylfurfural.

The selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bishydroxymethyltetrahydrofuran (BHMTHF), a vital fuel precursor and solvent, is crucial for biomass refining. Herein, we report highly selective and stable PdNi nanoalloy catalysts for this deep hydrogenation process. A CO2-assisted green method was developed for the controllable synthesis of various bimetallic and monometallic catalysts. The PdNi/SBA-15 catalysts with various Pd/Ni ratios exhibited a volcano-like trend between BHMTHF yield and Pd/Ni ratio. Among all catalysts tested, Pd2Ni1/SBA-15 achieved the best performance, converting 99.0% of HMF to BHMTHF with 96.0% selectivity, surpassing previously reported catalysts. Additionally, the Pd2Ni1/SBA-15 catalyst maintained excellent stability even after five recycling runs. Catalyst characterizations (e.g., HAADF-STEM) and DFT calculations confirmed the successful formation of the alloy structure with electron transfer between Ni and Pd, which accounts for the remarkable performance and stability of the catalyst. This work paves the way for developing highly selective and stable alloy catalysts for biomass valorization.

Aminophosphonium organocatalysts for the ring-opening copolymerisation of epoxide and cyclic anhydride.

The Kirsanov reaction has been used to synthesise air stable, efficient and selective bifunctional aminophosphonium catalysts for the alternating ring-opening copolymerisation of cyclohexene oxide and phthalic anhydride without the need for a co-initiator.

Computational design for enantioselective CO2 capture: asymmetric frustrated Lewis pairs in epoxide transformations.

Carbon capture and utilisation (CCU) technologies offer a compelling strategy to mitigate rising atmospheric carbon dioxide levels. Despite extensive research on the CO2 insertion into epoxides to form cyclic carbonates, the stereochemical implications of this reaction have been largely overlooked, despite the prevalence of racemic epoxide solutions. This study introduces an in silico approach to design asymmetric frustrated Lewis pairs (FLPs) aimed at controlling reaction stereochemistry. Four FLP scaffolds, incorporating diverse Lewis acids (LA), Lewis bases (LB), and substituents, were assessed via volcano plot analysis to identify the most promising catalysts. By strategically modifying LB substituents to induce asymmetry, a stereoselective catalytic scaffold was developed, favouring one enantiomer from both epoxide enantiomers. This work advances the in silico design of FLPs, highlighting their potential as asymmetric CCU catalysts with implications for optimising catalyst efficiency and selectivity in sustainable chemistry applications.

Electrode Materials for NO Electroreduction Based on Dithiolene Metal–Organic Frameworks: A Theoretical Study

To quickly and efficiently screen catalytic materials with both activity and selectivity for the nitric oxide reduction reaction (NORR), we adopted a strategy that considers the activity of the side reaction hydrogen evolution reaction (HER) first. It can be seen that Fe3(THT)2 (THT = triphenylene-2,3,6,7,10,11-hexathiol) has extremely excellent HER activity, with a Gibbs free energy change (ΔG) of 0.007 eV. Based on the relationship between ΔG and theoretical exchange current density, all TM3(THT)2 can be divided into two regions: one is the absolute values of ΔG greater than 1 eV, the other is the absolute values of ΔG greater than 0 eV and less than 1eV. Obviously, the candidates with the absolute values of ΔG greater than 1 eV have poor HER performance, but this precisely provides the possibility of obtaining NORR catalytic materials with both excellent selectivity and activity. Subsequent calculation results show that the maximum ΔG change of the rate-determining step of Ta3(THT)2 is unexpectedly only 0.05 eV. Therefore, Ta3(THT)2 may be regarded as the NORR catalytic material with both excellent performance and selectivity. Based on the electron transfer and partial density of states (PDOS) analysis, it can be seen that Ta plays a crucial role in the activation stage of NO. The approach that considers the activity of the side reaction HER first may provide a new idea for rapidly screening highly selective and active NORR catalysts.

The tunable double-layer self-supporting Sb-Ni(OH)2 catalyst for boosting electrocatalytic water splitting

Green hydrogen preparation by electrolysis of water is key to driving the energy transition revolution. The development of low-cost, highly active and highly selective catalysts is a top priority for the commercial application from electrolytic water. This paper presents the synthesis of Sb-doped Ni(OH)2 nanosheets growing in situ on Ni foam, which serves as a self-supporting electrode. A straightforward one-step hydrothermal technique was employed to craft a dual-layer catalyst with a tunable morphology. Under the 1 M KOH conditions, Sb-Ni(OH)2-2.5/NF emerged as a bifunctional electrocatalyst, demonstrating an impressive HER performance of 159 mV (η10) and an OER performance of 430.8 mV (η50). The Sb-Ni(OH)2-2.5/NF also demonstrated remarkable stability by 3000 CV cycling tests. The Sb-Ni(OH)2-2.5/NF catalytic material prepared in this paper under laboratory conditions has a simple and inexpensive synthesis method, which helps to move electrolytic water catalysts from the laboratory to industry.

Constructing efficient Pd/Al2O3 catalyst for reverse water-gas shift via alkali-modification

The intrinsic nature of irreducible oxides (e.g. Al2O3) makes it hard to tune the charge state of supported late-transition metals, then difficult to adjust the selectivity of catalysts in CO2 hydrogenation. Herein, we find that modifying the Pd/Al2O3 catalyst with alkali metals (especially potassium) is efficient to boost the CO formation in CO2 hydrogenation. In comparison to Pd/Al2O3, approximately twenty-fold promotion in reverse water–gas shift (RWGS) rate was achieved on K-modified catalysts with proper K/Pd proportions. Combined structural characterizations demonstrate that the enhanced Pd-O interactions through K mediation stabilize the ca. 2 nm sized Pd particles as well as the electron-deficient state of Pd, which are robust enough during long-termed evaluation with undamped performance. In situ spectroscopy unveils a bi-dentate *HCOO associated reaction mechanism taking effect on alkali-modified catalysts, which contributes to ∼ 100 % of CO selectivity and 3318.1 mmol∙gPd-1∙h−1 of CO formation rate at 340°C.

Cu Nanowires Encapsulated by ZIF67 for Efficient Ammonia Electrosynthesis from Nitrate.

Electrochemical NO3 - reduction reaction (NO3RR) represents a green and sustainable way to produce valuable NH3 for both NH3 production and nitrate contaminant removal, and developing efficient, durable, highly selective catalyst is the key. Herein, we report a facile method to fabricate a catalyst composed of ultrafine Cu nanowires (Cu NWs) encapsulated by ZIF67, namely, CuNW@ZIF67, for efficient NH3 electrosynthesis from nitrate. The CuNW@ZIF67 catalyst exhibited excellent catalytic performance toward NO3RR in alkaline electrolyte, manifested by a large NH3 Faradaic efficiency of 93.7 % at -0.5 V versus reversible hydrogen electrode (RHE), a high energy efficiency over 30 % at -0.7 V, and robust long-term stability. Such intriguing catalytic properties are mainly ascribed to its structural merits and the strong electronic interaction between Cu NWs and ZIF67. DFT calculations revealed that, the Cu site can easily convert NO3 - into NO2 -, while the Co site plays a critical role in catalyzing the NO2 --to-NH3 process. The study can shed light on rational design of efficient, durable, and highly selective catalysts for NO3RR and beyond.

Relay Catalysis of Isolated Rhodium-Alloyed Copper Boosts Urea Electrosynthesis from Nitrate and CO2.

Urea electrosynthesis from the coelectrolysis of NO3- and CO2 (UENC) presents a fascinating approach for simultaneously migrating NO3- pollutants and producing valuable urea. In this study, isolated Rh-alloyed copper (Rh1Cu) is explored as a highly active and selective catalyst toward the UENC. Combined in situ spectroscopic analysis and theoretical calculations reveal the relay catalysis of the Rh1 site and Cu site to promote the UENC energetics, in which the Rh1 site activates NO3- to form *NH2 while the Cu site activates CO2 to form *CO. The formed *CO is then migrated from the Cu substrate to the nearby Rh1 site, which promotes the C-N coupling of *NH2 and *CO toward the urea formation. Prominently, Rh1Cu achieves an exceptional UENC performance in the flow cell, exhibiting the highest urea-Faradaic efficiency of 67.10% and urea yield rate of 50.36 mmol h-1 g-1 at -0.6 V versus RHE.

Nanoporous Carbon-Supported Bimetallic (Ni, Cu, and Fe)-Mo Catalysts for Partial Hydrogenation of Biodiesel.

Upgrading biodiesel or hydrogenated fatty acid methyl esters (H-FAMEs) by partial hydrogenation is a second-generation biofuel with high specific fuel characteristics, such as superior cold flow properties, higher oxidative stability, and lower hazardous gas emissions, allowing this biofuel to provide excellent fuel properties, over conventional biodiesel. This study assessed the potential of using nanoporous carbon produced from cattail leaves (CL) as an alternative catalyst support. We synthesized various catalysts including monometallic Mo/NPC, Ni/NPC, Ce/NPC, and Fe/NPC catalysts, as well as bimetallic molybdenum-based catalysts doped with nickel, copper, or iron for the partial hydrogenation of soybean biodiesel. The NPC support demonstrated a surface area (S BET) of approximately 1,323 m2g-1, which greatly increases the catalytic activity through the efficient dispersion of catalyst active sites. The partial hydrogenation reaction of soybean FAME over the MoNi/NPC catalyst obtained the highest catalytic activity with enhanced oxidation stability from 3 to 14 h, and the cloud point and pour point increased from 2 to 13 °C and -1 to 10 °C, respectively. Hence, the selection of catalysts is crucial due to their impact on the feasibility of the process and its economic viability. This article focuses on highlighting the effectiveness of a highly promising catalyst for partial hydrogenation as well as examining the variables that influence the primary reaction pathway.

Catalyst Design and Engineering for CO2-to-Formic Acid Electrosynthesis for a Low-Carbon Economy.

Formic acid (FA) has emerged as a promising candidate for hydrogen energy storage due to its favorable properties such as low toxicity, low flammability, and high volumetric hydrogen storage capacity under ambient conditions. Recent analyses have suggested that FA produced by electrochemical carbon dioxide (CO2) reduction reaction (eCO2RR) using low-carbon electricity exhibits lower fugitive hydrogen (H2) emissions and global warming potential (GWP) during the H2 carrier production, storage and transportation processes compared to those of other alternatives like methanol, methylcyclohexane, and ammonia. eCO2RR to FA can enable industrially relevant current densities without the need for high pressures, high temperatures, or auxiliary hydrogen sources. However, the widespread implementation of eCO2RR to FA is hindered by the requirement for highly stable and selective catalysts. Herein, the aim is to explore and evaluate the potential of catalyst engineering in designing stable and selective nanostructured catalysts that can facilitate economically viable production of FA.

Coupling In nanoclusters and Bi nanoparticles in nitrogen-doped carbon for enhanced CO2 electroreduction to HCOOH

CO2 electrochemical reduction reaction (CO2RR) to formic acid (HCOOH) is beneficial for the recycling of carbon resources, which needs the highly selective catalysts with long-term stability for HCOOH production. In this study, the coupling of In nanoclusters (Inclus) and Bi nanoparticles (Binps) in nitrogen-doped carbon was designed by the thermal decomposition of the mixture of bimetallic MOFs and dicyanamide. When the In/Bi molar ratio was 1:2 (Inclus/Binps-1:2), the hybrid catalyst achieved a HCOOH Faradaic efficiency (FEHCOOH) of 94.5 % at −1.1 V vs reversible hydrogen electrode (RHE) in an H-type electrolysis cell, superior to that of single metal counterparts. Moreover, the Inclus/Binps-1:2 can maintain high stability of structures during the catalytic process, leading to no significant decay of FEHCOOH over 32 h. The enhanced performance of Inclus/Binps-1:2 is attributed to the strong electron interactions induced by the charge transfer between the In and Bi sites in Inclus/Binps-1:2 catalyst. The tuned electronic structure results in an offset effect that optimizes the binding energy to HCOO* intermediate, thus accelerating the CO2 to HCOOH conversion, as proven by the in-situ ATR-SEIRAS and density functional theory (DFT) calculations.

Catalytic amination of 1,6-hexanediol for synthesis of N, N, N’, N’-tetramethyl-1,6-hexanediamine over Cu/Ni/Zn catalysts

Synthesis of N, N, N’, N’-tetramethyl-1,6-hexanediamine(TMHDA) by the amination of 1,6-hexanediol(HDO) and dimethylamine(DMA) at normal pressure over an outstanding Cu/Ni/Zn catalyst supported on aluminum oxide(γ-Al2O3) was studied in this article. Cu/Ni/Zn/γ-Al2O3(Cu: Ni: Zn = 28: 7: 12) exhibited excellent catalytic performance, which HDO was almost completely transformed and TMHDA reached 85 % selectivity at 200 °C. The amination of HDO required two hydrogenations and two dehydrogenations, and the selectivity of the amination catalyst depended on the balance of dehydrogenation and hydrogenation. Various characterization (TEM, BET, XRD, H2-TPR, XPS) demonstrated that the addition of Zn to the Cu/Ni catalyst could reduce the agglomeration of Cu/Ni particles and change the valence distribution of Cu. The Cu/Ni/Zn/γ-Al2O3 catalyst was a very promising and green method for the synthesis of tertiary diamines through amination of diols.

Heterobimetallic NiFe Complex for Photocatalytic CO2 Reduction: United Efforts of NiFe Dual Sites.

Catalytic CO2 reduction poses a significant challenge for the conversion of CO2 into chemicals and fuels. Ni-Fe carbon monoxide dehydrogenase ([NiFe]-CODH) effectively mediates the reversible conversion of CO2 and CO at a nearly thermodynamic equilibrium potential, highlighting the heterobimetallic cooperation for the design of CO2 reduction catalysts. However, numerous NiFe biomimetic model complexes have realized little success in CO2 reduction catalysis, which underscores the crucial role of precise bimetallic configuration and functionality. Herein, we presented a heterobimetallic NiFe complex for the photocatalytic reduction of CO2 to CO, demonstrating significantly enhanced catalytic performance compared to the homonuclear NiNi catalyst. Photocatalytic and mechanistic investigations revealed that with the assistance of a redox-active phenanthroline ligand, NiFe achieves dual-site activation of CO2 through a pivotal intermediate, NiII(μ-CO22--κC:κO)FeII, where the Lewis acidity of the FeII site plays an important role, as corroborated in the homonuclear FeFe system. This study introduces the first heteronuclear NiFe molecular catalyst capable of efficiently catalyzing the reduction of CO2 to CO, deepening insights into heterobimetallic cooperation and offering a novel strategy for designing highly active and selective CO2 reduction catalysts.

Copper-Based Metal–Organic Framework: Synthesis, Characterization and Evaluation for the Hydrogenation of Furfural to Furfuryl Alcohol

AbstractA novel Cu-MOF was synthesized at room temperature from commercially available and inexpensive reagents. The pre-catalyst was characterized using X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, inductively coupled plasma-optical emission spectroscopy, Fourier transform-infrared spectroscopy, powder X-ray diffraction, Brunauer-Emmet-Teller (BET) and scanning electron microscopy-energy dispersive X-ray spectroscopy. The Cu-MOF was characterized as microporous material with BET surface area and pore volume of 7.47 m2/g and 0.27 cm3/g, respectively, and is stable in most solvents. The MOF was evaluated as a heterogeneous catalyst for the hydrogenation of furfural to furfuryl alcohol (FA). Cu-MOF exhibited a high conversion of FF (76%) with selectivity towards FA (100%) at 140 °C, 50 bar for 24 h. The MOF was reused four consecutive times with a loss in catalytic performance. The decrease in catalytic activity could be attributed to the formation of inactive Cu(0) as revealed by HR-TEM and XPS studies. The HR-TEM of spent Cu-MOF showed a uniform particle size diameter of 3.5 nm. This work is significant in providing new strategies for the design and fabrication of highly selective MOF catalysts for the FF upgrading.

Important structural parameter for curvature effect of TM-N4 embeded C70 fullerenes as electrocatalysts for CO2 reduction interpreted with machine learning and first-principles calculations

In this work, TM-N4 sites embedded on curved C70 Fullerenes (TMN4(n)@C64, n = 1–5 which denote the doping positions and TM = Sc-Zn) were designed as efficient catalysts for electrochemical CO2 reduction reaction (ECO2RR). With interpretable machine learning (ML) and first-principles calculations, the performance of TM-N4 sites as possible electrocatalysts for ECO2RR under the curvature effect were revealed. After the screen procedure of catalyst stability, CO2 activation and selectivity of 50 designed systems, VN4(3), CrN4(3), MnN4(2), FeN4(2, 3, 5)@C64 were identified as high performance catalysts for ECO2RR to CH4, with limiting potential of -0.41 V, -0.26 V, -0.28 V, -0.35 V, -0.25 V and -0.17 V respectively, outperform the TM-N4 catalysts on the flat surface. A key structural descriptor K which can reflect the curvature effect of TM-N4 sites on the curved surface was identified with ML models. The gradient boosting regression (GBR) and sure independence screening and sparsifying operator (SISSO) algorithm reveal that the structural parameter K have strong association with the CO2 adsorption and significant influence on the selectivity of catalysts. Interestingly, the structural parameter K can influence more the binding of O-bonded intermediates than C-bonded intermediates. With the GBR algorithm, an effective model for the prediction of the limiting potential for C1 products were obtained. This study clarified the curvature effect of TM-N4 supported on the curved surface, and provides valuable guidance for the designing of TM-N4 single atom catalysts for ECO2RR on curved surface.

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.

Insights into the Effect of Crystal Facets and Sulfur Defects on the Product Selectivity of Various CdS Configurations for CO2 Photoreduction: A DFT Study

CO2 photoreduction into valuable hydrocarbons, such as CO, CH4, and C2H4, delivers a promising approach to address both environmental and energy challenges. Transition metal chalcogenides, particularly cadmium sulfide (CdS), have emerged as prominent candidates due to their tunable electronic properties and availability. This study delves into a comprehensive investigation of how CdS crystalline facets and sulfur-deficient surfaces modulate the product selectivity. Through employing density functional theory (DFT), we unravel the catalytic performance of various CdS crystal orientations and sulfur vacancy configurations. The results have shown that different CdS facets exhibit unique electronic characteristics and surface energetics, which influence the adsorption dynamics and reaction pathways. The introduction of sulfur vacancies further modulates the nature of active sites, leading to substantial shifts in product selectivity. A detailed investigation on the reaction mechanisms unveils that specific facets preferentially facilitate the formation of CO, while others are more conducive to the generation of hydrocarbons such as CH4 and C2H4, due to the variations in activation barriers and intermediate stabilities. These findings underscore the importance of crystal facet engineering and defect manipulation in tailoring catalyst performance thus providing valuable insights for the rational design of efficient and selective CO2 reduction metal catalysts.