Catalyst For Reaction Research Articles

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction.

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt-free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt-free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.

Instantaneous Thermal Energy for Swift Synthesis of Single-Atom Catalysts for Unparalleled Performance in Metal-Air Batteries and Fuel Cells.

Based on experimental and computational evidence, phthalocyanine (Pc) compounds in the form of quaternary bound metal-nitrogen (N) atoms are the most effective catalysts for oxygen reduction reaction (ORR). However, the heat treatment process used in their synthesis may compromise the ideal structure, causing the agglomeration of transition metals. To overcome this issue, we developed a novel method for synthesizing iron (Fe) single-atom catalysts with ideal structures supported by thermally exfoliated graphene oxide (GO). This was achieved through a short heat-treatment of only 2.5min involving FePc and N,N-dimethylformamide in the presence of GO. According to the synthesis mechanism revealed by this study, carbon monoxide acts as a strong linker between the single Fe atoms and graphene. It facilitates the formation of a structure containing oxygen species between FeN4 and graphene, which provides high activity and stability for the ORR. These catalysts possess an enormous number of active sites and exhibit enhanced activity towards the alkaline ORR. They have demonstrated excellent performance when applied to real electrochemical devices, such as zinc-air batteries and anion exchange membrane fuel cells. We expect that the instantaneous heat treatment method developed in our study will aid in the development of high-performing single-atom catalysts. This article is protected by copyright. All rights reserved.

Understanding mechanism conversion in hydrogen evolution reaction on PtSe2: Role of layer number explored by density functional theory

The emerging two-dimensional (2D) transition metal dichalcogenide PtSe2 is a promising catalyst for hydrogen evolution reactions (HER). In this study, we performed density functional theory (DFT) calculations to investigate the mechanism conversion of the HER over PtSe2 with respect to the changes in the number of layers of the catalyst. We found that the adsorption energy of hydrogen (ΔGH) changed with an increase in the number of 2D material layers, and the most significant change occurred when the number of layers was increased from one to two. Furthermore, we conducted dynamic calculations to reveal the mechanisms of the HER on the basal and Vse surfaces. Owing to the changes in ΔGH, the HER mechanism undergoes a conversion between Volmer–Heyrovsky and Volmer–Volmer'–Tafel mechanisms. Through frontier orbitals analysis, layer-stacking altered the bonding capability between hydrogen and PtSe2 surfaces by altering the electronic structure of the PtSe2 surface. This study demonstrates the synergistic effect of interlayer interactions on the HER over PtSe2 catalysts and can be helpful in stimulating innovative ideas for 2D material design.

Enhancing the physicochemical properties of nickel cobaltite catalyst for oxygen evolution reaction in anion exchange membrane water electrolyzers

Enhancing the physicochemical properties of nickel cobaltite catalyst for oxygen evolution reaction in anion exchange membrane water electrolyzers

Effects of porous structure and oxygen functionalities on electrochemical synthesis of hydrogen peroxide on ordered mesoporous carbon

Two-electron oxygen reduction reaction (2e− ORR) is a promising alternative to energy-intensive anthraquinone process for hydrogen peroxide (H2O2) production. Metal-free nanocarbon materials have garnered intensive attention as highly prospective electrocatalysts for H2O2 production, and an in-depth understanding of their porous structure and active sites have become a critical scientific challenge. The present research investigates a range of porous carbon catalysts, including non-porous, microporous, and mesoporous structures, to elucidate the impacts of porous structures on 2e− ORR activity. The results highlighted the superiority of mesoporous carbon over other porous materials, demonstrating remarkable H2O2 selectivity. Furthermore, integration of X-ray photoelectron spectroscopy (XPS) data analysis with electrochemical assessment results unravels the moderate surface oxygen content is the key to increase 2e− ORR activity. These results not only highlight the intricate interplay between pore structure and oxygen content in determining catalytic selectivity, but also enable the design of carbon catalysts for specific electrochemical reactions.

Optimized porous nanostructure of carbon fibers enabling excellent stability of Pt-based catalysts for oxygen reduction reaction

Facile synthesis of highly-dispersed Pt-based electrocatalysts on porous carbon supports with strong durability is extremely desirable for oxygen reduction reaction but remains challenging. The influence of pores in carbon supports on the stability and activity of catalysts is ambiguous and needs to be elucidated. Targeting this aim, herein, we prepared a series of carbon nanofibers with tunable pore diameter and specific surface area using the resorcinol-formaldehyde (RF) resins as a model system. Homogeneous composite precursors composed of RF resins and silica colloids were synthesized by the surfactant-assisted simultaneous polycondensation of RF resins and tetraethylorthosilicate (TEOS). The diameter of the pores induced by removal of silica could be controllable tailored through thermal treatment of the composite under various target temperatures. Pt3Co alloy nanoparticles loaded on the as-synthesized porous carbon nanofibers were prepared by an optimized wet-impregnation method. The experimental results indicated that the carbon nanofibers with pore size distribution focused on ∼1.27 nm and ∼2.34 nm provided the best stability without limiting current density decay, and negative shift of half-wave potential (E1/2) and mass activity (MA) loss of Pt after 20000 potential cycles are relatively mild. Conversely, negative shift of 21 mV, 15 mV and 22 mV in E1/2 and mass activity loss of 51.8%, 30.2% and 33.0% were observed for the Pt3Co nanoparticles supported on MC-60, MC-100 and MC-140 matrices which have pore size distribution focused on ∼2.73 nm, ∼2.73 nm as well as ∼4.66 nm, and ∼4.66 nm, respectively. This work demonstrates the importance of micropores and small mesopores for activity and long-term stability enhancement of carbon supported Pt-based electrocatalysts.

A review on Fe2O3‐based catalysts for toluene oxidation: catalysts design and optimization with the formation of abundant oxygen vacancies

Volatile organic compounds (VOCs) are typical pollutants with hazards for humans and the environment, and can be efficiently mitigated by catalytic combustion. Fe2O3‐based catalysts are a promising choice due to their low cost and strong redox ability. Several attempts have been made to promote the catalytic performance of Fe2O3 at low temperatures. This review summarizes the research progress on Fe2O3‐based catalysts for the oxidation of toluene, one of the most common and harmful VOC. Firstly, the properties and catalytical performance for Fe2O3‐based catalysts were summarized, and the reaction mechanisms for toluene oxidation on the surface of Fe2O3 were detailed to comprehend the role of oxygen vacancy. Then, the modification for single Fe2O3 catalysts, including synthesis parameters, structure and morphology control, has been introduced to reveal the correlation between physicochemical properties of catalysts and their activity. In addition, composite Fe2O3 catalysts, which can promote catalytic performance significantly due to the synergetic effect between different components, were comprehended. Finally, waste‐derived Fe2O3 catalysts with sustainable merit as converting waste into worth have been discussed. Moreover, the advanced machine learning tools, which are helpful in accelerating catalyst design, configuration optimization and reactivity prediction, have been introduced as an emerging research opportunity for the future.

Unraveling Oxidation and Spin States of a Single Fe-Based Meso-Macroporous Silica Catalyst in Fenton-like Reaction by Magnetic Measurements

Unraveling Oxidation and Spin States of a Single Fe-Based Meso-Macroporous Silica Catalyst in Fenton-like Reaction by Magnetic Measurements

The Influence of Ligands on the Pd-Catalyzed Diarylation of Vinyl Esters

The impact of ligands on the palladium-catalyzed 1,2-diarylation reaction course is presented. The application of Pd-dmpzc as a catalyst provides an efficient, chemoselective and sustainable protocol for the synthesis of valuable 1,2-diphenylethyl acetates. The reaction is conducted in water under mild conditions. Reaction products can be easily separated from the reaction mixture and catalyst by simple extraction. What is more, the rational choice of catalyst significantly reduces the leaching of the metal into the product and its contamination (0.1 ppm). Efficient phase separation and ultralow Pd leaching enable the reuse of the water medium containing the Pd-dmpzc catalyst several times without a significant loss of activity and with even higher selectivity (from 95% to 100% in the third cycle). The recyclability of both the catalyst and the reaction medium together with high chemoselectivity and low palladium leaching reduces the amount of waste and the cost of the process, exhibiting an example of a sustainable and green methodology.

Evaluating the Fe-doping effect on intermediate adsorption modulation for Co-based vanadates toward separation of hydrogen from water electrolysis

The optimization of intermediate adsorption is pivotal for enhancing the efficacy of catalysts in oxygen evolution reaction (OER). However, many Co-based catalysts exhibit excessive binding energy toward intermediates, thereby restricting the desorption process. To address this issue, we utilized the Co-based vanadates (CoV) as a model and observed that the incorporation of Fe can effectively mitigate the substantial accumulation of intermediates around the catalysts, achieving a balance between the adsorption and desorption. It can be attributed to the Fe-doping, which modulated the electronic structure of CoV, subsequently increasing the catalytic sites and intrinsic activity. As a result, the CoV-Fe exhibited a low overpotential of 260 mV at 20 mA cm−2, which decreased by 82 mV compared to pristine CoV. Besides, the electrolyzer based on CoV-Fe maintained a low cell of 1.46 V for water splitting and held a considerable attenuation of 4.49 % after 200 h of long-term operation.

Magnetic Field Enhanced Cobalt Iridium Alloy Catalyst for Acidic Oxygen Evolution Reaction.

Magnetic field mediated magnetic catalysts provide a powerful pathway for accelerating their sluggish kinetics toward the oxygen evolution reaction (OER) but remain great challenges in acidic media. The key obstacle comes from the production of an ordered magnetic domain catalyst in the harsh acidic OER. In this work, we form an induced local magnetic moment in the metallic Ir catalyst via the significant 3d-5d hybridization by introducing cobalt dopants. Interestingly, CoIr nanoclusters (NCs) exhibit an excellent magnetic field enhanced acidic OER activity, with the lowest overpotential of 220 mV at 10 mA cm-2 and s long-term stability of 120 h under a constant magnetic field (vs 260 mV/20 h without a magnetic field). The turnover frequency reaches 7.4 s-1 at 1.5 V (vs RHE), which is 3.0 times higher than that without magnetization. Density functional theory results show that CoIr NCs have a pronounced spin polarization intensity, which is preferable for OER enhancement.

Synergistic Effects of MOFs and Noble Metals in Photocatalytic Reactions: Mechanisms and Applications.

Photocatalytic technology can efficiently convert solar energy to chemical energy and this process is considered as one of the green and sustainable technology for practical implementation. In recent years, metal-organic frameworks (MOFs) have attracted widespread attention due to their unique advantages and have been widely applied in the field of photocatalysis. Among them,noblemetals have contributed significant advances to the field as effective catalysts in photocatalytic reactions. Importantly, noblemetals can also form a synergistic catalytic effect with MOFs to further improve the efficiency of photocatalytic reactions.However, how to precisely control the synergistic effect between MOFs and noblemetals to improve the photocatalytic performance of materials still needs to be further studied.In this review, the synergistic effects of MOFs and noblemetal catalysts in photocatalytic reactionsare firstly summarizedin terms of noblemetal nanoparticles, noblemetal monoatoms, noblemetal compounds, and noblemetal complexes, and focus on the mechanisms and advantages of these synergistic effects, so as to provide useful guidance for the further research and application of MOFs and contribute to the development of the field of photocatalysis.

Thermochemical Activation of Wood with NaOH, KOH and H3PO4 for the Synthesis of Nitrogen-Doped Nanoporous Carbon for Oxygen Reduction Reaction

Carbonization of biomass residues followed by activation has great potential to become a safe process for the production of various carbon materials for various applications. Demand for commercial use of biomass-based carbon materials is growing rapidly in advanced technologies, including in the energy sector, as catalysts, batteries and capacitor electrodes. In this study, carbon materials were synthesized from hardwood using two carbonization methods, followed by activation with H3PO4, KOH and NaOH and doping with nitrogen. Their chemical composition, porous structure, thermal stability and structural order of samples were studied. It was shown that, despite the differences, the synthesized carbon materials are active catalysts for oxygen reduction reactions. Among the investigated carbon materials, NaOH-activated samples exhibited the lowest Tafel slope values, of −90.6 and −88.0 mV dec–1, which are very close to the values of commercial Pt/C at −86.6 mV dec–1.

Metal Doping Regulates Electrocatalysts Restructuring during Oxygen Evolution Reaction.

High-efficiency and low-cost catalysts for oxygen evolution reaction (OER) are critical for electrochemical water splitting to generate hydrogen, which is a clean fuel for sustainable energy conversion and storage. Among the emerging OER catalysts, transition metal dichalcogenides have exhibited superior activity compared to commercial standards such as RuO2, but inferior stability due to uncontrolled restructuring with OER. In this study, we create bimetallic sulfide catalysts by adapting the atomic ratio of Ni and Co in CoxNi1-xSy electrocatalysts to investigate the intricate restructuring processes. Surface-sensitive X-ray photoelectron spectroscopy and bulk-sensitive X-ray absorption spectroscopy confirmed the favorable restructuring of transition metal sulfide material following OER processes. Our results indicate that a small amount of Ni substitution can reshape the Co local electronic structure, which regulates the restructuring process to optimize the balance between OER activity and stability. This work represents a significant advancement in the development of efficient and noble metal-free OER electrocatalysts through a doping-regulated restructuring approach.

Facile construction of core-shell AuPd nanochain networks in one-pot for ethanol oxidation

Palladium (Pd)-based catalysts have been extensively investigated in direct ethanol fuel cells (DEFCs) since the urgent energy and environmental problems. Rational design Pd-based catalyst with outstanding structure can optimize its electrocatalytic performance for ethanol oxidation reaction (EOR) catalyst. In this work, a facile strategy was proposed to prepare AuPd nanochain networks (NNWs) with core-shell structure by adjusting the reduction rate by slowly dropping the acidic reducing agent to the alkaline precursor solution system. The resulting catalysts exhibit a porous self-supporting structure with twisted features, exposing a large number of active sites. The optimized AuPd NNWs catalyst displays much-improved activity (3289.62 mA mg−1 Pd) and greatly enhanced electrocatalytic stability for EOR in comparison with that of commercial Pd/C catalysts. This enhanced activity can be attributed to the synergic effect of the Pd shell with the Au core as well as the twisted and self-supporting structure which can expose much more active sites and provide rich mass and electron transfer channels.

Copper-bonded polyoxomolybdates-based framework as a heterogeneous catalyst for the cascade click reaction and bromination

The selective conversion of alkynes into bromotriazoles over a single-component catalyst is highly desirable but presents significant challenges. In this study, we developed a robust copper-bonded polyoxomolybdates-based framework [Cu2(Mo6O20)]·2H2O (CPF-1), and it integrates the catalytic ability of Cu(I) site with the multielectron-transfer ability of polyoxometalates. As a result, CPF-1 exhibits favorable bifunctional catalytic activity for click chemistry and achieves 99% yield in the conversion of corresponding products to bromotriazoles. To our knowledge, CPF-1 represents the first heterogeneous catalyst that significantly enhances cascade reaction with excellent efficiency and sustainable recyclability. Additionally, the possible cascade catalytic mechanisms of these two reactions are also proposed.

Magnetic Aerogels for Room-Temperature Catalytic Production of Bis(indolyl)methane Derivatives

The potential of aerogels as catalysts for the synthesis of a relevant class of bis-heterocyclic compounds such as bis(indolyl)methanes was investigated. In particular, the studied catalyst was a nanocomposite aerogel based on nanocrystalline nickel ferrite (NiFe2O4) dispersed on amorphous porous silica aerogel obtained by two-step sol–gel synthesis followed by gel drying under supercritical conditions and calcination treatments. It was found that the NiFe2O4/SiO2 aerogel is an active catalyst for the selected reaction, enabling high conversions at room temperature, and it proved to be active for three repeated runs. The catalytic activity can be ascribed to both the textural and acidic features of the silica matrix and of the nanocrystalline ferrite. In addition, ferrite nanocrystals provide functionality for magnetic recovery of the catalyst from the crude mixture, enabling time-effective separation from the reaction environment. Evidence of the retention of species involved in the reaction into the catalyst is also pointed out, likely due to the porosity of the aerogel together with the affinity of some species towards the silica matrix. Our work contributes to the study of aerogels as catalysts for organic reactions by demonstrating their potential as well as limitations for the room-temperature synthesis of bis(indolyl)methanes.

Design and Synthesis of Electrocatalysts Base on Catalysis‐Unit Engineering

AbstractIt is a pressing need to develop new energy materials to address the existing energy crisis. However, screening optimal targets out of thousands of materials candidates remains a great challenge. Herein, we propose and validate an alternative concept for highly effective materials screening based on dual‐atom salphen catalysis units. Such an approach simplifies the design of catalytic materials and reforms the trial‐and‐error experimental model into a building‐blocks‐assembly like process. Firstly, density functional theory (DFT) calculations were performed on a series of potential catalysis units which were possible to synthesize. Then, machine learning (ML) was employed to define the structure‐performance relationship and acquire chemical insights. Afterwards, the projected catalysis units were integrated into covalent organic frameworks (COFs) to validate the concept Electrochemical tests confirm that Ni‐SalphenCOF and Co‐SalphenCOF are promising conductive agent‐free oxygen evolution reaction (OER) catalysts. This work provides a fast‐tracked strategy for design and development of functional materials, which serves as a potentially workable framework for seamlessly integrating DFT calculations, ML, and experimental approaches.This article is protected by copyright. All rights reserved

Starch Sodium Octenylsuccinate as a New Type of Stabilizer in the Synthesis of Catalytically Active Gold Nanostructures

Here, starch derivatives, i.e., sodium starch octenylsuccinate (OSA starch, hereinafter referred to as OSA), were employed as both reducing and stabilizing agents for the unique, inexpensive, and simple synthesis of gold nanoparticles (OSA-AuNPs) in an aqueous solution with gold salt. The obtained OSA-AuNPs were characterized by UV-vis spectrophotometry, transmission electron microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic activity of the obtained gold colloids was studied in the reduction of organic dyes, including methylene blue (C.I. Basic Blue 9) and rhodamine B (C.I. Basic Violet 10), and food coloring, including tartrazine (E102) and azorubine (E122), by sodium borohydride. Moreover, OSA-AuNPs were utilized as signal amplifiers in surface-enhanced Raman spectroscopy. The obtained results confirmed that gold nanoparticles can be used as effective catalysts in reduction reactions of selected organic dyes, as well as signal enhancers in the SERS technique.

Analyzing the Active Site and Predicting the Overall Activity of Alloy Catalysts.

As one of the potential catalysts, disordered solid solution alloys can offer a wealth of catalytic sites. However, accurately evaluating their activity localization structure and overall activity from each individual site remains a formidable challenge. Herein, an approach based on density functional theory and machine learning was used to obtain a large number of sites of the Pt-Ru alloy as the model multisite catalyst for the hydrogen evolution reaction. Subsequently, a series of statistical approaches were employed to unveil the relationship between the geometric structure and overall activity. Based on the radial frequency distribution of metal elements and the distribution of ΔGH, we have identified the surface and subsurface sites occupied by Pt and Ru, respectively, as the most active sites. Particularly, the concept of equivalent site ratio predicts that the overall activity is highest when the Ru content is 20-30%. Furthermore, a series of Pt-Ru alloys were synthesized to validate the proposed theory. This provides crucial insights into understanding the origin of catalytic activity in alloys and thus will better guide the rational development of targeted multisite catalysts.