Original Catalyst Research Articles

Synergistic iron enhanced aerogel and peracetic acid for degradation of emerging organic contaminants

In response to the urgent need for efficient degradation of emerging organic contaminants, this study has developed a novel catalytic system based on an original Fe-doped aerogel catalyst (FeCAS) and its carbonization-enhanced variant (FeCAS-400), designed to improve the activation performance of peracetic acid (PAA). The FeCAS/PAA achieves a remarkable 96.1% degradation of sulfamethoxazole (SMX) without external energy input, while the FeCAS-400/PAA further elevates the SMX removal rate to 98.4% (kobs = 0.326 min−¹) and demonstrates effectiveness across a broad pH range of 3–11. Theoretical calculations reveal that carbonization enhances electron transfer between iron–carbon substrates, which contributes to improved catalytic performance. The system also exhibits versatility in removing a wide range of prevalent contaminants and proves effective in real water matrices. This synergistic approach, combining aerogels with metal–carbon electron transfer, holds promise for an extension to other advanced oxidation processes, contributing to the assurance of water quality safety and sustainability.

Tailoring of electrocatalytic oxygen evolution reaction performance of 2D conductive Co-catecholate metal-organic frameworks

Herein, we report the microwave hydrothermal synthesis of highly porous and conductive 2D Co-catecholate MOFs (Co-CATs) in the absence (Co-CAT-WO) and presence (Co-CAT-W) of N-methyl-2-pyrrolidone (NMP) polar solvent, and the study of these Co-CATs as electrocatalysts for oxygen evolution reaction (OER). The OER performance of Co-CAT-WO and Co-CAT-W is compared. The as-synthesized Co-CATs exhibit a 2D layered hexagonal structure. The electrical conductivity of Co-CAT-WO and Co-CAT-W is 6.9 and 5.8 S/m, respectively. The good conductivity and porous structure can initiate charge transport to achieve better OER performance under the 4e--transfer process. The as-prepared Co-CAT-WO and Co-CAT-W, respectively, show an overpotential of 455 and 424 mV at 10 mA/cm2 after performing the durability and chronoamperometry experiments for 13 h in 1 M KOH. From the electrochemical studies, it is apparent that the Co-CAT-W exhibits better OER performance with low overpotential, high current density, and excellent stability over extended cycling. Moreover, the lower HOMO-LUMO gap for Co-CAT-W than that of the Co-CAT-WO endorses its better electrocatalytic activity. The post-OER results show that the Co-CAT-W electrocatalyst acts as a "precatalyst" rather than the original catalyst, and it undergoes electrochemical transformation to metal hydroxide and metal oxyhydroxide after the OER studies, promoting the OER kinetics. The findings of this work offer valuable insights into the synthetic strategies for developing 2D conducting metal-catecholate MOF catalysts for efficient and sustainable OER processes, which is crucial in water splitting for sustainable energy production.

Engineering the accessibility of active sites in mixed 1 T-2H MoS2 nanoflowers via NaClO etching for deep hydrodesulfurization of dibenzothiophene

A NaClO etching strategy was adopted to engineer the active structure of mixed 1T-2H MoS2 nanoflowers and prepare efficient hydrodesulfurization (HDS) catalysts. In the original MoS2-P catalyst, the 2H-MoS2 phase was exposed after MoS2 slabs were etched using NaClO. Sodium ion insertion with high concentrations increased the interlayer spacing of MoS2 slabs and increased the transformation of 2H-MoS2 to 1T-MoS2 phases. With increase in the concentration of NaClO solution, the proportions of 1T-MoS2 in the MoS2-N-x catalysts initially increased and then decreased. They then reached a maximum when the NaClO concentration was 1.0 mol/L. Owing to the thermodynamic instability of 1T-MoS2, the proportions of 1T-MoS2 in the sulfided MoS2-P and MoS2-N-x catalysts were less than those of the corresponding unsulfided catalysts. However, among sulfided MoS2-P and MoS2-N-x catalysts, the sulfided MoS2-N-1.0 catalyst demonstrated the highest proportion of the 1T-MoS2 phase, the best dispersion of the MoS2 slabs, and the most coordinatively unsaturated sites, thus providing itself with the optimal HDS performance for removing dibenzothiophene.

Effect of promoters on the performance of CuNi catalysts for hydrogen production from methanol decomposition

Abstract Utilizing the exhaust heat from engines to decompose methanol for hydrogen production, and subsequently introducing this hydrogen into the combustion chamber, is one of the crucial approaches for achieving energy savings and emission reductions. The role of an efficient and stable catalyst for methanol decomposition is paramount in this application. Therefore, CuNi-based catalysts modified with promoters such as Zr, La, Mn, and Mg were prepared using a stepwise impregnation method. The developed catalysts were tested using various analytical methods and characterization techniques. The results indicate that the addition of the Zr enhances the dispersion of active components, improves the catalyst’s reducibility. This, in turn, enhances the catalyst’s activity and hydrogen selectivity. The hydrogen yield of the Zr modified catalyst increased by an average of 12% compared to the original catalyst. Furthermore, the Zr modified catalyst exhibits exceptional stability after prolonged use. La can enhance the low-temperature activity of the catalyst but performs poorly at high temperatures. The promoter Mn has a minimal impact on the overall performance of the catalyst. Conversely, the addition of Mg as a promoter inhibits the dispersion of active components, resulting in adverse effects on the catalyst.

Surface reconstruction of Fe doping NiC2O4 by the electrocatalytic reaction to improve the performance of overall water splitting

The most environmentally friendly method for producing hydrogen is through the electrolysis of water, reliable and effective catalysts play a crucial role in enhancing hydrogen production efficiency. In this paper, Fe–NiC2O4/NF in block form was prepared by hydrothermal method on nickel foam (NF) for electrolysis of water under alkaline conditions. The surface reconstruction of the Fe–NiC2O4/NF was further investigated via XRD, FTIR, and XPS during the oxygen evolution reaction (OER). The catalytic activity of Fe–Ni(OH)2/NiOOH formed after reconstruction was considerably enhanced in comparison to the original catalyst. The overpotentials for hydrogen evolution reaction (HER) at 10 mA cm−2 and OER at 100 mA cm−2 were 126 mV and 260 mV, respectively. Meanwhile, applying it in a two-electrode, total hydrolysis device only requires 1.53 V at 10 mA cm−2. This investigation introduces a novel method for surface reconstruction of electrocatalysts to facilitate electrolytic water reaction.

ZnGA/DMC catalysts for the synthesis of high molecular weight poly(propylene carbonate): The crucial role of water treatment

Zinc glutarate (ZnGA) is a prominent catalyst for the production of CO2-based poly(propylene carbonate). The original catalysts, ZnO-GA (Cat 1) and ZnAc2-GA (Cat 3), were prepared using ZnO and ZnAc2 as Zn sources, respectively. ZnO-GA-H2O (Cat 2) and ZnAc2-GA-H2O (Cat 4) were prepared by water treatment of Cat 1 and Cat 3, respectively. After water treatment, both Cat 2 and Cat 4 showed enhanced performance for copolymerization of CO2 and propylene oxide. The characterizations demonstrated that H2O is a critical component that not only improves the crystallinity and external surface area of ZnGA, but also increases the number of surface Zn-OH groups. By adding a portion of cyanide, further modification on Cat 4 resulted in a group of ZnAc2-GA-H2O/DMC catalysts (m-Cat 4). The polymerization reached a high yield of 1729 g poly/g Cat and a selectivity of 98.7 % at molar ratio of DMC/ZnGA = 1: 10 (t = 24 h; T = 70 °C; P = 4 MPa). The modified ZnGA/DMC catalyst exhibited remarkable yield and selectivity for the copolymerization of CO2 and propylene oxide to produce high molecular weight alternating copolymers (2.3 × 105 g/mol).

Leveraging Limited Experimental Data with Machine Learning: Differentiating a Methyl from an Ethyl Group in the Corey-Bakshi-Shibata Reduction.

We present a case study on how to improve an existing metal-free catalyst for a particularly difficult reaction, namely, the Corey-Bakshi-Shibata (CBS) reduction of butanone, which constitutes the classic and prototypical challenge of being able to differentiate a methyl from an ethyl group. As there are no known strategies on how to address this challenge, we leveraged the power of machine learning by constructing a realistic (for a typical laboratory) small, albeit high-quality, data set of about 100 reactions (run in triplicate) that we used to train a model in combination with a key-intermediate graph (of substrate and catalyst) to predict the differences in Gibbs activation energies ΔΔG‡ of the enantiomeric reaction paths. With the help of this model, we were able to select and subsequently screen a small selection of catalysts and increase the selectivity for the CBS reduction of butanone to 80% enantiomeric excess (ee), the highest possible value achieved to date for this substrate with a metal-free catalyst, thereby also exceeding the best available enzymatic systems (64% ee) and the selectivity with Corey's original catalyst (60% ee). This translates into a >50% improvement in relative ΔG‡ from 0.9 to 1.4 kcal mol-1. We underscore the transformative potential of machine learning in accelerating catalyst design because we rely on a manageable small data set and a key-intermediate graph representing a combination of catalyst and substrate graphs in lieu of a transition-state model. Our results highlight the synergy of synthetic chemistry and data-centric approaches and provide a blueprint for future catalyst optimization.

Facet effect on nanosheet Co3O4 catalysts for toluene oxidation: Decisive role of Co3+ and reaction-induced oxygen vacancy

Co3O4 is recognized as an advantageous material for harmful VOC abatement. In this paper, three types of Co3O4 catalysts exhibiting either nanosheet morphology or nanosheet tissue structure were synthesized and applied in the combustion of toluene. The characterization results highlight the significance of Co3+ species over surface oxygen. Moreover, the oxygen vacancies of the catalyst formed during the reaction process were found to play a more critical role in influencing the catalytic performance than the oxygen vacancies present in the original catalyst. Through this study, we gained valuable insights into the facets, Co3+ species, and oxygen vacancies, which hold promising potential for enhancing the development of Co3O4 catalytic material for practical applications in toluene degradation.

Designing a MnF2/MnO2 heterostructure for enhanced electrocatalysis in the oxygen reduction reaction

Studying noble-metal-free oxygen reduction reaction (ORR) catalysts is crucial for advancing fuel cells. Manganese dioxide (MnO2) has garnered widespread attention due to its convenient synthesis, low cost, high electrochemical activity, and diverse structures. However, it still faces challenges, such as poor conductivity and relatively lower inherent catalytic activity. In this study, a novel ORR electrocatalyst is introduced by constructing a heterostructure of manganese fluoride (MnF2) and MnO2, referred to as MnF2/MnO2. In a 0.1 M KOH solution, the ORR half-wave potential (E1/2) of MnF2/MnO2 is measured at 0.804 V, surpassing that of the original MnO2 catalyst (0.69 V). Compared to the MnO2 electrocatalyst, the MnF2/MnO2 heterostructure exhibits faster ORR reaction kinetics and a larger electrochemically active surface area. Density functional theory (DFT) calculations confirm that the MnF2/MnO2 heterostructure possesses enhanced intrinsic conductivity, facilitating the rapid transfer of ions of and electrons. Therefore, this study provides a promising pathway for enhancing the ORR catalytic activity of noble-metal-free electrocatalysts through rational heterostructure design.

Specific Discrimination Polymerization for Highly Isotactic Polyesters Synthesis.

Isotactic polymers have emerged with unique and excellent properties in material sciences. Specific discrimination polymerization provides an ideal pathway to achieve highly isotactic polymers from their racemic monomers, which is of great significance and a challenge in polymeric chemistry. Although an enantioselective catalyst-mediated asymmetric kinetic resolution polymerization (AKRP) process makes it possible, a general and well-defined strategy for catalyst design is still rarely reported. Here, based on a novel dual-ligand strategy, a new type of chiral (BisSalen)Al complex with high enantioselectivity has been described, in which perfect AKRP of racemic phenethylglycolide (Pegl) is achieved for the first time. The more confined asymmetric microenvironment formed by a dual ligand is the key to improve the enantioselectivity of the original catalyst. To illustrate the generality of this strategy, a series of (BisSalen)Al complexes with homo- or heterodual ligands were designed for the AKRP of Pegl.

An N-defective graphitic carbon nitride-supported Ir/Fe catalyst with low Ir-content as highly efficient oxygen evolution reaction catalyst for acidic water splitting

To develop a low-cost acidic water electrolysis catalyst with high efficiency and stability and low Ir content, a catalyst with highly dispersed Ir/Fe complex sites (∼ 5 wt% Ir) was synthesized by a simple carbonization and oxidation process. N-defective g-C3N4 (NCN) was introduced to enhance the support effect between metal nanoparticles and CN bases and the intrinsic catalytic activity for the oxygen evolution reaction (OER). NCN provided more active sites and adjusted the electronic structure of CN. Compared with the original single Ir catalyst, the electrons of the Ir-Fe metal catalyst were transferred from the base to the metal, which maintained the high OER performance and stability of the catalyst. Density functional theory calculations demonstrated that the Gibbs free energy of Ir/Fe@NCN was greatly reduced during O*→OOH* as the rate-determining step. The overpotential of the Ir/Fe@NCN catalyst was 242 mV at 10 mA/cm2, and its mass activity (612.6 A/g) was much higher than that of IrO2 (88.6 A/g), showing excellent OER performance. This study provides a new strategy for the design and optimization of highly efficient and low-cost acidic Ir/transition metal OER catalysts.

Latency for All: Enabling Latency of Hoveyda-Grubbs Second-Generation Catalysts by Adding Phosphite Ligands.

The Hoveyda-Grubbs catalyst (HG2, M720 Umicore) is among the most widely used catalysts in olefin metathesis reactions. Given the usefulness of HG2 and the great interest in developing latent olefin metathesis catalysts for numerous applications, we developed a method to introduce phosphite molecules as ancillary ligands into the precatalyst framework. This modification alters the geometry of the complex from an active trans-dichloro form to a latent cis-dichloro species. Most unusually, the ligands coordinate to HG2 only in solidified solutions (most likely due to entropic factors), providing latent catalysts that can be activated on demand by heat or light by regenerating the original HG2 catalyst. Of particular interest is the use of these latent catalysts in ring-opening metathesis polymerization (ROMP) reactions and 3D printing methods. Indeed, the novel complexes displayed the required latency toward ROMP monomers, even the most reactive dicyclopentadiene. Irradiation with 405 nm light readily results in the expedited formation of the desired polymers. This novel approach provides a general and straightforward way to access efficient and well-defined latent olefin metathesis catalysts.

Turning trash to treasure: Innovative use of exhausted desiccant waste supported zinc indium sulphide for sustainable photocatalytic abatement of tetracycline

Employing an affordable and sustainable visible-light-driven system is crucial for organic pollutant abatement, in the field of photocatalysis. In the present investigation, a pioneering photocatalyst zinc indium sulphide, ZnIn2S4 (ZIS) supported on a silica gel matrix, SiO2 (SG) which is the leftover material after multiple rounds of dehumidification processes, was synthesized. The fabrication of the heterojunction facilitated enhancement in light absorption and charge separation efficiency. The photocatalytic performance was evaluated through the degradation of tetracycline (TC) under light irradiation. The nano-photocatalyst experienced detailed analysis using spectroscopic and microscopic methods. The ZIS/SG catalyst exhibited remarkable efficiency in degrading TC under visible light conditions, achieving a nearly 98–99% degradation. This performance surpassed the degradation rates of the original ZIS and SG catalysts by 3.6 and 4.45 times, respectively. Additionally, the catalyst was effectively used to control TC levels in real-time within pharmaceutical plant effluent, resulting in a degradation efficiency of 78.2%. With affordability, enhanced TC mineralization, and recyclability for up to six runs (efficiency ∼ 85%), the ZIS/SG photocatalyst exhibits desirable qualities of an ideal one. This innovative nano-photocatalyst introduces new possibilities for improving the process of photocatalytic decontamination of tenacious emerging pollutants by providing satisfactory reusability and stability.

Engineering defective Co3O4 containing both metal doping and vacancy in octahedral cobalt site as high performance catalyst for methane oxidation

Advanced defective structure in Co3O4 catalyst plays a vital role in the boost of catalytic oxidation activity. In this study, a rational defects engineering strategy was developed by precise implanting Ce and Al in the octahedral site of Co3O4, followed by the partial de-doping of the Al atoms. Distorted crystal, abundant oxygen vacancies, higher specific surface area are synergistically incubated by the dual dopants combined with the metal vacancies. The Co3+O bond could be significantly stimulated to guarantee an excellent methane oxidation activity, with methane conversion rate more than 1.5 times compared with the original Co3O4 catalyst at 300 °C. This work exemplifies the importance of accurate multi-defects manipulation in Co3O4 for intrinsic oxidizability improvement.

Chemical-Dealloying-Derived PtPdPb-Based Multimetallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application.

In this work, we report a novel multimetallic nanoparticle catalyst composed of Pt, Pd, and Pb and its electrochemical activity toward dimethyl ether (DME) oxidation in liquid electrolyte and polymer electrolyte fuel cells. Chemical dealloying of the catalyst with the lowest platinum-group metal (PGM) content, Pt2PdPb2/C, was conducted using HNO3 to tune the catalyst activity. Comprehensive characterization of the chemical-dealloying-derived catalyst nanoparticles unambiguously showed that the acid treatment removed 50% Pb from the nanoparticles with an insignificant effect on the PGM metals and led to the formation of smaller-sized nanoparticles. Electrochemical studies showed that Pb dissolution led to structural changes in the original catalysts. Chemical-dealloying-derived catalyst nanoparticles made of multiple phases (Pt, Pt3Pb, PtPb) provided one of the highest PGM-normalized power densities of 118 mW mgPGM-1 in a single direct DME fuel cell operated at low anode catalyst loading (1 mgPGM cm-2) at 70 °C. A possible DME oxidation pathway for these multimetallic catalysts was proposed based on an online mass spectrometry study and the analysis of the reaction products.

1.42-fold enhancement of formate selectivity by linker conversion on the Zn-based metal organic framework catalyst

Electro-reduction of carbon dioxide (ERCO2) is considered an effective method to alleviate the greenhouse effect and produce value-added chemicals. Achieving the dominant selectivity of Zn-based catalysts for formate remains a challenge. In this article, the ZnIn-E12 catalyst is successfully prepared by solvent assisted ligand exchange (SALE) method to convert organic ligands, achieving a Faradaic efficiency of 72.28% for formate at −1.26 V vs. RHE (VRHE), which is 1.42 times higher than the original catalyst. Evidence shows that the successful conversion of organic ligands can transform the catalyst from the original large size polyhedron to cross-linked network of particles with a diameter of about 30 nm. The increased specific surface area can expose more active sites and facilitate the electrocatalytic conversion of CO2 to formate. This work is expected to provide inspiration for the regulation of formate selectivity and catalyst size in Zn-based catalysts.

Nanocluster-mediated electron–hole separation for efficient CO2 photoreduction

Poor capability of charge-holes separation and slower surface CO2 reaction kinetics hinder photocatalytic performance. Here, SnS2 atomic layer with Pt3Co alloy nanoclusters have been successfully prepared. Nanoclusters could be used as highly catalytic active sites, which not only facilitates the carrier separation and transport kinetics, but enriches electrons lowered the reaction barrier. As expected, the CO evolution rate of the champion SnS2/Pt3Co catalyst was 13.6 times higher than that of the original SnS2 catalyst under white light irradiation. In-situ DRIFTS identifies key intermediate in the photoreduction process. In-situ XPS and DFT calculation further verifies the electron transport direction and charge density distribution at the SnS2/Pt3Co interface. Our work uncovers the role of nanoclusters in carrier separation and transport as well as proton transport, opening new chances for obtaining efficient photoreduction CO2 property.

Analyzing Transition Metal Catalytic Converter Impact on Four-Stroke Motorcycle Fuel Consumption

Increased exhaust emissions from motor vehicles have become a major concern in efforts to reduce air pollution. One developed solution is the use of transition metallic catalytic converter (TMCC) technology in vehicle exhaust systems. This study aims to compare the fuel consumption efficiency of three types of exhaust systems, namely standard exhaust without a catalyst (STD WC), the standard exhaust with Original Equipment Manufacturer catalyst (STD OEM), and an exhaust system equipped with a Copper-Coated Chrome Metallic Catalytic Converter (TMCC CuCr). The data analysis method employed a quantitative approach by collecting fuel consumption data at each rpm and analyzing the mean and standard deviation. The research findings indicate that STD OEM has a lower average fuel consumption (0.80 liters per hour) and smaller standard deviation (0.06) compared to TMCC CuCr (0.83 liters per hour and 0.07). Although TMCC CuCr demonstrates good efficiency, STD OEM remains the best choice in terms of fuel efficiency. However, if the differences in fuel consumption and standard deviation are considered insignificant, TMCC CuCr could be a more economical alternative with its affordable price and greater material availability. Furthermore, its fuel consumption performance is not significantly different from that of STD OEM.

Regulating the reactive site density of two-dimensional N self-doped carbon for boosted Fenton-like catalytic ability

The mediocre catalytic ability of metal-free carbon-based catalysts limits its practical application in wastewater treatment. Herein, a facile “steam-etching” method is utilized to boost the catalytic ability of N self-doped carbon (NSDC) catalysts. Compared to the original NSDC catalyst (NSDC-N2), the NSDC-H2O-50 catalyst modified with the water vapor content of 50 % exhibits much better catalytic performance. The pseudo-first-order kinetic rate constant k of NSDC-H2O-50 is 4.88 times that of NSDC-N2. The presence of water vapor can cause a massive vacancy-like defects in the carbon structure, which is conducive to form more edge reactive groups. Pyrrolic N and CN groups are proved to be the reactive sites for the catalytic reaction. Reactive site density can be easily adjusted by changing the water vapor content. The prepared NSDC-H2O catalysts can effectively activate peroxydisulfate (PDS) to degrade various organic pollutants with high efficiency in the pH range of 2.02–10.28. In addition, the NSDC-H2O/PDS system exhibits strong anti-interference ability to common anions and humic acid. The catalytic ability has not been affected in actual water sources. By a simple calcination treatment, most of the catalytic ability can be restored. Therefore, the prepared NSDC-H2O catalysts show strong application potential in organic wastewater treatment. Furthermore, singlet oxygen is proved to be the main active species in the NSDC-H2O/PDS system, and sulfate radical and superoxide radical play an auxiliary role.

Enoch’s Green Apocalypse: The Source Material of Aronofsky’s Noah

Abstract A cataclysmic event, often spelling disaster for the environment, is an essential element to the backstory of any post-apocalyptic tale. In these stories, the presupposed ecological tragedy may have severely altered the environment, but it has not annihilated it. In fact, what has happened is that the apocalyptic catastrophe has neutralized the ecological threats that were the original catalysts for the devastation in the first place, resulting in an opportunity for the environment to rebound once its abusers have faced judgment. In other words, Earth may get beaten black-and-blue, yet the final effect is a green apocalypse—an event that rids Earth of its destructive inhabitants or at least counterbalances their negative effects, giving the global ecosystem a chance to renew. In this article I offer readings of two apocalyptic stories—1 Enoch and Darren Aronofsky’s Noah. My approach to these stories utilizes elements from a method of ecological hermeneutics that has been developed by Norman Habel and others from the Earth Bible team. The Noahic flood story is one of the earliest examples of a “green” apocalypse, in which the penultimate event may have been devastation on the planet, but the ultimate end was a renewal of Earth. It is my hope that these ecological readings with their attention to the concept of a green apocalypse may be useful in appreciating the possibility of eco-friendly interpretations of apocalyptic texts.