Catalytic Pathway Research Articles

Rational Design of Loop Dynamics for a Barrel-Shaped Enzyme by Introducing Disulfide Bonds.

Loop dynamics redesign is an important strategy to manipulate protein function. Cellobiose 2-epimerase (CE) and other members of its superfamily are widely used for diverse industrial applications. The structural feature of the loops connecting barrel helices contributes greatly to the differences in their functional characteristics. Inspired by the in-silico mutation with molecular dynamics (MD) simulation analysis, we propose a strategy for identifying disulfide bond mutation candidates based on the prediction of protein flexibility and residue-residue interaction. The most beneficial mutant with the newly introduced disulfide bond would simultaneously improve both its thermostability and its reaction propensity to the targeting isomerization product. The ratio of the isomerization/epimerization catalytic rate was improved from 4:103 to 9:22. MD simulation and binding free energy calculations were applied to provide insights into molecular recognition upon mutations. The comparative analysis of enzyme/substrate binding modes indicates that the altered catalytic reaction pathway is due to less efficient binding of the native product. The key residue responsible for the observed phenotype was identified by energy decomposition and was further confirmed by the mutation experiment. The rational design of the key loop region might be a promising strategy to alter the catalytic behavior of all (α/α)6-barrel-like proteins.

Mn-Ag bimetals supported on plate-like ZSM-5 as efficient and stable catalysts for the catalytic combustion of toluene: Synergistic effects and catalytic mechanisms

Ag-modified MnO2 loaded on plate-like ZSM-5 (PZ5) with different Ag/Mn ratios were synthesized by an in-situ growth method and used as catalysts for toluene combustion, as a probe molecule of volatile organic compounds (VOCs). The results showed that Ag doping greatly enhanced the toluene combustion activity (Mn50Agy/PZ5). Among them, Mn50Ag0.04/PZ5 showed the highest catalytic activity for toluene combustion with 90 % conversion of toluene at 234 °C (T90), and the reaction rate calculated per unit mass of Mn was 1.22×10−7 at 220 °C, which was 2.7 times higher than that of MnO2. In addition, Mn50Ag0.04/PZ5 exhibited excellent long-term stability and water resistance. Various characterizations indicated that the excellent performance of Mn50Ag0.04/PZ5 was attributed to its higher Mn2++Mn3+/Mn4+ ratios, higher reducibility, and more active surface adsorbed oxygen species. Finally, in-situ DRIFTS studies confirmed that Ag doping did not alter the catalytic combustion pathway of toluene over the Mn50Ag0.04/PZ5 catalyst but could accelerate the rate of conversion of toluene to the final products because the transfer of electrons from Ag+ to lattice oxygen persuaded the weaken of the Mn-O bond, and then made it easier for bulk lattice oxygen to migrate towards the Ag-MnO2 interface or catalysts’ surface, thus showing the better catalytic performance for toluene combustion.

Selective lignin arylation for biomass fractionation and benign bisphenols.

Lignocellulose is mainly composed of hydrophobic lignin and hydrophilic polysaccharide polymers, contributing to an indispensable carbon resource for green biorefineries1,2. When chemically treated, lignin is compromised owing to detrimental intra- and intermolecular crosslinking that hampers downstream process3,4. The current valorization paradigms aim to avoid the formation of new C-C bonds, referred to as condensation, by blocking or stabilizing the vulnerable moieties of lignin5-7. Although there have been efforts to enhance biomass utilization through the incorporation of phenolic additives8,9, exploiting lignin's proclivity towards condensation remains unproven for valorizing both lignin and carbohydrates to high-value products. Here we leverage the proclivity by directing the C-C bond formation in a catalytic arylation pathway using lignin-derived phenols with high nucleophilicity. The selectively condensed lignin, isolated in near-quantitative yields while preserving its prominent cleavable β-ether units, can be unlocked in a tandem catalytic process involving aryl migration and transfer hydrogenation. Lignin in wood is thereby converted to benign bisphenols (34-48wt%) that represent performance-advantaged replacements for their fossil-based counterparts. Delignified pulp from cellulose and xylose from xylan are co-produced for textile fibres and renewable chemicals. This condensation-driven strategy represents a key advancement complementary to other promising monophenol-oriented approaches targeting valuable platform chemicals and materials, thereby contributing to holistic biomass valorization.

Nitrate-promoted gas–solid reactions of H2 and CaCO3 for mid-temperature integrated CO2 capture and methanation

Integrated CO2 capture and methanation (ICCM) technology has attracted increasing attention for Carbon Neutrality. However, in the mid-temperature ICCM studies dominated by MgO, which involves the gas–gas catalytic pathway, the problems of high CO2 escape and low CH4 yield are common. Replacing MgO with CaO reduced CO2 escape because the reaction proceeded via the gas–solid pathway. However, the lower CaCO3 conversion rate limits its further applications. Here, we present an ICCM process with efficient CaCO3 conversion using alkali metal nitrates (KNO3, LiNO3, and (Li-K)NO3) to promote Ru/CeO2-CaO. The results showed that the doping of nitrates led to a decrease in the specific surface area of CaO, thus losing part of the CO2 capture performance. On the other hand, forming the molten liquid layer facilitated the gas–solid reaction between CaCO3 and H2, which improved the CaCO3 conversion. Compared with the Ru/CeO2-Neat CaO without nitrate promotion, the CaCO3 conversion of Ru/CeO2-KNO3/CaO was increased by 42% and CH4 yield by 52% after five ICCM cycles. Furthermore, kinetic analysis and in situ DRIFTS experiments demonstrated that molten KNO3 facilitated mass transfer in the diffusion-controlled stage of direct CaCO3 hydrogenation.

CO Oxidation Mechanism of Silver-Substituted Mo/Cu CO-Dehydrogenase - Analogies and Differences to the Native Enzyme.

The aerobic oxidation of carbon monoxide to carbon dioxide is catalysed by the Mo/Cu-containing CO-dehydrogenase enzyme in the soil bacterium Oligotropha carboxidovorans, enabling the organism to grow on the small gas molecule as carbon and energy source. It was shown experimentally that silver can be substituted for copper in the active site of Mo/Cu CODH to yield a functional enzyme. In this study, we employed QM/MM calculations to investigate whether the reaction mechanism of the silver-substituted enzyme is similar to that of the native enzyme. Our results suggest that the Ag-substituted enzyme can oxidize CO and release CO2 following the same reaction steps as the native enzyme, with a computed rate-limiting step of 10.4 kcal/mol, consistent with experimental findings. Surprisingly, lower activation energies for C-O bond formation have been found in the presence of silver. Furthermore, comparison of rate constants for reduction of copper- and silver-containing enzymes suggests a discrepancy in the transition state stabilization upon silver substitution. We also evaluated the effects that differences in the water-active site interaction may exert on the overall energy profile of catalysis. Finally, the formation of a thiocarbonate intermediate along the catalytic pathway was found to be energetically unfavorable for the Ag-substituted enzyme. This finding aligns with the hypothesis proposed for the wild-type form, suggesting that the creation of such species may not be necessary for the enzymatic catalysis of CO oxidation.

Directional Formation of Reactive Oxygen Species Via a Non-Redox Catalysis Strategy That Bypasses Electron Transfer Process.

A broad range of chemical transformations driven by catalytic processes necessitates the electron transfer between catalyst and substrate. The redox cycle limitation arising from the inequivalent electron donation and acceptance of the involved catalysts, however, generally leads to their deactivation, causing substantial economic losses and environmental risks. Here, a "non-redox catalysis" strategy is provided, wherein the catalytic units are constructed by atomic Fe and B as dual active sites to create tensile force and electric field, which allows directional self-decomposition of peroxymonosulfate (PMS) molecules through internal electron transfer to form singlet oxygen, bypassing the need of electron transfer between catalyst and PMS. The proposed catalytic approach with non-redox cycling of catalyst contributes to excellent stability of the active centers while the generated reactive oxygen species find high efficiency in long-term catalytic pollutant degradation and selective organic oxidation synthesis in aqueous phase. This work offers a new avenue for directional substrate conversion, which holds promise to advance the design of alternative catalytic pathways for sustainable energy conversion and valuable chemical production.

Mechanism of Ni-Catalyzed Photochemical Halogen Atom-Mediated C(sp3)-H Arylation.

Within the context of Ni photoredox catalysis, halogen atom photoelimination from Ni has emerged as a fruitful strategy for enabling hydrogen atom transfer (HAT)-mediated C(sp3)-H functionalization. Despite the numerous synthetic transformations invoking this paradigm, a unified mechanistic hypothesis that is consistent with experimental findings on the catalytic systems and accounts for halogen radical formation and facile C(sp2)-C(sp3) bond formation remains elusive. We employ kinetic analysis, organometallic synthesis, and computational investigations to decipher the mechanism of a prototypical Ni-catalyzed photochemical C(sp3)-H arylation reaction. Our findings revise the previous mechanistic proposals, first by examining the relevance of SET and EnT processes from Ni intermediates relevant to the HAT-based arylation reaction. Our investigation highlights the ability for blue light to promote efficient Ni-C(sp2) bond homolysis from cationic NiIII and C(sp2)-C(sp3) reductive elimination from bipyridine NiII complexes. However interesting, the rates and selectivities of these processes do not account for the productive catalytic pathway. Instead, our studies support a mechanism that involves halogen atom evolution from in situ generated NiII dihalide intermediates, radical capture by a NiII(aryl)(halide) resting state, and key C-C bond formation from NiIII. Oxidative addition to NiI, as opposed to Ni0, and rapid NiIII/NiI comproportionation play key roles in this process. The findings presented herein offer fundamental insight into the reactivity of Ni in the broader context of catalysis.

Heterogeneous Oxidase-Type Catalysis for H2 Generation at Low Temperatures.

The long-term objective in the field of heterogeneous catalysis is to develop an enzyme-like catalytic pathway that can achieve exceptional catalytic performance even at low temperatures. Herein, we have demonstrated a heterogeneous oxidase-type catalysis on the ZnO-supported Ru clusters (Ru/ZnO) for efficient H2 generation from an aqueous solution of formaldehyde (HCHO) at low temperatures. Due to its unique reaction pathway, the Ru/ZnO catalysts exhibited a temperature-insensitive activity for H2 generation at the temperature of 15 to 45 °C. Remarkably, even at a low temperature of 5 °C, the Ru/ZnO catalysts still enabled an H2 generation rate of 13.8 mmol gcat-1 h-1 with a turnover frequency (TOF) of 1678 h-1. Additionally, instead of producing a CO2/CO molecule, the HCHO molecule underwent a transformation into formic acid and/or formate as the byproduct. This finding presents a novel class of heterogeneous catalysts to expand the potential application scenarios of liquid hydrogen storage and transportation systems.

Assessment of Nucleobase Protomeric and Tautomeric States in Nucleic Acid Structures for Interaction Analysis and Structure-Based Ligand Design.

With increasing interest in RNA as a therapeutic and a potential target, the role of RNA structures has become more important. Even slight changes in nucleobases, such as modifications or protomeric and tautomeric states, can have a large impact on RNA structure and function, while local environments in turn affect protonation and tautomerization. In this work, the application of empirical tools for pKa and tautomer prediction for RNA modifications was elucidated and compared with ab initio quantum mechanics (QM) methods and expanded toward macromolecular RNA structures, where QM is no longer feasible. In this regard, the Protonate3D functionality within the molecular operating environment (MOE) was expanded for nucleobase protomer and tautomer predictions and applied to reported examples of altered protonation states depending on the local environment. Overall, observations of nonstandard protomers and tautomers were well reproduced, including structural C+G:C(A) and A+GG motifs, several mismatches, and protonation of adenosine or cytidine as the general acid in nucleolytic ribozymes. Special cases, such as cobalt hexamine-soaked complexes or the deprotonation of guanosine as the general base in nucleolytic ribozymes, proved to be challenging. The collected set of examples shall serve as a starting point for the development of further RNA protonation prediction tools, while the presented Protonate3D implementation already delivers reasonable protonation predictions for RNA and DNA macromolecules. For cases where higher accuracy is needed, like following catalytic pathways of ribozymes, incorporation of QM-based methods can build upon the Protonate3D-generated starting structures. Likewise, this protonation prediction can be used for structure-based RNA-ligand design approaches.

Production of 1,4-Butanediol from Succinic Acid Using Escherichia Coli Whole-Cell Catalysis.

The widespread attention towards 1,4-butanediol (BDO) as a key chemical raw material stems from its potential in producing biodegradable plastics. However, the efficiency of its biosynthesis via current bioprocesses is limited. In this study, a dual-pathway approach for 1,4-BDO production from succinic acid was developed. Specifically, a double-enzyme catalytic pathway involving carboxylic acid reductase and ethanol dehydrogenase was proposed. Optimization of the expression levels of the pathway enzymes led to a significant 318 % increase in 1,4-BDO titer. Additionally, the rate-limiting enzyme MmCAR was engineered to enhance the kcat/KM values by 50 % and increase 1,4-BDO titer by 46.7 %. To address cofactor supply limitations, an NADPH and ATP cycling system was established, resulting in a 48.9 % increase in 1,4-BDO production. Ultimately, after 48 hours, 1,4-BDO titers reached 201 mg/L and 1555 mg/L in shake flask and 5 L fermenter, respectively. This work represents a significant advancement in 1,4-BDO synthesis from succinic acid, with potential applications in the organic chemical and food industries.

Realizing synergy between Cu, Ga, and Zr for selective CO2 hydrogenation to methanol

Hydrogenating CO2 to methanol with high yields and selectivity remains a kinetic challenge. We report ternary Cu-Ga-Zr catalysts with promising performances. Methanol productivity and selectivity were highest on coprecipitated samples containing approximately 20 wt% of each metal. At 7% isoconversion, this ternary system was more selective to methanol (60 ± 1%) than CuZrOx (51 ± 1%) and CuGaOx (53 ± 3%) at the same Cu loading. We uncover the importance of the Cu/Zr interface for CO2 adsorption, Cu/Ga interface for H adsorption, and metallic Cu for H–H dissociation. Methanol formation on these catalysts was found to be first order in H2, implying the reaction was likely to be rate-limited by hydrogen activation. In fact, the methanol space-time yield correlated linearly with the H2/D2 exchange rate. We propose a catalytic pathway wherein the production of the byproduct CO is hindered by the presence of adsorbed H.

Termolecular Eley–Rideal pathway for catalytic oxidation of nitric oxide on [Pt2]0,± dimers using O2

AbstractA comprehensive density functional theory (DFT) investigation of the catalytic oxidation of NO to NO2 on neutral and charged [Pt2]0,± dimers has been considered employing M06L/def2TZVP level of theory. Single as well as co‐adsorption energies of NO and O2 molecules suggest that the traditional Langmuir Hinshelwood (LH) mechanism and less explored termolecular Eley–Rideal (TER) and termolecular Langmuir Hinshelwood (TLH) mechanisms, are suitable for a full catalytic reaction pathway in which two NO molecules are converted to two NO2 molecules, initiated by an activated O2 molecule. Activation barrier reveals that the TER mechanism is found to be more reliable in converting two NO molecules into two NO2 molecules on [Pt2]¯ dimer. In addition to shedding light on the intrinsic characteristics of Pt2 dimers, the study will serve as a benchmark for investigating the oxidation process of NO to NO2 utilizing models of termolecular chemical processes.

Two-step synthesis of coconut shell biochar-based ternary composite to efficiently remove organic pollutants by photocatalytic degradation

Designing environmentally friendly, low cost and efficient photocatalysts is vitally important for degradation of organic pollutants. Herein, a ternary composite-ZnO/ACSC@TiO2, constituted by activated coconut shell derived biochar (ACSC), TiO2 and ZnO, was successfully synthesized by two-step hydrothermal method. It demonstrated that TiO2 could be uniformly wrapped on ACSC surface during first step to form core-shell structures (ACSC@TiO2). It was beneficial not only to enhance adsorption capacity for organic pollutants and absorption ability for light, but also to form C-doped TiO2 with a relatively narrow bandgap to expand light absorption of TiO2 from UV to visible light. Subsequently, ZnO was introduced through second step to generate type-II heterojunctions with ACSC@TiO2, which further reduced bandgap value of the ternary photocatalyst to promote photogenerated carrier generation and efficiently diminished recombination of e--h+ pairs. As expected, the optimal prepared catalyst with 10 wt% of ZnO (10%ZnO/ACSC@TiO2) exhibited excellent adsorptive and photocatalytic abilities for removal of tetracycline (TC) and Rhodamine B (RhB) with different initial concentrations. Particularly, its total removal efficiency for TC and RhB was 97.6% and 99.4%, respectively under 300 W xenon lamp irradiation (25 mg/L of organic pollutants, 1.0 g/L catalyst and natural pH in 60 min). Investigations on catalytic mechanism and degradation pathways proved that 10%ZnO/ACSC@TiO2 could remove RhB and TC by deep degradation. Its enhanced synergy of adsorption and photocatalysis could efficiently accelerate mineralization rates of RhB and TC. This biomass derived biochar-based ternary composite as photocatalyst with optimized energy band structures and microstructures would have good industrial application potential.

Improving plant adaptation to soil antimony contamination: the synergistic contribution of arbuscular mycorrhizal fungus and olive mill waste

BackgroundThis study aimed to investigate the alterations in biochemical and physiological responses of oat plants exposed to antimony (Sb) contamination in soil. Specifically, we evaluated the effectiveness of an arbuscular mycorrhizal fungus (AMF) and olive mill waste (OMW) in mitigating the effects of Sb contamination. The soil was treated with a commercial strain of AMF (Rhizophagus irregularis) and OMW (4% w/w) under two different levels of Sb (0 and 1500 mg kg−1 soil).ResultsThe combined treatment (OMW + AMF) enhanced the photosynthetic rate (+ 40%) and chlorophyll a (+ 91%) and chlorophyll b (+ 50%) content under Sb condition, which in turn induced more biomass production (+ 67–78%) compared to the contaminated control plants. More photosynthesis in OMW + AMF-treated plants gives a route for phenylalanine amino acid synthesis (+ 69%), which is used as a precursor for the biosynthesis of secondary metabolites, including flavonoids (+ 110%), polyphenols (+ 26%), and anthocyanins (+ 63%) compared to control plants. More activation of phenylalanine ammonia-lyase (+ 38%) and chalcone synthase (+ 26%) enzymes in OMW + AMF-treated plants under Sb stress indicated the activation of phenylpropanoid pathways in antioxidant metabolites biosynthesis. There was also improved shifting of antioxidant enzyme activities in the ASC/GSH and catalytic pathways in plants in response to OMW + AMF and Sb contamination, remarkably reducing oxidative damage markers.ConclusionsWhile individual applications of OMW and AMF also demonstrated some degree of plant tolerance induction, the combined presence of AMF with OMW supplementation significantly enhanced plant biomass production and adaptability to oxidative stress induced by soil Sb contamination.

Catalytic mechanism of calcium ion on the NOx precursors formation during the pyrolysis of kitchen waste

Calcium ion (Ca2+) in kitchen waste exerts a significant impact on the formation of NOx precursors to affect the release of nitrogen oxides during the incineration process. However, the catalytic mechanism of Ca2+ is still unclear. Herein, 2,4-imidazolidinedione is employed as the nitrogen-containing model to study the effect of Ca2+ on the generation of NOx precursors during pyrolysis. Through density functional theory calculations (DFT) and wave function analysis of the catalytic effect of Ca2+, the results indicate that Ca2+ has different degrees of impact on the energy barriers of the initial ring opening reaction. Ca2+ not only changes the rate determining steps of NOx precursors formation pathways, but also reduces the total energy barriers formed by NH3. At the same time, the total energy barriers of all paths formed by HCN are raised. This work theoretically explains the phenomenon of Ca2+ promoting the formation of NH3, whereas inhibiting the release of HCN in pyrolysis experiments. In addition, Ca2+ promotes partial reaction pathways for the formation of HNCO, and the total energy barriers of catalytic pathways are lower than that of the uncatalyzed pathways. Therefore, under the catalysis of Ca2+, the generation pathway of HNCO is more competitive and it is conducive to the formation of HNCO.

Biochar-mediated removal of various pollutants from the environment

Abstract The growing concern regarding various environmentally hazardous pollutants has arisen due to their potential hazards to public health. Managing ecological concerns has become a pressing global priority. The utilisation of biochar in wastewater treatment to remove various hazardous substances impeded by its limited adsorption capacity, despite its low cost and good effectiveness. To enhance the efficiency of biochar in eliminating multiple pollutants, mixed methods have been used to change biochar and give it different physical and chemical properties; this results in distinctive adsorption outcomes, behaviours, and mechanisms. This study comprehensively analyses the efficient techniques, impacts, and mechanisms of modified biochar in eliminating hazardous substances, such as emerging contaminants, in the ecosystem. Modified biochar has enhanced efficacy in removing these substances, with removal processes mainly using adsorption and catalytic degradation pathways. Future endeavours should prioritise the development of uniform assessment standards for cost, efficacy, and environmental hazards while utilising emerging technologies to expand the potential uses of modified biochar to remove emerging contaminants.

A DFT Study of CO Hydrogenation on Graphene Oxide: Effects of Adding Mn on Fischer–Tropsch Synthesis

The hydrogenation of carbon monoxide (CO) offers a promising avenue for reducing air pollution and promoting a cleaner environment. Moreover, by using suitable catalysts, CO can be transformed into valuable hydrocarbons. In this study, we elucidate the mechanistic aspects of the catalytic conversion of CO to hydrocarbons on the surface of manganese-doped graphene oxide (Mn-doped GO), where the GO surface includes one OH group next to one Mn adatom. To gain insight into this process, we have employed calculations based on the density functional theory (DFT) to explore both the thermodynamic properties and reaction energy barriers. The Mn adatoms were found to significantly activate the catalyst surface by providing stronger adsorption geometries. Our study concentrated on two mechanisms for CO hydrogenation, resulting in either CH4 production via the reaction sequence CO → HCO → CH2O → CH2OH → CH2 → CH3 → CH4 or CH3OH formation through the CO → HCO → CH2O → CH2OH → CH3OH pathway. The results reveal that both products are likely to be formed on the Mn-doped GO surface on both thermodynamic grounds and considering the reaction energy barriers. Furthermore, the activation energies associated with each stage of the synthesis show that the conversion reactions of CH2 + OH → CH3 + O and CH2O + OH → CH2OH + O with energy barriers of 0.36 and 3.86 eV are the fastest and slowest reactions, respectively. The results also indicate that the reactions: CH2OH + OH → CH2 + O + H2O and CH2OH + OH → CH3OH + O are the most exothermic and endothermic reactions with reaction energies of −0.18 and 1.21 eV, respectively, in the catalytic pathways.

Investigating the Sole Olefin-Based Cycle in Small-Cage MCM-35-Catalyzed Methanol-to-Olefins Reactions.

Small-pore zeolites catalyze the methanol-to-olefins (MTO) reaction via a dual-cycle mechanism, encompassing both olefin- and aromatic-based cycles. Zeolite topology is crucial in determining both the catalytic pathway and the product selectivity of the MTO reaction. Herein, we investigate the mechanistic influence of MCM-35 zeolite on the MTO process. The structural properties of the as-synthesized MCM-35 catalyst, including its confined cages (6.19 Å), were characterized, confirming them as the catalytic centers. Then, the MTO reactions were systematically performed and investigated over a MCM-35 catalyst. Feeding pure methanol to the reactor yielded minimal MTO activity despite the formation of some aromatic species within the zeolite. The results suggest that the aromatic-based cycle is entirely suppressed in MCM-35, preventing the simultaneous occurrence of the olefin-based cycle. However, cofeeding a small amount of propene in methanol can obviously enhance the methanol conversion under the same studied reaction conditions. Thus, the exclusive operation of the olefin-based cycle in the MTO reaction, independent of the aromatic-based cycle, was demonstrated in MCM-35 zeolite.

Promoting effect and kinetic analysis of Fe-Co bimetallic doping on the LaMnO3 catalytic activity for methane combustion

To enhance the catalyst’s properties, a modified sol–gel method is developed in this study, and a unique perovskite catalyst, LaMnxFeyCo1-x-yO3, is successfully synthesized by doping Fe-Co into the lattice of LaMnO3. The catalytic activity of the synthesized catalysts is initially determined by applying them to methane oxidation. Then, the structural, chemical, and surface properties of these catalysts are systematically evaluated utilizing XRD, BET, O2-TPD, H2-TPR, SEM, and XPS analyses. The modified LaMn0.8Fe0.15Co0.05O3 is shown to exhibit excellent activity (T90 at 486.5 ℃) in methane catalytic combustion, comparable to several standard noble metal materials. Experimental findings indicate that such perovskite structures have a larger specific surface area, an elevated molar ratio of Mn4+, desirable low-temperature reducibility, and excellent oxygen mobility relative to the original LaMnO3. Meanwhile, more efficient electron transfer from Mn4+/Mn3+ redox cycles, as well as the emergence of oxygen defects, significantly contribute to the robust interaction between Fe-Co and LaMnO3. Further reaction kinetic analysis is conducted to determine changes in species components and identify possible catalytic pathways. Notably, Fe-Co co-doping leads to an improvement in the increase of lattice oxygen and CH4 adsorption. In addition, the MVK kinetic mechanism governs methane combustion over LaMn0.8Fe0.15Co0.05O3. This study provides new insights into enhancing energy conversion performance and efficient utilization of ventilation air methane (VAM) through the implementation of highly efficient perovskites.

Enriching surface-ordered defects on WO3 for photocatalytic CO2-to-CH4 conversion by water

Defect engineering has been widely applied in semiconductors to improve photocatalytic properties by altering the surface structures. This study is about the transformation of inactive WO3 nanosheets to a highly effective CO2-to-CH4 conversion photocatalyst by introducing surface-ordered defects in abundance. The nonstoichiometric WO3-x samples were examined by using aberration-corrected electron microscopy. Results unveil abundant surface-ordered terminations derived from the periodic {013} stacking faults with a defect density of 20.2%. The {002} surface-ordered line defects are the active sites for fixation CO2, transforming the inactive WO3 nanosheets into a highly active catalyst (CH4: O2 = 8.2: 16.7 μmol h-1). We believe that the formation of the W-O-C-W-O species is a critical step in the catalytic pathways. This work provides an atomic-level comprehension of the structural defects of catalysts for activating small molecules.