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g-C3N4 emerges as a promising metal-free semiconductor photocatalyst due to its cost-effectiveness, facile synthesis, suitable visible light response, and robust thermal stability. However, its practical application in photocatalytic hydrogen evolution reaction (HER) is impeded by rapid carrier recombination and limited light absorption capacity. In this study, we successfully develop a novel g-C3N4-based step-scheme (S-scheme) heterojunction comprising two-dimensional (2D) sulfur-doped g-C3N4 nanosheets (SCN) and one-dimensional (1D) FeCo2O4 nanorods (FeCo2O4), demonstrating enhanced photocatalytic HER activity. The engineered SCN/FeCo2O4 S-scheme heterojunction features a well-defined 2D/1D heterogeneous interface facilitating directed interfacial electron transfer from FeCo2O4 to SCN, driven by the lower Fermi level of SCN compared to FeCo2O4. This establishment of electron-interacting 2D/1D S-scheme heterojunction not only facilitates the separation and migration of photogenerated carriers, but also enhances visible-light absorption and mitigates electron-hole pair recombination. Band structure analysis and density functional theory calculations corroborate that the carrier migration in the SCN/FeCo2O4 photocatalyst adheres to a typical S-scheme heterojunction mechanism, effectively retaining highly reactive photogenerated electrons. Consequently, the optimized SCN/FeCo2O4 heterojunction exhibits a substantially high hydrogen production rate of 6303.5 µmol·g−1·h−1 under visible light excitation, which is 2.4 times higher than that of the SCN. Furthermore, the conjecture of the S-scheme mechanism is confirmed by in situ XPS measurement. The 2D/1D S-scheme heterojunction established in this study provides valuable insights into the development of high-efficiency carbon-based catalysts for diverse energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

HCHO is one of the volatile organic compounds (VOCs), whose toxicity and volatility have a significant effect on health and the environment. In this study, Sc/Cr2CO2 as a single-atom catalyst was investigated for the oxidation of HCHO using thermal catalysis and density functional theory (DFT). Sc/Cr2CO2 shows excellent thermal stability as revealed from ab initio molecular dynamic (AIMD) simulations. With an increase in temperature, the adsorption of O2 and HCHO on Sc/Cr2CO2 is enhanced. The results of Gibbs free energy indicate that the catalytic reactivity of Sc/Cr2CO2 is enhanced for HCHO when temperature is increased. For the dissociation of O–H bonds, the diffusion barriers of high temperature (448 K) are lower than those of room temperature (298 K) at the Eley-Rideal (ER) path, which indicates that the reaction can be promoted for the ER path at high temperatures. Thus, Sc/Cr2CO2 can be a promising high-temperature HCHO oxidation candidate. This work may pave the way for the next generation of advanced catalytic materials for high-efficiency catalytic HCHO oxidation with the kiln exhaust gas. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable energy solutions, the carbon dioxide reduction reaction (CO2RR) holds immense promise for converting CO2 into valuable chemicals and fuels. In this view, the exploration of magnetic MXene catalysts is crucial for understanding their reactivity and performance in electrochemical reactions to improve the CO2 conversion process. Herein, two distinct magnetic configurations, ferromagnetic (FM) and antiferromagnetic (AFM), were considered for La-doped Ti3C2O2 (La-Ti3C2O2). Using density functional theory (DFT) calculations, the first principles simulation was carried out to evaluate the electronic properties, magnetic properties, and CO2RR potential of these configurations. Our findings reveal an enhancement in semiconductivity and surface reactivity of the La-Ti3C2O2 catalyst, resulting in improved electron transfer characteristics. This facilitates CO2 adsorption and decreases the formation energy barrier of intermediate species towards the CO2 hydrogenations. The La-Ti3C2O2 catalyst showed a better performance than the parent molecule Ti3C2O2, which suffers from an insufficiency of reactivity on its surface. Furthermore, the study demonstrates the AFM structure of La-Ti3C2O2 to be the soundest, which thereby displays a better efficiency than the FM structure. Considering our findings, during the current CO2 conversion process, the reaction pathway with a less energy consumption must be preferred over others. [ABSTRACT FROM AUTHOR]

The most employed strategies for adjusting the electrocatalytic activity and selectivity of covalent organic frameworks (COFs) in the oxygen reduction reaction involve modifying the number and placement of heteroatoms, degree of asymmetry, and molecular configuration of the building units. However, the utilization of linkage conversion, which can induce huge local structure change, has been rarely explored for achieving such goals. In this work, we present the successful conversion of imine linkages into nonsubstituted quinoline within thiazolo-[5,4-d]thiazole-based COFs via a Rh-catalyzed C–H activation strategy. This conversion resulted in improved performance in the oxygen reduction reaction, specifically the production of hydrogen peroxide with a selectivity of 61–69% in acid solution (pH = 3.1), a high production rate (106.3 mg L−1 in 100 min), and good durability. Control experiments and theoretical calculations were conducted to investigate the underlying mechanisms, indicating that the active sites could be the quinoline nitrogen and thiazole nitrogen. Furthermore, an analysis of the electronic structure revealed that the enhanced performance following linkage conversion was attributed to an increase in in-plane π electron delocalization. This delocalization induced charge redistribution around the active sites, optimizing the adsorption of oxygen intermediates. Overall, the work paves novel pathways to fine-tune the oxygen reduction reaction performance of COFs linked by imine bonds. [ABSTRACT FROM AUTHOR]

The direct electrocatalytic synthesis of urea from nitrogen (N2) and carbon dioxide (CO2) under mild conditions is of great significance in promoting energy and environmental strategies. However, the current strategy operated under mild conditions suffers from many technical bottlenecks, such as a complex synthesis process, high overpotential of an electrocatalytic synthesis reaction, low conversion efficiency, and poor product selectivity. Therefore, it is important to design high-performance electrocatalysts for urea synthesis with an efficient mechanism. In this work, we present a double transition-metal MXene (Mo2VC2-MXene) as an excellent candidate with high selectivity for the electrocatalytic synthesis of urea under mild conditions. The key intermediate precursor *CO is unraveled through full reaction energy calculations by taking into account the related reaction pathways. Transition state assessments were also performed for the C–N coupling step and resulted in the targeted kinetic potentials, which are lower potential barriers than that of the Pd–Cu catalyst (0.79 eV). The selectivity performance of the Mo2VC2 surface is demonstrated in the electrocatalytic synthesis of urea for the first time. This work consolidates the fundamental theoretical approach for the promising electrocatalytic synthesis of urea. Furthermore, the effort highlights the importance of newly emerged MXenes towards highly efficient electrocatalytic synthesis of urea. [ABSTRACT FROM AUTHOR]

CoS2 is considered to be a promising electrocatalyst for hydrogen evolution reaction (HER). However, its further widespread applications are hampered by the unsatisfactory activity due to relatively high chemisorption energy for hydrogen atom. Herein, theoretical predictions of first-principles calculations reveal that the introduction of a Cl-terminated MXenes-Ti3CNCl2 can significantly reduce the HER potential of CoS2-based materials and the Ti3CNCl2@CoS2 core-shell nanostructure has Gibbs free energy of hydrogen adsorption (∣ΔGH∣) close to zero, much lower than that of the pristine CoS2 and Ti3CNCl2. Inspired by the theoretical predictions, we have successfully fabricated a unique Ti3CNCl2@CoS2 core-shell nanostructure by ingeniously coupling CoS2 with a Cl-terminated MXenes-Ti3CNCl2. Interface-charge transfer between CoS2 and Ti3CNCl2 results in a higher degree of electronic localization and a formation of chemical bonding. Thus, the Ti3CNCl2@CoS2 core-shell nanostructure achieves a significant enhancement in HER activity compared to pristine CoS2 and Ti3CNCl2. Theoretical calculations further confirm that the partial density of states of CoS2 after hybridization becomes more non-localized, and easier to interact with hydrogen ions, thus boosting HER performance. In this work, the success of oriented experimental fabrication of high-efficiency Ti3CNCl2@CoS2 electrocatalysts guided by theoretical predictions provides a powerful lead for the further strategic design and fabrication of efficient HER electrocatalysts. [ABSTRACT FROM AUTHOR]

Abstract Although its role to prevent secondary cardiovascular complications has been well established, how acetyl salicylic acid (ASA, aspirin) regulates certain key molecules in the atherogenesis is still not known. Considering the role of matrix metalloproteinase-9 (MMP-9) to destabilize the atherosclerotic plaques, the roles of the scavenger receptor class BI (SR-BI) and ATP-binding cassette transporter A1 (ABCA1) to promote cholesterol efflux in the foam cells at the plaques, and the role of NF-κB in the overall inflammation related to the atherosclerosis, we addressed whether these molecules are all related to a common mechanism that may be regulated by acetyl salicylic acid. We investigated the effect of ASA to regulate the expressions and activities of these molecules in THP-1 macrophages. Our results showed that ASA inhibited MMP-9 mRNA expression, and caused the decrease in the MMP-9 activities from the cell culture supernatants. In addition, it inhibited the nuclear translocation of NF-κB p65 subunit, thus the activity of this inflammatory molecule. On the contrary, acetyl salicylic acid induced the expressions of ABCA1 and SR-BI, two molecules known to reduce the progression of atherosclerosis, at both mRNA and protein levels. It also stimulated the cholesterol efflux out of macrophages. These data suggest that acetyl salicylic acid may alleviate symptoms of atherosclerosis by two potential mechanisms: maintaining the plaque stability via inhibiting activities of inflammatory molecules MMP-9 and NF-κB, and increasing the cholesterol efflux through inducing expressions of ABCA1 and SR-BI.

Highlights: [•] FXR up-regulates apoF. [•] It binds to ER1 element. [•] It activates apoF gene promoter. [ABSTRACT FROM AUTHOR]

Inspired by MXene nanosheets and their regulation of surface functional groups, a series of Ti 3 C 2 -MXene-based single TM atom electrocatalysts with a doped boron (B) atom (TM@Ti 3 C 2 O 2- x B x , TM is V, Cr, Mn, Fe, Co or Ni, x = 0.11) are proposed for achieving a high performance catalytic CO 2 reduction reaction (CO 2 RR). The results reveal that the doped B atom involves in the adsorption reaction of CO 2 molecules and CO intermediates in the CO 2 RR. The TM-to-C and B-to-C π-back bonding contribute to the activation of the CO 2 molecules and CO intermediates in the CO 2 RR. Enough electrons from the single TM atom and B atom occupied orbitals can be injected into the CO 2 molecules and *CO intermediates through direct bonding interactions, which effectively alleviates the difficulty of the first hydrogenation reaction step and further helps CO reduction towards CH 4 . The calculated values of Δ G for the first hydrogenation reaction and the formation of *CHO on Ti 3 C 2 O 2- x B x are significantly smaller than those of other single-atom catalysts (SACs). Fe@Ti 3 C 2 O 2- x B x is found to have the highest electrocatalytic activity with a limiting potential of ∼0.40 V and exhibits a high selectivity for obtaining CH 4 through the CO 2 RR compared with the hydrogen evolution reaction. This work is expected to open a research path for engineering the charge-orbital state of the innate atoms of a substrate based on mechanistic insights, which guides the rational design of highly selective MXene-based CO 2 RR electrocatalysts.

Ammonia (NH 3 ) detection at the early stage is an important precaution for human health and agricultural production. However, conventional sensing materials are difficult to achieve all the targeted operational performances such as low power consumption and high selectivity. MXenes are a type of graphene-like emergent material equipped with abundant surface sites benefiting gas-sensing applications. In the work, we discuss the sensing performance of Ti 3 C 2 O 2 to anticipate harmful and polluting NH 3 gases by density functional theory and nonequilibrium Green's function. The adsorption geometry, charge difference density, and partial density of states are discussed to understand the nature of interactions between gas molecules and Ti 3 C 2 O 2 . The theoretical results show that only NH 3 adsorbs onto the nanosheet through chemisorption. Then, a two-electrode Ti 3 C 2 O 2 -based gas sensor device is built to unravel the transport properties. Current under different bias voltages indicates the Ti 3 C 2 O 2 -based sensor could maintain extremely high sensitivity, demonstrating that Ti 3 C 2 O 2 has great potential for the NH 3 sensor with high selectivity, excellent sensitivity, and low energy consumption. Upon external electric fields, the adsorption energy and charge transfer can be tuned effectively, suggesting that Ti 3 C 2 O 2 is a versatile agent as an ammonia-sensing material., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

To examine the reactivity of noble-metal-free Ni 3 C towards hydrogen evolution reaction (HER), we report a comprehensive first-principles density functional theory (DFT) study on the stability, geometric structure, electronic characteristics, and catalytic activity for HER on the Ni 3 C crystal (113) surfaces with different surface terminations, namely the C-rich and Ni-rich terminated surface of Ni 3 C (113). The results indicate that C-rich and some stoichiometric surfaces are thermodynamically stable. The bridge-site of C-rich Ni 3 C (113) is indispensable for HER because it not only displays improved electrocatalytic activity, but also possesses appropriate hydrogen adsorption energy, overpotential and robust stability. The Δ G H (0.02 eV) and overpotential obtained by C-rich Ni 3 C outperformed that obtained by Pt determined by computation (Δ G H = -0.07 eV). Thus, the bridge-sites of C-rich Ni 3 C (113) function as both excellent and stable active sites and adsorption/desorption sites. Increasing the density of active sites through doping or enlarging the surface area renders a prospective strategy to ameliorate the HER activity further. Overall, this study elucidates new insights into the surface properties of Ni 3 C for HER from water splitting and opens up a fascinating avenue to optimize the performance of solar energy conversion devices by synthesizing preferentially exposed catalyst facets., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)