Active Co Sites Research Articles

Constructing the highly efficient Ni/ZrO2/SiO2 catalyst by a combustion-impregnation method for low-temperature CO2 methanation

CO2 methanation is conducive to the storage of renewable electricity and the utilization of CO2. Exploiting highly efficient Ni-based catalysts with a simple method is of significance for this reaction. To achieve an excellent low-temperature activity, the attention is focused on the small Ni particles and ZrO2 promoter in this work, which can increase the amounts of H2 and CO2 active sites. Firstly, the simple combustion-impregnation method was employed, forming small Ni particles (about 6 nm). More metal-support interface and increased basicity could be generated in the meantime. Hence, the higher H2 dissociation and CO2 adsorption ability were attained. Secondly, ZrO2 serving as a promoter was beneficial to the formation of oxygen vacancies, which played an important role in CO2 activation and CH4 formation. These oxygen vacancies could weaken the CO bonds, improving the CO2 activation. In addition, they might serve as the H reservoir, increasing the H2 adsorption capacity. Because of the H spillover effect from Ni to ZrO2, the activated H atoms on Ni could react with activated CO2 to generate CH4. Therefore, with more active sites for H2 and CO2 activation, the Ni/ZrO2-COM catalyst exhibited the excellent catalytic performance at 300 °C. This work is of great significance in developing highly efficient Ni-based catalysts at low temperatures for CO2 methanation with a facile method.

Effects of different pretreatment strategies during porous carbonaceous materials fabrication on their peroxydisulfate activation for organic pollutant degradation: Focus on mechanism

Metal-free porous carbonaceous materials (PCM) are compelling for peroxydisulfate (PDS) activation. However, pore-creating processes are multifarious and their influences on PDS activation performance for organic degradation have not been elucidated. Herein, several PCM were synthesized via different pretreatment strategies, including manual grinding (MG), impregnation (IP) and ball milling (BM), to probe their influence on PDS activation efficiency. Therein, the PCM fabricated via BM for 60 min (BM60) was superior to all other varieties. The quantitative structure–activity relationship (QSAR) unveiled that BM accelerated the vertical expansion of turbostratic domains on PCM. The rate constant (kobs) of sulfadiazine (SDZ) degradation in PCM/PDS system positively correlated to the defective degree over PCM and CO content, indicating that the abundant defective structures over PCM contributed to enhance the PDS activation capacity by exposing more CO active sites. The CO groups can efficiently donate electrons to S2O82− inducing the breakage of peroxy bond because of the brilliant electron donating capacities of BM60, which resulted in the generation of radicals. Robust mechanism studies by multiple electrochemical methods and in situ Raman technology suggested metastable intermediates (BM60/PDS*) with a higher redox potential was the predominant oxidant which can extract electrons from SDZ via a one-electron-transfer regime, while radicals were the secondary oxidants. This finding for the first time explicitly illuminated the electron transfer direction in the nonradical pathways of PDS activation for organics degradation by PCM and deepened the fundamental understanding on the electron-transfer pathway.

DFT calculations of double vacancies MoS2 catalyzing water gas shift reaction: S vacancies as electron bridge promote electron transfer to H2O and CO molecules

The poor activity of molybdenum disulfide (MoS2) basal plane is the key scientific problem to limit efficient hydrogen production. In this paper, MoS2 with single (VS-MoS2) and double sulfur vacancy (VS, S-MoS2) have been constructed and used for water gas shift reaction (WGSR). Results show that the adsorption energy of VS, S-MoS2 for CO molecule is −1.43 eV, which is 28.6 times and 1.1 times than original MoS2 and VS, S-MoS2, respectively. The energy barrier of the rate-determining step in the association mechanism of VS, S-MoS2 is 1.78 eV, which is 21% lower than pristine MoS2. S vacancies are active sites for CO and H2O adsorption. The delocalized electrons enrichment in S vacancies break the electron transfer barrier between the surface and molecules. Sulfur vacancies as medium make electrons continuously transferred to CO and H2O molecules.

High Efficient Catalyst of N‐doped Carbon Modified Copper Containing Rich Cu−N−C Active Sites for Electrocatalytic CO2 Reduction

AbstractThe synthesis of multi‐carbon products through electrochemical CO2 reduction reactions has attracted great interest from researchers. Herein, nitrogen‐ and carbon‐doped copper nanocatalyst (NC−Cu) containing abundant Cu−N−C active sites was prepared by thermal decomposition of the complexes containing copper and melamine. The NC−Cu catalyst exhibited an ideal current density of 22 mA cm−2 at −0.93 V versus reversible hydrogen electrode (vs. RHE) in CO2‐saturated 0.5 M KHCO3 medium, with ethanol as the predominant product at −0.93 V (vs. RHE) and a maximum Faraday efficiency of 31 %. The current density of the catalyst remained almost unchanged after 20 h of electrolysis, indicating its excellent stability. The excellent catalytic ability is attributed to the abundant Cu−N−C active sites of NC−Cu with 3D porous microstructure.

Crystal Surface Engineering Induced Active Hexagonal Co2 P-V2 O3 for Highly Stable Lithium-Sulfur Batteries.

Purposeful control of the highly active crystal planes is an effective strategy to improve the nanocrystalline catalytic activity. Therefore, Co2 P nanocrystals with high exposure of (211) lattice plane loaded at 2D hexagonal V2 O3 nanosheets (H-Co2 P-V2 O3 ) are designed via the control of morphology. After optimization, this H-Co2 P-V2 O3 boosts the redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs), which is due to the increase of the Co-active sites by exposing more (211) lattice planes of Co2 P, and the high adsorption and catalysis characteristic of H-Co2 P-V2 O3 for the conversion of LiPSs into LSBs. In the case of modification separator by H-Co2 P-V2 O3 composite, the battery achieves an outstanding reversibility of 876.9 mAh g-1 over 500 cycles at 1 C, a superior rate property of 611.5 mAh g-1 at 8 C, and a long-term cycling performance with a low attenuation of 0.04% per cycle over 1000 cycles at 4 C for LSBs. Impressively, a remarkable areal capacity of 12.38 mAh cm-2 is retained under the high sulfur loading of 14.5mg cm-2 after 100 cycles. It is believed that the crystal surface engineering provides guidance to further improve the electrochemical performance of the LSB field.

Atomic- and Molecular-Level Modulation of Dispersed Active Sites for Electrocatalytic CO2 Reduction.

Global climate changes have been impacted by the excessive CO2 emission, which exacerbates the environmental problems. Electrocatalytic CO2 reduction (CO2 RR) offers the solution for utilising CO2 as feedstocks for value-added products while potentially mitigating the negative effects. Owing to the extreme stability of CO2 , selectivity and efficiency are crucial factors in the development of CO2 RR electrocatalysts. Recently, single-atom catalysts have emerged as potential electrocatalysts for CO2 reduction. They generally comprise of atomically- and molecularly dispersed active sites over conductive supports, which enable atomic-level and molecular-level modulations. In this minireview, catalyst preparations, principle of modulations, and reaction mechanisms are summarised together with related recent advances. The atomic-level modulations are first discussed, followed by the molecular-level modulations. Finally, the current challenges and future opportunities are provided as guidance for further developments regarding the discussed topics.

Cover Feature: Atomic‐ and Molecular‐Level Modulation of Dispersed Active Sites for Electrocatalytic CO2 Reduction (Chem. Asian J. 12/2022)

Electrocatalytic CO2 reduction represents a promising approach to mitigate problems from excessive CO2 emission and to enable the conversion of CO2 into value-added chemicals. Single-atom catalysts with dispersed active sites have received considerable attention thanks to their atomic utilization and facile modification. Herein, recent advances in atomic- and molecular-level modulation of dispersed active sites for electrocatalytic CO2 reduction are discussed and summarized. Moreover, current challenges are detailed and future opportunities proposed as guidance for future development. More information can be found in the Review by Pannee Leeladee et al.

Dual-Site Single-Atom Catalysts with High Performance for Three-Way Catalysis.

In response to growing levels of air pollution and emission regulations, novel three-way catalysts (TWCs) with high efficiency are highly coveted. Herein, a multi-step heating strategy to fabricate a unique dual-site catalyst composed of strongly coupled Pt and Pd atoms located in neighboring positions on the surface of CeO2 is demonstrated. Outstanding three-way catalytic performance is demonstrated, especially for NO elimination. Based on comprehensive investigations, the enhancement is attributed to the strong interactions between the neighboring Pt and Pd atoms, which can separately serve as active sites for CO and NO adsorption, efficiently reducing the energy barrier and accelerating the reaction rate. These findings not only contribute to designing and constructing next-generation catalysts, but also provide a promising opportunity to improve fuel efficiency and control emissions.

Cobalt/calcium bimetallic oxides based on bio-waste eggshells for the efficient degradation of norfloxacin by peroxymonosulfate activation

Cobalt-calcium bimetallic oxide (ECCO) was successfully prepared using eggshells and cobalt nitrate, which could be used to activate peroxymonosulfate (PMS) to remove norfloxacin (NOR). The compositional structure and surface properties of the catalysts were explored by various characterization analysis. The degradation efficiency of ECCO was 7.86 and 440 times higher than that of cobalt oxide and calcium oxide, respectively. The prepared ECCO (0.1 g/L) had a high degradation efficiency of over 90% against NOR (10 mg/L, 100 mL) by activating the PMS (0.15 g/L) at a wide pH range of 3.0–9.0 in 35 min. With a NOR removal efficiency of 91.4% after five cycles, the catalyst showed good reusability. The high degradation efficiency of NOR was resulted from enhanced electron transfer capability, the low point of zero charge and diversified reactive oxygen species (ROS). The ROS were identified as SO4•−, •OH and 1O2, which were produced by activating PMS on the active sites of Co and oxygen vacancies. It is the first report of the use of eggshells to synthesize cobalt-calcium bimetallic oxides ECCO for the activation of PMS to eliminate NOR, which is important for the development of green and efficient catalysts.

Zn2+–Modulated bimetallic carbides synergized with macro-mesoporous N-rich carbon enabling accelerated polysulfides conversion for high-performance Li-S batteries

• Zn 2+ modulated Co 3 ZnC-based catalysts are constructed via a one-pot approach. • Zn 2+ could regulate the valence states of the cobalt active sites. • Co 3 ZnC@NC interlayer can promote the adsorption and redox kinetic of polysulfides. • Co 3 ZnC@NC contributes to superb cycling capacities and high-rate performance. Metal cations could serve as the active sites to adsorb lithium polysulfides (LiPSs) and catalyze the associated multi-electrons redox reactions. Valence modulating/engineering of the metal active centers is an underlying tactic to expedite the sluggish kinetics of LiPSs for high performance lithium-sulfur (Li-S) batteries. Herein, we craft Zn 2+ -modulated bimetallic carbides electrocatalyst of Co 3 ZnC-embedded carbon submicrospheres anchoring on 3D macro-mesoporous N-doped carbon (denoted as Co 3 ZnC@NC) via a facile one-pot synthesis that employs dicyandiamide as the carbon/nitrogen precursor. Results demonstrate that the balance of the predominantly active Co 2+ /Co 0 pair can be effectively modulated by the incorporated zinc cations, which leads to inhibited shuttle effect and accelerates the catalytic conversion kinetics of LiPS intermediates. When acted as the interlayer to modify commercial separator, Co 3 ZnC@NC confers the superb cycling stability on corresponding Li-S batteries with high discharge capacities and exceptionally high-rate performance, owing to the well-defined surface structure and the increased Co 2+ active sites of Co 3 ZnC@NC. Even the sulfur loading is kept at 4 mg cm −2 , the battery achieves an areal capacity of 3.22 mAh cm −2 after 50 cycles. This work unveils the potential of cation modulated bimetal-based electrocatalysts and also inspires an alternative avenue to exploit surface-mediated redox electrocatalysts for high-performance Li-S batteries.

Structural reconstruction of Sn-based metal–organic frameworks for efficient electrochemical CO2 reduction to formate

In-situ construction of Sn nanoclusters from Sn-based MOFs for efficient electrochemical CO 2 reduction to formate. MOF-based materials have been widely explored in electrochemical CO 2 reduction reactions for the production of valuable chemicals. Understanding the reconstruction of those catalysts under working conditions is crucial for the identification of active sites and clarification of reaction mechanism. Herein, a series of six N coordinated Sn-based metal-organic frameworks (Sn-N6-MOFs) are newly developed for electrochemical CO 2 reduction (CO 2 RR). 2% Sn-N6-MOF achieves the optimal catalytic performance with a formate Faradaic efficiency of ∼85% and a current density of 23 mA·cm −2 at −1.23 V vs. RHE. In-situ Raman results combined with ex-situ 119 Sn Mössbauer measurements reveal the structural reconstruction of Sn-N6-MOFs during CO 2 RR, generating tin nanoclusters as the real active sites for CO 2 electroreduction to HCOOH.

Implanting Single Zn Atoms Coupled with Metallic Co Nanoparticles into Porous Carbon Nanosheets Grafted with Carbon Nanotubes for High‐Performance Lithium‐Sulfur Batteries

AbstractThe electrochemical performance of lithium‐sulfur (Li‐S) batteries is severely hindered by the sluggish sulfur redox kinetics and the shuttle effect of lithium polysulfides (LiPSs). Herein, an integrated composite catalyst consisting of Co nanoparticles and single‐atom (SA) Zn co‐implanted in nitrogen‐doped porous carbon nanosheets grafted with carbon nanotubes (Co/SA‐Zn@N‐C/CNTs) is rationally developed toward this challenge. Experimental and theoretical investigations indicate that the synergistically dual active sites of Co and atomic Zn‐N4 moieties with an optimal charge redistribution not only strongly confine the LiPSs but also effectively catalyze its conversion reactions by lowering the energy barrier from Li2S2 to Li2S while the N‐doped porous carbon‐grafted CNTs enables a large surface area for more active site exposure and provides a fast electron/ion pathway. Benefiting from synergies, Li‐S batteries equipped with the Co/SA‐Zn@N‐C/CNTs‐based sulfur cathode exhibit a high reversible capacity of 1302 mAh g−1 at 0.2 C and a low capacity fading rate of 0.033% per cycle over 800 cycles at 1 C. Moreover, a high areal capacity of 4.5 mAh cm−2 at 0.2 C with the sulfur loading of 5.1 mg cm−2 can be achieved. The present work may provide new insight into the design of high‐performance sulfur‐based cathodes for Li‐S batteries.

Impurity Tolerance of Unsaturated Ni-N-C Active Sites for Practical Electrochemical CO2 Reduction

Impurity Tolerance of Unsaturated Ni-N-C Active Sites for Practical Electrochemical CO₂ Reduction

In-situ activated ultramicroporous carbon materials derived from waste biomass for CO2 capture and benzene adsorption

With the development of economy and the improvement of environmental protection awareness, more pollutants such as CO2 and benzene in coal-fired fuel gas need be controlled. Here, a novel preparation strategy of in-situ activated porous carbons based on tobacco stem was proposed. The C–OOH and C–OH groups in tobacco stem could coordinate with zinc ions through hydrothermal process to form Zn-hydrochars. The presence of Zn in Zn-hydrochars (MPC-1) provides an additional 144% ultramicropore volume, contributing to superior CO2 uptake capacity of 209 and 146 mg g−1 under 1 bar at 0 °C and 25 °C respectively. The selectivity of CO2/N2 on MPCs is 16.4–26.6 at 1 bar and 25 °C. Based on experimental data and molecular simulation, we found that CO2 uptake and separation decreasing with the pore widths increasing. The oxygen and nitrogen atoms can increase electronegativity of carbon framework and provide more CO2 active sites, thereby enhancing CO2 capture and selectivity. Besides, the MPC-1 exhibits superior benzene adsorption capacities of 97 mg g−1 and 202 mg g−1 at concentration of 10 ppm and 50 ppm, respectively. The molecular simulation shows that MPCs facilitate the benzene adsorption at a low concentration, even in environments/indoor environments with the sub-ppm range.

Inhibition of the master regulator of Listeria monocytogenes virulence enables bacterial clearance from spacious replication vacuoles in infected macrophages.

A hallmark of Listeria (L.) monocytogenes pathogenesis is bacterial escape from maturing entry vacuoles, which is required for rapid bacterial replication in the host cell cytoplasm and cell-to-cell spread. The bacterial transcriptional activator PrfA controls expression of key virulence factors that enable exploitation of this intracellular niche. The transcriptional activity of PrfA within infected host cells is controlled by allosteric coactivation. Inhibitory occupation of the coactivator site has been shown to impair PrfA functions, but consequences of PrfA inhibition for L. monocytogenes infection and pathogenesis are unknown. Here we report the crystal structure of PrfA with a small molecule inhibitor occupying the coactivator site at 2.0 Å resolution. Using molecular imaging and infection studies in macrophages, we demonstrate that PrfA inhibition prevents the vacuolar escape of L. monocytogenes and enables extensive bacterial replication inside spacious vacuoles. In contrast to previously described spacious Listeria-containing vacuoles, which have been implicated in supporting chronic infection, PrfA inhibition facilitated progressive clearance of intracellular L. monocytogenes from spacious vacuoles through lysosomal degradation. Thus, inhibitory occupation of the PrfA coactivator site facilitates formation of a transient intravacuolar L. monocytogenes replication niche that licenses macrophages to effectively eliminate intracellular bacteria. Our findings encourage further exploration of PrfA as a potential target for antimicrobials and highlight that intra-vacuolar residence of L. monocytogenes in macrophages is not inevitably tied to bacterial persistence.

Dynamic Evolution of Active Sites in Electrocatalytic CO2 Reduction Reaction: Fundamental Understanding and Recent Progress

AbstractAdvancing the development of electrocatalytic CO2 reduction reaction (CO2RR) to address the environmental issues caused by excessive consumption of fossil fuels requires rational design of remarkable electrocatalysts, where the identification of active sites and further understanding of structure–performance relationship are the bases. However, the notable dynamic evolution often appears on the catalysts, with typical examples of Cu‐based catalysts, under operating conditions, causing great difficulty in identifying the real active sites and further understanding the correlations between structure and catalytic property. In this context, understanding the dynamic evolution process of catalytically active sites during CO2RR is of particular importance, which inspires to organize the present review. Herein, the fundamental principles of dynamic evolution in CO2RR including thermodynamics and kinetics aspects, followed by the introduction of operando techniques employed to probe the evolution under operating conditions are first highlighted. The dynamic evolution behaviors, involving atomic rearrangement and change in chemical state, on typical catalysts are further discussed, with emphasis on the correlations between evolution behaviors and catalytic properties (activity, selectivity, and stability). The emerging CO2 pulsed electrolysis technique that behaves promise to manipulate the dynamic evolution and future opportunities are finally discussed.

ZnIn2S4 nanosheet growth on amine-functionalized SiO2 for the photocatalytic reduction of CO2

The growth of ZnIn2S4 nanosheets on NH–SiO2 promotes charge carrier separation and provides active sites for CO2 activation, therefore significantly boosting CO2 photoreduction efficiency.

Uniform cobalt grafted on vanadium nitride as a high efficient oxygen evolution reaction catalyst

The rational design of highly effective and low-cost catalysts for oxygen evolution reaction (OER) is of prime importance for the development of water splitting. However, the activity of electrocatalysts still needs enhancement to satisfy the practical application. Herein, we report Co nanoparticles grafted on vanadium nitride (VN) surface via in situ phase separation method by nitriding Co2V2O7 precursor. Benefiting the advantages of abundant active sites of Co, high conductivity and corrosion resistance of VN, the Co/VN achieves incredibly high activity and durability for OER with a low overpotential of 320 mV at a current density of 10 mV cm−2 with a small Tafel slope of 50.4 mV dec−1 and long-term stability. In addition, the in situ Raman further reveals the synergistic effect of Co and VN. Significantly, this study may enrich our knowledge and it can be extended to prepare other interconnected framework structures for the development of OER catalysts.

Double Active Sites in Co–Nx–C@Co Electrocatalysts for Simultaneous Production of Hydrogen and Carbon Monoxide

The hydrogen evolution reaction (HER) by electrocatalytic water splitting is a prospective and economical route. However, the approach is severely hindered by the sluggish anodic OER, poor reactivity of electrocatalysts, and low-value-added byproducts at the anode. Herein, formaldehyde was added as an anode sacrificial agent, and a bifunctional Co-Nx-C@Co catalyst containing abundant Co-N4 sites and Co nanoparticles was successfully fabricated and evaluated as both a cathodic and an anodic material for the HER and formaldehyde selective oxidation reaction (FSOR), respectively. Co-Nx-C@Co displayed a remarkable electrocatalytic performance simultaneously for both HER and FSOR with high hydrogen (H2) and carbon monoxide (CO) selectivity. Density functional theory calculations combined with experiments identified that Co-N4 and Co nanoparticles were dominating active sites for CO and H2 generation, respectively. The coupling tactic of FSOR at the anode not only expedites the reaction rate of HER but also offers a high-efficiency and energy-saving means for the generation of valuable H2/CO syngas.

Insights on the Catalytic Active Site for CO2 Reduction on Copper-based Catalyst: A DFT study

• CO 2 RR reaction mechanism on cu and CuO was studied by DFT. • The favorable pathways for CO 2 RR into CH 3 OH production were determined. • Surface h on CuO has significant effect on CO hydrogenation reaction kinetics. • New fundamental insights on CO 2 RR mechanism were unveiled. Cu oxide and Cu are widely used catalyst in CO 2 reduction reaction (CO 2 RR) for methanol (CH 3 OH) production. However, due to the complexity of the oxidation states on catalyst surfaces, the active sites of Cu-based catalysts for CO 2 RR are still unclear. In this study, density functional theory (DFT) calculations were performed to investigate the active sites for CO 2 RR reduction into CH 3 OH on Cu (111) and CuO (111) surface. The most favored adsorption sites and reaction energetics involved in CO 2 activation and sequent CO hydrogenation steps for CH 3 OH formation were determined. It has been found that, for CO 2 reduction, the CO 2 →COOH*→CO* pathway prefers to occur on both Cu (111) and CuO (111) surfaces. More importantly, the analysis reveals that, compared with Cu (111) and clean CuO (111), sequent CO hydrogenation into CH 3 OH is promoted by the H pre-covered CuO (111), on which the surface H is set on Cu site (H Cu ). That is, in CO 2 RR, the catalytic active sites for CH 3 OH production are the H-covered Cu sites on CuO (111) surface. These new insights on the catalytic active sites for CH 3 OH production on Cu-based catalyst would potentially guide the design of efficient CO 2 RR catalysts.