Dual Active Sites Research Articles

First-Principles Study of Bimetallic Pairs Embedded on Graphene Co-Doped with N and O for N2 Electroreduction.

The electrocatalytic nitrogen reduction reaction (NRR) is considered a viable alternative to the Haber-Bosch process for ammonia synthesis, and the design of highly active and selective catalysts is crucial for the industrialization of the NRR. Dual-atom catalysts (DACs) with dual active sites offer flexible active sites and synergistic effects between atoms, providing more possibilities for the tuning of catalytic performance. In this study, we designed 48 graphene-based DACs with N4O2 coordination (MM'@N4O2-G) using density functional theory. Through a series of screening strategies, we explored the reaction mechanisms of the NRR for eight catalysts in depth and revealed the "acceptance-donation" mechanism between the active sites and the N2 molecules through electronic structure analysis. The study found that the limiting potential of the catalysts exhibited a volcano-shaped relationship with the d-band center of the active sites, indicating that the synergistic effect between the bimetallic components can regulate the d-band center position of the active metal M, thereby controlling the reaction activity. Furthermore, we investigated the selectivity of the eight DACs and identified five potential NRR catalysts. Among them, MoCo@N4O2-G showed the best NRR performance, with a limiting potential of -0.20 V. This study provides theoretical insights for the design and development of efficient NRR electrocatalysts.

Fast Joule heating for transformation of Fe-MIL-125(Ti) to Fe/TiO2 with enhanced photocatalytic activity in N2 fixation

It is critical to develop a highly efficient catalyst for the photocatalytic fixation of nitrogen to produce ammonia under ambient conditions. Herein, we reported on a fast Joule heating (FJH) method to synthesize 1.0 wt% Fe-doped TiO2 (JH Fe/TiO2) derived from MIL-125(Ti). For comparison, Fe/TiO2 calcined in a tube furnace was also prepared (TF Fe/TiO2). The photocatalytic production rate of ammonia on JH Fe/TiO2 was increased to 56.87 μmol g−1 h−1, which was 1.5 times higher than that of TF Fe/TiO2. As detected, FJH might lead to the formation of lattice defects with oxygen vacancies (OVs) formation. These OVs and defects had the potential to act as adsorption and reactive sites for N2. Furthermore, in-situ infrared (FT-IR) along with Density Functional Theory (DFT) simulation were applied to study the possible reaction pathways of photocatalytic reduction of N2. As calculated, the substitution of Feδ+ for Ti4+ with the formation of Fe-Ti dual active sites synergistically interacted with the OVs to facilitate the photocatalytic reduction process. Moreover, an alternative pathway was more favorable for the production of NH3. The reasonable design of Fe-doped transition metal oxides and the proposed Fe-Ti dual active sites opened a new approach for highly efficient photocatalytic N2 fixation.

Efficient and Stable Dual-Active-Site of Core-Shell NiFe-Layered Double Hydroxide Anchored on FeMnON-N-Doped Carbon Nanotubes as Bifunctional Oxygen Electrocatalysts for Zn-Air Batteries

The bifunctional air electrodes with numerous dual-active sites and low cost are desirable to modify the performance of Zn-air batteries (ZABs). Metal–oxygen-nitrogen–carbon substrate (M = Mn, Fe, Ni, etc.) and NiFe-layered double hydroxide (NiFe-LDH) nanosheets are excellent catalysts in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes, respectively. Hereby, we investigate a bifunctional electrocatalytic substrate with a 3D core–shell hierarchical architecture by anchoring high OER-active NiFe-LDH on ORR-active FeMnZIF-8@gC3N4-derived FeMnON-N doped carbon nanotubes bamboo like (NiFe-LDH@FeMnON-NC). This nanocomposite has unique features such as robust synergistic effects, high conductivity, balance, and optimization of surface chemical valences of Fe, Mn, and Ni atoms to boost the bifunctional ORR and OER properties and stability in ZABs. The NiFe-LDH@FeMnON-NC nanocomposite not only exhibited superior OER electroactivity with a low onset overpotential of 235 mV (10 mA cm−2) but also had excellent ORR activity with a current density of −5.48 mA cm−2 and onset potential of 1.04 V, which is better than or comparable to those of commercial Pt/C and RuO2. Rechargeable ZABs constructed by bifunctional NiFe-LDH@FeMnON-NC have a peak power density (235.41 mW cm−2), open-circuit potential (OCV) (1.53 V), small discharge/charge band gap of 0.74 V and excellent discharge stability.

Synergistic enhanced kinetics and dual active sites in PANI@V2O5 nanoflower for superior Ca2+ ion storage

Calcium-ion batteries (CIBs) have attracted growing interest owing to abundant Ca resources and its high gravimetric capacity. However, potent electrostatic interactions between Ca2+ ions and host material, can lead to slow diffusion kinetics and crystal structure destabilization. A pre-intercalation strategy involving polyaniline (PANI) was employed in this study to enhance the cathode material performance of PANI@V2O5 (PVO) for CIBs. PANI pre-intercalation improved both the diffusion kinetics and capacity by increasing the distance between the V-O layers (13.8 Å) and significantly enhancing the material conductivity. Meanwhile, the intercalation of PANI as extra active sites also can participate in the redox reaction, providing additional capacity. Moreover, density functional theory calculations demonstrated that the PANI intercalation improved the conductivity and relieved the electrostatic repulsion between Ca2+ ions and the V–O layer. Benefiting from a large layer spacing and dual active sites, PVO achieved a high specific capacity of 205 mAh g−1 at 100 mA g−1. This work provides insight into the mechanism of PANI intercalation to improve electrochemical performance, which sheds light on the rational design of organic–inorganic cathode materials for calcium ion batteries.

Salen-based ionic polymers as efficient heterogeneous catalysts for CO2 cycloaddition

A Salen-functionalized ionic polymer (Zn-Salen-IP) was synthesized through a metal-assisted method. The structure and microstructure were characterized by using different characterization methods. Subsequently, the cycloaddition of CO2 with epoxide was used to investigate the catalytic activity of Zn-Salen-IP. The relationship between the types of ions within Zn-Salen-IP and its catalytic performance was thoroughly explored. Single-factor investigations were used to determine the optimal reaction conditions for catalytic CO2 cycloaddition used Zn-Salen-IP. The universality and recyclability of Zn-Salen-IP were systematically studied under the optimized conditions. Finally, Density functional theory calculations were employed to research the mechanism and pathway of the CO2 cycloaddition reaction catalyzed by Zn-Salen-IP with dual functional active sites. This provided a deep understanding for the rate-determining step and the influence of the nucleophilicity of the halogen anion in cycloaddition reaction of CO2 and epoxide.

Efficient synthesis of furfural over mZSM-5@SO42-/mSiO2 core–shell catalyst by targeted regulating B/L acids

A core–shell catalyst mZSM-5@SO42-/mSiO2 composed of mZSM-5 core and SO42-/mSiO2 shell was prepared by the soft template method. Core-shell structure could promote the building of Brønsted -Lewis (B-L) acids interface and significantly improve the synergistic effect of B-L. In this paper, the Brønsted/Lewis (B/L) of mZSM-5@SO42-/mSiO2 was targeted regulating by innovatively introducing Brønsted acid (BA) sites into the shell. The optimal mZSM-5@SO42-/mSiO2 catalyst (B/L = 0.142) could achieve 72.1 % furfural yield at 140 ℃ for 1 h. In addition, 70.2 % furfural yield could be obtained after the catalyst was recycled and regenerated for 5 times. Combining In-situ IR and 13C NMR, the reaction path was revealed in detail: xylose was first isomerized to xylulose and then dehydrated to furfural. This paper provides a research idea for the directional regulation of dual active sites of cascade reaction catalysts.

Nb1-Zr dual active sites constructed on ZrO2 boost nitrite-to-ammonia electroreduction

Electrochemical nitrite-to-ammonia reduction offers a promising avenue for wastewater treatment and sustainable electrosynthesis of NH3. In this study, we immobilize Nb single atoms on a ZrO2 substrate (Nb1–ZrO2) as an efficient NO2RR catalyst. It is demonstrated that the created Nb1-Zr dual sites on Nb1-ZrO2 enhance the adsorption and activation of NO2, optimize the adsorption of key·NH3 intermediate to lower the reaction energy barrier, resulting in an overall enhancement of the NO2RR activity. Remarkably, by assembling Nb1-ZrO2 in a flow cell, we achieve the maximum FENH3 of 95.87 % and NH3 yield rate of 1588.78 µmol h−1cm−2 at a high current density of 263.59 mA cm−2, as well as the stable operation of 100 h, performing among the best of reported NO2RR electrocatalysts.

Self-Assembly Dual Active Site Nanocomposite Anode Ce0.6Mn0.3Fe0.1O2-δ/NiFe/MnOx for Electrooxidative Dehydrogenation of Ethane to Ethylene.

As the demand for ethylene grows continuously in industry, conversion of ethane to ethylene has become more and more important; however, it still faces fundamental challenges of low ethane conversion, low ethylene selectivity, overoxidation, and instability of catalysts. Electrooxidative dehydrogenation of ethane (EODHE) in a solid oxide electrolysis cell (SOEC) is an alternative process. Here, a multiphase oxide Ce0.6Mn0.3Fe0.1O2-δ-NiFe-MnOx has been fabricated by a self-assembly process and utilized as the SOEC anode material for EODHE. The highest ethane conversions reached 52.23% with 94.11% ethylene selectivity at the anode side and CO with 10.9 mL min-1 cm-2 at the cathode side, at 1.8 V at 700 °C. The remarkable electrooxidative performance of CMF-NiFe-MnOx is ascribed to the NiFe alloy and MnOx nanoparticles and improvement of the concentration of oxygen vacancies within the fluorite substrate, generating dual active sites for C2H6 adsorption, dehydrogenation, and selective transformation of hydrogen without overoxidizing the ethylene generated. Such a tailored strategy achieves no significant degradation observed after 120 h of operation and constitutes a promising basis for EODHE.

Multi‐Interface Engineering of Self‐Supported Nickel/Yttrium Oxide Electrode Enables Kinetically Accelerated and Ultra‐Stable Alkaline Hydrogen Evolution at Industrial‐Level Current Density

AbstractThe development of highly active and robust non‐noble‐metal electrocatalysts for alkaline hydrogen evolution reaction (HER) at industrial‐level current density is the key for industrialization of alkaline water electrolysis. Herein, a superhydrophilic self‐supported Ni/Y2O3 heterostructural electrocatalyst is constructed by a high‐temperature selective reduction method, which demonstrates excellent catalytic performance for alkaline HER at high current density. Concretely, this catalyst can drive 10 mA cm−2 at a low overpotential of 61.1 ± 3.7 mV, with a low Tafel slope of 52.8 mV dec−1. Moreover, it also shows outstanding long‐term durability at high current density of 1000 mA cm−2 for 500 h in 1 m KOH, evidently exceeding the metallic Ni and Pt/C(20%) catalysts. The superior HER activity can be attributed to the multi‐interface engineering of the Ni/Y2O3 electrode. Construction of Ni/Y2O3 heterogeneous interface with dual active sites lowers the energy barrier of water dissociation and optimizes the hydrogen adsorption energy, thus synergistically accelerating the overall HER kinetics. Also, its superhydrophilic self‐supported electrode structure with the firm electrocatalyst‐substrate interface and weakened electrocatalyst‐bubble interfacial force ensures rapid charge transfer, prevents catalyst shedding, and expedites the H2 gas bubble release timely, further enhancing the catalytic activity and stability at high current density.

Zonal activation of molecular carbon dioxide and hydrogen over dual sites Ni-Co-MgO catalyst for CO2 methanation: Synergistic catalysis of Ni and Co species

An in-depth mechanism in zonal activation of CO2 and H2 molecular over dual-active sites has not been revealed yet. Here, Ni-Co-MgO was rationally constructed to elucidate the CO2 methanation mechanism. The abundant surface nickel and cobalt components as active sites led to strong Ni-Co interaction with charge transfer from nickel to cobalt. Notably, electron-enriched Coδ− species participated in efficient chemisorption and activation of CO2 to generate monodentate carbonate. Simultaneously, plentiful available Ni0 sites facilitated H2 dissociation, thus CO2 and H2 were smoothly activated at zones of Coδ− species and Ni0, respectively. Detailed in situ DRIFTS, quasi situ XPS, TPSR, and DFT calculations substantiated a new formate evolution mechanism via monodentate carbonate instead of traditional bidentate carbonate based on synergistic catalysis of Coδ− species and Ni0. The zonal activation of CO2 and H2 by tuning electron behaviors of double-center catalysts can boost heterogeneous catalytic hydrogenation performance.

Targeted Delivery of Active Sites by Oxygen Vacancy-Engineered Bimetal Silicate Nanozymes for Intratumoral Aggregation-Potentiated Catalytic Therapy.

Biodegradable silicate nanoconstructs have aroused tremendous interest in cancer therapeutics due to their variable framework composition and versatile functions. Nevertheless, low intratumoral retention still limits their practical application. In this study, oxygen vacancy (OV)-enriched bimetallic silicate nanozymes with Fe-Ca dual active sites via modification of oxidized sodium alginate and gallic acid (GA) loading (OFeCaSA-V@GA) were developed for targeted aggregation-potentiated therapy. The band gap of silica markedly decreased from 2.76 to 1.81 eV by codoping of Fe3+ and Ca2+, enabling its excitation by a 650 nm laser to generate reactive oxygen species. The OV that occurred in the hydrothermal synthetic stage of OFeCaSA-V@GA can anchor the metal ions to form an atomic phase, offering a massive fabrication method of single-atom nanozymes. Density functional theory results reveal that the Ca sites can promote the adsorption of H2O2, and Fe sites can accelerate the dissociation of H2O2, thereby realizing a synergetic catalytic effect. More importantly, the targeted delivery of metal ions can induce a morphological transformation at tumor sites, leading to high retention (the highest retention rate is 36.3%) of theranostic components in tumor cells. Thus, this finding may offer an ingenious protocol for designing and engineering highly efficient and long-retention nanodrugs.

Synergistic enhancement of electrocatalytic nitroarene hydrogenation over Mo2C@MoS2 heteronanorods with dual active-sites.

Electrocatalytic hydrogenation (ECH) enables the sustainable production of chemicals under ambient conditions, in which catalysts catering for the different chemisorption of reactants/intermediates are desired but still challenging. Here, Mo2C@MoS2 heteronanorods with dual active-sites are developed to accomplish efficient nitroarene ECH according to our theoretical prediction that the binding of atomic H and nitro substrates would be synergistically strengthened on Mo2C-MoS2 interfaces. They afford high faradaic efficiency (>85%), yield (>78%) and selectivity (>99%) for the reduction of 4-nitrostyrene (4-NS) to 4-vinylaniline (4-VA) in neutral electrolytes, outperforming not only the single-component counterparts of Mo2C nanorods and MoS2 nanosheets, but also recently reported noble-metals. Accordingly, in situ Raman spectroscopy combined with electrochemical tests clarifies the rapid ECH of 4-NS on Mo2C-MoS2 interfaces due to the facilitated elementary steps, quickly refreshing active sites for continuous electrocatalysis. Mo2C@MoS2 further confirms efficient and selective ECH toward functional anilines with other well-retained reducible groups in wide substrate scope, underscoring the promise of dual-site engineering for exploring catalysts.

Discovery of highly efficient dual-atom catalysts for propane dehydrogenation assisted by machine learning.

Propane dehydrogenation (PDH) is a highly efficient approach for industrial production of propylene, and the dual-atom catalysts (DACs) provide new pathways in advancing atomic catalysis for PDH with dual active sites. In this work, we have developed an efficient strategy to identify promising DACs for PDH reaction by combining high-throughput density functional theory (DFT) calculations and the machine-learning (ML) technique. By choosing the γ-Al2O3(100) surface as the substrate to anchor dual metal atoms, 435 kinds of DACs have been considered to evaluate their PDH catalytic activity. Four ML algorithms are employed to predict the PDH activity and determine the relationship between the intrinsic characteristics of DACs and the catalytic activity. The promising catalysts of CuFe, CuCo and CoZn DACs are finally screened out, which are further validated by the whole kinetic reaction calculations, and the highly efficient performance of DACs is attributed to the synergistic effects and interactions between the paired active sites.

Photosynthesis of urea from N2 and CO2 using dual active site SiW6Mo6@MIL-101(Cr) at room temperature

SiW6Mo6@MIL-101(Cr) serves as a bifunctional photocatalyst, offering dual active sites for the reduction of N2 and CO2 to photosynthesize urea.

Constructing asymmetric dual active sites through symbiotic effect for achieving efficient and selective photoreduction of CO2 to C2H4

Asymmetric dual active sites are constructed through symbiotic effect. Owing to the differences in electron density, adsorption capacity and dipole–dipole repulsion, the energy barriers are reduced, leading to selective C2H4 production.

Breaking Sabatier's vertex via switching the oxygen adsorption configuration and reaction pathway on dual active sites for acidic oxygen reduction

Switching the oxygen adsorption configuration and reaction pathway breaks Sabatier's vertex and achieves an extraordinary acidic oxygen reduction performance.

CoNi-bimetallic coordination polymers as catalyst for boosting oxygen evolution reaction activity

One-dimensional CoxNi1−x–CAs with dual active sites offer a practical approach to enhancing the OER electrocatalytic performance.

Dual active sites of single-atom copper and oxygen vacancies formed in situ on ultrathin TiO2(B) nanosheets boost the photocatalytic dehalogenative C–C coupling synthesis of bibenzyl

The combination of photocatalytic dehalogenation of halogenated aromatics and C–C coupling synthesis of valuable organics is an interesting method for the elimination of pollutants and synthesis of valuable chemicals.

Porphyrin-silver acetylide cluster catalysts with dual active sites for the electrochemical reduction of CO2.

A one-step synthesis of porphyrin-silver acetylide clusters from tetra alkyne-substituted porphyrin is described. The solid-state properties of three 2D-like compounds were fully characterised using XPS and XRD while their catalytic properties under CO2 electroreduction reaction conditions were assessed and their faradaic efficiency quantified.

Double metals sites synergistically enhanced photocatalytic N2 fixation performance over Bi24O31Br10@Bi/Ti3C2Tx Ohm junctions

At present, it is a research hotspot to realize green synthetic ammonia by using solar energy. Exploring cheap and efficient co-catalysts for enhancing the performance of photocatalysts is a challenge in the field of energy conversion. In order to boost the charge separation/transfer of the photocatalyst and widen the visible light absorption, Bi24O31Br10@Bi/Ti3C2Tx with double Ohm junction is successfully fabricated by in situ growth of metal Bi and loading Ti3C2Tx MXene on the surface of Bi24O31Br10. The dual active sites of Bi and Ti3C2Tx MXene not only broaden the light adsorption of Bi24O31Br10 but also serve as excellent ‘electronic receptor’ for synergically enhancing the separation/transfer efficiency of photogenerated electrons/holes. Meanwhile, temperature programmed desorption (TPD) result revealed that MXene and Bi can promote N2 adsorption/activation and NH3 desorption over Bi24O31Br10@Bi/Ti3C2Tx. As a result, under mild conditions and without the presence of hole scavenger, the ammonia synthesis efficiency of Bi24O31Br10@Bi/Ti3C2Tx-20 % reached 53.86 μmol g-1cat for three hours which is 3.2 and 53.8 times of Bi24O31Br10 and Ti3C2Tx, respectively. This study offers a novel scheme for the construction of photocatalytic systems and demonstrates Ti3C2Tx MXene and metal Bi as a promising and cheap co-catalyst.