Strong Electronic Interaction Research Articles

Chain-Like Pentanuclear Complexes: Syntheses, Crystal Structures and Long-Range Electronic Interactions of Cyanido-Bridged M2Ru3 (M=Fe, Ru).

In this work, we report the design and synthesis of two chain-like pentanuclear cyanido-bridged complexes trans-[Ru(bpy)2(μ-CN)2][cis-Ru(bpy)2(μ-NC)M(dppe)Cp*]2[PF6]4 (M=Fe, 14+; M=Ru, 24+) and the electronic communication properties of their oxidized products 1m+ (m=6, 7, 8) and 2n+ (n=5, 6, 7, 8). The single-crystal X-ray diffraction analysis of 1m+ (m=4, 6, 7) and 24+ show that 14+ and 24+ possess a Z-type array structure, 17+ is a U-type one, and 16+ exhibits both the types. The investigations indicate that both 1 and 2 show an extraordinarily strong electronic interaction between the two side Ru across the central NC-Ru-CN, leading to the formation of a fully delocalized cyanidometal Ru-Ru-Ru bridge for both three-electron oxidized states 17+ and 27+. Moreover, it should be noted that in 1 there exists no electronic interaction between the two terminal Fe ions. Upon substitution of Fe by Ru, however, 2 exhibits an electronic interaction between the two terminal metal ions across the trinuclear cyanidometal CN-Ru-NC-Ru-CN-Ru-NC bridge which is up to 20 Å.

Lattice Strain Regulated by Hetero/Homo Atom Interface Merging on NiMo Nanocluster for High-Performance Hydrogen Production.

Lattice strain engineering represents a cutting-edge approach capable of delivering enhanced performance across various applications. The lattice strain can affect the performance of electrochemical catalysts by changing the binding energy between the surface-active sites and intermediates. In this work, lattice strain is regulated through a homo/heterogeneous atomic interface merging. The strong lattice strain and electronic interactions between Ni and Mo facilitated the reaction kinetic of HER. The prepared NiMo@SSM exhibits excellent HER catalytic performance with 70 mV overpotential at the current density of 10 mA cm-2 and long-term stability. The method of controlling lattice strain through hetero/homo atom interface merging provides a new strategy for designing high-performance alkaline HER electrocatalysts.

Exploration on structure-activity relationship over substituted Co-doped spinel AlFe2O4 for enhanced CO2 hydrogenation into C2-C4 hydrocarbons

As the main greenhouse gas, CO2 has caused some serious environmental problems. Hence the abatement of CO2 allows of no delay. Among all strategies for CO2 reduction, CO2 hydrogenation reveals the great potential for industrial application, and becomes the efficient path to achieve target of “Carbon Neutral”. In this work, the Co-doped AlFe2O4 catalysts were firstly reported for CO2 hydrogenation test, and the enhancement of Co doping on activity was explored systematically via a series of conventional characterization methods. The Fischer-Tropsch synthesis-based CO2 hydrogenation was conducted over Co-doped AlFe2O4, thus the dissociation of CO2 and the carbon chain growth were both important. The observation of CoFe2O4 in the composites indicated the strong electronic interaction between Co and Fe species. This could strengthen the electrons transfer to generate more metallic Co and Fe species during H2 reduction, and then increased the Fe3C percentage during CO2 hydrogenation process. Moreover, the generated Co0 species could provide the additional adsorption sites for reactant gas. Therefore, the strategy of Co doping could strengthen the CO2 hydrogenation performance, reflected in the increase of CO2 conversion, the selectivity and space time yield of C2-C4 products. However, the formed “too stable” structure in the condition of the excessive Co doping prohibited the electrons transfer and the generation of Fe3C active species, thus existing an optimum Co doping amount.

Laser-Regulated Iridium-Diffused Nitrogen-Carbon Sites for Enhanced Hydrazine-Assisted Alkaline Seawater Splitting and Zinc-Hydrazine Batteries.

The current study presents a quick and simple method for synthesizing Ir nanoclusters decorated on an N-doped carbon (NC) matrix via pulsed laser ablation in liquid, followed by pyrolysis. The resulting Ir-NC material acts as a dual-functional electrocatalyst, efficiently facilitating hydrogen generation through the hydrazine oxidation reaction (HzOR) and the hydrogen evolution reaction (HER) in alkaline seawater. The optimized Ir-NC-2 catalyst exhibits a low operating potential of 23mV versus the reversible hydrogen electrode for HzOR and a remarkably low overpotential of 24mV for HER, achieving a current density of 10mAcm-2 in alkaline seawater, surpassing the performance of the Pt/C catalyst. Notably, the Ir-NC-2 catalyst also demonstrates superior dual-functionality in overall hydrazine-assisted seawater splitting, requiring only 0.1V at 10mAcm-2 while maintaining stability. Moreover, density functional theory calculations reveal that the strong electronic interaction between the Ir nanoclusters and the NC matrix enhances mass transfer and electron conductivity, significantly boosting HER activity and accelerating the kinetics of hydrazine dehydrogenation. Consequently, the Ir-NC-2 catalyst performs efficiently in a Zn-hydrazine battery, achieving high energy efficiency of 95.5% and demonstrating excellent stability for 120h (360 cycles), indicating its potential for practical applications.

Fractional quantum Hall phases in high-mobility n-type molybdenum disulfide transistors

AbstractTransistors based on semiconducting transition metal dichalcogenides can, in theory, offer high carrier mobilities, strong spin–orbit coupling and inherently strong electronic interactions at the quantum ground states. This makes them well suited for use in nanoelectronics at low temperatures. However, creating robust ohmic contacts to transition metal dichalcogenide layers at cryogenic temperatures is difficult. As a result, it is not possible to reach the quantum limit at which the Fermi level is close to the band edge and thus probe electron correlations in the fractionally filled Landau-level regime. Here we show that ohmic contacts to n-type molybdenum disulfide can be created over a temperature range from millikelvins to 300 K using a window-contacted technique. We observe field-effect mobilities of over 100,000 cm2 V−1 s−1 and quantum mobilities of over 3,000 cm2 V−1 s−1 in the conduction band at low temperatures. We also report evidence for fractional quantum Hall states at filling fractions of 4/5 and 2/5 in the lowest Landau levels of bilayer molybdenum disulfide.

Enhanced Electromagnetic Energy Conversion in an Entropy‐driven Dual‐magnetic System for Superior Electromagnetic Wave Absorption

AbstractThermochemical conversion is a highly effective method for upgrading organic solid wastes into high‐value materials, contributing to carbon neutrality and peak, carbon emission goals. It also serves as a pathway to develop energy‐efficient electromagnetic wave absorbing (EMWA) materials. In this study, fish skin to successfully in situ nitrify Prussian Blue into Fe3N under external thermal driving condition, resulting in high saturation magnetization is utilized. The resulting Fe3N@C demonstrates outstanding EMWA property, achieving a minimum reflection loss of −71.3 dB. Furthermore, by introducing cellulose nanofiber, a portion of the iron nitride is transformed into iron carbide, resulting in Fe3C/Fe3N@C. This composite exhibits enhanced EMWA properties owing to wider local charge redistribution and stronger electronic interactions, achieving an effective absorption bandwidth (EAB) of 6.64 GHz. Electromagnetic simulations and first‐principles calculations further elucidate the EMWA mechanism, and the maximum reduction value of the radar‐cross section reached 37.34 dB·m2. The design of multilayer gradient metamaterials demonstrated an ultra‐broadband EAB of 11.78 GHz. This paper presents an efficient strategy for atomic‐level biomass waste utilization to prepare Fe3N, provides novel insights into the conversion between metal nitrides and metal carbides, and offers a promising direction for the development of advanced EMWA materials.

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Rational Design of Ultrahigh-Loading Ir Single Atoms on Reconstructed Mn─NiOOH for Enhanced Catalytic Performance in Urea-Water Electrolysis.

Investigating advanced electrocatalysts is crucial for improving the efficacy of water splitting to generate environmentally friendly fuel. The discovery of highly effective electrocatalysts, capable of driving oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in urea-alkaline environments, is pivotal for advancing large-scale hydrogen production. This study aims to introduce a new method that involves creating nanosheets of high-loading iridium single atoms embedded in a manganese-containing nickel oxyhydroxide matrix (Ir@Mn─NiOOH). These nanostructures are derived from self-supported hydrate pre-catalyst nanosheets grown on nickel foam and then activated through electrochemical etching pretreatment. The Ir@Mn─NiOOH nanoarchitecture displays outstanding electrocatalytic activity, having a low overpotential of just 258mV and a potential of 1.319V (at 10mAcm-2) for OER and UOR, respectively. Such extraordinary catalytic characteristics of Ir@Mn─NiOOH is mainly owing to the strong synthetic electronic interaction between Ir single atoms and Mn─NiOOH, which can change its electronic characteristics and boost electrochemical catalytic sites. This research presents a new way to produce exceptionally efficient catalysts by adding a synergistic effect to complex multi-electron processes.

Constructing 2D PtSe2/PtCo Heterojunctions by Partial Selenization for Enhanced Hydrogen Evolution

AbstractThe rational design and fabrication of 2D heterojuctions are proven a promising strategy for boosting the performance of electrocatalysts. Although 2D platinum diselenide (PtSe2) exhibits catalytic activity for hydrogen evolution reaction (HER), the catalytic performance is still unsatisfactory due to its inert basal plane, wide bandgap, and poor electron transfer ability. Herein, a new strategy is reported to construct PtSe2/PtCo heterojunctions by partial selenization of PtCo alloy for high‐efficiency HER electrocatalyst, which exhibits a low overpotential of 38 mV at the current density of 10 mA cm−2, a small Tafel slope of 22 mV dec−1, and a superior stability over 24 h and 1000 cycles. The outstanding HER activity of the catalyst arises from the strong electronic interactions between PtSe2 and PtCo in the heterojunctions, which induce electron transferring from PtSe2 to PtCo and the d‐band center down shifting, and thus optimize the H* adsorption/desorption. This work provides a novel strategy for constructing highly efficient heterostructure electrocatalysts, which facilitates the applications of hydrogen energy conversion.

D-Band Center Engineering of Nickel Nanoparticles Accelerates Water Dissociation for Hydrogen Evolution in Neutral NaCl Solution.

While Pt is highly efficient for hydrogen evolution reaction (HER), its widespread use is limited by scarcity and high cost. Herein, a vertically aligned electrocatalyst is present comprising Ni3S2 nanotube arrays (NTAs) and Ni nanoparticles (NPs) (Ni3S2/Ni NTAs) for neutral HER. In a neutral 4 wt.% NaCl solution (pH = 7), the Ni3S2/Ni NTAs achieves a current density of 100mA cm-2 at a low overpotential of 540mV, outperforming both Ni3S2 NTAs and Ni NTAs and even the commercial Pt plate. The hollow tubular structure offers ample mass transfer channels, and strong electronic interaction between Ni3S2 and Ni is observed. Theoretical studies reveal that the lowered d-band center (ɛd) of Ni 3d orbital significantly reduces the activation energy for H2O dissociation and facilitates the movement of an H atom in H2O away from OH to form a transition state, consequently promoting H2 evolution. When Ni3S2/Ni NTAs is used as the cathode in a two-electrode diaphragm-free electrolyzer with a RuSnTi anode, efficient H2 production and energy-saving Cl2 evolution are achieved. This work highlights the potential of uniquely structured electrocatalysts for HER in neutral NaCl solutions.

Surface Cladding Engineering via Oxygen Sulfur Distribution for Stable Electrocatalytic Oxygen Production

AbstractInevitable leaching and corrosion under anodic oxidative environment greatly restrict the lifespan of most catalysts with excellent primitive activity for oxygen production. Here, based on Fick’ s Law, we present a surface cladding strategy to mitigate Ni dissolution and stabilize lattice oxygen triggering by directional flow of interfacial electrons and strong electronic interactions via constructing elaborately cladding‐type NiO/NiS heterostructure with controlled surface thickness. Multiple in situ characterization technologies indicated that this strategy can effectively prevent the irreversible Ni ions leaching and inhibit lattice oxygen from participating in anodic reaction. Combined with density functional theory calculations, we reveal that the stable interfacial O−Ni−S arrangement can facilitate the accumulation of electrons on surficial NiO side and weaken its Ni−O covalency. This would suppress the overoxidation of Ni and simultaneously fixing the lattice oxygen, thus enabling catalysts with boosted corrosion resistance without sacrificing its activity. Consequently, this cladding‐type NiO/NiS heterostructure exhibits excellent performance with a low overpotential of 256 mV after 500 h. Based on Fick's law, this work demonstrates the positive effect of surface modification through precisely adjusting of the oxygen‐sulfur exchange process, which has paved an innovative and effective way to solve the instability problem of anodic oxidation.

N, S-Codoped 3D Carbon Protected Nanoporous MnS With Record High Sodium Ion Storage Performance for Potential Industry Applications.

With a high theoretical capacity, the MnS anode, however, exhibits a rather complex sodium diffusion kinetics and poor mechanical stability that hinder its application in sodium-ion batteries (SIBs). In this work, a simple, economical, and scalable strategy is developed to inherently coat nanoporous MnS with a 3D N, S co-doped thin carbon layer by using commercially available MnCO3 as precursors. Specifically, the strategy involves a two-step annealing process, which converts the MnCO3 microparticles into nanoporous Mn2O3 and MnS step by step. The 3D N, S codoped carbon layer is in situ formed during the second annealing process by first coating the nanoporous Mn2O3 with a polyaniline layer. Due to the inherent 3D carbon protection and the strong electronic interaction between N, S dopants and MnS, the N, S codoped carbon protected MnS obtained at 900 °C (NS-C@MnS-900) anode displays a high specific capacity of 845mAhg-1 at 0.1Ag-1, which is higher than all reported MnS-based SIB anodes. It also shows an outstanding cyclability and rate performance, maintaining a stable capacity of ≈493mAhg-1 after 1300 cycles at 10Ag-1, which is also the best according to knowledge. These exceptional electrochemical performances and the scalable/simple/low-cost synthesis make the NS-C@MnS-900 attractive for industry application.

Growth Modulation of High-Entropy Alloys for Electrocatalytic Methanol Oxidation Reaction.

High-entropy alloy (HEA) electrocatalysts have exhibited remarkable catalytic performance because of their synergistic interactions among multiple metals. However, the growth mechanism of HEAs remains elusive, primarily due to the constraints imposed by the current synthesis methodologies for HEAs. In this work, an innovative electrodeposition method was developed to fabricate Pt-based nanocomposites (Pt1Bi2Co1Cu1Ni1/CC), comprising HEA nanosheets and carbon cloths (CCs). The reaction system could be effectively monitored by taking samples out from the system during the reaction process, facilitating in-depth insight into the growth mechanism underlying the material formation. In particular, Pt1Bi2Co1Cu1Ni1/CC nanocomposites show superior methanol oxidation reaction (MOR) performance (mass activity up to 5.02 A mgPt-1). Upon structural analysis, the d-band center of Pt1Bi2Co1Cu1Ni1/CC is lower in comparison with that of Pt1Bi2/CC and Pt/CC, demonstrating the formation of a rich-electron structure. Both the uniformity of HEAs and the carbon-supported effect could provide additional active sites. These findings suggest that the strong electronic interaction within HEAs and additional active sites can effectively modulate the catalytic structure of Pt, which benefits the enhanced CO tolerance and MOR performance.

Cu Nanowires Encapsulated by ZIF67 for Efficient Ammonia Electrosynthesis from Nitrate.

Electrochemical NO3 - reduction reaction (NO3RR) represents a green and sustainable way to produce valuable NH3 for both NH3 production and nitrate contaminant removal, and developing efficient, durable, highly selective catalyst is the key. Herein, we report a facile method to fabricate a catalyst composed of ultrafine Cu nanowires (Cu NWs) encapsulated by ZIF67, namely, CuNW@ZIF67, for efficient NH3 electrosynthesis from nitrate. The CuNW@ZIF67 catalyst exhibited excellent catalytic performance toward NO3RR in alkaline electrolyte, manifested by a large NH3 Faradaic efficiency of 93.7 % at -0.5 V versus reversible hydrogen electrode (RHE), a high energy efficiency over 30 % at -0.7 V, and robust long-term stability. Such intriguing catalytic properties are mainly ascribed to its structural merits and the strong electronic interaction between Cu NWs and ZIF67. DFT calculations revealed that, the Cu site can easily convert NO3 - into NO2 -, while the Co site plays a critical role in catalyzing the NO2 --to-NH3 process. The study can shed light on rational design of efficient, durable, and highly selective catalysts for NO3RR and beyond.

Nitrogen-doped carbon nanosheet confined PtNi alloy for efficient acidic electrocatalytic hydrogen evolution reaction

Low intrinsic electrocatalytic activity and inferior conductivity limit the application of Ni/NC in acidic electrocatalytic hydrogen evolution reaction (HER). Herein, we prepared nitrogen-doped carbon nanosheet confined PtNi alloy electrocatalysts (PtNi/NC-10) using PtCl62− electrostatic adsorption coupling melamine pyrolysis nitriding strategy. PtNi alloying was confirmed by the crystallinity decrease and lattice expansion of Ni/NC. The alloying and confinement effect of Metal-Organic Frameworks (MOFs) suppresses the oxidation and agglomeration of metal nanoparticles during pyrolysis, thus significantly reducing particle size, increasing specific surface area, and promoting the exposure of active sites. The strong electronic interaction between Pt and Ni optimizeds the surface charge distribution, enhancing the adsorption of H species on electron-rich Pt sites, thereby improving reaction kinetics. In addition, PtNi alloying improves the conductivity of the material, accelerating charge transfer and proton transport. Consequently, the prepared PtNi/NC-10 exhibits superior HER performance than Ni/NC in 0.5 M H2SO4 solution, even comparable to commercial 20 wt% Pt/C, with the overpotentials of 35 mV at 0.01 A cm−2. Furthermore, the electrocatalysts assembled PtNi/NC-10-CP‖RuO2-TFF proton exchange membrane (PEM) electrolyzer only requires 2.32 V cell voltage to achieve 1 A cm−2, presenting practical application prospects. Our work provides a novel idea for designing efficient and stable MOFs confined to alloy-based HER electrocatalysts.

Boosting OER activity of Fe-N Moieties via Ni induced d-Orbital Tailoring for durable rechargeable Zn-Air batteries

Fe-N-C-based catalysts are considered the most promising Pt candidates due to their high oxygen reduction reaction (ORR) activity and low cost, whereas their oxygen evolution reaction (OER) performance is extremely poor due to the sluggish O-O coupling process, which hampers the practical application of rechargeable zinc-air batteries. Here, we in situ infiltrate Ni and Fe ions into metal triazolidine (MET)-derived N-doped porous carbon via a microporous confinement-pyrolysis strategy to enhance the OER activity of the Fe-N sites. The introduction of Ni induced the electronic delocalization of Fe atoms at the Fe-N center, which lowered the adsorption energy barriers for the decisive velocity step (O*→OOH*), thus accelerating the O-O bond coupling and OER kinetics. In addition, the preferential formation of NiOOH at high OER potentials ensures the catalytic stability of zinc-air batteries by trapping Fe ions escaping from carbon corrosion to form FeOOH. The optimized catalyst (FeNi-NC) has an overpotential of only 351 mV at a current density of 50 mA cm−2 under alkaline conditions. More importantly, the assembled ZABs can be stably charged and discharged for more than 500 h at 10 mA cm−2, demonstrating excellent battery charging and discharging stability. This work shows the great potential of strong electronic interactions between polymetals to improve Fe-N-C catalysts.

Coupling In nanoclusters and Bi nanoparticles in nitrogen-doped carbon for enhanced CO2 electroreduction to HCOOH

CO2 electrochemical reduction reaction (CO2RR) to formic acid (HCOOH) is beneficial for the recycling of carbon resources, which needs the highly selective catalysts with long-term stability for HCOOH production. In this study, the coupling of In nanoclusters (Inclus) and Bi nanoparticles (Binps) in nitrogen-doped carbon was designed by the thermal decomposition of the mixture of bimetallic MOFs and dicyanamide. When the In/Bi molar ratio was 1:2 (Inclus/Binps-1:2), the hybrid catalyst achieved a HCOOH Faradaic efficiency (FEHCOOH) of 94.5 % at −1.1 V vs reversible hydrogen electrode (RHE) in an H-type electrolysis cell, superior to that of single metal counterparts. Moreover, the Inclus/Binps-1:2 can maintain high stability of structures during the catalytic process, leading to no significant decay of FEHCOOH over 32 h. The enhanced performance of Inclus/Binps-1:2 is attributed to the strong electron interactions induced by the charge transfer between the In and Bi sites in Inclus/Binps-1:2 catalyst. The tuned electronic structure results in an offset effect that optimizes the binding energy to HCOO* intermediate, thus accelerating the CO2 to HCOOH conversion, as proven by the in-situ ATR-SEIRAS and density functional theory (DFT) calculations.

Quantum Geometry and Stabilization of Fractional Chern Insulators Far from the Ideal Limit.

In the presence of strong electronic interactions, a partially filled Chern band may stabilize a fractional Chern insulator (FCI) state, the zero-field analog of the fractional quantum Hall phase. While FCIs have long been hypothesized, feasible solid-state realizations only recently emerged, largely due to the rise of moiré materials. In these systems, the quantum geometry of the electronic bands plays a critical role in stabilizing the FCI in the presence of competing correlated phases. In the limit of "ideal" quantum geometry, where the quantum geometry is identical to that of Landau levels, this role is well understood. However, in more realistic scenarios only empiric numerical evidence exists, accentuating the need for a clear understanding of the mechanism by which the FCI deteriorates, moving further away from these ideal conditions. We introduce and analyze an anisotropic model of a |C|=1 Chern insulator, whereupon partial filling of its bands, an FCI phase is stabilized over a certain parameter regime. We incorporate strong electronic interaction analytically by employing a coupled-wires approach, studying the FCI stability and its relation to the quantum metric. We identify an unusual anti-FCI phase benefiting from nonideal geometry, generically subdominant to the FCI. However, its presence hinders the formation of FCI in favor of other competitive phases at fractional fillings, such as the charge density wave. Though quite peculiar, this anti-FCI phase may have already been observed in experiments at high magnetic fields. This establishes a direct link between quantum geometry and FCI stability in a tractable model far from any ideal band conditions, and illuminates a unique mechanism of FCI deterioration.

Highly active ternary Ir/In2O3-ZrO2 catalyst for CO2 hydrogenation towards methanol: The role of zirconia

Indium oxide supported iridium catalyst has been verified to be highly active and selective for CO2 hydrogenation to methanol. In this work, zirconia is introduced into the Ir/In2O3 system as a novel Ir/In2O3-ZrO2 ternary catalyst. The solid solution generated between ZrO2 and In2O3 exhibits a strong electronic metal-support interaction with iridium, rendering the supported iridium species highly dispersed in a form of clusters. Thereout, an active interface between iridium and the solid-solution carrier is thus generated, on which electron transport is more feasible with a stronger CO2 adsorption than that of on the Ir−In2O3 interfacial site. Moreover, compared to Ir/In2O3, this ternary catalyst exhibits better catalytic activity as well as the stability. Density functional theory (DFT) simulations, combined with the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, further demonstrate the CO-hydrogenation pathway is the most favored for methanol synthesis, providing a rationale for the superior methanol selectivity of the Ir/In2O3-ZrO2 catalyst during CO2 hydrogenation.

Insight into the synthesis of alkali metal modified Co-doped ZnFe2O4 with faveolate spinel structure and their enhanced selectivity of olefins during CO2 hydrogenation

Emission reduction of CO2 allows of no delay, and CO2 hydrogenation strategy reveals the great potential to achieve target of “Carbon Neutral”. Trapped with the low selectivity of olefins in our previous work of Co-doped ZnFe2O4, the alkali metal (Na, K) modified Co-doped ZnFe2O4 were synthesized, and their enhanced selectivity of olefins were present. The promotion caused by alkali metal modification revealed that more generation of metallic Fe and the additional generation of Fe5C2 species could be ascribed for the enhanced selectivity of C2-C4 olefins and C5+ products. The introduced alkali metal via the strong electronic interaction increased the outer electrons density around Fe atoms, which could promote the adsorption of CO2 and prohibited the secondary hydrogenation reaction of the formed olefins. Therefore, the enhanced selectivity of C2-C4 olefins over the alkali metal (Na, K) modified Co-doped ZnFe2O4 was emerged, while the CO2 conversion was suppressed (caused by the less generation of Fe3O4). Compared with Na-modified samples, the introduced K could make more generation of Fe5C2 to promote the carbon chain growth, due to its stronger alkalinity, thus leading to the highest selectivity of C5+ products over K-modified samples while the highest selectivity of C2-C4 olefins over Na-modified samples.