Electronic Perturbation Research Articles

Valence Band-Tunable NiFe Electrocatalyst Triggered by the Dynamic Mo Exudation and Re-Deposition for Superior High Current Density Oxygen Evolution Reaction.

Developing energy- and time-efficient strategies to derive high-performance non-precious electrocatalysts for anodic oxygen evolution reaction (OER), especially stably working at industrial-demanding current density, is still a big challenge. In this work, a concise molten salt erosion scenario was devised to rapidly modulate the smooth surface of the commercial NiMo foam substrate into the rough, electronically coupled, and hierarchically porous Ni/Fe/Mo(oxy)hydroxide catalyst layer assembled by the nanosphere array. This self-supported catalyst is super-hydrophilic for the alkaline electrolyte and distinguished by a balanced Mo leaching/surface-readsorption process to tune the metal d band center and electronic perturbation. The altered electronic environment with the favored OER intermediate adsorption behavior attains the outstanding OER activity in terms of a very small overpotential of 230.21 mV at 10 mA cm-2 and an ultra-long stability for 1179.45 h to sustain the initial commercial-level current density of ca. 1000 mA cm-2. This superb performance transcends most of the edge-cutting transition metal peers reported recently and can satisfy the standards of industrial applications. This industrial-compatible synthesis technology holds profound implications for hydrogen production via water splitting and other electrochemical applications.

Key roles of surface Cr in the NiFe layered double hydroxides for an efficient oxygen evolution reaction via adaptive reconfiguration

Cr doping is a new strategy to enhance the OER (Oxygen Evolution Reaction) performance of NiFe-LDH (NiFe-Layered Double Hydroxides) by optimizing surface states and offering a scalable production process. However, as an additive element, Cr itself has weak OER performance, so its promotion on the Ni- and Fe-active site by electron perturbation and structural stabilization in NiFeCr-LDH has been the focus. Herein, a one-step hydrothermal method is used to incorporate Cr into NiFe-LDH, systematically investigating the relationship between Cr content and the material's microstructure. The results of physical characterization show that Cr ion plays a leading role in the electron perturbation Ni/Fe-active center, which causes the increasing of Fe3+ and Ni3+ content. Furthermore, variations in Cr content resulted in the lattice stretching and morphology evolving synchronously. The optimized NiFeCr-LDH exhibited significantly enhanced OER activity and durability compared to undoped NiFe-LDH and outperformed commercial RuO2 catalysts. Additionally, a microstructure comparison was made between the initial- and long-term used-NiFeCr-LDH. The findings reveal that the material's distinctive structural evolution behavior confers it with exceptional self-adaptability to the OER reaction, which results in a consistent enhancement of activity lasting up to 12 h during long-term I-t test showing a new idea for the design of high performance NiFeCr-LDH.

Regulating Functional Groups to Construct a Mild Passivator Enhancing the Efficiency and Stability of Carbon-Based Perovskite Solar Cells.

The abundant defects on the perovskite surface greatly impact the efficiency improvement and long-term stability of carbon-based perovskite solar cells. Molecules with electron-donating or electron-withdrawing functional groups have been cited for passivating various defects. However, few studies have investigated the potential adverse effects arising from the synergistic interactions among functional groups. Herein, we investigate the correlation between functional group configurations and passivation strength as well as the potential adverse impacts of strong electrostatic structures by methodically designing three distinct interface molecules functionalized with different ending groups, which both belong to biguanide derivatives, including 1-(3,4-dichlorophenyl) biguanide hydrochloride (DBGCl), metformin hydrochloride (MFCl), and biguanide hydrochloride (BGCl). The results indicate that DBGCl establishes comparatively mild active sites, not only passivates defects but also aids in forming a surface with a uniform potential. Conversely, MFCl exerts a more pronounced adverse effect on the perovskite surface, which is attributable to the electronic state perturbations induced by its functional groups. Due to the lack of hydrophobic groups, devices treated with BGCl demonstrate insufficient moisture resistance. Devices passivated with DBGCl demonstrate superior average efficiency, showcasing a 12% enhancement relative to the pristine. Furthermore, DBGCl-treated devices exhibit enhanced stability in three different environments, respectively, achieving the highest PCE retention rates under nitrogen conditions (25 °C), room-temperature air conditions (25 °C, RH = 40 ± 2%), and high-temperature air conditions (65 °C, RH = 40 ± 2%).

Analysis of an induced Langmuir wave by ponderomotive forces and its applicability for plasma diagnostics

We present a numerical study on the electron and ion density perturbation in low-temperature plasmas driven by the frequency detuning of two intense laser beams. Our study is performed in the hydrodynamic regime, which becomes applicable when the plasma grating period induced by the beating of the laser beams is greater than the Debye length and collective processes such as plasma oscillations can be excited. Our findings show a resonance in electron density perturbation as the frequency detuning approaches a value consistent with the Bohm–Gross dispersion relation in low- and high-pressure plasmas. We discuss the potential of this resonance as a diagnostic tool for precisely measuring electron temperature and density in low-temperature plasmas through coherent scattering.

Electronic perturbation of Cu nanowire surfaces with functionalized graphdiyne for enhanced CO2 reduction reaction

Abstract Electronic perturbation of Cu catalysts surface is crucial for optimizing electrochemical CO2 reduction activity, yet still poses great challenges. Herein, nanostructured Cu nanowires (NW) with fine-tuned surface electronic structure are achieved via surface encapsulation with electron-withdrawing (–F) and -donating (–Me) group-functionalized graphdiynes (R-GDY, R = –F and –Me), and the resulting catalysts, denoted as R-GDY/Cu NW, display distinct CO2 reduction performances. In-situ electrochemical spectroscopy revealed that the *CO (a key intermediate of the CO2 reduction reaction) binding affinity and consequent *CO coverage positively correlate to the Cu surface oxidation state, leading to the favorable C–C coupling on F-GDY/Cu NW over Me-GDY/Cu NW. Electrochemical measurements corroborate the favorable C2H4 production with an optimum C2+ selectivity of 73.15% ± 2.5% observed for F-GDY/Cu NW, while the predominant CH4 production is favored by Me-GDY/Cu NW. Furthermore, leveraging the *Cu–OH/*CO ratio as a descriptor, mechanistic investigation reveals that the protonation of distinct adsorbed *CO facilitated by *Cu–OH is crucial for the selective generation of C2H4 and CH4 on F-GDY/Cu NW and Me-GDY/Cu NW, respectively.

Low-coordinated copper facilitates the *CH2CO affinity at enhanced rectifying interface of Cu/Cu2O for efficient CO2-to-multicarbon alcohols conversion

The carbon−carbon coupling at the Cu/Cu2O Schottky interface has been widely recognized as a promising approach for electrocatalytic CO2 conversion into value-added alcohols. However, the limited selectivity of C2+ alcohols persists due to the insufficient control over rectifying interface characteristics required for precise bonding of oxyhydrocarbons. Herein, we present an investigation into the manipulation of the coordination environment of Cu sites through an in-situ electrochemical reconstruction strategy, which indicates that the construction of low-coordinated Cu sites at the Cu/Cu2O interface facilitates the enhanced rectifying interfaces, and induces asymmetric electronic perturbation and faster electron exchange, thereby boosting C-C coupling and bonding oxyhydrocarbons towards the nucleophilic reaction process of *H2CCO-CO. Impressively, the low-coordinated Cu sites at the Cu/Cu2O interface exhibit superior faradic efficiency of 64.15 ± 1.92% and energy efficiency of ~39.32% for C2+ alcohols production, while maintaining stability for over 50 h (faradic efficiency >50%, total current density = 200 mA cm−2) in a flow-cell electrolyzer. Theoretical calculations, operando synchrotron radiation Fourier transform infrared spectroscopy, and Raman experiments decipher that the low-coordinated Cu sites at the Cu/Cu2O interface can enhance the coverage of *CO and adsorption of *CH2CO and CH2CHO, facilitating the formation of C2+ alcohols.

Co and Ni Ratio Modulation‐Derived Electron Deficient Pd Trimetallic Catalysts for Enhanced Formic Acid Electrooxidation

AbstractPdCoNi trimetallic catalysts attracted extensive interest in direct formic acid fuel cells due to high poisoning resistance and high activity for formic acid electro‐oxidation (FAO). Herein, a series of Pd0.75CoxNiy/C alloys with a modulated ratio of Co and Ni are synthesized to investigate the effect of Co and Ni content on the electronic structure of Pd for FAO. The physical analysis demonstrated that the introduction of Co and Ni induces the lattice strain effect compared to monometallic Pd catalysts. As a consequence of fixing the total amount of Co and Ni, the strain effect is restricted, and the electronic perturbation of Pd is successfully regulated by varying the ratio of Co and Ni in Pd0.75CoxNiy/C trimetallic alloys. Pd loses more electrons, the bond strength of Pd−H is weakened, and FAO activity is enhanced first and then decreased as the Co content increases. Among the trimetallic catalysts, Pd0.75Co0.125Ni0.125/C trimetallic catalyst exhibits the highest current density of 3.253 mA cm−2 owing to the optimum electronic perturbation and Pd−H bond strength. This work provides a valuable guideline for future studies of Pd‐based trimetallic alloys.

Fe-N co-doped carbon nanofibers with Fe3C decoration for water activation induced oxygen reduction reaction

ABSTRACT Proton activity at the electrified interface is central to the kinetics of proton-coupled electron transfer (PCET) reactions in electrocatalytic oxygen reduction reaction (ORR). Here, we construct an efficient Fe3C water activation site in Fe-N co-doped carbon nanofibers (Fe3C-Fe1/CNT) using an electrospinning-pyrolysis-etching strategy to improve interfacial hydrogen bonding interactions with oxygen intermediates during ORR. In situ Fourier transform infrared spectroscopy and density functional theory studies identified delocalized electrons as key to water activation kinetics. Specifically, the strong electronic perturbation of the Fe–N4 sites by Fe3C disrupts the symmetric electron density distribution, allowing more free electrons to activate the dissociation of interfacial water, thereby promoting hydrogen bond formation. This process ultimately controls the PCET kinetics for enhanced ORR. The Fe3C-Fe1/CNT catalyst demonstrates a half-wave potential of 0.83 V in acidic media and 0.91 V in alkaline media, along with strong performance in H2-O2 fuel cells and Al-air batteries.

Heterobimetallic praseodymium-nickel active sites with Pr-N4C2 and Ni-N4 moieties enabling synergistic catalysis of CO2 electroreduction

Lanthanide metals have attracted particular interest in the catalysis of electrochemical CO2 reduction. The synthesis and precise spatial distribution of active sites are fundamental important but still formidably challenging owing to the strong oxygen affinity of lanthanide. Here, heteronuclear Pr1-Ni1 single atoms are supported on the carbon matrix containing surface framework defects from lanthanide contraction. The Pr/Ni-NC catalyst exhibits a CO Faradaic efficiency of 99.1 % with a commercial-scale current density of 237 mA cm−2 and a turnover frequency as high as 18,038 h−1 at −1.1 V due to d-f coupling effect and electronic structure perturbation of Pr. Furthermore, mechanistic investigations unveil that the diatomic active sites effectively reduce the energy barrier of the crucial *COOH formation, in which the Pr site facilitates CO2 activation and the Ni site enables H2O dissociation to accelerate the proton transfer process, thereby ensuring the synergy of catalytic sites to greatly facilitate CO2-to-CO conversion.

Regulating the Third Metal to Design and Engineer Multilayered NiFeM (M: Co, Mn, and Cu) Nanofoam Anode Catalysts for Anion‐Exchange Membrane Water Electrolyzers

AbstractAlkaline anion‐exchange membrane water electrolyzers (AEMWEs) for green hydrogen production have received intensive attention due to their feasibility of using earth‐abundant platinum group metal (PGM)‐free catalysts. Herein, the third metal is incorporated into NiFe‐based catalysts to regulate their electronic structures and morphologies, aiming to achieve sufficient oxygen evolution reaction (OER) activity and performance in AEMWEs. The ternary NiFeM (M: Cu, Co, or Mn) catalysts are featured with multiple layered structures and nanofoam network morphologies, consisting of highly OER‐active amorphous Ni‐rich oxide shells and electrically conductive metallic alloy cores. The physical and electronic perturbations to the NiFe induced by a third element lead to a fine‐tuning of the redox ability of the metal sites at the reaction centers, which breaks the scaling relationship between OH* and O* intermediates at the reaction centers. Thus, the unique structural configuration and electronic regulation simultaneously benefit catalytic activity and performance improvements. These NiFeM nanofoam catalysts demonstrated promising anode performance in actual AEMWEs, comparable to the IrO2 reference, especially at high current densities. Notably, using various electrolytes (e.g., KOH solution or pure water) for AEMWEs exhibited a different performance trend among studied NiFeM catalysts, likely due to dynamic changes of catalysts under various OER environments.

Investigating a Possible Correlation between NOAA-Satellite-Detected Electron Precipitations and South Pacific Tectonic Events

On 4 March 2021, a devastating M8.1 earthquake struck the Kermadec Islands of New Zealand. Given the tremendous energy released during the event, we sought to investigate the event’s potential impact on the ionosphere and the inner Van Allen Belt using data from the high-energy electron detectors on board the NOAA-18 satellite. The survey was also extended to the strongest shallow M6.5+ earthquakes occurring between 150° and 190° in longitude, and between −5° and −35° in latitude over the previous ten years. In nearly all cases, evident electron fluxes entering the loss cone were observed. To explore the possibility of a connection between ionospheric signals and tectonic events in this intensely active region, we analyzed electron losses from the inner Van Allen Belt, taking into account latitude, longitude, day/night times, and proximity to the South Atlantic Anomaly. Compared to previous studies, here only the most significant loss phenomena persistent in the ionosphere were considered. Particular interest was reserved for the intense electron loss events that had a duration spanning from a few to several minutes and occurred several hours before and after strong seismic events. Thereafter, time series of electron counting rates and strong Southern Pacific earthquakes were transformed into binary series, and the series multiplication was investigated. The results suggest four peaks of association, including a first couple between electron perturbations detected for ascending semi-orbits and seismic events and a second one between electron perturbations detected in the southern ionosphere and seismic events. They both anticipated the occurrence of earthquakes, occurring around 4 h before them. Other couples were observed between electron perturbations detected for descending semi-orbits and seismic events and between electron perturbations detected in the northern ionosphere and seismic events. They both occurred around 3 h after the occurrence of earthquakes. The case of perturbations anticipating seismic events has the intriguing properties of sustaining the hypothesis that a physical interaction occurred around 6 h before seismic events as in the West Pacific case. A physical model of electrons detected far several thousands of km from the earthquake epicenters was also presented. However, a simulation of random seismic events suggested that the null hypothesis cannot be fully rejected for these associations, prompting many more analyses and case studies.

Spin-Flip via Subtle Electronic Perturbation in Axially Ligated Diiron(III) Porphyrin Dimer.

Spin state switching in the metal center is a crucial phenomenon in many enzymatic reactions in biology. The spin state alteration, a critical step in cytochrome P450 catalysis, is driven most likely through a weak perturbation upon substrate binding in the enzyme, which is still not well clarified. In the current work, the spin state transition of iron(III) from high to intermediate via an admixed state is observed upon a subtle electronic perturbation to the sulphonate moieties coordinated axially to a diiron(III)porphyrin dimer. While electron-donating substituents stabilize the high-spin state of iron(III), strongly electron-withdrawing groups stabilize an intermediate-spin state, whereas the moderate electron-withdrawing nature of axial ligands resulted in an admixed state. Confirmation of the molecular structures and their spin states have been made utilizing single-crystal X-ray structure analysis, Mössbauer, magnetic, EPR, and 1H NMR spectroscopic investigations. The position of the signals of the porphyrin macrocycle in the paramagnetic 1H NMR is found to be very characteristic of the spin state of the iron center in solution. The Curie plot for the pure high-spin complexes shows the signals' temperature dependency in line with the Curie law. Conversely, the pure intermediate-spin state of iron exhibits an anti-Curie temperature dependence, whereas the admixed-spin state of iron displays significant curvature of the lines in the Curie plot. An extensive DFT analysis displays a linear dependence between the energy difference between d and d orbital versus Fe-Npor distance for the complexes reported here. Furthermore, a strong linear correlation between the Fe-O distance and the spin density over the oxygen atom, as well as the Fe-Npor distance for the complexes, has been observed. Thus, a slight electronic perturbation at the axial ligand of the diheme resulted in a large change in the electronic structures with a spin-flip. This is at par with the metalloenzymes, which employ minute perturbations around the periphery of the active sites, leading to spin state transitions.

Fe2+-NTA synergized UV254 photolytic defluorination of perfluorooctane sulfonate (PFOS): Enhancing through intramolecular electron density perturbation via electron acquisition

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant posing a risk in environmental persistence, bioaccumulation and biotoxicity. This study was to reach a comprehensive and deeper understanding of PFOS elimination in a UV254 photolytic treatment with the co-presence of Fe2+ and nitrilotriacetic acid trisodium salt (NTA). PFOS defluorination was noticeably enhanced in the UV/Fe2+-NTA treatment compared with UV/NTA, UV/Fe2+ and our previously studied UV/Fe3+ treatments. UV–vis, FTIR, and UPLC/MS-MS results indicated the formation of PFOS-Fe2+-NTA complex in PFOS, Fe2+ and NTA mixture. The transition energy gap of PFOS-Fe2+-NTA decreased below the excitation energy supplied by UV254 irradiation, corresponding with red shift appearing in UV–vis scanning spectrum. This favored intramolecular electron transfer from Fe2+-NTA to PFOS under UV254 irradiation to form electron-accepting PFOS. Molecular electrostatic potential and atom charge distribution analyses suggested electron density rearrangement and perturbation in the perfluorinated carbon chain of electron-accepting PFOS, leading to the decrease in bond dissociation energies. Intermediate products detection suggested the parallel defluorination pathways of PFOS desulfonation, middle carbon chain scission and direct C-F cleavage. NTA exhibited crucial functions in the UV/Fe2+-NTA treatment by holding Fe2+/Fe3+ in soluble form as a chelant and favoring water activation to generate hydrated electrons (eaq−) under UV irradiation as a photosensitizer. Fe2+ acting as the conduit for electron transfer and the bridge of PFOS anion and NTA was thought functioning best at 200 µM in this study. The degree of UV/Fe2+-NTA -synergized PFOS defluorination also depended on eaq− yield and UV254 photon flux. The structure dependence on the electron transfer process of PFOS and PFOA was explored incorporating molecular structure descriptors. Because of possessing greater potential to acquire electrons or less likeliness to donate its electrons than PFOA, PFOS exhibited faster defluorination kinetics in the published “reduction treatments” than “oxidation” ones. Whereas, PFOA defluorination kinetics were at similar level in both “reduction” and “oxidation” treatments.

Effects of Electron-Withdrawing and Electron-Donating Groups on Aromaticity in Cyclic Conjugated Polyenes.

Determining the aromaticity of various fluorinated benzenes is challenging as easily obtained experimental aromaticity [Δδ(Houter - Hinner)] necessitates the chemical shifts of inner and outer protons. This issue was addressed in porphyrinoids by replacing the electron-withdrawing (E.W.) groups at the meso-positions of porphyrins and allyliporphyrins. Electronic effects on aromaticity in porphyrinoids have not been thoroughly examined in the literature. In porphyrins, the effect of E.W. groups is minimal, making it difficult to establish a clear relationship between the aromaticity strength and E.W. groups. Conversely, in allyliporphyrins, stronger E.W. groups, such as indandione (IND) derivatives, significantly reduce the aromaticity of the parent structure. The IND derivatives disrupted the aromatic pathway of allyliporphyrin more effectively than those attached to porphyrins. This is attributed to the absence of β-carbons in allyliporphyrins. The effect of electron-donating (E.D.) groups on porphyrins and allyliporphyrins was further investigated. Contrary to the initial assumption that the E.D. groups might enhance aromaticity owing to their ability to increase electron density, as the strength of the E.D. groups increased, the aromaticity of the porphyrinoids decreased. Despite the modest reduction in aromaticity, any form of electron perturbation reduces aromaticity. The aromaticity of various fluorinated benzenes is expected to parallel our observations of porphyrinoids as representative aromatic polyenes.

The role of carboxylate ligand orbitals in the breathing dynamics of a metal-organic framework by resonant X-ray emission spectroscopy.

Metal-organic frameworks (MOFs) exhibit structural flexibility induced by temperature and guest adsorption, as demonstrated in the structural breathing transition in certain MOFs between narrow-pore and large-pore phases. Soft modes were suggested to entropically drive such pore breathing through enhanced vibrational dynamics at high temperatures. In this work, oxygen K-edge resonant X-ray emission spectroscopy of the MIL-53(Al) MOF was performed to selectively probe the electronic perturbation accompanying pore breathing dynamics at the ligand carboxylate site for metal-ligand interaction. It was observed that the temperature-induced vibrational dynamics involves switching occupancy between antisymmetric and symmetric configurations of the carboxylate oxygen lone pair orbitals, through which electron density around carboxylate oxygen sites is redistributed and metal-ligand interactions are tuned. In turn, water adsorption involves an additional perturbation of π orbitals not observed in the structural change solely induced by temperature.

Electronic perturbation-promoted interfacial pathway for facile C–H dissociation

Interface has often played significant role in the behavior of metal-based catalysts during various heterogeneous reactions. Herein, we reported a novel interfacial pathway for propane dehydrogenation on Pt-GaOx dual sites. The active ensemble, composing Pt particles and Ga2O3 clusters, facilitates the facile dissociation of C–H bonds (energy barrier < 0.30 eV) through H-abstraction by O sites, coupled with alkyl stabilization on the Pt surface. Notably, the electronic perturbation of the Pt slab induces higher-lying O 2p states at the interface, accompanied by a substantial density of states around fermi level. This is in stark contrast to the O species present in Ga2O3 crystals or clusters alone, leading to an exceptionally strong affinity for H and a robust ability for C–H scission. The Pt/Ga-Al2O3 catalysts prepared with Pt nanoparticles decorated by Ga oxide exhibit superior performance compared to Pt/Al2O3 and PtSn/Al2O3 catalysts. This insight into interfacial catalysis contributes to a broader understanding of the origin of the high catalytic efficiency observed in metal-based catalysts.

A high density nanopore 3-triangulene kagome lattice.

Nanopore-containing two-dimensional materials have been explored for a wide range of applications including filtration, sensing, catalysis, energy storage and conversion. Triangulenes have recently been experimentally synthesized in a variety of sizes. In this regard, using these systems as building blocks, we theoretically examined 3-triangulene kagome crystals with inherent holes of ∼12 Å diameter and a greater density array of nanopores (≥1013 cm-2) compared to conventional 2D systems. The energetic, electronic, and transport properties of pristine and B/N-doped 3-triangulene kagome crystals were evaluated through a combination of density functional theory and non-equilibrium Green's function method. The simulated scanning tunneling microscopy images clearly capture electronic perturbation around the doped sites, which can be used to distinguish the pristine system from the doped systems. The viability of precisely controlling the band structure and transport properties by changing the type and concentration of doping atoms is demonstrated. The findings presented herein can potentially widen the applicability of these systems that combine unique electronic properties and intrinsically high-density pores, which can pave the way for the next generation of nanopore-based devices.

Valence electronic engineering of superhydrophilic Dy-evoked Ni-MOF outperforming RuO2 for highly efficient electrocatalytic oxygen evolution

Tackling the problem of poor conductivity and catalytic stability of pristine metal-organic frameworks (MOFs) is crucial to improve their oxygen evolution reaction (OER) performance. Herein, we introduce a novel strategy of dysprosium (Dy) doping, using the unique 4f orbitals of this rare earth element to enhance electrocatalytic activity of MOFs. Our method involves constructing Dy-doped Ni-MOF (Dy@Ni-MOF) nanoneedles on carbon cloth via a Dy-induced valence electronic perturbation approach. Experiments and density functional theory (DFT) calculations reveal that Dy doping can effectively modify the electronic structure of the Ni active centers and foster a strong electronic interaction between Ni and Dy. The resulting benefits include a reduced work function and a closer proximity of the d-band center to the Fermi level, which is conducive to improving electrical conductivity and promoting the adsorption of oxygen-containing intermediates. Furthermore, the Dy@Ni-MOF achieves superhydrophilicity, ensuring effective electrolyte contact and thus accelerating reaction kinetics. Ex-situ and in-situ analysis results manifest Dy2O3/NiOOH as the actual active species. Therefore, Dy@Ni-MOF shows impressive OER performance, significantly surpassing Ni-MOF. Besides, the overall water splitting device with Dy@Ni-MOF as an anode delivers a low cell voltage of 1.51 V at 10 mA cm−2 and demonstrates long-term stability for 100 h, positioning it as a promising substitute for precious metal catalysts.

Electronic Perturbation of Isolated Fe Coordination Structure for Enhanced Nitrogen Fixation.

Modulation of the local electronic structure of isolated coordination structures plays a critical role in electrocatalysis yet remains a grand challenge. Herein, we have achieved electron perturbation for the isolated iron coordination structure via tuning the iron spin state from a high spin state (FeN4) to a medium state (FeN2B2). The transition of spin polarization facilitates electron penetration into the antibonding π orbitals of nitrogen and effectively activates nitrogen molecules, thereby achieving an ammonia yield of 115 μg h-1 mg-1cat. and a Faradaic efficiency of 24.8%. In situ spectroscopic studies and theoretical calculations indicate that boron coordinate sites, as electron acceptors, can regulate the adsorption energy of NxHy intermediates on the Fe center. FeN2B2 sites favor the NNH* intermediate formation and reduce the energy barrier of rate-determining steps, thus accounting for excellent nitrogen fixation performance. Our strategy provides an effective approach for designing efficient electrocatalysts via precise electronic perturbation.

Stable Dication Diradicals of Triply Fused Metallo Chlorin-Porphyrin Heterodimers: Impact of the Bridge on the Control of Spin Coupling to Reactivity.

We report an unexpected rearrangement, controlled by the nature of the bridge, leading to the formation of novel, remarkably stable triply fused dinickel(II)/dicopper(II) chlorin-porphyrin dication diradical heterodimers in excellent yields. Here, a dipyrromethene bridge gets completely fused between two porphyrin macrocycles with two new C-C and one C-N bonds. The two macrocycles exhibit extensive π-conjugation through the bridge, which results in an antiferromagnetic coupling between the two π-cation radicals. In addition, the macrocyclic distortion also favours a rare intramolecular ferromagnetic interaction between the CuII and π-cation radical spins to form a triplet state. The structural and electronic perturbation in the unconjugated dication diradical possibly enables the bridging pyrrolic nitrogen to undergo a nucleophilic attack at the nearby β-carbon of the porphyrin π-cation radical with a computed free energy barrier of >20 kcal mol-1 which was supplied in the form of reflux condition to initiate such a rearrangement process. UV-vis, EPR and ESI-MS spectroscopies were used to monitor the rearrangement process in situ in order to identify the key reactive intermediates leading to such an unusual transformation.