Modulation Of Electronic States Research Articles

Bimetallic Coupling Strategy Modulating Electronic Construction to Accelerate Sulfur Redox Reaction Kinetics for High-Energy Flexible Li-S Batteries.

Lithium-sulfur (Li-S) batteries are considered the most promising energy storage battery due to their low cost and high theoretical energy density. However, the low utilization rate of sulfur and slow redox kinetics have seriously limited the development of Li-S batteries. Herein, the electronic state modulation of metal selenides induced by the bi-metallic coupling strategy is reported to enhance the redox reaction kinetics and sulfur utilization, thereby improving the electrochemical performance of Li-S batteries. Theoretical calculations reveal that the electronic structure can be modulated by Ni-Co coupling, thus lowering the conversion barrier of lithium polysulfides (LiPSs)and Li+, and the synergistic interaction between NiCoSe nanoparticles and nitrogen-doped porous carbon (NPC) is facilitating to enhance electron transport and ion transfer kinetics of the NiCoSe@NPC-S electrodes. As a result, the assembled Li-S batteries based on NiCoSe@NPC-S exhibit high capacities (1020mAhg-1 at 1C) and stable cycle performance (80.37% capacity retention after 500 cycles). The special structural design and bimetallic coupling strategy promote the batteries working even under lean electrolyte (7.2µLmg-1) with a high sulfur loading (6.5mgcm-2). The proposed bimetallic coupling strategy modulating electronic construction with N-doping porous carbon has jointly contributed the good redox reaction kinetics and high sulfur utilization.

Microenvironment and electronic state modulation of Pd nanoparticles within MOFs for enhancing low-temperature activity towards DCPD hydrogenation

Microenvironment and electronic state modulation of Pd nanoparticles within MOFs for enhancing low-temperature activity towards DCPD hydrogenation

Giant Tunneling Electro‐Resistance in Ultrathin Ferroelectric Tunnel Junctions: The Interface Barrier Gain Mechanism

AbstractUltrathin ferroelectric tunnel junctions (FTJs) hold considerable promise for next‐generation, high‐speed, low‐power, and high‐density nonvolatile memory applications. Achieving a substantial tunneling electro‐resistance (TER) remains a challenge as the ferroelectric layer is thinned to nanoscale dimensions, often resulting in a diminished or lost polarization. An innovative interface barrier gain mechanism is introduced, employing interface electronic state modulation to precisely control the size of an additional interface barrier. This strategy lessens the dependency of the tunneling barrier on ferroelectric polarization strength, facilitating a remarkable TER even at ferroelectric thicknesses as minimal as ≈1 nm. The focus is on composite FTJs using In2Se3/MTe2 (M = Mo, W), where the inclusion of an MTe2 monolayer disrupts the asymmetric electrode configuration. The weak ferroelectric polarization reversal of the In2Se3 monolayer effectively modulates the electronic state coupling at the In2Se3/MTe2 interface. This modulation leads to variations in the width and height of the Schottky barrier at the heterojunction‐electrode interface corresponding with the ferroelectric polarization reversal, establishing a beneficial Ohmic contact in the “on” state and resulting in an exponential TER increase up to 5.4 × 106%. This work introduces a universal mechanism to overcome the thickness limitations traditionally associated with enhancing TER, marking a significant advancement in the development of ultrathin ferroelectric nonvolatile devices.

Amino-Induced Modulation of Electronic State and Neighboring Site Distance through Second Shell Boosted Catecholase-Mimicking Activity of Electron-Rich Cu Center.

Boosting the biomimetic catalytic activity of nanozyme is important for its potential application. One common strategy to achieve this goal mainly focused on manipulating the electronic state of metal site through the first coordination shell to modulate the adsorption/desorption strength of related reactant, intermediate and/or product, but remained challenging. Taking Cu-based catecholase-mimicking nanozyme for example, this work herein reports a different strategy involving amino-induced modulation of electronic state through the second shell to raise the electron density of Cu site, which further triggers the repulsion effect between neighboring geminal Cu centers to increase the Cu─Cu distance. The resulting nanozyme with electron-rich Cu site (DT-Cu) presents a lower work function and an upshifted d-band center in comparison with its counterpart (i.e., relatively electron-deficient TA-Cu), which promotes the electron transfer and enhances the adsorption strengths of Cu site for O2, catechol and H2O2 intermediate. The longer Cu─Cu distance of DT-Cu accelerated the O─O bond dissociation of H2O2 intermediate. This expedites the oxygen reduction process during catecholase-like catalysis, which together with the enhanced O2/H2O2/catechol adsorption corporately boosts the catecholase-like activity of DT-Cu.

Impact of doping and hydrostatic pressure on structural, electronic, optical, and mechanical properties of novel double halide perovskite Cs2LiGaBr6

The emergence of lead-free halide double perovskites exhibiting bandgaps within the visible spectrum represents a substantial advancement in engineering environmentally benign perovskite solar cells. In this work, we investigated the structural, optical, electronic, and mechanical properties of Cs-based lead-free Cs2LiGaBr6 double halide perovskites with Mn and Cr doping under hydrostatic pressure ranging from 2 to 80 GPa using density functional theory (DFT). The introduction of dopants consistently alters the lattice parameters because of the mismatch in atomic radii, whereas increasing the pressure leads to a reduction in these constants. All the studied Cs2LiGaBr6 compounds exhibited direct band gaps, which increased slightly with doping. This is attributed to the modulation of electronic states by dopant-related defect levels. The bandgap variation under pressure is primarily attributed to changes in the quantum confinement effects induced by compressive strain. Analysis of the density of states and optical properties revealed enhanced absorption in the visible spectrum for the doped compositions, and in the UV spectrum under pressure. The study of mechanical stability confirms the ductile nature of both the doped and pristine compounds under pressure, underscoring their suitability for thin film production. This study contributes to the understanding of sustainable alternatives for perovskite optoelectronic applications, emphasizing Cs2LiGaBr6's potential under diverse conditions and dopant influences.

Electronic state modulation of Ag30 nanoclusters within a ring-shaped polyoxometalate.

Atomically precise Ag nanoclusters display distinctive properties that are dictated by their structures and electronic states. However, manipulating the electronic states of Ag nanoclusters is challenging owing to their inherent instability and susceptibility to undesired structural changes, decomposition, and aggregation. Recently, we reported the synthesis of a body-centered cubic {Ag30}22+ nanocluster encapsulated within a ring-shaped polyoxometalate (POM) [P8W48O184]40- by reacting 16 Ag+-containing [P8W48O184]40- with Ag+ using N,N-dimethylformamide (DMF) as a mild reducing agent. This led to a redox-induced structural transformation into a face-centered cubic {Ag30}16+ nanocluster. In this study, we demonstrated the modulation of the electronic states of Ag30 nanoclusters within the ring-shaped POM through two different approaches. A face-centered cubic {Ag30}18+ nanocluster, featuring distinct oxidation states compared to previously reported {Ag30}22+ and {Ag30}16+ nanoclusters, was synthesized using tetra-n-butylammonium borohydride, a stronger reducing agent than DMF, in the reaction of 16 Ag+-containing [P8W48O184]40- and Ag+. Additionally, by leveraging the acid-base properties of POMs, we demonstrated the reversible, stepwise modulation of the charge distribution in the Ag30 nanocluster through controlling protonation states of the ring-shaped POM ligand. These results highlight the potential of engineering POM-stabilized Ag nanoclusters with diverse structures and electronic states, thereby facilitating the exploration of novel properties and applications utilizing the unique characteristics of the POM ligands.

Promoted Photocatalytic Hydrogen Evolution by Tuning the Electronic State of Copper Sites in Metal‐Organic Supramolecular Assemblies

AbstractThe electronic state in terms of charge and spin of metal sites is fundamental to govern the catalytic activity of a photocatalyst. Herein, we show that modulation of the electronic states of Cu sites, without changing the coordination environments, of two metal‐organic supramolecular assemblies based on π⋅⋅⋅π stacking can significantly improve photocatalytic activity. The use of these heterogeneous photocatalysts, without using noble metal cocatalysts, resulted in an increase of the hydrogen production rate from 522 to 3620 μmol h−1 g−1. A systematical analysis revealed that the charge density and spin density of the metal centers are efficiently modulated via the modulation of the coordination fields around active copper (II) centers by the variation of the non‐coordination groups of terminal ligands, leading to the significant enhancement of photocatalytic activity. This work provides an insight into the electronic state of active metal centers for designing high‐performance photocatalysts.

Surface electronic state modulation promotes photoinduced aggregation and oxidation of trace CO for lossless purification of H2 stream

Although photogenerated hydroxyl radicals can oxidize CO without H2 consumption, the nonselective collision severely lowers photocatalytic photon utilization. We here demonstrate that electronic state modification of TiO2 resulted from magnesium doping can promote hydroxyl radical generation by weakening the adsorption of oxygen species and facilitating semiconductor-cocatalyst interfacial electron transfer. Importantly, the partial deprivation of electronic cloud from cationic sites can strengthen σ-donation and π-backdonation that synergistically promote the electrostatic interaction for aggregating CO in the vicinity of semiconductor. The resulted photocatalyst thus exhibits growing superiority over common counterpart in target reaction as CO concentration lowers. By these merits, CO in H2 stream can be reduced to < 1 × 10−6 with efficient photon utilization.

Electronic-State Modulation of Metallic Co-Assisted Co7 Fe3 Alloy Heterostructure for Highly Efficient and Stable Overall Water Splitting.

Manipulating electronic structure of alloy-based electrocatalysts can eagerly regulate its catalytic efficiency and corrosion resistance for water splitting and fundamentally understand the catalytic mechanisms for oxygen/hydrogen evolution reactions (OER/HER). Herein, the metallic Co-assisted Co7 Fe3 alloy heterojunction (Co7 Fe3 /Co) embeds in a 3D honeycomb-like graphitic carbon is purposely constructed as a bifunctional catalyst for overall water splitting. As-marked Co7 Fe3 /Co-600 displays the excellent catalytic activities in alkaline media with low overpotentials of 200mV for OER and 68mV for HER at 10mAcm-2 . Theoretical calculations reveal the electronic redistribution after coupling Co with Co7 Fe3 , which likely forms the electron-rich state over interfaces and the electron-delocalized state at Co7 Fe3 alloy. This process changes the d-band center position of Co7 Fe3 /Co and optimizes the affinity of catalyst surface to intermediates, thus promoting the intrinsic OER/HER activities. For overall water splitting, the electrolyzer only requires a cell voltage of 1.50V to achieve 10mAcm-2 and dramatically retains 99.1% of original activity after 100h of continuous operation. This work proposes an insight into modulation of electronic state in alloy/metal heterojunctions and explores a new path to construct more competitive electrocatalysts for overall water splitting.

Surface-bulk-passivated perovskite films via 2-thiophenemethylammonium bromide and PbBr2 for air-processed perovskite solar cells with high-stability

Suppressing non-radiative recombination induced by defect is of much concern to efficient and stable perovskite solar cells (PSCs). We report a cooperative strategy to passivate both interfacial and bulk defects in perovskite layer by coupling interface engineering and additive engineering. 2-Thiophenemethylammonium bromide (2-ThMAB) is synthesized by recrystallization. PbBr2 used as an additive is introduced into the perovskite precursor solution. 2-ThMAB features with an electron-rich π-system and 2-thiophene group. Br− ions have an impact on perovskite lattice reorganization. The synergistic modification of 2-ThMAB and PbBr2 enables the external electronic state modulation and internal bandgap adjustment of perovskite, which is beneficial to passivate defect and inhibit ion migration. As a result, a modified PSC exhibits a high-power conversion efficiency of 20.01% with negligible hysteresis for an all-air-processed device. More importantly, a non-encapsulated device exhibits excellent long-term stability of T98 of > 720 h. This study thus provides a new way to obtain highly stable all-air-processed PSCs..

Intermediate State between MoSe2 and Janus MoSeS during Atomic Substitution Process

Janus transition metal dichalcogenides (TMDCs), with dissimilar chalcogen atoms on each side of TMDCs, have garnered considerable research attention because of the out-of-plane intrinsic polarization in monolayer TMDCs. Although a plasma process has been proposed for synthesizing Janus TMDCs based on the atomic substitution of surface atoms at room temperature, the formation dynamics and intermediate electronic states have not been completely examined. In this study, we investigated the intermediate state between MoSe2 and Janus MoSeS during plasma processing. Atomic composition analysis and atomic-scale structural observations revealed the intermediate partially substituted Janus (PSJ) structure. Combined with theoretical calculations, we successfully clarified the characteristic Raman modes in the intermediate PSJ structure. The PL exhibited discontinuous transitions that could not be explained by the theoretical calculations. These findings will contribute toward understanding the formation process and electronic-state modulation of Janus TMDCs.

Bi‐Metallic Coupling‐Induced Electronic‐State Modulation of Metal Phosphides for Kinetics‐Enhanced and Dendrite‐Free Li–S Batteries (Adv. Funct. Mater. 14/2023)

Bi-Metallic Coupling In article number 2213310, Ming Li and co-workers report the in-situ construction of bi-metallic phosphides nanoparticles-anchored N, P-co-doped porous carbons (NiCoP-NPPC) by a laser-induced micro-explosion strategy, exhibiting the well-matched distribution of electronic-state modulation via Ni-Co coupling. The proposed bi-metallic coupling effect can realize kinetics-enhanced and dendrite-free Li-S batteries, thereby offering an effective approach for developing high-performance Li-S batteries.

Roles of Metal Oxide Nanostructure-Based Substrates in Sustainable Electrochemical Water Splitting: Recent Development and Future Perspective

Increasing energy demand to find everlasting and eco-friendly resources is now mainly dependent on green hydrogen production technology. Water electrolysis has been regarded as a clean route for green H2 production with zero carbon emission, but different bottlenecks in the development of electrodes impeded its realization. Recently, transition metal oxides (TMO) have gained tremendous attention as suitable cathodes and anodes due to their sustainability under harsh conditions, high redox features, maximum supportive capability, easy modulation in valence states, and enhanced electrical conductivity. In this review, we have highlighted the role of transition metal oxides as active and supported sites for electrochemical water splitting. We have proposed different perspectives for the rational design of TMO-based electrode materials, i.e., electronic state modulation, modification of the surface structure to control the aerophobicity and hydrophilicity, acceleration of the charge and mass transport, and stability of the electrocatalyst in harsh environments. We have systemically discussed the insights into the relationship among catalytic activity, certain specified challenges, research directions, and perspectives of electrocatalysis of the OER and HER.

Modulation of electronic states in bimetallic-doped nitrogen-carbon based nanoparticles for enhanced oxygen reduction kinetics

Controlling tire local electronic structure of active ingredients to improve the adsorption-desorption characteristics of oxygen-containing intermediates over the electrochemical liquid-solid interfaces is a critical challenge in the field of oxygen reduction reaction (ORR) catalysis. Here, we offer a simple approach for modulating the electronic states of metal nanocrystals by bimetal co-doping into carbon-nitrogen substrate, allowing us to modulate the electronic structure of catalytic ao five centers. To test our strategy, we designed a typical bimetallic nanoparticle catalyst (FeCo NP/NC) to flexibly alter the reaction kinetics of ORR. Our results from synchrotron X- ray absorption spectroscopy and X-ray photoelectron spectroscopy showed that the co-doping of iron and cobalt could optimize the intrinsic charge distribution of Fe-Co NP/NC catalyst, promoting the oxygen reduction kinetics and ultimately achieving remarkable ORR activity. Consequently, the carefully designed Fe-Co NP/NC exhibits an ultra-high kinetic current density at the operating voltage (71.94 mA/cm2 at 0.80 V), and the half-wave potential achieves 0.915 V, which is obviously better than that of the corresponding controls including Fe NP/NC, Co NP/NC. Our findings provide a unique perspective for optimizing the electronic structure of active centers to achieve higher ORR catalytic activity and faster kinetics.

Electronic State Modulation by Large A-Site Cations in Quasi-Two-Dimensional Organic–Inorganic Lead Halide Perovskites

Organic–inorganic lead halide perovskites (OLHPs) with the general chemical formula of APbX3 have attracted wide interest for their application in the optoelectronics field within the past decade. Despite the performance breakthroughs enabled by modifying A-site cations, a fundamental understanding of the mechanistic origins is still largely neglected. Especially, the critical role of A-site cations in modulating the physicochemical properties of perovskites is challenging to reveal because the choice of A-site cations is limited by the geometrical Goldschmidt tolerance factor. Herein, we for the first time successfully incorporated two large A-site cations in the lead halide cage by relaxing the tolerance factor in a 2D Ruddlesden–Popper system, and we obtained two novel single crystals, namely, (PA)2(Gua)Pb2I7 and (PA)2(Ace)Pb2I7, where PA = n-pentylamine, Gua = guanidine, and Ace = acetamidine. The sizes of Gua (278 pm) and Ace (277 pm) are almost identical and thus enable us to individually study the influence of other properties of the A-site cation on the optoelectronics properties including the polarity, electron donating abilities, etc. By combining with first-principles theoretical perspectives, we deliver insights into the electronic and structural features of perovskites associated with A-site electron donating properties. This adds more versatility to the roles of the A site cations in OLHPs.

Inhibiting Sulfur Dissolution and Enhancing Activity of SnS for CO2 Electroreduction via Electronic State Modulation

Heteroatom doping can facilitate intrinsic activity via the tuning of electronic states. However, it is still rare to elucidate the role of a specific metal sulfide electronic state and simultaneously enhance the CO2 electroreduction reaction (CO2RR) stability. SnS is well-known for its ability to produce HCOOH; however, its long-term operational stability is limited by sulfur dissolution. Herein, we propose a strategy to reinforce the S atoms via heteroatom (In) doping. In situ Raman tests and theoretical calculations demonstrate that In atoms with fewer valence electrons (compared with Sn) can tune the electronic state of SnS and strengthen the S–metal bond energy. Consequently, sulfur dissolution was inhibited, and the reaction pathway was optimized. Further, the In-SnS/C achieves a Faradaic efficiency of 96.6% for formate at −0.6 V vs RHE and a catalyst stability of 50 h at a current density of ∼37 mA cm–2. This study shows that altering the electronic structure of SnS via heteroatoms is a strategy to optimize both the activity and stability of electrocatalysts for the CO2RR.

Alloying at a Subnanoscale Maximizes the Synergistic Effect on the Electrocatalytic Hydrogen Evolution.

Bonding dissimilar elements to provide synergistic effects is an effective way to improve the performance of metal catalysts. However, as the properties become more dissimilar, achieving synergistic effects effectively becomes more difficult due to phase separation. Here we describe a comprehensive study on how subnanoscale alloying is always effective for inter-elemental synergy. Thirty-six combinations of both bimetallic subnanoparticles (SNPs) and nanoparticles (NPs) were studied systematically using atomic-resolution imaging and catalyst benchmarking based on the hydrogen evolution reaction (HER). Results revealed that SNPs always produce greater synergistic effects than NPs, the greatest synergistic effect was found for the combination of Pt and Zr. The atomic-scale miscibility and the associated modulation of electronic states at the subnanoscale were much different from those at the nanoscale, which was observed by annular-dark-field scanning transmission electron microscopy (ADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively.

Alloying at a Subnanoscale Maximizes the Synergistic Effect on the Electrocatalytic Hydrogen Evolution

AbstractBonding dissimilar elements to provide synergistic effects is an effective way to improve the performance of metal catalysts. However, as the properties become more dissimilar, achieving synergistic effects effectively becomes more difficult due to phase separation. Here we describe a comprehensive study on how subnanoscale alloying is always effective for inter‐elemental synergy. Thirty‐six combinations of both bimetallic subnanoparticles (SNPs) and nanoparticles (NPs) were studied systematically using atomic‐resolution imaging and catalyst benchmarking based on the hydrogen evolution reaction (HER). Results revealed that SNPs always produce greater synergistic effects than NPs, the greatest synergistic effect was found for the combination of Pt and Zr. The atomic‐scale miscibility and the associated modulation of electronic states at the subnanoscale were much different from those at the nanoscale, which was observed by annular‐dark‐field scanning transmission electron microscopy (ADF‐STEM) and X‐ray photoelectron spectroscopy (XPS), respectively.

Intersite Charge Transfer Enhanced Oxygen Evolution Reactivity on A 2IrO3 (A=Li, Na, Cu) Delafossite Electrocatalysts

Exploring a simple model system to realize the intrinsic guidelines of activity for oxide electrocatalysts is urgent and important. Here, we introduce delafossite oxides A 2IrO3 (A = Li, Na, Cu) as a family of oxygen evolution reaction electrocatalysts in alkaline media. We show that, in Cu2IrO3, the intrinsic intersite charge transfer between Cu and Ir improves the electrocatalytic activity by simultaneously increasing the conductivity and reducing the Tafel slope down to 51 mV dec−1 with an overpotential η 10 = 361 mV. Through a comparative study, the improved activity of Cu2IrO3 is attributed to the increase of Ir 5d projected electronic density of states with extended Ir–O bond length. This study provides insights into advanced catalyst design through tailoring the active site of oxides by the modulation of electronic states in a given structural motif.

Modulation of electronic state in copper-intercalated 1T-TaS2

Modulation of electronic state in copper-intercalated 1T-TaS2