Modification Of Electronic Structure Research Articles

Interface engineering of Ce/La-doped hydrochar-supported nickel catalysts for enhanced tar reforming performance at low temperature

Catalytic reforming of biomass tar to syngas-especially under mild temperature-is an attractive albeit elusive route, necessitating the manufacture of highly efficient catalysts, in particular, from inexpensive, sustainable, and renewable resources as a prerequisite. Two interface-engineering strategies, including one-pot hydrothermal carbonization (HTC) approach and two-step HTC-impregnation method, were applied to fabricate a series of Ce/La-doped hydrochar-supported nickel catalysts, employing pinewood sawdust-derived hydrochar as the support, nickel as the active sites, and Ce or La as the promoter species. After the optimization of synthetic variables and operation conditions, the Ni0.1/Ce0.05-HC catalysts prepared by the two-step HTC-impregnation method simultaneously exhibited boosted activity, selectivity and recyclability than the Ni/HC counterpart without Ce addition as well as reported state-of-the-art catalysts in steam reforming of biomass tar at a low temperature of 600 °C. This exceptional catalytic performance was mainly attributed to the modulation of geometric structure and electronic structure of the exposed active sites by appropriate inclusion of cerium on the hydrochar-based nickel catalyst, which favored the water-gas shift, boudouard reaction and coke gasification, thereby imparting the materials with remarkable resistance against metal sintering and coke deposition during the steam reforming process. The result in this work underscores that the controlled interface between Ni species and hydrochar support by addition of Ce, which pertain to the hydrothermal processing technique, is a promising blueprint toward effective fuel production from waste biomass.

Rational element-doping of FeOOH-based electrocatalysts for efficient ammonia electrosynthesis

Rational modulation of the Fe d-orbital electronic structure to strengthen d–π* orbital interaction and activate N2.

Theory-guided design of S-doped Fe/Co dual-atom nanozymes for highly efficient oxidase mimics.

The advent of dual-atom nanozymes (DAzymes) featuring distinctive bimetallic active sites garnered significant attention, representing enhanced iterations of conventional single-atom nanozymes. The quest for an effective and universal strategy to modulate the catalytic activity of DAzymes posed a formidable challenge, yet few published reports addressed this. Herein, we designed and synthesized S-doped Fe/Co DAzymes (S-FeCo-NC) under theoretical guidance and revealed their excellent oxidase-like activity. Experimental and theoretical calculations indicated that the superior oxidase-like activity exhibited by S-FeCo-NC was attributed to the S-doping, which modulated the local electronic structure of the dual-atom active site. This modulation of the local electronic structure significantly optimizes oxygen adsorption energy, thereby accelerating the rate of enzyme-catalyzed reactions. As a proof-of-concept, this study integrated S-FeCo-NC with the cascade inhibition reaction of acetylcholinesterase (AChE) to devise a sensitive analytical platform for detecting organophosphorus pesticides. This study paved the way for elucidating the correlation between the local electronic structure of the active site and enzyme activity, offering novel methodologies and insights for the rational design of DAzymes.

An Organic−Inorganic Heterojunction Electrocatalyst for Highly Efficient Urea Oxidation

Constructing p−n heterojunction allows the modulation of the interface electronic structure and boosts electron transfer, leading to enhanced electrocatalytic performance. Herein, an organic−inorganic heterojunction electrocatalyst made of Ni(OH)2, triazine−based covalent...

Electronic band structure modulation for sonodynamic therapy

Sonodynamic therapy (SDT) is a burgeoning and newfangled therapy modality with great application potential. Sonosensitizers are most essential factors to ensure the effectiveness of SDT. For the past few years,...

Dual cation-modified hierarchical nickel hydroxide nanosheet arrays as efficient and robust electrocatalysts for the urea oxidation reaction.

The rational modification of electronic structures to create catalytically active sites has been proved to be a promising strategy to efficiently facilitate the urea oxidation reaction (UOR). Herein, a well-defined nanosheet arrays catalyst of Ni(OH)2 doped with dual cations of Co and Mn on Ni foam (NF) (Co/Mn-Ni(OH)2) is synthesized through a simple hydrothermal process. Benefiting from the advantages of unique structures and modified binding strengths, it is found experimentally that the obtained Co/Mn-Ni(OH)2 catalyst only requires a potential of 1.38 V to deliver a current density of 100 mA cm-2 and exhibits a small Tafel slope of 35 mV dec-1, outperforming single-component-incorporated Ni(OH)2. Moreover, the catalyst has shown excellent stability for 25 h at a current density of 50 mA cm-2. Additionally, first-principles calculations demonstrate that the co-incorporation of Co and Mn remarkably lowers the adsorption barrier of CO(NH2)2* on the catalyst surface, and accelerates the dissociation of the CO(NH2)2* intermediate into CO* and NH* intermediates, which synergistically improve the UOR reaction kinetics. This work provides a generic paradigm for designing advanced and effective catalysts toward the UOR.

Electronic structure modification of ultrathin MnFeOOH and integration with Ni3S2 as bifunctional electrocatalysts for improved alkaline water splitting

Ultrathin porous MnFeOOH was electrodeposited on Ni3S2/NF to form MnFeOOH/Ni3S2/NF with abundant heterogeneous interfaces, affording high-performance bifunctional water splitting electrocatalysts.

Electronic structure modification of SnO2 to accelerate CO2 reduction towards formate.

A systematic theoretical study probing the catalytic potential of metal-doped SnO2(110) was conducted. The incorporation of metals such as Zr, Ti, W, V, Hf, and Ge is shown to drive electron transfer to Sn. The increased charge of Sn is injected into anti-bonding orbitals, finely tuning the catalytic activity and reducing the overpotential to -0.34 V. AIMD simulations show the stability of the modified structures. This work sheds light on the rational design of low-cost metal oxides with a high catalytic performance for CO2ER to formate.

Electronic structure modification of metal phthalocyanines by a carbon nanotube support for efficient oxygen reduction to hydrogen peroxide.

An active and selective two-electron oxygen reduction reaction (2e- ORR) is required for efficient electrosynthesis of H2O2. This reaction can be promoted by metal phthalocyanines (MPcs), which serve as model catalysts with well-defined structures. MPc molecules have mostly been evaluated on conductive carbon-based substrates, including glassy carbon (GC) and carbon nanotubes (CNTs), yet their influence on the electrocatalytic properties is not well understood. This study demonstrated that the ORR activity per surface area was improved by up to 4-fold with MPc molecules supported on CNTs (MPc/CNTs, M = Co, Mn, and Fe) compared to MPc loaded directly on GC. Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that the CNTs modified the electronic structure of the MPc molecules to optimize the *OOH binding energy and boost the heterogeneous electron transfer rates. Detailed kinetic analysis enabled multiple reaction pathways to be decoupled to extract the metal-dependent intrinsic 2e-/4e- ORR activities. Finally, MPc/CNT catalysts were employed in an H2O2 electrosynthesis flow cell, which delivered an industrial-scale current density of -200 mA cm-2 and an H2O2 faradaic efficiency of 88.7 ± 0.6% with the CoPc/CNT catalyst in a neutral electrolyte.

Effective photosensitized emission of a Tb(III) complex using a β-diketonate photosensitizer and an oxygen barrier system in a thermally populated triplet state.

Photosensitizer design of luminescent terbium (Tb(III)) complexes with narrow bandwidths is important for advancing luminescent materials. In this study, we report an effective photosensitizer model in a thermally populated lowest excited triplet (T1) state during Tb(III) emission. The Tb(III) complex comprises a Tb(III) ion (serving as an emission center), hexafluoroacetylacetonates (acting as photosensitizer ligands), and bulky cyclohexyl group-attached phosphine-oxide-type ligands (functioning as an oxygen barrier system). Emission properties including emission and excitation spectra, ligand-excited emission quantum yields, and emission lifetimes were evaluated in the absence and presence of oxygen. Coordination geometry structures were determined through analysing single-crystal structures. The electronic structure based on 4f-orbitals was estimated from radiative rate constants and quantum chemical calculations. The bulky phosphine oxide ligand not only provides an oxygen barrier system but also induces an electronic structural modulation based on 4f-orbitals, allowing for effective photosensitized Tb(III) emission in a thermally populated ligand T1 state in air.

Chalcogen alloying mediated electronic structure modulation in ultrathin Nb(SxSe(1−x))2 nanosheets for the hydrogen evolution reaction

We report composition tuning of Nb(SxSe(1−x))2 alloy nanosheets (NSs) via colloidal synthesis demonstrating the role of modulating d-electron density and defect engineering in alloy structures for application in the hydrogen evolution reaction (HER).

Electronic structure modulation of Mo sites in anion and cation co-doped MoO2 nanospheres for electrocatalytic water oxidation.

Herein, we synthesized a type of anion/cation co-doped MoO2 nanosphere as an efficient OER catalyst. The optimized Ni/N-MoO2 exhibited a lower overpotential of 270 mV at 10 mA cm-2 in 24 h. This work provides a unique direction for the synthesis of efficient and stable MoO2-based electrocatalysts for water splitting.

Donor–acceptor iron phthalocyanine-based hyper-crosslinked polymers with a modulated electronic structure for efficient oxygen reduction reaction in aluminum–air batteries

Poly-FePc-based HCPs with TTF modification are constructed and applied as ORR catalyst for Al–air batteries. The donor–acceptor structure was incorporated into poly-FePc-HCP to achieve structural and electronic regulation.

Integrated design and construction of the NiMoS4@Co9S8/Ni3S2 hollow core–shell heterostructure for high-performance asymmetric supercapacitors

A multi-component NiMoS4@Co9S8/Ni3S2 heterostructure with hollow core–shell morphology exhibits excellent electrochemical performances for asymmetric supercapacitor.

Anion-tuning in cobalt chalcogenides for a comparative study on electro-oxidation of glucose

Electronic structure modulation is of great important to enhance the electrocatalytic ability for glucose oxidation and follow up the electrochemical sensing performance. In this work, Co3X4 (X = O, S, Se) synthesized by oxidation, sulfurization and selenylation of ZIF-67 precursor, respectively, are served as electrocatalysts and then modified on conductive indium tin oxide (ITO) to construct sensing electrodes. The Co3S4/ITO electrode shows a highest sensitivity of 1109.9 μA−1 mM−1 cm−2 when compared with those of the Co3Se4/ITO electrode (515.9 μA−1 mM−1 cm−2), Co3O4/ITO electrode (227.7 μA−1 mM−1 cm−2), and even the relative reported sensing electrodes, enabling more efficient electro-oxidation of glucose by S substitution in Co3X4. The experimental characterization and theoretical calculation elucidate that tuning the anion components in cobalt chalcogenides can modulate their electrochemical active surface area, hydrophilicity, electrical conductivity and binding energies for glucose adsorption, in turn, the electrocatalytic ability. This work provides not only an effective strategy for performance improvement but also a significant understanding of how the anion component of electrocatalyst affect their glucose oxidation ability.

Enhanced Oxygen Evolution Reaction Activity of Fe-Doped Lithium Nickel-Based Metal Oxide through Modification of Nickel Oxidation State

The oxygen evolution reaction (OER) involves the four-electron transfer process of water oxidation to produce oxygen gas and protons. However, this reaction is kinetically sluggish and requires high overpotential compared to hydrogen evolution reaction (HER). Herein, we have fabricated Fe-doped LiNiO2 using electrospray deposition (ESD) technique. With this technique, we can modify the electronic structure of LiNiO2 by controlling amounts of Fe, and the morphology can be controlled with various parameters such as applied voltage, spray rate, and substrate temperature. The synergistic effect of iron doping can modify the electronic structure of the surface Ni ions and increase oxidation state of Ni2+ to Ni3+. Through this oxidation state change, Ni becomes more electrophilic and then adsorbed oxygen in the M – O step, which is considered as rate-determining step in OER, easily reacts with OH ions. In electrochemical analysis, the optimized Fe-doped LiNiO2 showed improved OER performance compared to LiNiO2. The surface chemical compositions of the Fe-doped LiNiO2 electrode were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). From our result, we can improve OER performance and stability with simple control of ESD technique parameters and electronic structure modification by Fe doping.

NiFe sulfide electronic structure modulation via metal doping towards enhanced urea oxidation reaction performance

Enhancement of urea oxidation reaction (UOR) activity of NiFe sulfide via metal doping, including V, Zn, Cr, Ag, and Ti, is demonstrated. X-ray photoelectron and absorption spectroscopy analyses show different degrees of electronic structure modulation of the Ni site due to the doping of the third metals having different t2g and eg occupancies. Cr reduces the energy needed for the in-situ formation of the oxyhydroxide, followed by Ti, V, and Ag. The reaction kinetics is accelerated by Ti, followed by Ag, Cr, and Zn. Ti also optimizes the d-band center and CO2 adsorption energy, which is supported by density functional theory calculation. Self-reconstructed sulfate-containing oxyhydroxide during UOR is demonstrated via in-situ Raman and post-transmission electron microscopy analyses. The sulfate is also found to affect the potential required for the formation of the oxyhydroxide. The optimized NiFeTi-containing sulfide exhibits an excellent UOR potential of 1.36 V at 100 mA cm−2 and is stable up to 80-h. This work provides a strategy and deep understanding in enhancing UOR performance of sulfide catalyst.

FeNiCo|MnGaOx Heterostructure Nanoparticles as Bifunctional Electrocatalyst for Zn-Air Batteries.

Driven by the pressing demand for stable energy systems, zinc-air batteries (ZABs) have emerged as crucial energy storage solutions. However, the quest for cost-effective catalysts to enhance vital oxygen evolution and reduction reactions remains challenging. FeNiCo|MnGaOx heterostructure nanoparticles on carbon nanotubes (CNTs) are synthesized using liquid-phase reduction and H2 calcination approach. Compared to its component, such FeNiCo|MnGaOx/CNT shows a high synergistic effect, low impedance, and modulated electronic structure, leading to a superior bifunctional catalytic performance with an overpotential of 255mV at 10mAcm-2 and half-wave potential of 0.824V (ω=1600rpm and 0.1m KOH electrolyte). Moreover, ZABs based on FeNiCo|MnGaOx/CNT demonstrate notable features, including a peak power density of 136.1mWcm-2, a high specific capacity of 808.3mAhgZn -1, and outstanding stability throughout >158h of uninterrupted charge-discharge cycling. Theoretical calculations reveal that the non-homogeneous interface can introduce more carriers and altered electronic structures to refine intermediate adsorption reactions, especially promoting O* formation, thereby enhancing electrocatalytic performance. This work demonstrates the importance of heterostructure interfacial modulation of electronic structure and enhancement of adsorption capacity in promoting the implementation of OER/ORR, ZABs, and related applications.

High Entropy Induced γ-NiOOH Formation in Layered Double Hydroxide as Highly-Active and Ultra-Stable Electrocatalyst for Oxygen Evolution Reaction

Developing a low-cost and highly efficient oxygen evolution reaction (OER) electrocatalyst and understanding the underlying reaction mechanism are critical for sustainable renewable energy conversion and storage. In this study, high entropy layered double hydroxide (LDH) was self-supported on nickel foam using a simple hydrothermal method. The resulting binder-free high entropy LDH consisting of five different transition metals of Fe, Ni, Co, Mn, and Cr exhibits an excellent OER activity in alkaline condition with a low overpotential of 218 mV at a current density of 50 mA cm-2. It is superior to the binary, ternary, and quaternary-metal LDH counterparts. We demonstrate that the high entropy LDH possesses ultra-stable electrochemical stability at a high current density of 400 mA cm-2 for 600 h. The modulation of electronic structure facilitates the formation of the highly active γ-NiOOH and the shifting of the d-band center, resulting the outstanding OER performance. The excellent catalytic activity and stability of the high entropy LHD make it is as a highly potential candidate for commercial use.

Electrochemically Modulated Multi-Metal Sulfides/3D-Graphene Scaffold for Sustainable Energy Generation and Storage

Transition metal-based compounds (TMCs), especially sulfides and phosphides represent a class of promising non-precious metal oxygen electrocatalysts (OER and ORR) due to their advantages of abundance, low cost, and environmental friendliness. The effective modulation of electronic structure from synergistic interactions between the constituents and the favourable adsorption of crucial intermediates during electrochemical reactions is possible while using multi-metal transition metal-based sulfides and phosphides. Moreover, recent studies report that TMCs with heteroatom-doped carbonaceous materials display excellent bifunctional ORR/OER properties in alkaline environment, benefitting from the fast interfacial electron transfer and the synergistic effects originating from the chemical coupling between metallic atoms and carbon materials. In this regard, Graphene could effectively enhance the electrical properties and limit the volume expansion of the TMCs, improving the durability of the catalyst. However, there are several challenges associated processing of these catalysts or catalyst systems in a scalable route. Designing these scalable electrodes as porous structures is critical for their effective utilization in energy systems. Electrodeposition is an ideal and sustainable strategy that eliminates the calcination step in electrode processing and saves time. In the case of metal sulfides, adopting electrodeposition over 3D foams like of graphene will help to eliminatesimultaneous steps and reduce the toxic gas evolution during heating of precursors. The electrochemical processing will also help to achieve structural designs capable of delivering higher catalytic sites and a controlled ratio of metal elements, enabling excellent catalytic performance for the composition. More importantly, a sturdy interaction between the substrates and the deposited coatings, forming composite structures gives the electrocatalysts exceptional durability.Herein, we report an electrodeposition process of ternary, quaternary, and quinary transition metal-based sulfide electrocatalysts for OER and ORR in alkaline media. We will be discussing the versatile deposition process for multi-metal sulfides over 3D porous graphene foams materialized by chemical vapour deposition. The detailed electrochemical characterization of the catalyst compositions will be supported by first principle-based investigations on oxygen electrochemistry over modelled catalyst surfaces. Finally, the the practical application of rechargeable structural batteries using these transition metal-based catalysts will be demonstrated along with the performance factors.References Jaime et al, All-Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High-Performance Alkaline Batteries, Small 2022, 18, 2106403Xue et al, Structure and performance of the LiFePO4cathode material: from the bulk to the surface, Nanoscale 2020, 12, 4816.Wang et al ,One-Pot Growth of 3D Reduced Graphene Oxide Foams Embedded with NiFe Oxide Nanocatalysts for Oxygen Evolution Reaction, Electrochem. Soc. 2016 ,163 F3158