Sp2 Carbon Research Articles

Rational design of nitrogen-doped carbon for palladium catalysts in hydrogenation of hydrazo compounds

We synthesized CN11, a carbon nitride material rich in sp3 hybrid graphitic nitrogen (sp3-N), employing a facile oxalic acid-assisted melamine molecular assembly strategy. CN11 promoted the formation of Pd nanoparticles (NPs) predominantly exposing {200} facets, termed Pd/CN11-2. This facet-specific configuration significantly boosted hydrogen adsorption, leading to notable improvements in catalytic activity. Compared to Pd/XC-72-2 and Pd/g-C3N4-2, Pd/CN11-2 exhibited a remarkable two-fold and nineteen-fold increase in catalytic yield for hydrazo compound hydrogenation, respectively. Pd/CN11-2 also demonstrated robust performance across a range of reaction conditions, maintaining excellent yield. This study emphasizes the critical role of tailored support structures in controlling Pd NPs facets, thereby enhancing hydrogenation efficiency. It provides valuable insights for advancing the industrial application of Pd-based catalysts, underscoring the importance of strategic support modulation for optimizing catalytic performance.

The effect of MoS2 modified with Transition Metal (Fe, Co, Ni, Cu) on H2O adsorption: A first principle study

MoS2 has great potential as a humidity sensor, and doping is considered the most promising method to enhance the adsorption of H2O molecule by MoS2. Unfortunately, vacancy doping sacrifices the stability of the material while enhancing adsorption efficiency. Here, we use Fe, Co, Ni, Cu to modify the surface of MoS2 and study the adsorption characteristics of H2O molecule on MoS2 before and after modification. The first principles calculations further indicate that partial transition metal (TM) doping can induce spin polarization in MoS2. Spin polarization further enhances orbital hybridization between atoms, thereby improving adsorption performance. On the basis of qualitative analysis of thermodynamic stability and electrical properties, quantitative analysis was conducted on adsorption energy and charge transfer. The results indicate that the adsorption energy, in descending order, is Fe-MoS2 > Co-MoS2 > Ni-MoS2 > Cu-MoS2 > MoS2. Compared with MoS2, Fe-MoS2 has the best adsorption effect among the four doping systems, with an adsorption energy increase of 22.1 times. Importantly, simulations of desorption time have demonstrated that Fe-MoS2 and Co-MoS2 exhibit a significant reduction in desorption time with increasing temperature and can be rapidly recycled.

P-type doped AlxGa1-xAs nanowire photocathode: A theoretical perspective on structural and optoelectronic properties

In this work, the effect of p-type doping on the structural, electronic, and optical properties of AlxGa1-xAs nanowires are investigated by first-principles calculations. Different doping elements (Be, Mg, Zn), doping methods (interstitial and substitution doping) and doping concentration are considered. The calculations of formation energy suggest that the structural stability of p-type AlxGa1-xAs nanowires is gradually weaken as the rise of doping concentration and Al composition. Besides, the difficulty of forming substitution doping for different doping elements obeys the following order: Be<Mg<Zn. In addition, the substitution doping atom tends to replace Ga atom rather than Al atom to form substitution doping structure. After substitution doping, all energy bands shift to higher energy region due to the orbital hybridization of electronic states induced by impurity atom and nanowire atoms. Moreover, the substitution doping leads to the Fermi level entering into the valence band, resulting in obviously p-type conductivity. The p-type modulation doping is indeed effective in the axial type AlxGa1-xAs nanowires with p-type carrier concentration varying between 1.85×1020 cm-3 and 4.42×1020 cm-3, and the conductivity will be further enhanced with increasing substitution doping concentration or Al composition. Finally, the optical absorption of AlxGa1-xAs nanowire photocathodes can be effectively enhanced through BeGa doping. Our findings not only present a comprehensive understanding of p-type doping mechanism of AlxGa1-xAs nanowires, but also provide a theoretical basis for preparing AlxGa1-xAs nanowire based photoelectric devices with p-type properties.

Constructing high-performance bulk thermoelectric composites by incorporating uniformly dispersed fullerene sub-nanoclusters

Sub-nanomaterials possess unprecedented size-dependent properties compared to conventional nanomaterials, which endow them with great potential in catalysis, biomedicine, sensors, and so on. However, their applications in thermoelectrics are unknown due to poor thermal stability and low yields. Herein, we construct a series of thermoelectric composites by incorporating highly thermally stable and commercial fullerene sub-nanoclusters (C60 or C70). We find that sub-nanoclusters as the second phase can conduce to optimized carrier concentration through charge transfer at interfaces while the carrier mobility is significantly enhanced due to atom orbital hybridization and size-dependent electrical scattering mechanism. Furthermore, the ultra-low thermal conductivity of C60 due to its distorted chemical bonding and sub-nanometer pore, and the interfacial thermal resistance greatly suppress the phonon transport. Consequently, the 0.15 mol% C60/Bi0.4Sb1.6Te3 realizes an ultra-high ZT of ∼1.6 at 373 K, an excellent thermoelectric conversion efficiency of ∼7.4%, and a huge cooling performance of ∼73 K. This work demonstrates the application of sub-nanomaterials in thermoelectrics and may shed light on other fields such as electronic devices, thermal management, and fullerene chemistry.

Modifying d–p orbital hybridization of Ni/Fe[sbnd]O species by high-valence ruthenium doping to enhance oxygen evolution performance

The electron distribution of catalysts can be modulated by high-valence metal doping, thus enhancing the intrinsic activity. Herein, we adopt Ru modification to adjust the d–p orbital hybridization of Ni-Fe oxyhydroxides, significantly increasing the oxygen evolution reaction (OER) activity. The amorphous NiFe0.5Ru0.1OxHy catalyst synthesized by sol–gel method exhibits excellent OER activity, far superior to commercial RuO2. In situ Raman and XPS results confirm that the NiOOH/FeOOH active species gradually form with increasing applied voltage. Density functional theory (DFT) calculations reveal that high-valence Ru dopants can effectively regulate the hybridization of d–p orbital of Ni/FeO, significantly increase the electron density around Fermi level, promote charge transfer, make them have more anti-bonding orbitals, enhance the binding ability of active sites to intermediates, reduce the reaction energy barrier of the rate-determining step (H2O → *OH), and thus improve the OER activity. In addition, NiFeRuOxHy as a cathode catalyst in a rechargeable zinc-air battery shows an outstanding cycle life of 600 h. This study provides a promising hybrid orbital method for designing high-performance OER catalysts for water splitting and rechargeable zinc-air batteries.

Performance and mechanism of the structure formation and physical-mechanical properties of concrete by modification with nanodiamonds

Nanomodifying additives in the building materials production is a relevant and widely studied topic in current building materials science. Nanodiamonds are used in various fields of science and technology. However, they were not used as a modifying additive in the production of building composite materials. The purpose of this study is to investigate the mechanism of interaction of chemically pure cavitation synthesis nanodiamonds (КНА-НС) with cement concrete on the structure formation and mechanical properties of fresh and hardened concrete. These KHA-HC nanodiamonds are carbon sp3 hybridized nanoparticles with a diamond-like structure and a particle size in a cross section of not more than 3nm, shaped close to spherical and a clear mono modal distribution throughout the entire fractional composition, with a maximum of 1nm to 3nm. During the research, the initial components were selected, the compatibility of these components was checked, including the formation of test samples, the properties of fresh concrete, the density of hardened concrete, compressive and flexural strength at various ages of hardening (2, 7, 14 and 28 days) were studied using standard methods, and X-ray diffraction and scanning electron microscopy of concrete were also carried out. It has been established that the addition of KHA-HC accelerates the process of concrete strength gain. The greatest effect was recorded for concrete aged 2 days. With an optimal KHA-HC content of 0.4%, the increases in compressive and flexural strength were 28.6% and 26.1%, respectively. The addition of KHA-HC in all considered ranges from 0.1% to 1.0% has a positive effect on the strength properties of concrete. The most effective dosage is 0.4%. The increases in compressive and flexural strength of concrete at an age of 28 days were 15.1% and 15.7%, respectively. Nanomodification of concrete with the KHA-HC additive does not affect the phase composition of concrete. The effect of “self-reinforcement of cement matrix” put forward in this study is confirmed by images of the microstructure of the cement matrix with a large accumulation of calcium hydrosilicate zones.

Hydrogen Evolution Reactivity of Pentagonal Carbon Rings and p‐d Orbital Hybridization Effect with Ru

AbstractTopological defects are inevitable existence in carbon‐based frameworks, but their intrinsic electrocatalytic activity and mechanism remain under‐explored. Herein, the hydrogen evolution reaction (HER) of pentagonal carbon‐rings is probed by constructing pentagonal ring‐rich carbon (PRC), with optimized electronic structures and higher HER activity relative to common hexagonal carbon (HC). Furthermore, to improve the reactivity, we couple Ru clusters with PRC (Ru@PRC) through p‐d orbital hybridization between C and Ru atoms, which drives a shortcut transfer of electrons from Ru clusters to pentagonal rings. The electron‐deficient Ru species leads to a notable negative shift in d‐band centers of Ru and weakens their binding strength with hydrogen intermediates, thus enhancing the HER activity in different pH media. Especially, at a current density of 10 mA cm−2, PRC greatly reduces alkaline HER overpotentials from 540 to 380 mV. And Ru@PRC even exhibits low overpotentials of 28 and 275 mV to reach current densities of 10 and 1000 mA cm−2, respectively. Impressively, the mass activity and price activity of Ru@PRC are 7.83 and 15.7 times higher than that of Pt/C at the overpotential of 50 mV. Our data unveil the positive HER reactivity of pentagonal defects and good application prospects.

Stabilization of Ethane-like Dianionic Diborane(6) in Monometallic Titanium Complexes and its Subsequent B(sp3)-B(sp3) Bond Cleavage.

Treatment of [Cp*TiCl3] with [LiBH4∙THF] followed by thermolysis with [Ph2E2] (E = S or Se) resulted in the formation of classical diborane(6) complexes, [(Cp*Ti)(η4-B2H4LL')] (L = C6H4E; L' = C6H5E; 1a: E = S, 1b: E = Se), stabilized at titanium template. To the best of our knowledge, they are the first examples of mono-metallic classical diborane(6) complexes. The bonding analysis and theoretical studies suggest that the stabilization of these diborane(6) species is due to the presence of four bridging ligands in ĸ4-fashion, where two of them are phenyl thiolates/selenolates that provide more electrons to the electron-deficient titanium center. Reactions of these diborane(6) species with [M(CO)5∙THF] (M = Mo, W) led to the cleavage of electron-precise B(sp3)-B(sp3) bond that yielded ĸ3-hydridoborato complexes [(Cp*Ti)(ĸ3-BH3R)(μ-EPh)2{M(CO)4}] (2a-c: R = H, 3a-c: R = Ph). In an attempt to isolate the Te-analogue of 1a-b, a similar reaction was performed; however, the complex was too unstable to be isolated. Interestingly, the treatment of this unstable intermediate with [W(CO)5∙THF] yielded [(Cp*Ti)(ĸ3-BH3R)(μ-TePh)2{W(CO)4}] (2d: R = H, 3d: R = Ph) that are analogues of 2a-c and 3a-c, respectively. Formation of these species provide indirect evidence forexistence of unstable [(Cp*Ti)(η4-B2H4LL')] (L = C6H4Te; L' = C6H5Te; 1c).

Stabilization of Ethane‐like Dianionic Diborane(6) in Monometallic Titanium Complexes and its Subsequent B(sp3)‐B(sp3) Bond Cleavage

Treatment of [Cp*TiCl3] with [LiBH4∙THF] followed by thermolysis with [Ph2E2] (E = S or Se) resulted in the formation of classical diborane(6) complexes, [(Cp*Ti)(η4‐B2H4LL')] (L = C6H4E; L' = C6H5E; 1a: E = S, 1b: E = Se), stabilized at titanium template. To the best of our knowledge, they are the first examples of mono‐metallic classical diborane(6) complexes. The bonding analysis and theoretical studies suggest that the stabilization of these diborane(6) species is due to the presence of four bridging ligands in ĸ4‐fashion, where two of them are phenyl thiolates/selenolates that provide more electrons to the electron‐deficient titanium center. Reactions of these diborane(6) species with [M(CO)5∙THF] (M = Mo, W) led to the cleavage of electron‐precise B(sp3)‐B(sp3) bond that yielded ĸ3‐hydridoborato complexes [(Cp*Ti)(ĸ3‐BH3R)(μ‐EPh)2{M(CO)4}] (2a‐c: R = H, 3a‐c: R = Ph). In an attempt to isolate the Te‐analogue of 1a‐b, a similar reaction was performed; however, the complex was too unstable to be isolated. Interestingly, the treatment of this unstable intermediate with [W(CO)5∙THF] yielded [(Cp*Ti)(ĸ3‐BH3R)(μ‐TePh)2{W(CO)4}] (2d: R = H, 3d: R = Ph) that are analogues of 2a‐c and 3a‐c, respectively. Formation of these species provide indirect evidence for existence of unstable [(Cp*Ti)(η4‐B2H4LL')] (L = C6H4Te; L' = C6H5Te; 1c).

Remote Migratory Reductive Arylation of Unactivated Alkenes Enabled by Electrochemical Nickel Catalysis.

Transition metal-catalyzed cross-coupling reaction between organometallic reagents and electrophiles is a potent method for constructing C(sp2)-C(sp3) bonds. Given the characters of organometallic reagents, cross-reductive coupling is emerging as an alternative strategy. The resurgence of electrochemistry offers an ideal method for electrochemical reductive of cross-coupling electrophiles. Inspired by the mechanism of electrochemical metal hydride, our study proposed that Ni-H electrochemically catalyze the hydroarylation coupling of unactivated alkenes with aryl halides. 1,1-Diarylalkanes can be produced effectively. This method have advantages including mild conditions, excellent regioselectivity, and satisfactory yields.

Engineering 4f-2p-3d orbital hybridization on cerium-doped nickel–molybdenum phosphates for energy-saving hydrogen evolution

Engineering 4f-2p-3d orbital hybridization on cerium-doped nickel–molybdenum phosphates for energy-saving hydrogen evolution

Coordinatively Unsaturated Co Single-Atom Catalysts Enhance the Performance of Lithium-Sulfur Batteries by Triggering Strong d-p Orbital Hybridization.

The catalytic activities displayed by single-atom catalysts (SACs) depend on the coordination structure. SACs supported on carbon materials often adopt saturated coordination structures with uneven distributions because they require high-temperature conditions during synthesis. Herein, bisnitrogen-chelated Co SACs that are coordinatively unsaturated are prepared by integrating a Co complex into a conjugated microporous polymer (CMP-CoN2). Compared with saturated analogues, i.e., tetranitrogen-chelated Co SACs (denoted as CMP-CoN4), CMP-CoN2 exhibits higher electrocatalytic activity in polysulfide conversions due to an enhanced hybridization between the 3d orbitals of the Co atoms and the 3p orbitals of the S atoms in the polysulfide. As a result, sulfur cathodes prepared with CoN2 deliver outstanding performance metrics, including a high specific capacity (1393 mA h g-1 at 0.1 C), a superior rate capacity (673.2 mA h g-1 at 6 C), and a low capacity decay rate (of only 0.045% per cycle at 2 C over 1000 cycles). They also outperform sulfur cathodes that contain CMP-CoN4 or CMPs that are devoid of Co SACs. This work reveals how the catalytic activity displayed by SACs is affected by their coordination structures, and the rules that underpin the structure-activity relationship may be extended to designing electrocatalysts for use in other applications.

Redox-Neutral, Iron-Mediated Directed C-H Activation: General Principles and Mechanistic Insights.

Experimental and computational studies have been conducted and established the general principles for enabling redox-neutral C-H activation by iron(II) complexes. The idealized octahedral iron(II) dimethyl complex, (depe)2Fe(CH3)2 (depe = 1,2-bis(diethylphosphino)ethane) promoted the directed, regioselective ortho C(sp2)-H methylation of pivalophenone. The rate of the iron(II)-mediated C(sp2)-H functionalization depended on the lability of L-type phosphine ligands, the spin state of the iron center, and the size of the X-type ligands (halide, hydrocarbyl) in P4FeIIX2 complexes. The C(sp2)-H alkylation reaction proved general among multiple substrates with directing groups including carbonyl, imines and pyridines. Among these, ketones and aldehydes were identified as optimal and were compatible with various steric environments and presence of acidic α-hydrogens. With stronger nitrogen donors, higher barriers for product-forming reductive elimination were observed. The effect of orbital hybridization on the chemoselectivity of C-H activation through a σ-CAM pathway by dn>0 transition metals was also established by studying the stoichiometric reactivity of the differentially substituted (depe)2Fe(Me)R complexes (R = alkyl, aryl), where the Fe-R bond with greater s-character preferentially promoted selective C-H activation. Deuterium labeling and kinetic studies, coupled with computational analysis, supported a pathway involving phosphine dissociation and rate-determining C-H bond activation, leading to the observed products.

Inside Front Cover: Enhancing d/p‐2π* Orbitals Hybridization via Strain Engineering for Efficient Photoreduction CO2

Inside Front Cover: Enhancing d/p‐2π* Orbitals Hybridization via Strain Engineering for Efficient Photoreduction CO₂

Inside Front Cover: Enhancing d/p‐2π* Orbitals Hybridization via Strain Engineering for Efficient Photoreduction CO2

Inside Front Cover: Enhancing d/p‐2π* Orbitals Hybridization via Strain Engineering for Efficient Photoreduction CO₂

Customized Heteronuclear Dual Single‐Atom and Cluster Assemblies via D‐Band Orchestration for Oxygen Reduction Reaction

AbstractAdvanced oxygen reduction reaction (ORR) catalysts, integrating with well‐dispersed single atom (SA) and atomic cluster (AC) sites, showcase potential in bolstering catalytic activity. However, the precise structural modulation and in‐depth investigation of their catalytic mechanisms pose ongoing challenges. Herein, a proactive cluster lockdown strategy is introduced, relying on the confinement of trinuclear clusters with metal atom exchange in the covalent organic polymers, enabling the targeted synthesis of a series of multicomponent ensembles featuring FeCo (Fe or Co) dual‐single‐atom (DSA) and atomic cluster (AC) configurations (FeCo‐DSA/AC) via thermal pyrolysis. The designed FeCo‐DSA/AC surpasses Fe‐ and Co‐derived counterparts by 18 mV and 49 mV in ORR half‐wave potential, whilst exhibiting exemplary performance in Zn‐air batteries. Comprehensive analysis and theoretical simulation elucidate the enhanced activity stems from adeptly orchestrating dz2‐dxz and O 2p orbital hybridization proximate to the Fermi level, fine‐tuning the antibonding states to expedite OH* desorption and OOH* formation, thereby augmenting catalytic activity. This work elucidates the synergistic potentiation of active sites in hybrid electrocatalysts, pioneering innovative targeted design strategies for single‐atom‐cluster electrocatalysts.

Hydrogenation of graphene on Ni(111) by H2 under near ambient pressure conditions

Graphene hydrogenation on Ni(111) in the mbar region has been investigated by combining Near Ambient Pressure X-ray Photoemission Spectroscopy and Density Functional Theory calculations. A complete and nearly perfect graphene single layer and an incomplete defective monolayer were exposed to a methanation mixture (H2 + CO and H2 + CO2, respectively) with a large excess of H2. The observed behavior is quite different for the two systems. In the former case, the C 1s spectrum of the initially strongly interacting graphene shows the appearance of new components corresponding to hydrogenated C atoms and their first nearest neighbors. The defective carbon layer, grown in the presence of sulfur contamination and consisting of a mixture of strongly and weakly interacting graphene with a significant amount of dissolved C, initially shows the same C species and then evolves with the formation of sp3 carbon and patches of Ni oxide/hydroxide. NiO forms by CO2 dissociation, while sp3 carbon is indicative of a rumpling of the graphene adlayer induced by hydrogenation. Both species disappear when annealing in H2. Dissociation of H2 and graphene hydrogenation is possible thanks to the presence of the Ni substrate which makes the reaction weakly exothermic and significantly reduces the barrier for H2 dissociation.

Electronic structure, phonons, and born effective charges in CuLaO2: A first-principles study

This study presents a first-principles investigation of the structural, electronic, dielectric, and dynamical properties of CuLaO2 in its rhombohedral delafossite phase using density functional theory. Our analysis reveals that CuLaO2 is a stable indirect band gap semiconductor with a 2.35 eV band gap, showing significant Cu (3d, 4s) and O (2p) orbital hybridization. Phonon dispersion calculations confirm dynamical stability with no imaginary frequencies, and the material exhibits anisotropic dielectric behavior due to mixed ionic-covalent bonding. These findings suggest that CuLaO2 has potential applications in optoelectronics and energy technologies, providing a theoretical basis for future experimental validation.

Flexibility, Dispersion Property, and Giant Sunlight Absorption of Monolayer MX2 (M = Zr, Hf; X = S, Se) and Related Janus MXY (M = Zr, Hf; X = S, Y = Se)

IVB–VIA transition metal dichalcogenides (TMDs) MX2 (M = Zr, Hf; X = S, Se) and related Janus MXY (M = Zr, Hf; X = S, Y = Se) have garnered significant attention due to their unique optoelectronic properties. To further explore their potential in flexible photonics, their mechanical, band dispersion, and optical dielectric properties using orbital hybrid theory are investigated. The results reveal that the out‐of‐plane linear compression resistance of these materials is considerably lower than their in‐plane resistance, primarily because van der Waals interactions are much weaker compared to ionic bond interactions. This characteristic makes them less susceptible to external pressure and torsional forces, positioning them as promising candidates for flexible optoelectronic devices. Furthermore, the presence of multiple energy bands at the same momentum state suggests a tendency toward metal–insulator transitions. Notably, the materials exhibit a high photon flux, indicating robust photoelectric conversion capabilities, making them suitable for applications in photoelectric transducers. This study not only deepens the understanding of the optoelectronic and mechanical properties of IVB–VIA TMD materials, but also offers theoretical guidance for the development and application of flexible optoelectronic devices based on IVB‐VIA TMDs and related Janus materials.

Lead-Free Hybrid Perovskite: An Efficient Room-Temperature Spin Generator via Large Interfacial Rashba Effect.

Two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) shows great potential for developing flexible and wearable spintronic devices by serving as spin sources via the bulk Rashba effect (BRE). However, the practical application of BRE in 2D HOIP faces huge challenges, particularly due to the toxicity of lead, which is crucial for achieving large spin-orbit coupling, and the restrictions in 2D HOIP candidates to meet specific symmetry-breaking requirements. To overcome these obstacles, we designed a strategy to exploit the interfacial Rashba effect (IRE) of lead-free 2D HOIP (C6H5CH2CH2NH3)2CuCl4 (PEA-CuCl), manifesting as an efficient spin generator at room temperature. IRE of PEA-CuCl originates from the large orbital hybridization at the interface between PEA-CuCl and adjacent ferromagnetic layers. Spin-torque ferromagnetic resonance measurements further quantify a large Rashba effective field of 14.04 Oe per 1011 A m-2, surpassing those of lead-based HOIP and traditional all-inorganic heterojunctions with noble metals. Our lead-free 2D HOIP PEA-CuCl, which harnesses large IRE for spin generation, is efficient, nontoxic, and economic, offering huge promise for future flexible and wearable spintronic devices.