Nickel Atoms Research Articles

The Facile Synthesis of Nickel-Doped Composite Magnetic Ni@CoO@ZIF-67 as an Efficient Heterogeneous Catalyst for the Ring-Opening Polymerization of L-Lactide

The ring-opening polymerization of L-lactide is a crucial route for producing biodegradable polylactides (PLAs). Developing an efficient catalyst for this process poses significant challenges. Herein, we report the successful incorporation of nickel during the crystallization of ZIF-67, the derivation of the abundant and stable CoO source, to obtain the composite magnetic Ni@CoO@ZIF-67 using the solid-state thermal (SST) method. The characterization of the resulting materials revealed that nickel atoms are well dispersed in the composite CoO@ZIF-67, imparting additional magnetic properties. The composite Ni@CoO@ZIF-67 demonstrated superior performance as a heterogeneous catalyst for the ring-opening polymerization of L-lactide compared to reference materials such as Ni-Hmim, CoO, ZIF-67, and CoO@ZIF-67. Furthermore, the magnetic property of Ni@CoO@ZIF-67 offers practical advantages, enabling easier separation and recycling of the catalyst. Notably, the SST method facilitates the single-step synthesis of composite magnetic Ni@CoO@ZIF-67 under solvent-free conditions, representing a significant advancement in catalyst development. This approach not only simplifies the synthesis process but also inspires further developments of heterogeneous magnetic catalysts for a variety of effective and diverse reactions.

Hidden Impurities Generate False Positives in Single Atom Catalyst Imaging

AbstractSingle‐atom catalysts (SACs) are an emerging class of materials, leveraging maximum atom utilization and distinctive structural and electronic properties to bridge heterogeneous and homogeneous catalysis. Direct imaging methods, such as aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy, are commonly applied to confirm the atomic dispersion of active sites. However, interpretations of data from these techniques can be challenging due to simultaneous contributions to intensity from impurities introduced during synthesis processes, as well as any variation in position relative to the focal plane of the electron beam. To address this matter, this paper presents a comprehensive study on two representative SACs containing isolated nickel or copper atoms. Spectroscopic techniques, including X‐ray absorption spectroscopy, were employed to prove the high metal dispersion of the catalytic atoms. Employing scanning transmission electron microscopy imaging combined with single‐atom‐sensitive electron energy loss spectroscopy, we scrutinized thin specimens of the catalysts to provide an unambiguous chemical identification of the observed single‐atom species and thereby distinguish impurities from active sites at the single‐atom level. Overall, the study underscores the complexity of SACs characterization and establishes the importance of the use of spectroscopy in tandem with imaging at atomic resolution to fully and reliably characterize single‐atom catalysts.

Hidden Impurities Generate False Positives in Single Atom Catalyst Imaging.

Single-atom catalysts (SACs) are an emerging class of materials, leveraging maximum atom utilization and distinctive structural and electronic properties to bridge heterogeneous and homogeneous catalysis. Direct imaging methods, such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, are commonly applied to confirm the atomic dispersion of active sites. However, interpretations of data from these techniques can be challenging due to simultaneous contributions to intensity from impurities introduced during synthesis processes, as well as any variation in position relative to the focal plane of the electron beam. To address this matter, this paper presents a comprehensive study on two representative SACs containing isolated nickel or copper atoms. Spectroscopic techniques, including X-ray absorption spectroscopy, were employed to prove the high metal dispersion of the catalytic atoms. Employing scanning transmission electron microscopy imaging combined with single-atom-sensitive electron energy loss spectroscopy, we scrutinized thin specimens of the catalysts to provide an unambiguous chemical identification of the observed single-atom species and thereby distinguish impurities from active sites at the single-atom level. Overall, the study underscores the complexity of SACs characterization and establishes the importance of the use of spectroscopy in tandem with imaging at atomic resolution to fully and reliably characterize single-atom catalysts.

The electron-withdrawing properties of butanesultone-based polymer electrolytes facilitate stable operation at 4.6 V for solid-state lithium batteries with NCM811 cathodes

Polymer electrolyte (PEs) based solid-state lithium metal batteries (SSLMBs) featuring LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes offer high energy density and safety. However, their development is hampered by the poor anti-oxidation ability and severe interfacial reactions between the PEs and NCM811 cathode. Herein, the butanesultone-based polymer electrolytes (PBS-PEs) were synthesized via ring-opening polymerization, with different terminal groups tailored to optimize anti-oxidation ability and interface compatibility. The electron-withdrawing properties of sulfonate groups readily complex with nickel atoms, enhancing the anti-oxidation resistance of the PEs. Furthermore, PBS-PEs containing terminal –OCH3 and trifluoromethanesulfonate groups, exhibit superior electrochemical performance compared to those with terminal -OH groups. These variants offer a wide electrochemical stability window of 5.1 V (vs. Li+/Li) and ionic conductivity reaching up to 1.25 × 10−3 S cm−1 at 25 °C. The improved interfacial compatibility with NCM811 cathodes exhibiting a good capacity retention of 80 % after 150 cycles at a current density of 2 C when charged to 4.6 V. Thus, this study not only introduces a novel electron-withdrawing sulfonate groups PEs for pairing with high-voltage cathodes, but also advances the application of NCM811 cathode material in high-energy SSLMBs.

Sporadic binding of perchlorate and dicyanamide ions in trinuclear CuII2NiII complexes with a reduced di-Schiff base ligand: Synthesis, structures and spectral properties

Two new unusual trinuclear linear heterometallic complexes, [(CuLR)2Ni(ClO4)2{CO(CH3)2}2]·0.17H2O (1) and [(CuLR)2Ni(N3C2)2(0.5CH3OH)2] (2) have been synthesized by using [CuLR] as a “metalloligand” (where H2LR=N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine) in presence of anions perchlorate and dicyanamide, respectively. Both the complexes have been diagnosed by elemental analysis, spectroscopic investigations, and single crystal XRD study. In these complexes, the terminal “ligand complex” [CuLR] coordinates to the central nickel atom via double phenoxido oxygen atoms bridge, resulted in a linear trinuclear structures. In both structures, the anions (perchlorate for 1 and dicyanamide for 2) coordinate to the terminal Cu(II) centers of the trinuclear unit (Cu(II)-Ni(II)-Cu(II)) to complete the distorted octahedral geometry around Cu(II); whereas the central Ni(II) metal ion remains in square planar geometry. The binding of perchlorate or dicyanamide to the terminal Cu(II) instead of central Ni(II) ion is rather unusual compared to the complexes of analogous unreduced species.

Borrowing Hydrogen Mechanism in Amine Alkylation by Single Atom Nickel Catalysts

Borrowing Hydrogen Mechanism in Amine Alkylation by Single Atom Nickel Catalysts

Structural and computational insights into two completely unanticipated Cu(II) and Ni(II) complexes derived from a bifunctional salamo-type bis(pyridine)-arm ligand

A bifunctional Salamo-type bis(pyridine)-arm ligand H2L (4,4′-Methyl-6,6′-pyridinenitrilomethylidyne-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) was designed and synthesized, which can react with Cu(II) and Ni(II) nitrates to hydrolyze & break the C = N double bonds of new ligand H2L′ (4,4′-Methyl-6,6′-formal-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol). The ligand reacted with Cu(II) and Ni(II) salts to form respectively complexes [Cu(L′)] (1) and [Ni2(L′)(H2O)2](NO3)2 (2). They were elucidated by single crystal X-ray method. Many important noncovalent interactions, such as intramolecular hydrogen bonding, intermolecular hydrogen bonding and π···π stacking interactions, can be observed in the crystal structures of the two complexes. IR & UV–Vis absorbent spectroscopic analysis showed that the ligand unit is involved in the coordination with copper(II) and nickel(II) atoms, and ultraviolet titration and fluorescence titration spectra verified that the coordinating radios of the two complexes formed in liquid phase are in accordance with those of single-crystal X-ray diffraction. Through DFT theoretical calculations and electrostatic potential analyses (MESP) of the ligand and its complexes, the configuration of the ligand at the lowest energy were deeply understood, and it was demonstrated that the coordination reaction at salamo sites requires a great torsional force, and the weak intermolecular interaction force and the energy gaps of HOMO-LUMO orbitals were profoundly discussed, and the Cu(II) and Ni(II) complexes exhibit anomalous fluorescence enhancement behaviors.

Microsolvation of cobalt, nickel, and copper atoms with ammonia: a theoretical study of the solvated electron precursors.

The s-block metals dissolved in ammonia form metal-ammonia complexes with diffuse electrons which could be used for redox catalysis. In this theoretical paper, we investigated the possibility of the d-bloc transition metals (Mn, Fe, Co, Ni, and Cu) solvated by ammonia. It has been demonstrated that both Mn and Fe atoms undergo into an oxidative reaction with NH3 forming an inserted species, HMNH2. On the contrary, the Co, Ni, and Cu atoms can accommodate four NH3, via the coordination bond, to form the first solvation sphere within C2v, D2d, and Td point groups, respectively. Addition of a fifth NH3 constitute the second solvation shell by forming hydrogen bond with the other NH3s. Interestingly, M(NH3)4 (M = Co, Ni, and Cu) is a so-called solvated electron precursor and should be considered as a monocation M(NH3)4+ kernel in tight contact with one electron distributed over its periphery. This nearly free electron could be used to capture a CO2 molecule and engages in a reduction reaction. Geometry optimization of the stationary points on the potential energy surface was performed using density functional theory - CAM-B3LYP functional including the GD3BJ dispersion contribution - in combination with the 6-311 + + G(2d, 2p) basis set for all the atoms. All first-principles calculations were performed using the Gaussian 09 quantum chemical packages. The natural electron configuration of transition atom engaged in the compounds has been found using the natural bond orbital (NBO) method. We used the EDR (electron delocalization range) approach to analyze the structure of solvated electrons in real space. We also used the electron localization function (ELF) to measure the degree of electronic localization within a chemical compound. The EDR and ELF analyses are done using the TopMod and Multiwfn packages, respectively.

Unleashing unprecedented activation of high-valent Ni and Fe charge dynamics in CeF3-NiFe layered double hydroxide heterostructure: Demonstrating oxygen evolution reaction at an extremely high current density

The efficacy of any electrochemical reaction hinges on the extent of interaction achievable between reactive intermediates and the electrocatalytic active site. Any weak adsorption of these intermediates on the metal’s active site results in low oxygen evolution reaction (OER) rates, mainly when catalysed by the Ni-based layered double hydroxide. To tackle this challenge, a heterojunction consisting of nickel-iron layered double hydroxide (NiFe-LDH) and cerium trifluoride (CeF3) is synthesized. Both phases were developed in-situ to have an abundance of heterointerfaces. The charge transfer amid the NiFe-LDH and CeF3 phases is brought about via these heterointerfaces. As a result, the overall charge dynamics associated with nickel (Ni) and iron (Fe) atoms are somewhat increased, and an enhanced positive charge on the metal site makes it more active in grabbing the reactive species, thereby making the entire OER process faster. The CeF3-NiFeLDH catalyst reaches a current density of 1000 mA cm−2 at an overpotential of 340 mV. Such a high current density is highly significant for the industrial-scale production of the products. The catalyst demonstrated impressive durability, maintaining stable performance for 90 h while operating at 500 mA cm−2. The charge dynamics between both phases were thoroughly examined using X-ray photoelectron spectroscopy (XPS).

Effect of Gamma Irradiation on Electrophysical Parameters of Silicon Solar Cells Doped with Nickel

The results of the studies of changes in the electro-physical parameters (Voc – no-load voltage, Isc – short-circuit current density; τ – lifetime of nonequilibrium charge carriers) of photocells made on plates of monocrystalline silicon of the p-type conductivity with the specific resistance ρ 0.5 Ohm cm, doped with nickel, under irradiation with γ-quanta from 60Co source are presented. It is shown that the efficiency of the solar energy conversion in nickel-doped photovoltaic cells remains higher than in standard cells up to irradiation doses of 108 rad. It was established that with increasing diffusion temperature of nickel atoms radiation stability of electrophysical parameters of photovoltaic cells also increases. A decrease in the concentration of recombination-active radiation defects is due to the getterization by nickel atoms of technological (background) impurities and the action of nickel clusters as effluents for radiation-induced vacancies.

Synthesis and characterization of novel quinaldic acid based Ni, Fe, and Cr Complexes: A computational and experimental study

Complexes ([Ni(quin-2-c)2(H2O)2]•2H2O, [Fe(quin-2-c)2(H2O)2], [Cr(quin-2-c)2(H2O)2] were synthesized from aqueous solutions of metal salts, quinaldic acid, and semicarbazide. In the crystal structure of the first complex, the nickel atom is chelated by the deprotonated quinaldic acid molecule through the oxygen atom of the carboxyl group, and the heterocyclic nitrogen atom, as well as two water molecules, are coordinated. The other two water molecules are located in the outer sphere. In the structure of the iron and chromium complexes, the metal atoms have a similar complex formation but do not have water molecules in the outer sphere. In all compounds, quinaldic acid acts as a bidentate ligand to form five-membered metallocycles. The electronic structure properties were investigated through theoretical modeling using the B3LYP method at the 6–31 + G(d,p) computational level. Density functional theory (DFT) was employed in quantum chemistry simulations to refine proposed structures and explore the characteristics of frontier orbitals via analysis of frontier molecular orbitals (FMOs). These computations facilitated the identification of specific sites on the surface of molecules by generating molecular electrostatic potential maps and provided insights into the structural and reactive properties. Hirshfeld surface analysis was conducted to examine intermolecular interactions, revealing a prevalence of H⋅⋅⋅H interactions.

Exceptionally Stable Cobalt Nanoclusters on Functionalized Graphene

To improve reactivity and achieve a higher material efficiency, catalysts are often used in the form of clusters with nanometer dimensions, down to single atoms. Since the corresponding properties are highly structure‐dependent, a suitable support is thus required to ensure cluster stability during operating conditions. Herein, an efficient method to stabilize cobalt nanoclusters on graphene grown on nickel substrates, exploiting the anchoring effect of nickel atoms incorporated in the carbon network is presented. The anchored nanoclusters are studied by in situ variable temperature scanning tunneling microscopy at different temperatures and upon gas exposure. Cluster stability upon annealing up to 200 °C and upon CO exposure at least up to 1 × 10−6 mbar CO partial pressure is demonstrated. Moreover, the dimensions of the cobalt nanoclusters remain surprisingly small (<3 nm diameter) with a narrow size distribution. Density functional theory calculations demonstrate that the interplay between the low diffusion barrier on graphene on nickel and the strong anchoring effect of the nickel atoms leads to the increased stability and size selectivity of these clusters. This anchoring technique is expected to be applicable also to other cases, with clear advantages for transition metals that are usually difficult to stabilize.

The effect of different transition metal dopants on the magnetic properties of armchair antimonene, phosphorene, and their binary nanoribbons

Binary antimonene-phosphorene, a novel two-dimensional material with a medium band gap, high carrier mobility, and environmental stability, has attracted growing attention due to its wide applications in spintronics. Using density functional theory, we comprehensively investigate and compare the structural and magnetic properties of armchair Sb, P, and binary SbP nanoribbons doped with 3d transition metal atoms (Ti, Cr, Mn, Fe, Co, and Ni) with various concentrations of dopant atoms. We investigated magnetic properties, including magnetic moment, spin polarization, and spin density. It was found that the magnetic properties for single P and Sb nanoribbons do not depend on the substitution position of TM atoms. In contrast, for binary SbP nanoribbons, the substitution of TM atoms in P or Sb positions leads to different behaviors. For example, the magnetization for substitution of Fe and Co atoms in the P position of the binary SbP nanoribbon will be greater than those of the Sb position, but for other impurity atoms, the magnetization of the binary SbP nanoribbon does not strongly depend on the substitution position. The results show that with increasing the number of impurity atoms in the nanoribbon, the magnetic moment increases, except for the nickel atom in the Sb position of the SbP nanoribbon, in which the nanoribbon prefers the ferrimagnetic state. Also, the spin density results show that the magnetism of the doped systems is mainly attributed to the dopant atoms, and the neighboring atoms have a negligible contribution. The findings of antimonene-phosphorene nanoribbons doped with TM atoms may have potential applications in spintronic nanodevices.

Gas-Phase-Induced Engineering for Fabrication of 3D Hierarchical Porous Nickel and Its Application toward High-Performance Supercapacitors.

Commercial nickel foam (NF), which is composed of numerous interconnected ligaments and hundred-micron pores, is widely acknowledged as a current collector/electrode material for catalysis, sensing, and energy storage applications. However, the commonly used NF often does not work satisfactorily due to its smooth surface and hollow structure of the ligaments. Herein, a gas-phase-induced engineering, two-step gaseous oxidation-reduction (GOR) is presented to directly transform the thin-walled hollow ligament of NF into a three-dimensional (3D) nanoporous prism structure, resulting in the fabrication of a unique hierarchical porous nickel foam (HPNF). This 3D nanoporous architecture is achieved by utilizing the spontaneous reconstruction of nickel atoms during volume expansion and contraction in the GOR process. The process avoids the involution of acid-base corrosion and sacrificial components, which are facile, environmentally friendly, and suitable for large-scale fabrication. Furthermore, MnO2 is electrochemically deposited on the HPNF to form a supercapacitor electrode (HPNF/MnO2). Because of the fully open structure for ion transport, superhydrophilic properties, and the increased contact area between MnO2 and the current collector, the HPNF/MnO2 electrode exhibits a high specific capacitance of 997.5 F g-1 at 3 A g-1 and remarkable cycling stability with 99.6% capacitance retention after 20000 cycles in 0.1 M Na2SO4 electrolyte, outperforming most MnO2-based supercapacitor electrodes.

Highly Dispersed Ni Atoms and O3 Promote Room-Temperature Catalytic Oxidation.

Transition metal oxides are promising catalysts for catalytic oxidation reactions but are hampered by low room-temperature activities. Such low activities are normally caused by sparse reactive sites and insufficient capacity for molecular oxygen (O2) activation. Here, we present a dual-stimulation strategy to tackle these two issues. Specifically, we import highly dispersed nickel (Ni) atoms onto MnO2 to enrich its oxygen vacancies (reactive sites). Then, we use molecular ozone (O3) with a lower activation energy as an oxidant instead of molecular O2. With such dual stimulations, the constructed O3-Ni/MnO2 catalytic system shows boosted room-temperature activity for toluene oxidation with a toluene conversion of up to 98%, compared with the O3-MnO2 (Ni-free) system with only 50% conversion and the inactive O2-Ni/MnO2 (O3-free) system. This leap realizes efficient room-temperature catalytic oxidation of transition metal oxides, which is constantly pursued but has always been difficult to truly achieve.

Nickel-catalysed enantioselective alkene dicarbofunctionalization enabled by photochemical aliphatic C–H bond activation

The development of novel strategies to rapidly construct complex chiral molecules from readily available feedstocks is a long-term pursuit in the chemistry community. Radical-mediated alkene difunctionalizations represent an excellent platform towards this goal. However, asymmetric versions remain highly challenging, and more importantly, examples featuring simple hydrocarbons as reaction partners are elusive. Here we report an asymmetric three-component alkene dicarbofunctionalization capitalizing on the direct activation of C(sp3)–H bonds through the combination of photocatalysed hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for installing two vicinal carbon–carbon bonds across alkenes in an atom-economic fashion, providing a wide array of high-value chiral α-aryl/alkenyl carbonyls and phosphonates, as well as 1,1-diarylalkanes from ubiquitous alkane, ether and alcohol feedstocks. This method exhibits operational simplicity, broad substrate scope and excellent regioselectivity, chemoselectivity and enantioselectivity. The compatibility with bioactive motifs and expedient synthesis of pharmaceutically relevant molecules highlight the synthetic potential of this protocol.

Engineering of uniform dispersed Ni nanoparticles supported on carbon nanosheets for reduction of Nitroarenes to Aminoarenes

Facile synthesis of uniform supported metal catalysts is of great significance yet remains challenging for sustainable catalysis. Herein, a nanopore confinement strategy is developed to efficiently anchor metal ions in suitably sized polymer nanopores via strong coordinate bonds and ensure successful fabrication of uniform carbon-supported metal nanoparticles. Specifically, Ni2+-coordinated polydopamine (PDA) mesoporous layer was coated on GO nanosheets for the confinement of the nickel atoms (GO@PDA-Ni-x, x means pore size of PDA layer), resulting Ni@C-x nanosheets catalysts with uniformly dispersed Ni nanoparticles after pyrolysis in H2/Ar atmosphere. Characterization methods including SEM, TEM, and XPS reveal the intrinsic formation mechanism and physicochemical details. In the catalytic reaction of NaBH4-mediated hydrogenation of 4-nitrophenol (4-NP), the obtained Ni/C-10 exhibits exceptional catalytic performance with a rapid rate constant (0.686 min−1), outperforming many previously reported metal catalysts. Moreover, the catalytic activity remains almost unchanged after being recycled five times, proving the prominent stability. This work opens up an innovative avenue for rational design and synthesis of supported catalysts with controllable size for broad catalytic applications.

Molecular dynamics study of the interface fine structure and mechanical properties of Ni@SWCNT/Cu nanocrystalline composite materials

The use of carbon nanotubes (CNTs) as reinforcing phase in copper-based composites has been extensively studied. However, controlling the synthesis interface structure and explaining the nanoscale interface bonding mechanism through experimental methods still poses challenges. In this study, a model of single-walled carbon nanotube nanocrystalline copper composite was established based on molecular dynamics (MD) simulations to investigate the effects of grain boundaries and dislocations on the composite material. It was found that the addition of nickel atoms improved the interface bonding between carbon nanotubes and the copper matrix, reducing vacancies at the interface. Ni@SWCNT/Cu exhibited better mechanical properties. Structural changes and defect evolution during deformation were studied. The ultimate tensile strength of SWCNT/Cu and Ni@SWCNT/Cu composites increased by 62.29 % and 68.78 % respectively compared to nanocrystalline copper, while the Young's modulus increased by 25.91 % and 32.48 % respectively; moreover, the Young's modulus of these two composites increased by 45.24 % and 49.42 % respectively. Ni@SWCNT/Cu had the lowest wear rate and friction coefficient, with a minimum wear rate of 0.0055 and a minimum friction coefficient of 0.67, demonstrating better wear resistance. The effects of different friction speeds and depths of indentation on the friction performance of the composite materials were also investigated.

Local CO Generator Enabled by a CO-Producing Core for Kinetically Enhancing Electrochemical CO2 Reduction to Multicarbon Products.

CO plays a crucial role as an intermediate in electrochemical CO2 conversion to generate multicarbon (C2+) products. However, optimizing the coverage of the CO intermediate (*CO) to improve the selectivity of C2+ products remains a great challenge. Here, we designed a hierarchically structured double hollow spherical nanoreactor featuring atomically dispersed nickel (Ni) atoms as the core and copper (Cu) nanoparticles as the shell, which can greatly improve the catalytic activity and selectivity for C2+ compounds. Within this configuration, CO generated at the active Ni sites on the inner layer accumulates in the cavity before spilling over neighboring Cu sites on the outer layer, thus enhancing CO dimerization within the cavity. Notably, this setup achieves a sustained faradaic efficiency of 74.4% for C2+ production, with partial current densities reaching 337.4 mA cm-2. In situ Raman spectroscopy and finite-element method (FEM) simulations demonstrate that the designed local CO generator can effectively increase the local CO concentration and restrict CO evolution, ultimately boosting C-C coupling. The hierarchically ordered architectural design represents a promising solution for achieving highly selective C2+ compound production in the electroreduction of CO2.

Loading of Single Atoms of Iron, Cobalt, or Nickel to Enhance the Electrocatalytic Hydrogen Evolution Reaction of Two-Dimensional Titanium Carbide.

The rational design of advanced electrocatalysts at the molecular or atomic level is important for improving the performance of hydrogen evolution reactions (HERs) and replacing precious metal catalysts. In this study, we describe the fabrication of electrocatalysts based on Fe, Co, or Ni single atoms supported on titanium carbide (TiC) using the molten salt method, i.e., TiC-FeSA, TiC-CoSA, or TiC-NiSA, to enhance HER performance. The introduction of uniformly distributed transition-metal single atoms successfully reduces the overpotential of HERs. Overpotentials of TiC-FeSA at 10 mA cm-2 are 123.4 mV with 61.1 mV dec-1 Tafel slope under acidic conditions and 184.2 mV with 85.1 mV dec-1 Tafel slope under alkaline conditions, which are superior to TiC-NiSA and TiC-CoSA. TiC samples loaded with transition-metal single atoms exhibit high catalytic activity and long stability under acidic and basic conditions. Density functional theory calculations indicate that the introduction of transition-metal single atoms effectively reduces the HER barrier of TiC-based electrocatalysts.