Metal Atoms Research Articles

First-principles study of hydrogen sulfide decomposition on Sc-Ti3C2O2 single-atom catalyst.

Hydrogen sulfide gas poses significant risks to both human health and the environment, with the potential to induce respiratory and neurological effects, and a heightened fatality risk at elevated concentrations. This article investigates the catalytic decomposition of H2S on a Sc-Ti3C2O2 single-atom catalyst(SAC) using the density functional theory-based first-principles calculation approach. Initially, the adsorption behavior of H2S on Ti3C2O2-MXene was examined, revealing weak physical adsorption between them. Subsequently, the transition metal atom Sc was introduced to the Ti3C2O2 surface, and its stability was studied, demonstrating high stability. Further exploration of H2S adsorption on Sc-Ti3C2O2 revealed direct dissociation of H2S gas molecules into HS* and H*, with HS* binding to Sc and H* binding to O on the Ti3C2O2 surface, resulting in OH groups. Using the transition state search method, the dissociation of H2S molecules on the SAC's surface was investigated, revealing a potential barrier of 2.45eV for HS* dissociation. This indicates that the H2S molecule can be dissociated into H2 and S with the action of the Sc-Ti3C2O2 SAC. Moreover, the S atom left on the catalyst surface can aggregate to produce elemental S8, desorbing on the catalyst surface, completing the catalytic cycle. Consequently, the Sc-Ti3C2O2 SAC is poised to be an efficient catalyst for the catalytic decomposition of H2S. The Dmol3 module in Materials Studio software based on density functional theory is used in this study. The generalized gradient approximation method GGA-PBE is used for the exchange-correlation function. The complete LST/QST and the NEB methods in the Dmol3 module were used to study the minimum energy path of the dissociation of hydrogen sulfide molecules on the catalyst surface.

Au-doped PtCu2 nanonetworks with interface-rich for enhancing methanol electro-oxidation performance

Regulating the near-surface structure of platinum-based alloys by inserting transition metal atoms can significantly improve the electro-oxidative performance of small organic molecules. So far, it is rarely reported that a small amount of Au element is introduced into the interior of Pt-based alloys as an active auxiliary to adjust the electrocatalytic activity and stability of Pt-based alloys with special morphologies. Herein, a stable three-dimensional (3D) Au-doped PtCu2/C (Au-PtCu2/C) catalyst with nanonetwork structure and abundant interfaces has been successfully developed, in which the oxyphilic Cu atoms and stable Au atoms are implanted into the whole and inside of the Pt-based nanonetwork, respectively. Detailed physical characterizations of the Au-PtCu2/C catalyst illustrate that the insertion of Au atoms generates core-shell-like nanonetwork, highly-open structure, strong electronic effect, and sufficient active sites. The well-designed Au-PtCu2/C catalyst exhibits superior mass activity (MA) of 2355 mA·mgPt−1 and long-term durability of 500 cycles toward methanol oxidation reaction (MOR) in an acidic medium. Notably, the MA of the Au-PtCu2/C catalyst is 7.3 folds and 1.3 folds that of the Pt/C (322 mA·mgPt−1) and PtCu2/C (1821 mA·mgPt−1) catalysts, respectively. The kinetic and thermodynamics studies indicate that the Au-PtCu2/C catalyst is superior to PtCu2/C and Pt/C catalysts in reducing the electrochemical activation energy of MOR, promoting the mass transfer of methanol molecules, and enhancing electronic conductivity. This work proposes an advanced strategy to fabricate efficient and durable electrocatalyst with excellent electrocatalytic MOR performance, thereby enabling catalysts with special morphology to have greater application potential in direct methanol fuel cell.

Single-Atom Substituents in Copper Surfaces May Adsorb Multiple CO Molecules.

Copper is a good CO2 electroreduction catalyst as products beyond CO form, but efficiency and selectivity is low. Experiments have shown that an admixture of other elements can help, and computational screening studies have pointed out various promising candidates based on the adsorption of a single CO molecule as a descriptor. Our calculations of CO adsorption on surfaces where a first row transition metal atom replaces a Cu atom show that multiple CO molecules, not just one, bind to the substitutional atom. For Fe, Co, and Ni atoms, a decrease in binding energy is found, but the reverse trend, namely, increasing bond strength, is found for V, Cr, and Mn and the first three CO molecules. Magnetic moment, charge, and position of the substitutional atom are also strongly affected by the CO adsorption in most cases. Magnetic moment is stepwise reduced to zero, and the outward displacement of the substitutional atom increased.

Formation and growth of transition metal carbides in ferrite

Carbide nano-precipitates are commonly used to improve mechanical properties of steel. It has been experimentally observed that TiC, NbC, and VC carbide precipitates initially form as ‘plate-like’ particles oriented in the {100} planes of the ferrite lattice. These platelets share similarities with Guinier-Preston zones in Al-Cu alloys.The clustering of group IV and V transition metal atoms (M = Ti, Zr, Hf, V, Nb, Ta) in ferrite is studied using density functional theory. It is deduced that the transition metal carbides all form in a similar way. Furthermore, the transition from an initial M–C cluster to a NaCl-structured platelet to a NaCl-structured precipitate is examined through atomistic simulations using Modified Embedded Atom Method potentials. A route is established along which transition metal carbides form and transform into precipitates that possess the Baker-Nutting orientation relation with the ferrite matrix.

Structure Effects of Ligands in Gold-Ligand Complexes for Controlled Formation of Gold Nanoclusters.

Metal nanoclusters (NCs) are a special class of nanoparticles composed of a precise number of metal atoms and ligands. Because the proportion of ligands to metal atoms is high in metal NCs, the ligand type determines the physical properties of metal NCs. Furthermore, ligands presumably govern the entire formation process of the metal NCs. However, their roles in the synthesis, especially as factors in the uniformity of metal NCs, are not understood. It is because the synthetic procedure of metal NCs is highly convoluted. The synthesis is initiated by the formation of various metal-ligand complexes, which have different numbers of atoms and ligands, resulting in different coordinations of metal. Moreover, these complexes, as actual precursors to metal NCs, undergo sequential transformations into a series of intermediate NCs before the formation of the desired NCs. Thus, to resolve the complicated synthesis of metal NCs and achieve their uniformity, it is important to investigate the reactivity of the complexes. Herein, we utilize a combination of mass spectrometry, density functional theory, and electrochemical measurements to understand the ligand effects on the reactivity of AuI-thiolate complexes toward the reductive formation of Au NCs. We discover that the stability of the complexes can be increased by either van der Waals interactions induced by the long carbon chain of ligands or by non-thiol functional groups in the ligands, which additionally coordinate with AuI in the complexes. Such structural effects of thiol ligands determine the reduction reactivity of the complexes and the amount of NaBH4 required for the controlled synthesis of the Au NCs.

Engineering the Activity and Stability of the Zn-MOF Catalyst via the Interaction of Doped Zr with Zn.

Metallic atoms within metal-organic framework (MOF) materials exhibit a distinctive and adaptable coordination structure. The three-dimensional (3D) pore configuration of MOFs enables the complete exposure of metal active sites, rendering them prevalent in various catalytic reactions. In this study, zinc (Zn) atoms within Zn-based MOF materials, characterized by an abundance of valence electrons, are utilized for the transesterification of dimethyl carbonate (DMC). Additionally, the introduction of zirconium (Zr) effectively addresses the susceptibility of the MOFs' crystal structure to dissolution in organic solvents. The formulated catalyst, Zn-10%Zr-MOF(300), demonstrates remarkable catalytic performance with 91.5% DMC selectivity, 61.9% propylene carbonate (PC) conversion, and 56.6% DMC yield. Impressively, the catalyst maintains its high performance over five cycles. Results indicate that Zr interacts with Zn, forming new coordination bonds and enhancing the catalyst crystal structure stability. Moreover, electron transfer intensifies the alkalinity of the active Zn atoms, enhancing the overall catalyst performance. This research informs the development of transesterification heterogeneous catalysts and broadens the application scope of MOF catalysts.

Effect of biaxial tensile-compressive deformation on the optoelectronic properties of monolayers of MoTe2 with adsorbed alkali metals X (X = Li, Na, K, Rb, Cs): a first principles

Abstract Based on a first-principles approach, the effects of tensile-compression deformation on the structural stability, electronic structure, and optical properties of monolayers of MoTe2 adsorbed with alkali metal atoms X (X = Li, Na, K, Rb or Cs) were calculated. It was found that the structural stability of the MoTe2 monolayer after adsorption of Li atoms was the most stable, with the smallest adsorption and formation energies and the smallest adsorption height. The movement of the Fermi energy toward the conduction band makes the system an n-type semiconductor. Subsequently, the adsorbed Li-MoTe2 monolayers were selected for tensile-compressive deformation, and with the increase of tensile deformation, the band gap decreased to zero at 10% deformation and exhibited metallic properties. As compressive deformation grows, the band gap shifts from direct to indirect, and metallic characteristics emerge when deformation approaches -10%. The Te-s and Te-p orbital electrons near the Fermi energy level and Mo-d orbitals make the main contribution to the adsorbed alkali metal molybdenum ditelluride system. In terms of optical characteristics, the MoTe2 system after alkali metal adsorption deformation is blue-shifted/ red-shifted at the absorption/reflection peak. These discoveries may help to broaden the possible applications of MoTe2 in low-dimensional electron-emitting devices.

Metalloporphyrins as Building Blocks for Quantum Information Science

AbstractThe intrinsic quantum nature of molecules opens exciting opportunities for developing the field of quantum information science. In this context, porphyrins stand out as ideal building blocks for quantum technologies thanks to their unique optical and electrical properties as well as their capacity to accommodate metal atoms and ions. This review bridges the chemistry and physics of porphyrins, providing an overview of recent advances in porphyrin‐based molecular qubits. Starting from qubits, the review explores the potential of porphyrin units to combine, leading to the formation of quantum logic gates and hierarchical higher‐dimensional structures. Next, the exploitation of porphyrins' unique photophysical properties for realizing long‐lived high spin states is examined. These states are promising for the photogeneration of multi‐level systems and the optical initialization and control of molecular qubits. With a critical eye on the current state‐of‐the‐art, the review elucidates the future perspectives of porphyrins for advancing quantum technologies.

Barbituric acid‐derived azo dye metal complexes: Synthesis, characterization, DFT, and antimicrobial analysis

Two novel metal complexes, C1 and C2, were synthesized through the reaction of an azo dye ligand, obtained by coupling 4‐chloroaniline with 1,3‐dimethyl barbituric acid. The structure of the ligand was confirmed using Fourier‐transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR). UV–Vis spectroscopy was employed to assess the ligand's sensing ability toward six different metal ions. Comprehensive characterization of the synthesized metal complexes was conducted using elemental analysis, X‐ray photoelectron spectroscopy (XPS), thermogravimetric analysis–difference thermogravimetry (TGA‐DTG), FTIR, UV–Vis spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and single‐crystal X‐ray diffraction (SC‐XRD). X‐ray analysis revealed octahedral coordination geometry with a 2:1 ligand‐to‐metal ratio and dimethylformamide (DMF) coordination with the metal atom in both complexes. Hirshfeld analysis and 2D fingerprint plots were employed to investigate supramolecular and intermolecular interactions within the crystal system. Density functional theory (DFT/B3LYP) calculations were utilized to compute energy gaps and other important theoretical features. Sensing experiments with tetrabutylammonium fluoride (TBAF) were conducted at a concentration of 1 × 10−5 M. Furthermore, the bioactivity of the synthesized metal complexes and ligand L was evaluated through molecular docking studies against Protein Data Bank (PDB IDs) 4XUY (Staphylococcus aureus) and 3BQW (Aspergillus niger). Also, antimicrobial activity was assessed using the agar well diffusion technique, revealing that complexes C1 and C2 exhibited enhanced antimicrobial activities against the tested organisms compared to the parent azo dye ligand. The computational and experimental bioactivity data are in good agreement with each other.

Synergetic Manipulation Mechanism of Single-Atom M-N4 and M-OH (M = Mn, Fe, Co, Ni) Sites for Ozone Activation: Theoretical Prediction and Experimental Verification.

Carbon-based single-atom catalysts (SACs) have been gradually introduced in heterogeneous catalytic ozonation (HCO), but the interface mechanism of O3 activation on the catalyst surface is still ambiguous, especially the effect of a surface hydroxyl group (M-OH) at metal sites. Herein, we combined theoretical calculations with experimental verifications to comprehensively investigate the O3 activation mechanisms on a series of conventional SAC structures with N-doped nanocarbon substrates (MN4-NCs, where M = Mn, Fe, Co, Ni). The synergetic manipulation effect of the metal atom and M-OH on O3 activation pathways was paid particular attention. O3 tends to directly interact with the metal atom on MnN4-NC, FeN4-NC, and NiN4-NC catalysts, among which MnN4-NC has the best catalytic activity for its relatively lower activation energy barrier of O3 (0.62 eV) and more active surface-adsorbed oxygen species (Oads). On the CoN4-NC catalyst, direct interaction of O3 with the metal site is energetically infeasible, but O3 can be activated to generate Oads or HO2 species from direct or indirect participation of M-OH sites. The experimental results showed that 90.7 and 82.3% of total organic carbon (TOC) was removed within 40 min during catalytic ozonation of p-hydroxybenzoic acid with MnN4-NC and CoN4-NC catalysts, respectively. Phosphate quenching, catalyst characterization, and EPR measurement further supported the theoretical prediction. This contribution provides fundamental insights into the O3 activation mechanism on SACs, and the methods and ideals could be helpful for future studies of environmental catalysis.

Insight of hydrogen evolution reaction in slab SnO2 loaded with transition metal atoms

The utilization of hydrogen energy has emerged as a promising solution for clean and sustainable energy sources. The development of cost-effective catalysts with high activity and stability is crucial for efficient hydrogen production. In this work, we investigated the hydrogen evolution reaction (HER) catalytic activity of single transition metal atom (TM = V, Cr, Mn, Fe, Co, Ni) on slab SnO2 by using density functional theory. Our results revealed that the catalytic activity of the slab SnO2 can be significantly enhanced by loading the transition atom. By calculating the Gibbs free energies and exchange current densities in different adsorption configurations of TM-SnO2, single-atom catalyst (SAC) of Mn-loaded SAC exhibits excellent catalytic performance, characterized by a low Gibbs free energy barrier (−0.05 eV). Introducing a TM on the SnO2 surface breaks its local symmetry, while the strong coupling between the metal and H atoms enhances catalytic performance. The synergetic effect of symmetry breaking and metal-H interaction boosts overall catalytic activity. This work not only proposes a novel non-platinum HER catalyst based on SnO2 but also lays a solid foundation for future applications of SnO2-based catalysts.

Constructing Single-Atom Active Sites Embedded in Hexagonal Boron Nitride for Adsorption and Sensing of Lithium Battery Thermal Runaway Gases.

The utilization and selectivity of single atoms have garnered significant attention among researchers. However, they are easy to agglomerate because of their high surface energy. To overcome this challenge, it is crucial to seek suitable carriers to anchor single metal atoms to achieve optimal performance. In this work, the structures of transition metal single atoms embedded in hexagonal boron nitride (MB2N2, M = Fe, Co, Ni, Cu, Zn) are constructed and used for the adsorption and sensing of lithium battery thermal runaway gases (H2, CO, CO2, CH4) through the DFT method. The adsorption behavior of MB2N2 was evaluated through the adsorption energy, sensitivity, and recovery time. The calculation results indicate that CoB2N2 exhibits strong adsorption capacity for both H2 and CO. The sensitivity of FeB2N2 toward CO is as high as 3.232 × 1016. Subsequently, the adsorption mechanism was studied through TDOS and PDOS, and the results showed that hybridization between orbitals enhanced the gas adsorption performance. This study presents novel approaches for designing single-atom carriers and developing MB2N2 sensors for detecting lithium battery thermal runaway gases.

A lithium-aluminium heterobimetallic dimetallocene.

Homobimetallic dimetallocenes exhibiting two identical metal atoms sandwiched between two η5 bonded cyclopentadienyl rings is a narrow class of compounds, with representative examples being dizincocene and diberyllocene. Here we report the synthesis and structural characterization of a heterobimetallic dimetallocene, accessible through heterocoupling of lithium and aluminylene fragments with pentaisopropylcyclopentadienyl ligands. The Al-Li bond features a high ionic character and profits from attractive dispersion interactions between the isopropyl groups of the cyclopentadienyl ligands. A key synthetic step is the isolation of a cyclopentadienylaluminylene monomer, which also enables the structural characterization of this species. In addition to their structural authentication by single-crystal X-ray diffraction analysis, both compounds were characterized by multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, reactivity studies of the lithium-aluminium heterobimetallic dimetallocene with an N-heterocyclic carbene and different heteroallenes were performed and show that the Al-Li bond is easily cleaved.

Silica Confinement for Stable and Magnetic Co−Cu Alloy Nanoparticles in Nitrogen‐Doped Carbon for Enhanced Hydrogen Evolution

AbstractAmmonia borane (AB) with 19.6 wt % H2 content is widely considered a safe and efficient medium for H2 storage and release. Co‐based nanocatalysts present strong contenders for replacing precious metal‐based catalysts in AB hydrolysis due to their high activity and cost‐effectiveness. However, precisely adjusting the active centers and surface properties of Co‐based nanomaterials to enhance their activity, as well as suppressing the migration and loss of metal atoms to improve their stability, presents many challenges. In this study, mesoporous‐silica‐confined bimetallic Co−Cu nanoparticles embedded in nitrogen‐doped carbon (CoxCu1−x@NC@mSiO2) were synthesized using a facile mSiO2‐confined thermal pyrolysis strategy. The obtained product, an optimized Co0.8Cu0.2@NC@mSiO2 catalyst, exhibits enhanced performance with a turnover frequency of 240.9 molH2 ⋅ molmetal ⋅ min−1 for AB hydrolysis at 298 K, surpassing most noble‐metal‐free catalysts. Moreover, Co0.8Cu0.2@NC@mSiO2 demonstrates magnetic recyclability and extraordinary stability, with a negligible decline of only 0.8 % over 30 cycles of use. This enhanced performance was attributed to the synergistic effect between Co and Cu, as well as silica confinement. This work proposes a promising method for constructing noble‐metal‐free catalysts for AB hydrolysis.

Silica Confinement for Stable and Magnetic Co-Cu Alloy Nanoparticles in Nitrogen-Doped Carbon for Enhanced Hydrogen Evolution.

Ammonia borane (AB) with 19.6 wt % H2 content is widely considered a safe and efficient medium for H2 storage and release. Co-based nanocatalysts present strong contenders for replacing precious metal-based catalysts in AB hydrolysis due to their high activity and cost-effectiveness. However, precisely adjusting the active centers and surface properties of Co-based nanomaterials to enhance their activity, as well as suppressing the migration and loss of metal atoms to improve their stability, presents many challenges. In this study, mesoporous-silica-confined bimetallic Co-Cu nanoparticles embedded in nitrogen-doped carbon (CoxCu1-x@NC@mSiO2) were synthesized using a facile mSiO2-confined thermal pyrolysis strategy. The obtained product, an optimized Co0.8Cu0.2@NC@mSiO2 catalyst, exhibits enhanced performance with a turnover frequency of 240.9 molH2 ⋅ molmetal ⋅ min-1 for AB hydrolysis at 298 K, surpassing most noble-metal-free catalysts. Moreover, Co0.8Cu0.2@NC@mSiO2 demonstrates magnetic recyclability and extraordinary stability, with a negligible decline of only 0.8 % over 30 cycles of use. This enhanced performance was attributed to the synergistic effect between Co and Cu, as well as silica confinement. This work proposes a promising method for constructing noble-metal-free catalysts for AB hydrolysis.

Effect of the nitrogen/carbon ratio in the organic ligand of a nickel single-atom catalyst on its electrochemical activity in CO2 reduction

Simple, large-scale synthesis of metal single-atom catalysts (SACs) is limited by the aggregation of metal atoms on the support material surface. The N atoms in small organic ligands (SOLs) can anchor single metal atoms, affording abundant surface-active sites. In this study, we investigated the effect of the nitrogen/carbon ratio (N/C) in SOLs on the properties of the resultant Ni single-atom confined nitrogen-doped carbon black (Ni-NCB). The N/C ratio affected the thermal stability of Ni-NCB_N/Cs during carbonization, and the optimal Ni-NCB (Ni-NCB_0.5) was synthesized with the SOL 2-methylimidazole. Ni-NCB_0.5 achieved a CO partial current density of > 500 mA cm–2 and high CO Faradaic efficiency (96.4 %) in the CO2 reduction reaction. The 3- and 4-cell stack systems with Ni-NCB_0.5 (25 cm2 area per unit cell) exhibited an overall current of 10 A, high CO selectivity (> 96.0 %), and long-term stability (50 h). This synthetic strategy for SACs can be commercialized and even extended to other industrial electrocatalysts.

Tuning structural and electronic properties of metal-organic framework 5 by metal substitution and linker functionalization.

The chemical flexibility of metal-organic frameworks (MOFs) offers an ideal platform to tune structure and composition for specific applications, from gas sensing to catalysis and from photoelectric conversion to energy storage. This variability gives rise to a large configurational space that can be efficiently explored using high-throughput computational methods. In this work, we investigate from first principles the structural and electronic properties of MOF-5 variants obtained by replacing Zn with Be, Mg, Cd, Ca, Sr, and Ba and by functionalizing the originally H-passivated linkers with CH3, NO2, Cl, Br, NH2, OH, and COOH groups. To build and analyze the resulting 56 structures, we employ density-functional theory calculations embedded in an in-house developed library for automatized calculations. Our findings reveal that structural properties are mainly defined by metal atoms and large functional groups, which distort the lattice and modify coordination. The formation energy is largely influenced by functionalization and enhanced by COOH and OH groups, which promote the formation of hydrogen bonds. The charge distribution within the linker is especially influenced by functional groups with electron-withdrawing properties, while the metal nodes play a minor role. Likewise, the bandgap size is crucially determined by ligand functionalization. The smallest gaps are found with NH2 and OH groups, which introduce localized orbitals at the top of the valence band. This characteristic makes these functionalizations particularly promising for the design of MOF-5 variants with enhanced gas uptake and sensing properties.

The structure, magnetism and mechanical properties of L21-type full-Heusler alloy Cr2ZrSi: A first-principles study

Heusler alloy is a widely studied spintronic material in recent years, which has played a huge role in the field of spintronic devices due to its high spin polarization and high Curie temperature. Using first-principles calculation to predict the basic properties of Heusler alloy can not only save experimental costs and time but also provide a reliable theoretical basis for experimental research. This study used a first-principles calculation to study the magnetic and mechanical properties of full-Heusler alloy Cr2ZrSi with an L21-type structure. The research results indicate that the alloy is a half-metallic ferromagnetic material with a theoretical value of 100% spin polarization. The magnetism mainly comes from the asymmetric spin contribution of d-orbital electrons of transition metal atoms and their hybridization. At the same time, this complex hybridization coupling process is also a possible reason for the half-metallic band gaps. In terms of mechanical properties, the Cr2ZrSi alloy exhibits good ductility and anisotropy, with a Debye temperature of 303.848K. Our theoretical research results provide more choices and theoretical basis for subsequent experimental research.

Catalysts with Trimetallic Sites on Graphene-like C2N for Electrocatalytic Nitrogen Reduction Reaction: A Theoretical Investigation.

Electrocatalytic nitrogen reduction reaction (NRR) is a green and highly efficient way to replace the industrial Haber-Bosch process. Herein, clusters consisting of three transition metal atoms loaded on C2N as NRR electrocatalysts are investigated using density functional theory (DFT). Meanwhile, Ca was introduced as a promoter and the role of Ca in NRR was investigated. It was found that Ca anchored to the catalyst can act as an electron donor and effectively promote the activation of N2 on M3. In both M3@C2N and M3Ca@C2N (M = Fe, Co, Ni), the limiting potential (UL) is less negative than that of the Ru(0001) surface and has the ability to suppress the competitive hydrogen evolution reaction (HER). Among them, Fe3@C2N is suggested to be the most promising candidate for NRR with high thermal stability, strong N2 adsorption ability, low limiting potential, and good NRR selectivity. The concepts of trimetallic sites and alkaline earth metal promoters in this work provide theoretical guidance for the rational design of atomically active sites in electrocatalytic NRR.

Transition‐Metal‐Doped TiO2 Nanorods with High‐Visible‐Light Response via a Simple Hydrothermal Method

Transition‐metal‐ion doping is an effective method to shorten bandgap and enhance visible‐light absorption of TiO2, but there are still some serious challenges for most doping technologies, such as nonuniform doping, severe lattice damages, metal atoms agglomeration, and inactivated impurities. Herein, a simple and universal hydrothermal method is developed to realize the effective transition‐metal ions doping of TiO2 (including Fe, Co, Mn, Cu, V, and Cr). The photoelectrochemical water splitting performances of Cr‐doped TiO2 nanorods with multifarious Cr ion valence states (Cr3+ or Cr6+ ions), various Cr‐ion concentrations, with or without oxygen vacancy activation are emphatically and systematically studied. Experiments and theoretical calculations demonstrate that the remarkably enhanced carrier separation and injection efficiencies are the key factors to improve the visible‐light photoactivity, benefiting from the homogeneous distribution of impurity atoms and the incorporation of oxygen vacancies. The Cr3+‐ion‐doped TiO2 nanorod arrays with oxygen vacancy activation (Cr3+/Ov–TiO2) displays an impressive incident photon‐to‐electron conversion efficiency of 5.4% at 450 nm visible light, far superior to the pure TiO2 of 0.03%. Furthermore, no obvious photocurrent decay is observed in the Cr3+/Ov–TiO2 photoanode after 12 h continuous light illumination.