Cationic States Research Articles

Rydberg electron stabilizes the charge localized state of the diamine cation

A previous controversial discussion regarding the interpretation of Rydberg spectra of gaseous dimethylpiperazine (DMP) as showing the co-existence of a localized and delocalized mixed-valent DMP+ radical cation is revisited. Here we show by high-level quantum-chemical calculations that an apparent barrier separating localized and delocalized DMP+ minima in previous multi-reference configuration-interaction (MRCI) calculations and in some other previous computations were due to unphysical curve crossings of the reference wave functions. These discontinuities on the surface are removed in state-averaged MRCI calculations and with some other, orthogonal high-level approaches, which do not provide a barrier and thus no localized minimum. We then proceed to show that in the actually observed Rydberg state of neutral DMP the 3s-type Rydberg electron binds more strongly to a localized positive charge distribution, generating a localized DMP* Rydberg-state minimum, which is absent for the DMP+ cation. This work presents a case where interactions of a Rydberg electron with the underlying cationic core alter molecular structure in a fundamental way.

UV wavelength-dependent photoionization quantum yields for the dark 1nπ* state of aqueous thymidine.

Despite the important role of the dark 1nπ* state in the photostability of thymidine in aqueous solution, no detailed ultraviolet (UV) wavelength-dependent investigation of the 1nπ* quantum yield (QY) in aqueous thymidine has been experimentally performed. Here, we investigate the wavelength-dependent photoemission spectra of aqueous thymidine from 266.7 to 240 nm using liquid-microjet photoelectron spectroscopy. Two observed ionization channels are assigned to resonant ionizations from 1ππ* to the cationic ground state D0 (π-1) and 1nπ* to the cationic excited state D1 (n-1). The weak 1nπ* → D1 ionization channel appears due to ultrafast 1ππ* → 1nπ* internal conversion within the pulse duration of ∼180 fs. The obtained 1nπ* quantum yields exhibit a strong wavelength dependence, ranging from 0 to 0.27 ± 0.01, suggesting a hitherto uncharacterized 1nπ* feature. The corresponding vertical ionization energies (VIEs) of D0 and D1 of aqueous thymidine are experimentally determined to be 8.47 ± 0.12 eV and 9.22 ± 0.29 eV, respectively. Our UV wavelength-dependent QYs might indicate that different structural critical points to connect the multidimensional 1ππ*/1nπ* conical intersection seam onto the multidimensional potential energy surface of the 1ππ* state might exist and determine the relaxation processes of aqueous thymidine upon UV excitation.

Evidencing an elusive conical intersection in the dissociative photoionization of methyl iodide.

The valence-shell dissociative photoionization of methyl iodide (CH3I) is studied using double imaging photoelectron photoion coincidence (i2 PEPICO) spectroscopy in combination with highly-tunable synchrotron radiation from synchrotron SOLEIL. The experimental results are complemented by new high-level ab initio calculations of the potential energy curves of the relevant electronic states of the methyl iodide cation (CH3I+). An elusive conical intersection is found to mediate internal conversion from the initially populated first excited state, CH3I+(Ã2A1), into the ground cationic state, leading to the formation of methyl ions (CH3+). The reported threshold photoelectron spectrum for CH3+ reveals that the ν5 scissors vibrational mode promotes the access to this conical intersection and hence, the transfer of population. An intramolecular charge transfer takes place simultaneously, prior to dissociation. Upon photoionization into the second excited cationic state, CH3I+(B̃2E), a predissociative mechanism is shown to lead to the formation of atomic I+.

Dynamics of carbene formation in the reaction of methane with the tantalum cation in the gas phase.

The controlled activation of methane has drawn significant attention throughout various disciplines over the last few decades. In gas-phase experiments, the use of model systems with reduced complexity compared to condensed-phase catalytic systems allows us to investigate the intrinsic reactivity of elementary reactions down to the atomic level. Methane is rather inert in chemical reactions, as the weakening or cleavage of a C-H bond is required to make use of methane as C1-building block. The simplest model system for transition-metal-based catalysts is a mono-atomic metal ion. Only a few atomic transition-metal cations activate methane at room temperature. One of the most efficient elements is tantalum, which forms a carbene and releases molecular hydrogen in the reaction with methane: Ta+ + CH4 → TaCH2+ + H2. The reaction takes place at room temperature due to efficient intersystem crossing from the quintet to the triplet surface, i.e., from the electronic ground state of the tantalum cation to the triplet ground state of the tantalum carbene. This multi-state reactivity is often seen for reactions involving transition-metal centres, but leads to their theoretical treatment being a challenge even today. Chemical reactions, or to be precise reactive collisions, are dynamic processes making their description even more of a challenge to experiment and theory alike. Experimental energy- and angle-differential cross sections allow us to probe the rearrangement of atoms during a reactive collision. By interpreting the scattering signatures, we gain insight into the atomistic mechanisms and can move beyond stationary descriptions. Here, we present a study combining collision energy dependent experimentally measured differential cross sections with ab initio calculations of the minimum energy pathway. Product ion velocity distributions were recorded using our crossed-beam velocity map imaging experiment dedicated to studying transition-metal ion molecule reactions. TaCH2+ velocity distributions reveal a significant degree of indirect dynamics. However, the scattering distributions also show signatures of rebound dynamics. We compare the present results to the oxygen transfer reaction between Ta+ and carbon dioxide, which we recently studied.

Photoelectron spectra of benzene: Can path dependent diabatic surfaces provide unique observables?

While carrying out Beyond Born-Oppenheimer theory based diabatization, the solutions of adiabatic-to-diabatic transformation equations depend on the paths of integration over two-dimensional cross-sections of multi-dimensional space of nuclear degrees of freedom. It is shown that such path-dependent solutions leading to diabatic potential energy surface matrices computed along any two different paths are related through an orthogonal matrix, and thereby, those surface matrices should provide unique observables. While exploring the numerical validity of the theoretical framework, we construct diabatic Hamiltonians for the five low-lying electronic states (X̃2E1g, B̃2E2g, and C̃2A2u) of benzene radical cation (C6H6+) along three different approaches of contour integration over two dimensional nuclear planes constituted by seven non-adiabatically active normal modes. Three different diabatic surface matrices are further employed to generate the photoelectron spectra of the benzene molecule (C6H6). It is interesting to note that the spectral peak positions and intensity patterns for all three cases are almost close to each other and also exhibit very good agreement with the experimental results.

Unveiling the Anomaly of Reduction of Carborane-bis-silylene-Stabilised Silylone/Germylone Leading to Unusual Oxidation of Si0 /Ge0 to SiI /GeI with EDA-NOCV Analyses.

Researchers have successfully isolated Si0 /Ge0 species, termed silylone and germylone, with two lone pairs of electrons on them. These elusive compounds have been stabilised in singlet ground states by using different donor base ligands. Driess et al. in particular have made strides in this area, isolating carborane-bis-silylene-stabilised silylone/germylone and their N+ /Pb analogues. Carborane (C2 B10 H10 ) plays a pivotal role as a redox-active ligand, converting from closo-carborane to nido-carborane with the addition of two electrons. Notably, anomalous oxidation of Si0 /Ge0 centres in carborane-bis-silylene-stabilised species to SiI /GeI has been reported, resulting in the formation of dimeric SiI -SiI /GeI -GeI di-cationic units. The energy decomposition analysis coupled with natural orbital for chemical valence (EDA-NOCV) study focuses on the carborane-bis-silylene ligand in the free state, and its three other species, including silylone/germylone species. Interestingly, it reveals that the carborane unit in an anionic doublet state tends to form one electron-sharing bond and one dative bond with the counter fragment in its cationic doublet state. This helps us to rationalise why the carborane unit undergoes intramolecular electronic rearrangements leading to the formation of a di-anionic carborane unit with a significantly elongated C-C bond (2.38-2.68 Å) and undergoes unusual oxidation of Si0 /Ge0 to SiI /GeI .

Reference-Quality Free Energy Barriers in Catalysis from Machine Learning Thermodynamic Perturbation Theory.

For the first time, we report calculations of the free energies of activation of cracking and isomerization reactions of alkenes that combine several different electronic structure methods with molecular dynamics simulations. We demonstrate that the use of a high level of theory (here Random Phase Approximation-RPA) is necessary to bridge the gap between experimental and computed values. These transformations, catalyzed by zeolites and proceeding via cationic intermediates and transition states, are building blocks of many chemical transformations for valorization of long chain paraffins originating, e.g., from plastic waste, vegetable oils, Fischer-Tropsch waxes or crude oils. Compared with the free energy barriers computed at the PBE+D2 production level of theory via constrained ab initio molecular dynamics, the barriers computed at the RPA level by the application of Machine Learning thermodynamic Perturbation Theory (MLPT) show a significant decrease for isomerization reaction and an increase of a similar magnitude for cracking, yielding an unprecedented agreement with the results obtained by experiments and kinetic modeling.

Reference‐Quality Free Energy Barriers in Catalysis from Machine Learning Thermodynamic Perturbation Theory

AbstractFor the first time, we report calculations of the free energies of activation of cracking and isomerization reactions of alkenes that combine several different electronic structure methods with molecular dynamics simulations. We demonstrate that the use of a high level of theory (here Random Phase Approximation—RPA) is necessary to bridge the gap between experimental and computed values. These transformations, catalyzed by zeolites and proceeding via cationic intermediates and transition states, are building blocks of many chemical transformations for valorization of long chain paraffins originating, e.g., from plastic waste, vegetable oils, Fischer–Tropsch waxes or crude oils. Compared with the free energy barriers computed at the PBE+D2 production level of theory via constrained ab initio molecular dynamics, the barriers computed at the RPA level by the application of Machine Learning thermodynamic Perturbation Theory (MLPT) show a significant decrease for isomerization reaction and an increase of a similar magnitude for cracking, yielding an unprecedented agreement with the results obtained by experiments and kinetic modeling.

Auger-Meitner and X-ray Absorption Spectra of Ethylene Cation: Insight into Conical Intersection Dynamics.

We present a theoretical investigation of the near-edge X-ray absorption fine structure and the Auger-Meitner decay spectra of ethylene and its cation. Herein, we demonstrate that our method, coupled with the nuclear ensemble approach, successfully reproduces the natural bandwidth structure of the experimental resonant Auger-Meitner decay spectra of ethylene, which is not very well reproduced within the Franck-Condon approximation. Furthermore, we analyze the Auger-Meitner decay spectra of the ethylene cation in light of minimum energy conical intersection structures involving the two lowest cationic states (D1 and D0), providing valuable insights into the ultrafast D1/D0 relaxation dynamics. Our results suggest that Auger-Meitner electron spectroscopy can help elucidate the mechanism behind the initial 20 fs of the relaxation dynamics.

Trapping of toxic heavy metals from water by GN–nanocage: Application of nanomaterials for contaminant removal technique

Gallium nitride nanocage (GaN_NC) can select toxic heavy metals from water. Therefore, it has been found a selective competition for metal cations in the GaN_NC. The electromagnetic and thermodynamic attributes of heavy metals cations trapped GaN_NC was depicted by material modeling. The data displays those heavy metals cations-trapped in the GaN_NC system are resistant materials, with the most firm adsorption zone in the center of the cage. Furthermore, charge transfer from GaN_NC to the heavy metals cations demonstrates clear n-type adsorbing manner. The encapsulation of heavy metals cations occurs via chemisorption. In this article, it was observed the behavior of trapping of main group cations of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ by GaN_NC for sensing the water metal cations. The nature of covalent features for these complexes has represented the analogous energy amount and vision of the partial density of states (PDOS) for the p states of N and d states of heavy metal cations of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ through water treatment. The PDOS can also evaluate an appointed charge group between Cr3+, Co2+, Cu2+, Ni2+, Pb2+, As3+ and GaN_NC which indicate the most stable complex of metallic visage and a certain degree of covalent specifications between heavy metals cations and GaN_NC. Furthermore, the nuclear magnetic resonance (NMR) analysis indicated the notable peaks surrounding metal elements of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ through the trapping in the GaN_NC during ion detection and removal from water; however, it can be seen some fluctuations in the chemical shielding treatment of isotropic and anisotropy tensors. Based on the results in this research, the selectivity of metal ion adsorption by GaN_NC (ion sensor) has been approved as: Ni2+˃˃˃ Cu2+ ˃Co2+˃ Cr3+˃˃ Pb2+ ˃ As3+.

Electrochemical Investigations of Double Perovskite M2NiMnO6 (Where M = Eu, Gd, Tb) for High-Performance Oxygen Evolution Reaction

Double perovskites are known for their special structures which can be utilized as catalyst electrode materials for electrochemical water splitting to generate carbon-neutral hydrogen energy. In this work, we prepared lanthanide series metal-doped double perovskites at the M site such as M2NiMnO6 (where M = Eu, Gd, Tb) using the solid-state reaction method, and they were investigated for an oxygen evolution reaction (OER) study in an alkaline medium. It is revealed that the catalyst with a configuration of Tb2NiMnO6 has outstanding OER properties such as a low overpotential of 288 mV to achieve a current density of 10 mAcm−2, a lower Tafel slope of 38.76 mVdec−1, and a long cycling stability over 100 h of continuous operation. A-site doping causes an alteration in the oxidation or valence states of the NiMn cations, their porosity, and the oxygen vacancies. This is evidenced in terms of the Mn4+/Mn3+ ratio modifying electronic properties and the surface which facilitates the OER properties of the catalyst. This is discussed using electrochemical impedance spectroscopy (EIS) and electrochemical surface area (ECSA) of the catalysts. The proposed work is promising for the synthesis and utilization of future catalyst electrodes for high-performance electrochemical water splitting.

Exploring the Functional Significance of Lysosomes in Cancer Drug Resistance

Chemotherapy stands as a primary therapeutic approach for tackling a spectrum of malignancies. Nonetheless, the emergence of resistance to chemotherapeutic agents poses a significant hurdle in achieving curative cancer treatments. Lysosomes, recognized as acidic cellular organelles predominantly engaged in intracellular digestion, have garnered increasing attention due to their implications in cancer biology. Notably, their relevance to cancer manifests in several ways: Firstly, the extracellular release of lysosomal enzymes actively promotes tumorigenesis. Secondly, the leakage of lysosomal hydrolases into the cytosol induces apoptosis. Lastly, weak chemotherapeutic bases, upon traversing the lysosomal membrane, become sequestered within lysosomes while adopting a cationic state. This sequestration of drugs within lysosomes diminishes their cytotoxic potential, restricts their availability at target sites, and contributes significantly to the development of drug resistance in cancer. This review comprehensively explores diverse mechanisms underpinning lysosomal drug sequestration and delves into their repercussions on the phenomenon of multidrug resistance in cancer. Furthermore, we delve into strategies aimed at surmounting drug resistance by leveraging lysosomes as subcellular targets, with the aim of reversing drug sequestration and thwarting drug resistance in the context of cancer therapy

Atomic reconstructions and dynamic-evolutionary pathways on a polar surface of a wurtzite ionic crystal: Ga-doped ZnO(0001)

Preparing atomic reconstructions and tracking their evolutionary pathways on polar surfaces of wurtzite ionic crystals remain a big challenge in surface science. Here, we addressed this challenge by introducing Ga surface segregation through Ar+ bombardment and subsequent annealing treatment. By employing ZnO(0001) surface as a model system for wurtzite ionic crystals, we generated various atomic reconstructions and observed three distinct evolutionary pathways. These pathways involved complex dynamic processes including atom desorption and movement, and each pathway started with a disordered surface and ended with a (2 × 8) reconstruction. Tracking all the pathways, the overall reconstruction route can be put in order as “disorder → (√3 × √3)R30° → (2 × 2) → (2 × 4) → (2 × 8)”, as the surface Ga concentration is increased. These atomic reconstructions are proposed to originate from the alternations in the valence state of cation and the influence of surface segregation on the vacant states of dangling bonds. Our discoveries present a comprehensive framework for generating a multitude of atomic reconstructions and elucidating their evolutionary pathway on intricate polar surfaces of wurtzite ionic crystals.

Co3O4 Catalysts for Complete Toluene Oxidation: Review including Meta-Analysis of Catalyst Activity Data

Designing highly active catalysts for the oxidation of volatile organic compounds (VOCs) involves fine-tuning the catalytic surface and improving its interaction with VOCs. The present review assesses various studies conducted in the last decade on Co3O4 catalysts for the complete oxidation of toluene (C7H8) and provides information on the synthesis and physicochemical characterization of these catalysts. Taking this one step further, data from the literature were carefully chosen for an extensive meta-analysis aiming at elucidating the structure sensitivity of toluene oxidation over Co3O4 catalysts. Specifically, the specific reaction rate was calculated and correlated with the physicochemical properties of the catalysts, namely, the specific surface area, faceting, and Co3+/Co2+ ratio. Based on this analysis, the specific surface area does not exert a significant impact on the specific activity of Co3O4 catalysts for the total oxidation of toluene. Instead, the specific reaction rates are influenced by the morphology, surface concentration, exposed crystallographic planes, and oxidation state of cobalt cations. These factors determine the catalyst’s specific activity by creating defects, oxygen vacancies, or oxygen species with different reactivities. It was also found that a high surface Co3+/Co2+ ratio is necessary for achieving high catalytic performance in the oxidation of VOCs.

Late-Stage Halogenation of Peptides, Drugs and (Hetero)aromatic Compounds with a Nucleophilic Hydrazide Catalyst.

Unlike its other halogen atom siblings, chlorination of a bioactive compound can change its physiological characteristics, improve its pharmacological profile, and function as a point of diversification through cross-coupling reactions. As a result, it has been a crucial strategy for drug discovery and development. However, functional groups such as amines, amides, hydroxy groups, or carboxylic acids trap the Cl+ , severely limiting the reactivity and making direct chlorination far too difficult to be practical. Herein, we introduce a nucleophilic sulfonohydrazide catalyst for late-stage halogenation of peptides and drugs. This direct, mild and metal-free protocol shows high functional-group tolerance and is compatible with a range of structurally diverse peptides, drugs and aromatic compounds. Furthermore, DFT studies indicate that the reaction most likely proceeds via a cationic transition state. The gram-scale synthesis, high stability and efficiency of the catalyst provide a facile route for late-stage functionalization and intermediates for further derivatization.

Late‐Stage Halogenation of Peptides, Drugs and (Hetero)aromatic Compounds with a Nucleophilic Hydrazide Catalyst

AbstractUnlike its other halogen atom siblings, chlorination of a bioactive compound can change its physiological characteristics, improve its pharmacological profile, and function as a point of diversification through cross‐coupling reactions. As a result, it has been a crucial strategy for drug discovery and development. However, functional groups such as amines, amides, hydroxy groups, or carboxylic acids trap the Cl+, severely limiting the reactivity and making direct chlorination far too difficult to be practical. Herein, we introduce a nucleophilic sulfonohydrazide catalyst for late‐stage halogenation of peptides and drugs. This direct, mild and metal‐free protocol shows high functional‐group tolerance and is compatible with a range of structurally diverse peptides, drugs and aromatic compounds. Furthermore, DFT studies indicate that the reaction most likely proceeds via a cationic transition state. The gram‐scale synthesis, high stability and efficiency of the catalyst provide a facile route for late‐stage functionalization and intermediates for further derivatization.

Revealing the effect of metal-support interactions at the Ni/In2O3(111) interface on the selective CO2 hydrogenation

In2O3-supported Ni catalysts exhibit remarkable catalytic activity and selectivity in CO2 hydrogenation to methanol, but the underlying mechanisms and metal-oxide interactions during the reaction remain elusive. Herein, we investigate the Ni-In2O3 interaction by physical vapor deposition of Ni onto well-defined In2O3(111) thin films. In-situ near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) was employed to probe the CO2 hydrogenation processes on these Ni/In2O3(111) model systems. Our results reveal that the small Ni clusters supported on the In2O3(111) surface at low Ni coverages exhibit cationic states. The chemical bonding and associated electron transfer at the Ni/In2O3(111) interface play crucial roles in the activation of H2 and CO2. Importantly, reaction intermediates (CO3*, OH, and HCOO*) are readily formed and desorbed under CO2 hydrogenation conditions. Our study highlights the significance of metal-support interactions on the selectivity of CO2 hydrogenation. These findings provide valuable insights into the rational design of advanced In2O3-based catalysts for CO2 hydrogenation.

In-depth study of structural, magnetic and XPS behavior of the double perovskite La2-xCex/2Erx/2NiMnO6

Structural, morphological, X-ray photoelectron spectroscopy (XPS) and magnetic details of La2-xCex/2Erx/2NiMnO6 (x = 0.00 and 0.025) prepared by the traditional ceramic method were investigated. X ray-diffraction refinements by Rietveld method indicate that our samples have a monoclinic system with the space group P 21/n No. (14). A small amount of MnNi6O8 impurity was detected in both samples. Morphological analysis reveals that our samples contain grains of different sizes equal to 1.249 µm and 1.260 µm for x = 0.00 and 0.025. Mapping and EDX analysis confirm the existence and homogeneous distribution of elements on the surface of our samples. According to the x-ray photoelectron spectroscopy (XPS) analysis, the presence of a trivalent oxidation state La and RE ions, along with a mixed-valence state of Ni and Mn ions, has been confirmed in the samples. For magnetic analysis, a double transition temperature is detected from the dM/dT variation for the FC curve. The initial transition (T1) occurs at lower temperatures, approximately 105 K and 110 K for x = 0.00 and x = 0.025, respectively. On the other hand, the second transition T2 (Tc) takes place at higher temperatures, around 250 K and 265 K, respectively, for x = 0.00 and x = 0.025. These two magnetic transition temperatures are attributed to distinct spin states of Mn and Ni cations. Thus, the low-temperature transition (T1) can be attributed to a vibronic super-exchange interaction involving trivalent oxidation states, specifically Ni3+–O–Mn3+. The higher temperature transition T2 (Tc) was defined as the Curie temperature when the system undergoes a transition from the ferromagnetic (FM) to the paramagnetic state (PM). The magnetocaloric effect (MCE) exhibits the presence of two prominent peaks. The first one is at low temperature around 80 K. The second is at high temperature around 250 K. A phonemological approach called Landau theory was used to deduce the variation of the magnetic entropy (-ΔSM). Good agreement is obtained between the experimental behavior of (- ΔSM) and that predicted by this theory.

A systematic study on spectroscopic and transition properties of the phosphorus mononitride cation

The potential energy curves (PECs) of 28 Λ–S states of the phosphors mononitride cation have been constructed by using the internally contracted multireference configuration interaction (icMRCI) method plus Davidson correction (+Q). The effect of core correlation and scalar relativistic treatment of electron, and the basis-set extrapolation to the complete basis set limit are considered. The spin–orbit coupling is computed via the full Breit-Pauli Hamiltonian. The transition dipole moments (TDMs) for the dipole-allowed and spin-forbidden transitions are calculated. Utilizing the PECs and TDMs, the spectroscopic and transition properties of bound states are then evaluated. The current spectroscopic parameters, vibrational band origins, Einstein coefficients, and Franck-Condon factors well match the available measured values. And the radiative lifetimes for most excited states are estimated for the first time. These results can be useful in the analysis and assignment of molecular spectra or as guidelines for detecting these states spectroscopically.

ZrO2 modification of homogeneous nitrogen-doped oxide MgTa2O6−xNx for promoted photocatalytic water splitting

Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen, but currently the poor charge separation severely limits their photocatalytic performances. In this work, a homogeneous nitrogen-doped tunneled oxide of MgTa2O6−xNx with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO2 modification on the charge separation as well as photocatalytic performance. It is interesting to observe that the formation of the reduced tantalum species, regarded as recombination centers, in the MgTa2O6−xNx sample could be effectively inhibited via the surface passivation with ZrO2 nanoparticles, based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted. Together with modification of the deposited Pt cocatalyst, the optimized H2 evolution rate over Pt-ZrO2/MgTa2O6−xNx (Zr/Ta = 0.10) photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa2O6−xNx sample free of ZrO2 modification, whose apparent quantum yield at 420 nm (± 15 nm) achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts. The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO2 modification, which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species. This work extends the application territory of ZrO2 modification to the homogeneous nitrogen-doped oxide photocatalysts, and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.