XPS Measurements Research Articles

One pot synthesis of donor-acceptor carbon nitride with distinct thiophene rings accelerate photocatalytic hydrogen evolution

Graphitic carbon nitride (g-CN) with a donor-acceptor structure was synthesized by urea and cross-linking thiophene precursors at the terminal sites, achieved through calcination of urea with four different thiophene-based precursors under atmospheric conditions. Among these, UDB-2-1, which incorporates dibenzothiophene-2-carboxyaldehyde (DB-2) 1 mg, demonstrated a hydrogen evolution activity of 650 μmol/g·h, approximately six times higher than pristine graphitic carbon nitride (U). The apparent quantum yield (AQY) was measured to be 4.01 %, 4.89 %, and 3.72 % at 400 nm, 420 nm, and 450 nm, respectively, in the presence of potassium hydrogen phosphate (KPH). This enhanced performance is attributed to increased visible light absorption from the n-π∗ transition introduced by the thiophene ring and enhanced charge separation due to the donor-acceptor (DA) structure, with DB-2 acting as an electron donor. Prepared photocatalysts were characterized by XRD, XPS, FTIR, SEM, TEM, BET, ESR, EIS, Mott-Schottky, DRS, PL, and TRPL measurement. This study provides a simple and effective strategy to improve carbon nitride performance and underscores the importance of functional group positioning and structural isomers in molecular design for solar-energy applications.

Effect of Fe3+ on sulfidation flotation behavior of anglesite from zinc leaching residue

The recovery of anglesite (PbSO4) from zinc leaching residue (ZLR) via flotation is a valuable research topic. In practical production, Fe3+ is inevitably present in the anglesite flotation from ZLR. In this study, the effect of Fe3+ on the sulfidation-xanthate flotation of anglesite was investigated by flotation tests. Micro-flotation results indicated that the anglesite flotation was depressed with Fe3+ pretreatment. The xanthate adsorption quantity, zeta potential, XPS, and FTIR measurements revealed that hydrophilic FeOOH species was adsorbed on the surface of the anglesite, thereby inducing the reduction of xanthate adsorption quantity. The bench-scale flotation results indicated that Fe3+ concentration in slurry decreased from 658.57 to 29.46 mg/L with acid washing ZLR three times. Consequently, Pb grade and recovery were increased from 9.91 % to 20.43 % and from 37.63 % to 67.74 %, respectively. These results might have guiding significance for the practical application of anglesite flotation from ZLR.

Plasma-assisted construction of waterfall-type IEF in N-TiO2/WO3 S-scheme heterojunction for efficient visible-light-driven degradation of Cl-VOCs

Constructing S-scheme heterojunctions with a robust internal electric field (IEF) to enhance the photocatalytic degradation of chlorinated volatile organic compounds (Cl-VOCs) presents a significant challenge. Herein, an innovative S-scheme heterojunction of N-doped titanium dioxide (TiO2) and tungsten trioxide (WO3) with abundant oxygen vacancies (OVs) was synthesized and manipulated for the first time via an eco-friendly two-step plasma. The charge transfer pathway between TiO2 and WO3 was analyzed using UV–Vis DRS, XPS, UPS, and EPR measurements, confirming the successful formation of the S-scheme heterojunction. Interestingly, two novel types of IEF, stream-type and waterfall-type were proposed for the first time to distinguish the IEF strength before and after regulation. Under visible light, 5NTW, with the optimal ratio of 4.66 at% nitrogen and 5 wt% WO3, achieved the highest degradation efficiency and carbon dioxide mineralization rate, 95.4% and 94.1% for chlorobenzene, respectively. The performance enhancement was attributed to the fact that N-doping modifies the electronic structure and work function of TiO2, enhancing the Fermi level difference (ΔEf) with WO3. Meanwhile, the plasma treatment roughened the surface topography of the catalyst and increased the content of OVs, which serve as charge traps and bolster active sites. These synergies led to a transformation from a stream-type IEF of TW to a waterfall-type IEF of 5NTW. KPFM, zeta potential tests, and DFT calculations confirmed that the IEF strength and the number of electron transfers in the waterfall-type IEF are 3.17 and 2.04 times greater, respectively, than those in the stream-type IEF. This strategy transcends the limitations of previous work, offering a novel perspective on the integrated optimization of photocatalysts for superior performance and also further broadens the application prospects of nonthermal plasma technology.

Preparation of tannic acid-based conversion coating and corrosion protection performances for steel in chlorinated simulated concrete pore solution

A tannic acid-based conversion coating (TACC) has been developed on steel surface to protect carbon steel within a chlorinated simulated concrete pore solution (Cl-SCPS). The morphology, composition, and protective efficacy of TACC for carbon steel are examined through using SEM, FT-IR, Raman, EDS, XPS, and electrochemical measurements. The findings reveal that TACC significantly enhances the corrosion resistance of carbon steel. The TACC with a 2-min treatment showcases the optimal corrosion protection for steel, sustaining a protection efficiency of 99.84 % even after a 7-day exposure period. As the samples are exposed to the Cl-SCPS, the passivation products formed serve to fill the pores in the TACC, thereby enhancing its compactness and protective capabilities.

Unleashing the Potential of Tailored ZnO-MgO Nanocomposites for the Enhancement of NO2 Sensing Performance at Room Temperature.

Surface functionalization of semiconducting metal oxides has emerged as a highly effective approach for enhancing their sensing capabilities. In the present work, the surface of randomly oriented zinc oxide (ZnO) nanowires is modified with an optimized thickness (7 nm) of magnesium oxide (MgO), which exhibits an exceptionally sensitive and selective behavior toward NO2 gas, yielding a response of approximately 310 for 10 ppm concentration at room temperature. The synergistic interplay between ZnO and MgO leads to a remarkable 20-fold improvement in sensor response compared to a pristine ZnO film and allows the detection of concentrations as low as 50 ppb. The ZnO-MgO composite was characterized using X-ray diffraction (XRD), XPS, and SEM-EDS to gain structural, compositional, and morphological insights. The interaction of the NO2 molecule with the sensor film was investigated using density functional theory (DFT) simulations, revealing that oxygen vacant sites on the MgO surface are most favorable for NO2 adsorption, with an adsorption energy of -3.97 eV and a charge transfer of 1.74e toward NO2. The XPS, photoluminescence (PL), and EPR measurements experimentally verified the presence of oxygen vacancies in the sensing material. The introduction of localized levels within the band gap by oxygen vacancies significantly promotes the interaction of gas molecules with these sites, which enhances the charge transfer toward NO2 gas molecules. This augmentation has a profound influence on the space charge region at the ZnO-MgO interface, which is pivotal for modulating the charge transport in the ZnO layer, resulting in the substantial improvement of NO2 response at room temperature.

Effect of oxygen vacancies on enhancing the photo-catalytic activity, photo-luminescence and electronic structure properties of nanostructured Y-doped CeO2

The exceptional characteristics of CeO2 and Ce1-xYxO2 (x = 0.03, 0.05 and 0.07) nanoparticles were reported in the manuscript supporting that Y3+replaces Ce3+/Ce4+leads to oxygen vacancies formation. The results of XRD measurements revealed FCC structure of decreased crystallite size of CeO2 with improved crystallinity. To investigate the surface morphology, HRTEM and SAED patterns were performed. EDX analyses were undertaken to discuss the elemental and compositional characteristics. The absorption spectra using UV–Vis–NIR spectroscopy were analyzed and red shifted absorbance was found to enhance with decreasing band gap values for increased Y doping. The Photoluminescence spectra depicted various emissions representing the development of various defects and oxygen vacancy with incorporation of Y content in the lattice with CCT values below 4000 K to be classified as warm yellow light for indoor applications. The development of oxygen vacancies in the CeO2 lattice was further supported by XPS measurements for core levels Ce 3d, O 1s and Y 3d. Furthermore, the XPS measurements also reported the valence states of elements, Ce with 3+ and 4+, Y with 3+ and O with 2- along with charged oxygen vacancies. The photo-catalytic analysis revealed that Y-doped CeO2 nanoparticles show better degradation using a variety of characterization. A degradation mechanism that illustrates the impact of oxygen vacancies created by Y-doping on the photo-degradation process has been proposed. The novelty of Y-doped CeO2 nanoparticles stems from their improved photo-catalytic activities, which are linked to structural changes and the formation of oxygen vacancies. This doping considerably affects the electrical structure, resulting in better light absorption and less electron-hole recombination. The detailed outcomes of present study suggested the use of Y-doped CeO2 nanoparticles in optoelectronics, spintronics devices and photo-catalyst applications.

Improved Pyroelectric Nanogenerator Performance of P(VDF-TrFE)/rGO Thin Film by Optimized rGO Reduction.

The pyroelectric nanogenerator (PyNG) has gained increasing attention due to its capability of converting ambient or waste thermal energy into electrical energy. In recent years, nanocomposite films of poly(vinylidene fluoride-co-trifluoro ethylene) (P(VDF-TrFE)) and nanofillers such as reduced graphene oxide (rGO) have been employed due to their high flexibility, good dielectric properties, and high charge mobility for the application of wearable devices. This work investigated the effect of rGO reduction on pyroelectric nanogenerator performance. To prepare rGO, GO was reduced with different reducing agents at various conditions. The resulting rGO samples were characterized by XPS, FT-IR, XRD, and electrical conductivity measurements to obtain quantitative and qualitative information on the change in surface functionalities. Molecularly thin nanocomposite films of P(VDF-TrFE)/rGO were deposited on an ITO-glass substrate by the Langmuir-Schaefer (LS) technique. A PyNG sandwich-like structure was fabricated by arranging the thin films facing each other, and it was subjected to the pyroelectric current test. For various PyNGs of the thin films containing rGO prepared by different methods, the average pyroelectric peak-to-peak current (APC) and the pyroelectric coefficient (p) values were measured. It was found that a more reduced rGO resulted in higher electrical conductivity, and the thin films containing rGO of higher conductivity yielded higher APC and p values and, thus, better energy-harvesting performance. However, the thin films having rGO of too high conductivity produced slightly reduced performance. The Maxwell-Wagner effect in the two-phase system successfully explained these optimization results. In addition, the APC and p values for the thin film with the best performance increased with increasing temperature range. The current PyNG's performance with an energy density of 3.85 mW/cm2 and a p value of 334 μC/(m2∙K) for ΔT = 20 °C was found to be superior to that reported in other studies in the literature. Since the present PyNG showed excellent performance, it is expected to be promising for the application to microelectronics including wearable devices.

Temperature dependent radiative and non-radiative recombination lifetimes of luminescent amorphous silicon oxynitride systems

In our previous work, we deeply researched the absolute photoluminescence (PL) quantum yields of luminescent modulating a-SiNxOy films with various N/Si atom ratios under different measurement temperatures. In this work, we further systematically studied the temperature dependent kinetic processes of radiative and non-radiative recombinations in a-SiNxOy systems in the visible light range. First, we investigated the structure of a-SiNxOy films and obtained the concentrations of both trivalent Si and N-Si-O defects related dangling bonds through XPS, FTIR and EPR measurements. Then we further tested the transient fluorescence attenuation of a-SiNxOy films detected at different emission wavelengths. We found that the PL lifetimes of a-SiNxOy films vary with the change of N-Si-O defect state concentrations, which is different from the typical PL decay characteristics of band tail related a-SiNx films previously reported. By combining the resulting PL IQE values with the ns-PL lifetimes, we further intensively redetermined the radiative and non-radiative recombination lifetimes of a-SiNxOy systems. The related radiative recombination rates were obtained (kr∼108 s−1), which can be compared to the results in the direct band gap.

Preparation and Characterization of Au Quantum Dots Using Laser in Benzene and Study of the Pulse Energy effect on Quantum Size

Here, findings from a study on pulsed laser ablating of noble Au targets submerged in benzene solvent and a study on the effect of pulse energy on quantum size are presented. Three samples of gold quantum dots (AuQDs) are synthesized at pulse fluence of 4, 8, and 12 J/cm2, which is referred to as F1, F2, and F3, respectively. The prepared AuQDs were characterized by UV-Vis, HR-TEM, XRD, XPS, EDX, FTIR, Raman spectroscopy and Photoluminescence measurement. AuQDs that were synthesized have monocrystalline and cubic (FCC) structure, according to XRD patterns. It was found that the direct optical energy gap of AuQDs is enhanced to 2.6 eV. The emission peak of AuQDs photoluminescence emission spectra is at roughly 481, 445, and 437 nm, for F1, F2, F3 samples, respectively. The quantum size was reduced to 2 nm for sample F3. This strategy has the ability to prepare pure AuQDs in one step, with promising biosensor and bioimaging applications.

Preparation of Ni-Cu-C composite catalysts prepared from mixed nickel and copper hydroxides for selective hydrogenation of 4-nitrophenol

A high-performance Ni-Cu-C composite catalyst was prepared from mixed nickel hydroxide and copper hydroxide, which were obtained by coprecipitation, by thermal treatment with acetylene-containing gas at 120 °C followed by hydrogen reduction at 180 °C. The characterization results of XRD, TEM, XPS, and H2-TPR measurements confirmed the presence of nickel carbide (Ni3C), copper carbide (CuxC), Cu, and Ni in the matrix of amorphous carbon in the composite catalyst. The mild preparation temperature and the porous carbon shell layers prevented the nano-sized particles from aggregation. The formation of interstitial Ni3C and CuxC significantly enhanced the dissociation of molecular hydrogen, accelerating the selective hydrogenation of 4-nitrophenol (4-NP) to yield 4-aminophenol (4-AP) at relatively mild conditions (80 °C and 1.0 MPa hydrogen pressure). The catalytic performance of the composite catalysts depended strongly on the Ni/Cu molar ratio, with an optimal Ni/Cu molar ratio of 4. In addition, the composite catalyst showed high conversion and selectivity to the corresponding aniline in the selective hydrogenation of other nitroarenes, including nitrobenzene, 4-nitrotoluene, 4-nitrochlorobenzene, 4-nitrobenzaldehyde, 4-nitroacetophenone, and 2-nitroaniline. The catalyst offers a novel approach to rational design and preparation of high-performance abundant metal catalysts for selective hydrogenation of nitroarenes.

Fundamentals of copper(II) adsorption on phyllosilicate minerals relevant to crud formation in solvent extraction from heap leach liquors

Because of the common presence of different silicate minerals, like kaolinite, montmorillonite and muscovite as gangue minerals in the beneficiation of copper oxide ores, the interaction between copper(II) ions in solution and each of these minerals is a field of strong interest, considering their implications on the aggregation of these minerals in the extreme pH conditions typical of hydrometallurgical unit operations for copper production. After copper adsorption isotherms determination at pH 2 and 4, specific adsorption data were fitted to both Langmuir and Freundlich models. It was found that adsorption is systematically larger at pH 4, and that montmorillonite is the mineral that displays a larger adsorption capacity, as in principle expected by its larger cation exchange capacity, CEC. A good fitting to the Langmuir model was obtained for the three samples, and montmorillonite also appears to conform to Freundlich isotherm predictions, as the tested concentrations of copper(II) do not allow to reach saturation. Furthermore, some desorption is measured for kaolinite and muscovite at the highest copper concentrations, probably because of significant interactions between the adsorbed ions. No such desorption was detected in montmorillonite samples. An XPS analysis of the surfaces of the three minerals suggests that copper adsorption in kaolinite is not associated to a cation exchange process but rather to electrostatic interactions between silica-like faces of the clay. In contrast, ionic exchange of structural calcium (for montmorillonite) or potassium (in the case of muscovite) seems to be the predominant mechanism of Cu(II) adsorption in the other two samples. Electrophoretic mobility determinations agree with this hypothesis: the mobility (always negative, with no traces of charge inversion) decreases in absolute value when kaolinite particles are in contact with solutions of increasing copper concentration at pH 2 or pH 4. On the other hand, the electrophoretic mobility values of muscovite and montmorillonite showed a weak pH and copper concentration dependence, a result that matches well with the ion exchange processes detected in the XPS measurements.

Analysis of time-dependent hydrophobic recovery on plasma-treated superhydrophobic polypropylene using XPS and wettability measurements

In specific applications like ice-repellent coatings or membrane separation technology, wettability is a key parameter affecting the applicability of commodity polymers. This study presents a technique to fine-control the wetting properties of a hierarchically structured polypropylene surface, enabling the transition between superhydrophobic and superhydrophilic states. To demonstrate the tunability of the wetting properties of polypropylene (PP) substrate, we prepared in a consecutive way superhydrophobic (advancing contact angle (CAadv) of 152°) and superhydrophilic (CAadv of 0°) material by solvent-treatment and mild air plasma treatment. The optimal plasma treatment parameters to achieve superhydrophilic wetting behaviour, which is stable for at least one week of storage in air was also explored. Water contact angle measurement and X-ray photoelectron spectroscopy were used to monitor the time dependency of hydrophobic recovery on a hierarchically structured PP surface. With a simple model considering structural and wetting parameters, we characterized the droplet spreading behaviour of plasma-treated roughened surfaces, which exhibited superhydrophilic wetting behaviour with equilibrium CAadv of nearly 0°. The proposed model, which aligns well with experimental data, can be used to compare the droplet spreading behaviour of plasma-treated roughened surfaces.

Sulfuration-induced enhancement of photodetection performance of photoconductive detector based on Bi2O2Se thin film

Significant interlayer transmission obstacles and numerous interface barriers in two-dimensional material thin films impede charge transfer, degrading device performance. However, appropriate impurity ions can enhance charge mobility by creating transfer channels and regulating interface defect states. Herein, a series of Bi2O2SxSe1-x films were prepared by a one-step hydrothermal sulfurization method. The XRD and XPS measurement and analysis can confirm that the Se atoms have been replaced by the S atoms. The introduction of S atoms can effectively enhance the number of defects in Bi2O2Se, resulting in an increase in carrier concentration, thereby improving the conductivity of Bi2O2Se film. The photoconductive detectors fabricated from these Bi2O2SxSe1-x films showed improved detection performance compared to those made from the pristine Bi2O2Se film, and the responsivity is increased by nearly 1000 times. Notably, the detector based on Bi2O2S0.37Se0.63 film has high responsivity (47.7 mA/W) and fast response time (15 ms/25 ms). The simple thin film preparation method and good device performance make it have great potential for large-scale preparation.

Green synthesis and antimicrobial study on the catechin-functionalized Fe3O4-Ag magnetic nanocomposites

In this study, catechin-functionalized Fe3O4-Ag nanocomposites were synthesized by a hydrothermal method. The motivation for this study was to develop a novel antibacterial agent with enhanced stability and biocompatibility. The objective was to create a nanocomposite combining the antimicrobial properties of silver with the antioxidant and bioactive characteristics of catechin. We hypothesized that the synergistic effect of catechin and Fe3O4-Ag would yield a highly effective antibacterial material against common pathogens. The obtained nanocomposites were characterized by TEM, SEM, AFM, XPS, XRD, FTIR and physical property measurement system (PPMS). TEM images indicated that catechin-functionalized Fe3O4-Ag nanocomposites have a spherical morphology with an average size of 25.7 nm. The SEM and AFM imaging revealed that the nanocomposites appear as a number of large particles with average diameter of 581 nm. XPS and XRD and FTIR measurement confirmed the presence of catechin components, Fe3O4 and Ag in the nanocomposites. Taken together, we conclude that the catechin-Fe3O4-Ag nanocomposites in this study have a jujube cake structure in which the Fe3O4-Ag alloy nanoparticles serve as the jujube and the condensed catechin form into the cake substrate. The antimicrobial test indicated the catechin-functionalized Fe3O4-Ag nanocomposites have obvious inhibitory effects on E.coli, S.aureus, and C.albicans.

Magnetic field-enhanced two-electron oxygen reduction reaction using CeMnCo nanoparticles supported on different carbonaceous matrices

The current study illustrates the successful synthesis of Ce1.0Mn0.9Co0.1 nanoparticles, characterized through XRD, EPR, magnetization curves, and TEM/HRTEM/EDX analyses. These nanoparticles were then loaded into the carbon Vulcan XC72 and the carbon Printex L6 matrices in varying amounts (1, 3, 5, and 10 % w/w) via wet impregnation method to fabricate electrocatalysts for the 2-electron ORR. Before experimentation, the material was characterized via XPS and contact angle measurements. The electrochemical results produced significant findings, indicating that the electrocatalysts with the nanostructures modifying both carbon blacks notably augmented currents in rotating ring-disk electrode measurements, signifying enhanced selectivity for H2O2 production. Moreover, our research underscored the significant impact of Magnetic Field-Enhanced Electrochemistry, employing a constant magnetic field strength of 2000 Oe, on 2-electron ORR experiments. Particularly noteworthy were the observed results surpassing the ones without the magnetic field, demonstrating heightened currents and improved selectivity for H2O2 production (more than 90 %) facilitated by CeMnCo nanoparticles. These significant findings in electrocatalytic efficiency have practical implications, suggesting the potential for developing more efficient and selective catalysts for the 2-electron ORR.

VBO3/V2O3@C heterogeneous anode material with high-specific-capacity and high-stability for lithium-ion batteries

The design and synthesis of high-performance anode materials is the key to further improve the performance of lithium-ion batteries. In this study, VBO3/V2O3 heterogeneous material with high crystallinity was prepared in vacuum quartz tubes by a facile high-temperature solid-phase method, and the electron transport capacity of VBO3/V2O3 was further improved by ball-milling with conductive carbon. As a result, the obtained VBO3/V2O3@C heterogeneous anode material delivers an initial discharge specific capacity of 927 mAh·g−1 and good cycling stability. Even at −20 °C, VBO3/V2O3@C still presents a discharge specific capacity of 432 mAh·g−1. In addition, ex-situ XRD and ex-situ XPS measurements reveal the conversion reaction and (de)intercalation reaction mechanism during charge/discharge. This work deepens the understanding of the structure-activity relationship of borate/oxide heterogeneous anode materials.

Bioactive modification of cyclic olefin copolymer (COC) film surfaces by hyaluronic acid and chitosan for enhanced cell adhesion

Cyclic olefin copolymer (COC) has recently emerged as an attractive material in biomedical fields for its high purity, excellent stability and chemical resistance, particularly in applications of microfluidic chips, prefilled syringes and bone regeneration. However, the high hydrophobicity of COC has inhibited the adhesion of cells and biological macromolecules, such as proteins, etc., significantly limiting its broader applications. In this study, we propose a new method to modify COC surfaces by sequential coating with polydopamine (PDA) followed by hyaluronic acid (HA) or O-carboxymethyl chitosan (CMC), while comparing the impacts of the positively charged HA and negatively charged CMC on protein adsorption and cell adhesion. FTIR and XPS measurements confirmed the successful modification on COC films, resulting in surfaces with highly increased hydrophilicity, anti-oxidative properties, and improved protein adsorption. Moreover, negatively charged HA, with signal transduction capabilities showed a greater effect in promoting cell adhesion. Thus, we present a straightforward strategy for enhancing the hydrophilicity of COC surfaces, offering new insights into COC modification and potential biomedical applications.

Magnetron sputtered ß-Ti coatings for biomedical application: A HiPIMS approach to improve corrosion resistance and mechanical behavior

This work presents the surface modification of commercially pure Ti specimens (c.p.-Ti) prepared by conventional powder metallurgy by depositing a thin film of a ß-Ti alloy (Ti-35Nb-7Zr-5Ta, wt. %, TNZT). Two types of pulsed technologies: conventional (p-DC) and high-power impulse magnetron sputtering (HiPIMS), with and without bias assistance (−60 V) under similar power conditions (250 W) were applied on titanium specimens and silicon substrates leading to different film morphologies and functional properties. Microstructural, X-ray diffraction, nanoindentation, surface wetting, XPS and electrochemical impedance measurements were done to characterize their functionality. All the coatings presented a reduced Young’s Modulus (E ≤ 80GPa) compared to the bulk Ti, representing a reduction of more than 30 %. This decrease can significantly contribute to the reduction of the stress-shielding effect, mitigating the risk of implant loosening and failure. The hardness values of TNZT coatings, slightly lower than c.p.-Ti substrate, range from 4.1 to 4.7 GPa. XPS analysis shows a passivation layer of TiO2, Nb2O5, and ZrO2, which offers high impedance and excellent corrosion resistance. The best compromise between mechanical and corrosion properties is achieved with the HiPIMS technology, thanks to its compact film microstructure with high electrical resistance, despite its limited thickness of about 1 μm.

Preparation of pigmentary grade bismuth vanadate Bi4V2O11 via coprecipitation method

ABSTRACT In this study, Bi4V2O11 pigments were synthesized using a coprecipitation method, and the pH value and calcination temperature were optimized from the viewpoint of red colorant. The obtained samples were characterized by XRF, XRD, Rietveld refinement, TEM, UV–vis diffuse reflectance spectrometry, SEM, XPS and color measurements. It was found that Bi4V2O11 samples with single-phase monoclinic structure could be prepared, when the calcination temperatures were 973 and 1073 K. The obtained single-phase Bi4V2O11 samples exhibited reddish hue. For the sample, which was prepared at pH = 7.0 and calcined at 973 K, its color coordinates were L* = 46.41, a* = +27.41, b* = +26.09.

Dual redox centers in MnCo2O4 nanorod cathode for highly efficient capacitive deionization

Capacitive deionization (CDI) technology via faradic electrodes with active redox pairs has achieved tremendous success in desalination. However, the inner collaborative mechanisms of multi-redox centers in electrodes are rarely deep-analyzed. Thus, this work intensively investigated the inner enhanced mechanisms of multi-redox centers, starting from the dual-redox-based MnCo2O4 nanorod (MCO-NR) cathode in capacitive desalination. The electrochemical tests indicated a surface capacitive ratio of MCO-NR as high as 86 % when the scan rate was 100 mV s−1. Multi-dimensional CDI tests demonstrated that the highest capacity of MCO-NR could reach 61.78 mg g−1, with four theory models elaborating the electrosorption kinetics and maximum desalination capability. The refined ex-situ XPS measurements, carefully designed comparative experiments, and DFT calculations were used to analyze the Na+ (de)intercalation characteristics, the inner enhanced electrosorption mechanisms of dual redox centers, and the effects that the Mn redox center exerts on the MnCo2O4 structure. These results showed the superiority of dual- or multi-redox-center-based faradic capacitive desalination, providing a new perspective for designing high-property faradic electrode materials.