Approach of fermi level and electron-trap level in cadmium sulfide nanorods via molybdenum doping with enhanced carrier separation for boosted photocatalytic hydrogen production

Effect of metal ion doping on the optical properties and the deactivation of photocatalytic activity of ZnO nanopowder for application in sunscreens

The effect of ion-doping on TiO2 nanotubes were investigated to obtain the optimal TiO2 nanotubes for the effective decomposition of humic acids (HA) through O3/UV/ion-doped TiO2 process. The experimental results show that changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the Brunauer-Emmett-Teller surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on HA removal increased when Ag+, Al3+, Cu2+, Fe3+, V5+, and Zn2+ were doped into the TiO2 nanotubes, whereas such activities decreased as a result of Mn2+- and Ni2+-doping. In the presence of 1.0 at.% Fe3+- doped TiO2 nanotubes calcined at 550°C, the removal efficiency of HA was 80% with a pseudo-first-order rate constant of 0.158 min–1. Fe3+ in TiO2 could increase the generation of •OH, which could remove HA. However, Fe3+ in water cannot function as a shallow trapping site for electrons or holes.

Dielectric response and current-voltage characteristic of Mo-doped diamond-like carbon thin films at room temperature

Developing non-noble metal photocatalysts for efficient photocatalytic hydrogen evolution is crucial for exploiting renewable energy. In this study, a photocatalyst of Ni2P/CdS nanorods consisting of cadmium sulfide (CdS) nanorods (NRs) decorated with Ni2P nanoparticles (NPs) was fabricated using an in-situ solvothermal method with red phosphor (P) as the P source. Ni2P NPs were tightly anchored on the surface of CdS NRs to form a core-shell structure with a well-defined heterointerface, aiming to achieve a highly efficient photocatalytic H2 generation. The as-synthesized 2%Ni2P/CdS NRs photocatalyst exhibited the significantly improved photocatalytic H2 evolution rate of 260.2 μmol∙h−1, more than 20 folds higher than that of bare CdS NRs. Moreover, the as-synthesized 2%Ni2P/CdS NRs photocatalyst demonstrated an excellent stability, even better than that of Pt/CdS NRs. The photocatalytic performance enhancement was ascribed to the core-shell structure with the interfacial Schottky junction between Ni2P NPs and CdS NRs and the accompanying fast and effective photogenerated charge carriers’ separation and transfer. This work provides a new strategy for designing non-noble metal photocatalysts to replace the noble catalysts for photocatalytic water splitting.

Structural and magnetic studies of Y3Fe5−5xMo5xO12

Achieving efficient self-trapped excitons emission by suppressing defect level in Sb3+ doped metal halide

Niobium pentoxide (Nb2O5) is a promising pseudocapacitive material for supercapacitor applications due to its high theoretical capacitance and electrochemical stability. However, its practical performance is limited by low electrical conductivity and poor ion transport kinetics. In this work, we report the enhancement of Nb2O5 electrode performance through molybdenum (Mo) doping and thermal calcination. Mo-doped Nb2O5 nanostructures were synthesized via a hydrothermal method followed by calcination at 500 °C. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed a rougher morphology and homogeneous Mo distribution in the doped sample. X-ray diffraction (XRD) revealed a structural transformation from a deformed orthorhombic phase in pristine Nb2O5 to a more crystalline pseudohexagonal phase in Mo-Nb2O5-500. Electrochemical analysis demonstrated a significant improvement in capacitive behavior, with Mo-Nb2O5-500 achieving a specific capacitance of 55.3 F/g at 5 mV/s, which is five times higher than the undoped sample. All electrodes exhibited stable cycling performance. These results highlight the synergistic role of Mo doping and calcination in enhancing the electrochemical properties of Nb2O5, offering a viable approach for developing high-performance pseudocapacitor electrodes.

This work outlines an experimental and theoretical investigation of the effect of molybdenum (Mo) doping on the oxygen vacancy formation and photocatalytic activity of TiO2. Analytical techniques such as x-ray diffraction (XRD), Raman, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to probe the anatase to rutile transition (ART), surface features and optical characteristics of Mo doped TiO2 (Mo–TiO2). XRD results showed that the ART was effectively impeded by 2 mol% Mo doping up to 750 °C, producing 67% anatase and 33% rutile. Moreover, the crystal growth of TiO2 was affected by Mo doping via its interaction with oxygen vacancies and the Ti–O bond. The formation of Ti–O–Mo and Mo–Ti–O bonds were confirmed by XPS results. Phonon confinement, lattice strain and non-stoichiometric defects were validated through the Raman analysis. DFT results showed that, after substitutional doping of Mo at a Ti site in anatase, the Mo oxidation state is Mo6+ and empty Mo-s states emerge at the titania conduction band minimum. The empty Mo-d states overlap the anatase conduction band in the DOS plot. A large energy cost, comparable to that computed for pristine anatase, is required to reduce Mo–TiO2 through oxygen vacancy formation. Mo5+ and Ti3+ are present after the oxygen vacancy formation and occupied states due to these reduced cations emerge in the energy gap of the titania host. PL studies revealed that the electron–hole recombination process in Mo–TiO2 was exceptionally lower than that of TiO2 anatase and rutile. This was ascribed to introduction of 5s gap states below the CB of TiO2 by the Mo dopant. Moreover, the photo-generated charge carriers could easily be trapped and localised on the TiO2 surface by Mo6+ and Mo5+ ions to improve the photocatalytic activity.

Investigating the effect of Mo doping on structural and ferroelectric properties of BaTiO3 using electron microscopy

Li2MnO3 plays significant roles in stabilizing the structure and ensuring a high specific lithium storage capacity of the Li-rich layered xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn, etc.) composites (or solid solutions) as cathode materials for lithium ion batteries (LIBs)1. Nevertheless, it meets challenges in irreversible structural transition and low coulombic efficiency due to the loss of oxygen in the initial charge process. In addition, its insulating property deteriorates the rate performance of the xLi2MnO3·(1-x)LiMO2. These drawbacks hinder the commercialization and application of the composites as cathode materials for LIBs. Elemental substitution or atom doping has been commonly applied to improve the electrochemical performances of Li2MnO3 2-4. In an electrochemical viewpoint, as Mn4+ cannot be further oxidized in octahedral coordination in the pristine Li2MnO3, the charge compensation has to be conducted by the oxidation of the O2- ions alone upon Li-ion extraction, leading to irreversible structural change and safety issues. In contrast, as Mo4+ is potentially oxidized to Mo6+, the charge compensation will be largely declined from oxygen if multi-electron transfer occurs on the doped transition metal atoms in Li2Mn1-x Mo x O3. Therefore, substituting Mn with Mo is expected to reduce the loss of oxygen and improve the stability of the structure. In addition, considering the difference of Li2MnO3 (red) and its iso-structured Li2MoO3 (black) in color, Mo substitution for Mn might also improve the conductivity and rate performance of Li2MnO3and its related cathode materials. In this work, first-principles calculations are conducted to predict the impacts of molybdenum (Mo) doping on the physical and electrochemical properties of Li2MnO3. It demonstrates that Mo doping is indeed beneficial in improving both the dynamic and thermodynamic properties of Li2MnO3: (1) It decreases the band gap and increases the number of states around the Fermi level; (2) It enhances Li-ion diffusion especially between the lithium layer and the transition-metal layer; (3) Extra charge is transferred from Mo to O, accompanied with the reduction of the delithiation potential; (4) The charge of the removed Li-ion is compensated by both Mo and O in the Mo-doped Li2MnO3 during delithiation, and (5) Mo doping delays oxygen release and reinforces the stability of the structural oxygen based on the calculated reaction enthalpy. Therefore, Mo doping is expected to be an effective way in improving the structural stability and rate performance of Li2MnO3 and xLi2MnO3·(1-x)LiMO2 cathode materials. These findings will facilitate the investigation and promote the development of Li2MnO3 and xLi2MnO3·(1-x)LiMO2 cathode materials. M. M. Thackeray, S.-H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek and S. A. Hackney, J. Mater. Chem., 17, 3112-3125 (2007).M. Tabuchi, Y. Nabeshima, K. Ado, M. Shikano, H. Kageyama and K. Tatsumi, J. Power Sources, 174, 554-559 (2007).D. Mori, H. Sakaebe, M. Shikano, H. Kojitani, K. Tatsumi and Y. Inaguma, J. Power Sources, 196, 6934-6938 (2011).S. Kim, J.-K. Noh, S. Yu, W. Chang, K. Y. Chung and B.-W. Cho, J. Electroceram., 30, 159-165 (2013).

The effects of Molybdenum (Mo) doping on the structural, optical, and electrical properties of alumina α-Al2−xMoxO3, (x = 0.02–0.14) synthesized via solid-state reaction method have been studied. X-ray diffraction (XRD) analysis confirms of single-phase hexagonal corundum structure in the range 0.06–0.14. The influence of Mo doping on the structural parameters was estimated from XRD data by applying the Rietveld profile fitting method and Fourier-transform infrared spectroscopy. XRD results revealed that replacing Al with Mo does not affect the unit cell dimensions owing to that Mo occupy the vacant sites available in the crystal structure. The electron density map revealed strong positive peaks corresponding to the position occupied by (Al/Mo) and the intensity of these peaks increases with increasing Mo doping. Optical properties revealed that the energy bandgaps (Eg) increase with increasing MoO3, due to the difference in the ionic radius of Al+3 and Mo+3. The dielectric properties indicated that the values of ε′ and tan δ increased as molybdenum concentration increased as a result of the free charges build-up at the interfaces. It was found that tanδ peak lies in the region where DC-conductivity dominates which is a clear indication of the contribution of ionic conduction to the dielectric loss.

Effective wastewater treatment is essential for mitigating organic pollutants, such as dyes and antibiotics. In this study, the enhancement of niobium pentoxide (Nb2O5) nanostructures via molybdenum (Mo) doping to improve adsorption efficiency, selectivity, and reusability is investigated. Mo doping, successfully confirmed by X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy, demonstrates effective integration into the Nb2O5 lattice, inducing lattice expansion and modifying its structural and surface properties. Mo‐doped Nb2O5 exhibits increased adsorption capacities for methylene blue (MB) and crystal violet (CV), improving from 26.9 and 17.0 (undoped) to 35.4 and 44.8 mg g−1, respectively. In contrast, the capacities for Congo red and tetracycline decrease from 31.6 and 36.8 to 16.7 and 32.0 mg g−1, respectively. Isotherm modeling shows Langmuir‐type adsorption with maximum capacities of 48.6 mg g−1 for MB and 52.4 mg g−1 for CV. Point of zero charge analysis indicates improved cationic dye selectivity, while recyclability tests demonstrate that Mo‐doped Nb2O5 can retain over 96% of its capacity after five cycles. In thermodynamic studies, an exothermic and spontaneous process is revealed, with pseudo‐second‐order kinetics confirming chemisorption as the dominant mechanism. In these findings, Mo‐doped Nb2O5 is established as a highly effective material for treatment applications.

Influence of molybdenum doping on the structural, electrical, and optical properties of germanium telluride thin films

The effect of metal ion doping on electronic band structure and charge carriers' effective mass of Ta2O5 were studied using hybrid functionals in density functional theory. PBE0 hybrid functional proved to be very efficient in predicting the band structure with less than 5% error compared to experimental data. The bandgap decreases monotonically as the percentage of the dopant increases. Furthermore, the indirect bandgap behavior of Ta2O5 was found to initially increase with doping before it decreases again to its original value of pristine Ta₂O₅. We found that high doping content or even mixing with another metal is required in order to modify the band structure of Ta₂O₅. The effect of doping on the crystal structure was also studied. XRD measurements show that the crystal lattice tends to expand upon doping with metals with larger atomic radius than Ta and this effect is more pronounced as the dopant content increases.

Co-doped TiO2 nanoparticles containing 0.0085, 0.017, 0.0255, 0.034, and 0.085 mol % Co(III) ion dopant were synthesized via sol-gel and dip-coating techniques. The effects of metal ion doping on the transformation of anatase to the rutile phase have been investigated. Several analytical tools, such as X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDAX) were used to investigate the nanoparticle structure, size distribution, and composition. Results obtained revealed that the rutile to anatase concentration ratio increases with increase of the cobalt dopant concentration and annealing temperature. The typical composition of Co-doped TiO2 was Ti(1-x)Co(x)O2, where x values ranged from 0.0085 to 0.085. The activation energy for the phase transformation from anatase to rutile was measured to be 229, 222, 211, and 195 kJ/mole for 0.0085, 0.017, 0.0255, and 0.034 mol % Co in TiO2, respectively.