Ni Co-doping Research Articles

Effect of Ni and Dy co-doping on the structural, electrical, and dielectric properties of Strontium Y-type hexaferrite

Effect of Ni and Dy co-doping on the structural, electrical, and dielectric properties of Strontium Y-type hexaferrite

Medium-entropy strategy to inhibit the surface Sr segregation and enhance the stability of Sr2Fe1.5Mo0.5O6-δ cathode for CO2 direct electrolysis

Solid oxide electrolysis cell (SOEC) is a promising solid-state electrochemical device that can convert CO2 into CO with high efficiency. However, the poor catalytic activity and Sr segregation of the cathode diminish the electrode reaction, hindering the large-scale application. Herein, a medium-entropy strategy is proposed to suppress the Sr enrichment while enhancing the catalytic activity for CO2. The surface Sr content on Sr2Fe1.2Ni0.1Cu0.1Co0.1Mo0.5O6-δ (SFNCCM) is significantly reduced after the Ni, Cu, and Co co-doping at Fe-site. Moreover, the oxygen surface exchange and bulk diffusion coefficient at 800 °C for SFNCCM oxide reach 2.42 × 10−4 cm2 s−1 and 2.28 × 10−5 cm2 s−1, which are 1.35 and 1.39 times higher than parent Sr2Fe1.5Mo0.5O6-δ(SFM) oxide. At 850 °C and 1.5 V, single with SFNCCM-Sm0.2Ce0.8O6-δ(SDC) composite exhibits a current density of 2.22 A cm−2 with good stability for up to 100 h. The results suggest that the medium-entropy strategy is a promising method to inhibit Sr segregation and enhance the performance of CO2 direct electrolysis.

Inhibiting the Jahn-Teller Effect of Manganese Hexacyanoferrate via Ni and Cu Codoping for Advanced Sodium-Ion Batteries.

Manganese (Mn)-based Prussian blue analogs (PBAs) are of great interest as a prospective cathode material for sodium-ion batteries (SIBs) due to their high redox potential, easy synthesis, and low cost. However, the Jahn-Teller effect and low electrical conductivity of Mn-based PBA cause poor structure stability and unsatisfactory performance during the cycling. Herein, a novel nickel- and copper-codoped K2Mn[Fe(CN)6] cathode is developed via a simple coprecipitation strategy. The doping elements improve the electrical conductivity of Mn-based PBA by reducing the bandgap, as well as suppress the Jahn-Teller effect by stabilizing the framework, as verified by the density functional theory calculations. Simultaneously, the substitution of sodium with potassium in the lattice is beneficial for filling vacancies in the PBA framework, leading to higher average operating voltages and superior structural stability. As a result, the as-prepared Mn-based cathode exhibits excellent reversible capacity (116.0 mAh g-1 at 0.01 A g-1) and superior cycling stability (81.8% capacity retention over 500 cycles at 0.1 A g-1). This work provides a profitable doping strategy to inhibit the Jahn-Teller structural deformation for designing stable cathode material of SIBs.

Synthesis and Properties of Eu and Ni Co-Doped ZnS Nanoparticles for the Detection of Ammonia Gas

Zinc sulfide nanoparticles were synthesized successfully via chemical co-precipitation, both in undoped form and co-doped with Europium (Eu) and Nickel (Ni). All prepared samples exhibited cubic zinc blende structure as confirmed by X-ray diffraction (XRD). The average particle size ranged from 3 to 6 nm for both pure and (Eu, Ni) co-doped ZnS, with no alteration in the crystal structure due to Eu and Ni co-doping. However, increasing the Ni dopant concentration (0, 2, 4, & 6 at%) while maintaining a constant Eu concentration (4 at%) led to an enhancement in the crystallite size. This was further validated by transmission electron microscopy (TEM), which showed particle sizes consistent with the XRD findings (3–5 nm). Microscopic analysis via scanning electron microscopy and TEM revealed spherical agglomerated morphology for the (Eu, Ni) co-doped nanoparticles. Energy-dispersive X-ray spectroscopy spectra confirmed the stoichiometric chemical composition of ZnS: Eu, Ni. Photoluminescence studies demonstrated an increased intensity of green luminescence at 6 at% Ni co-dopant concentration. Moreover, the synthesized samples exhibited promising gas sensing properties, particularly towards ammonia gas, with good selectivity. Notably, both pure and (Eu, Ni) co-doped ZnS nanoparticles showed rapid response and recovery times at room temperature, suggesting their potential applicability in gas sensing applications.

Boosting acetone response of p-type Co3O4 sensor via Sn and Ni co-doping for diabetes diagnosis

The hole accumulation layer (HAL) configuration of p-type oxides (including Co3O4) in ambient air causes intrinsically low gas response and hinders their promising applications in exhaled gas analysis. Herein, Sn and Ni co-doping has been proposed to trigger the response of chemiresistive Co3O4 sensor toward acetone (biomarker of diabetes). Via incorporating 1 at% Sn and 0.5 at% Ni doping (Co2.95Sn0.03Ni0.02O4), the response to 100 ppm acetone has been boosted ∼2 orders (from 1.24 to 125.6) at 70 °C, the limit of detection (LoD) has been reduced ∼4 times (from 47.9 to 12.4 ppb), the optimal operation temperature has been decreased from 130 °C to ∼70 °C. Various characterizations suggest that co-doping induced abundant surface asymmetric oxygen vacancy defects (Co-□-Ni, Sn-□-Ni), which facilitate the catalytic oxidation of acetone molecules at relatively low operation temperature. In addition to excellent reproducibility and long-term stability, Co2.95Sn0.03Ni0.02O4 sensor could also operate under highly humid air background and reliably detect acetone concentration in exhaled breath at 150 °C, opening the opportunity for the practical application of p-type oxide sensors for diabetes diagnosis.

Fabrication of Ni and Mn co-doped ZnFe2O4 spinel ferrites and their nanocomposites with rGO as an efficient photocatalyst for the remediation of organic dyes

Herein, we have synthesized Ni and Mn co-doped ZnFe2O4 ferrites using the simple co-precipitation method and their nanocomposites (NCs) with 10 % rGO using the ultra-sonication route. The structural investigation revealed the successful formation of single-phase ZnFe2O4 NPs with cubic spinel ferrite geometry. The crystallite size was determined to be in the range of 21 nm to 28 nm. The current–voltage (I-V) analysis revealed that Ni and Mn co-doping and the addition of rGO nanosheets in ZnFe2O4 NPs boosted the electrical responses of the fabricated Zn1-xNixFe2-yMnyO4/rGO NCs. The BET analysis indicates an increase in the surface area of Zn1-xNixFe2-yMnyO4/rGO NCs (132 m2/g) that might be attributed to the inclusion of rGO nanosheets, which prevents the NPs from agglomeration. The photocatalytic evaluation of the pristine ZnFe2O4 NPs, Ni and Mn co-doped Zn1-xNixFe2-yMnyO4 NPs, and Zn1-xNixFe2-yMnyO4/rGO NCs photocatalysts was tested by photodegradation of malachite green (MG) dye under sunlight irradiation. Results exhibited improved photocatalytic responses and degraded 94.6 % of MG dye in 45 min using Zn1-xNixFe2-yMnyO4/rGO NCs, which was much higher compared to the Ni and Mn co-doped Zn1-xNixFe2-yMnyO4 NPs (58.7 %) and pristine ZnFe2O4 NPs (38.3 %). The increased degradation potential of Zn1-xNixFe2-yMnyO4/rGO NCs was accredited to the highly conducting nature and 2D nano-sheets of rGO, which efficiently inhibited the recombination of charge carrier species. Ultimately, the remarkable photocatalytic capability exhibited by Zn1-xNixFe2-yMnyO4/rGO NCs implies that the synthesized NCs could have auspicious practical applications in the elimination of dyes from wastewater.

Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga1-x-y Fe x Ni y Sb

(Ga,Fe)Sb is a promising magnetic semiconductor (MS) for spintronic applications because its Curie temperature (T C) is above 300 K when the Fe concentration is higher than 20%. However, the anisotropy constant K u of (Ga,Fe)Sb is below 7.6 × 103 erg/cm3 when Fe concentration is lower than 30%, which is one order of magnitude lower than that of (Ga,Mn)As. To address this issue, we grew Ga1-x-y Fe x Ni y Sb films with almost the same x (≈24%) and different y to characterize their magnetic and electrical transport properties. We found that the magnetic anisotropy of Ga0.76-y Fe0.24Ni y Sb can be enhanced by increasing y, in which K u is negligible at y = 1.7% but increases to 3.8 × 105 erg/cm3 at y = 6.1% (T C = 354 K). In addition, the hole mobility (µ) of Ga1-x-y Fe x Ni y Sb reaches 31.3 cm2/(V∙s) at x = 23.7%, y = 1.7% (T C = 319 K), which is much higher than the mobility of Ga1-x Fe x Sb at x = 25.2% (µ = 6.2 cm2/(V∙s)). Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of (Ga,Fe)Sb by using Ni co-doping.

Flower-shaped 1 T/2H-phase molybdenum disulfide co-doped with nickel and iron grown on carbon cloth for enhanced water splitting

The development of an efficient, bifunctional, and affordable catalyst has emerged as a valuable approach for electrocatalysis, as it enhances the charge transfer capability and the number of active sites of the catalyst. Herein, we synthesized a flower-like structure of nickel and iron co-doped molybdenum disulfide on carbon cloth (Ni/Fe-MoS2/CC) using a facile hydrothermal method. The Ni/Fe-MoS2/CC sample exhibited remarkable activity towards the hydrogen evolution reaction, with low overpotentials of −116 mV and a Tafel slope of 43 mV/dec at −10 mA/cm2. It also showed excellent performance in the oxygen evolution reaction with an overpotential of 202 mV and a Tafel slope of 65 mV/dec to afford a current density of + 10 mA/cm2 along with high stability. This study illustrates the beneficial effect of Ni and Fe co-doping on the synthesized flower-shaped MoS2 with the formation of 1 T phase on MoS2/CC, demonstrating significant potential in the field of electrocatalysis.

Visible-light responsive BiVO4 nanocompositions: Enhanced photocatalytic, electrical and optical performance through Ni and Ni/Co doping

The pronounced light sensitivity of BiVO4 has garnered significant attention, establishing it as a visible light-responsive photocatalyst. This study was focused on enhancing the optical, dielectric constant properties, and photocatalytic activity of BiVO4 compositions. By employing a modified combustion method, pure BiVO4, Ni-mono-doped (BiNi0.02V0.98VO4), and Ni/Co-bi-doped (BiCo0.02Ni0.02V0.96VO4) were synthesized. X-ray diffraction (XRD) analysis validated the formation of a monoclinic BiVO4 phase. The incorporation of Ni2+ and Co2+ ions into the BiVO4 lattice was supported by variations in the lattice parameters, volume expansion and increased average crystallite size. Morphological investigation via scanning electron microscopy (SEM-EDAX) confirmed the purity of the synthesized nanocompositions and unveiled distinctive rod-like and needle-like particle shapes in BiNi0.02Co0.02V0.96VO4, with an aspect ratio of 0.07–0.1, indicating potential benefits for efficient charge separation in photocatalysis. Optical examination highlighted redshifts in band gap energy (2.36 eV) due to both Ni and (Co, Ni) co-doping, leading to direct band gaps of 2.34 eV and 2.32 eV, respectively. High refractive index values exceeding 2.5, conducive to optical applications, were observed across all samples. Through Ni and Ni/Co doping process, a notable enhancement in conductivity emerged, particularly within the low-frequency domain. The co-doping of Ni and Co demonstrated elevated relative permittivity (εʹ) values exclusively within the low-frequency span, up to 100 Hz. In contrast, the Ni-mono-doping interestingly disclosed an enhancement in (εʹ) across all frequency ranges. Photocatalytic results demonstrated heightened degradation activity in doped samples, with the BiNi0.02Co0.02V0.96VO4, sample exhibiting the highest rate, achieving 88 % degradation efficiency in 180 min. This exceptional performance can be attributed to its visible-light-responsive band gap, increased electron-hole trapping sites, and distinct morphology.

One-pot hydrothermal preparation of Ni and I co-doped brookite-anatase TiO2 nanoparticles with remarkably enhanced photoreduction activity of CO2 to CH4

Ni and I co-doped TiO2 nanoparticles with mixed anatase-brookite phase (Ni/I-TiO2) were synthesized by the hydrothermal-calcination method for photocatalytic CO2 reduction with H2O vapor. The I and Ni co-doping, anatase-brookite phase junction, as well as the presence of Ti(III) and Ni(III) endowed the catalyst with promoted visible light absorption, increased reduction ability of photogenerated electrons, facilitated charge separation and migration along with modulated CO2 adsorption mode and capacity, ultimately resulting in boosted photocatalytic activity and product selectivity as compared with those of pure TiO2. The CO, CH4 and O2 yields of the optimized Ni/I-TiO2 reached 3.49, 158.25 and 246.30 μmol/gcat after 15 h of light illumination, which decreased slightly after 9 cycles, and the product selectivity was above 98 % for photocatalytic reduction of CO2 to CH4 with Ni and I co-doping. The in-situ FTIR results with the observation of CH3O and CH3 intermediates confirmed CH4 formation, and the possible mechanism of photocatalytic CO2 reduction over Ni/I-TiO2 was elucidated. This work provides new insights to pursue efficient catalysts for the selective photocatalytic CO2 reduction to CH4.

First-principles prediction of enhanced photocatalytic activity in La-X (X = Sc, V, Cr, Mn, Fe, Co, Ni, or Cu) Co-doped SrTiO3

The influence of La-X (X = Sc, V, Cr, Mn, Fe, Co, Ni, or Cu) co-doping on the electronic structure and photocatalytic activity of SrTiO3 system was investigated using the open-source software package Quantum Espresso (QE) based on density functional theory. Defect formation energy calculations showed an energy advantage for co-doped systems under Ti-poor and O-rich conditions. The La-V, La-Cr, La-Mn, La-Fe, and La-Ni co-doped systems showed magnetic properties with corresponding total magnetization of 0.08 µB, 2.97 µB, 3.30 µB, 1.00 µB and 1.00 µB, respectively. The La-X (X = V, Cr, Mn, Fe, Ni, or Cu) co-doped system exhibits photoabsorption activity in the visible region as compared to the pure SrTiO3. The La-X (X = Cr, Fe, Ni, or Cu) co-doped SrTiO3 exhibits a long carrier lifetime, especially the La-Fe co-doped system with a high effective mass ratio of holes to electrons of 5.79. However, the redox potential of the water decomposition reaction of the La-Cu co-doped system is too large, making it unsuitable for water splitting. In summary, the La-X (X = Cr, Fe, or Ni) co-doped systems exhibited intermediate states in the band structure and density of states, which better meet the specific requirements for photocatalysis compared to systems without intermediate states, showing superior photocatalytic potential. The band edge alignment of the three co-doped systems with water redox potentials demonstrated good matching. These findings suggest that La-X (X = Cr, Fe, or Ni) co-doped SrTiO3 is a promising candidate material for solar-driven water splitting.

Binary metal doped and graphene anchored LaCrO3 perovskite with boost light harvesting properties for environmental remediation

This study developed visible light-driven ABO3 type (perovskite) lanthanum chromite (LaCrO3) and Co–Ni co-doped (La1-xCoxCr1-yNiyO3; LCCNO) photocatalyst using a straightforward micro-emulsion process. Later, LCCNO nanoparticles were deposited on reduced graphene oxide (r-GO) utilizing an ultrasonication approach to form nanocomposite (LCCNO/r-GO). The investigation included structural, morphological, and elemental analyses, which were conducted using techniques such as x-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) analysis. The present study investigated the impact of Co–Ni co-doping and rGO reinforcement on the bandgap and electrical conductivity in the context of optical analysis and current-voltage (I–V) experimentation. The nanomaterial's photocatalytic activity (PCA) was evaluated using crystal violet (CV), a well-recognized commercial dye. The composite as a photocatalyst exhibits superior CV dye photodegradation efficiency (99.02%; 100 min) compared to pure LCO (36.44%; 100 min) and co-doped LCCNO (73.74%; 100 min) counterparts due to its low band gap (2.14 eV), high conductivity (6.4 × 105 Sm−1), and large surface area (123.7 m2/g). Furthermore, a series of studies were conducted to examine the primary active free radicals generated by the composite material and to evaluate its long-term viability as a photocatalyst. The present research investigates the beneficial effects of co-doping and the incorporation of carbonaceous materials on the photocatalytic performance of ABO3-type perovskite.

(Invited) Confirmation of Na-O-Li Configuration for P2-Type Cathode Materials

Oxygen-redox-based cathode materials for sodium-ion batteries (SIBs) have attracted considerable attention in recent years owing to their possibility of delivering additional capacity in the high-voltage region. However, they still suffer from not only fast capacity fading but also poor rate capability. Herein, we introduce P2-Na0.75[Li0.15Ni0.15Mn0.7]O2, an oxygen-redox-based layered oxide cathode material for SIBs. The effect of Ni doping on the electrochemical performance was investigated by comparison with Ni-free P2-Na0.67[Li0.22Mn0.78]O2. The Na0.75[Li0.15Ni0.15Mn0.7]O2 delivered a specific capacity of ~160 mAh g-1 in the voltage region of 1.5–4.6 V at 0.1C in Na cells. Combined experiments (galvanostatic cycling, neutron powder diffraction (NPD), X-ray absorption spectroscopy (XANES), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (7Li NMR)) and theoretical studies (density functional theory, DFT calculations) confirmed that Ni substitution not only increases the operating voltage and decreases voltage hysteresis but also improves the cycling stability by reducing Li migration from transition metal (TM) to Na layers. This research demonstrates the effect of Li and Ni co-doping in P2-type layered materials and suggests a new strategy of using Mn-rich cathode materials via oxygen redox with optimization of doping elements for SIBs.

Abnormalities and preferences in divalent (Cu, Ni) co-doping in ZnO at lower proportions

Abnormalities and preferences in divalent (Cu, Ni) co-doping in ZnO at lower proportions

Modulating the coadsoption of hydroxyl and nitrogenous groups induced by Ni and Cu doping on FeOOH for accelerating dehydrogenation in the ammonia oxidation reaction

Owing to its high hydrogen content and carbon-free nature, ammonia is a promising energy carrier used in powering fuel cells and an alternative oxidation substrate to water in electrolytic hydrogen production devices. However, the insufficient mechanistic understanding and the lack of inexpensive and efficient catalysts for the ammonia electro-oxidation reaction (AOR) have hampered the development of the ammonia-based energy system. In this work, novel Ni and Cu co-doped porous FeOOH nanorods (NiCu-FeOOH) synthesized by a light-induced chemical precipitation method can serve as the AOR catalyst with efficient catalytic activity (1.41 V at an anodic current density of 10 mA cm−2) and enhanced stability in an aqueous ammonia solution. According to the experimental data and theoretical calculation results, the synergistic effect of heterogeneous Ni and Cu atoms makes Ni and Fe sites on the surface of NiCu-FeOOH exhibit a suitable electronic structure to coadsorb nitrogenous intermediates and hydroxyl groups at the top of the volcano plot and thereby accelerate dehydrogenation in the AOR. The backward shift of the rate-determining step (RDS) (⋆NH2 + ⋆OH formation step shifts to ⋆N2H3 + ⋆OH formation step) and the lower energy barrier of the RDS (0.86 eV) reveal that the Ni and Cu co-doping makes FeOOH crystals active for the AOR. The coadsorption reaction pathway involved in nitrogenous intermediates and hydroxyl groups has been in-novatively proposed to effectively describe and simulate the AOR process, which opens a new horizon to design low-cost and stable AOR catalysts.

Valence state, lattice incorporation, and resulting magnetic properties of Ni in Zn/Co-based magnetic oxides

Ni incorporation has been studied in a comprehensive range of Zn/Co-based magnetic oxides to elucidate its valence state and lattice incorporation. The resulting structural and magnetic properties of a range of related types of samples are studied in detail. On the one hand, Ni doping is studied in wurtzite ZnO which is either done by in-diffusion of the Ni into bulk ZnO or by reactive magnetron sputtering for Ni-doped thin films of ZnO. The latter is complemented by Ni and Co codoping of ZnO leading to altered magnetic properties which are then dominated by Co. On the other hand, the ZnCo2O4 spinel is codoped with varying amounts of Ni. In the wurtzite oxides, Ni is exclusively found on tetrahedral lattice sites in its formal 2+ oxidation state as deep donor. It behaves as an anisotropic paramagnet, and a limited solubility of Ni below 10% is found. Furthermore, the partial compensation of the antiferromagnetically coupled Co magnetic moments is induced by the Ni due to its smaller magnetic moment. In the ZnCo2O4 spinel, Ni is found to be incorporated in its formal 3+ oxidation state on octahedral sites and also couples antiferromagnetically to the Co moments. At low Ni concentrations, this leads to a lifting of the partial magnetic compensation of the antiferromagnetic ZnCo2O4 spinel and to ferrimagnetism at higher Ni concentrations. Increasing the Ni concentration even further leads to phase separation of cubic NiO resulting in a structurally less defined, exchange-biased composite magnetic oxide.

Ni, Co, and Yb Cation Co-doping and Defect Engineering of FeOOH Nanorods as an Electrocatalyst for the Oxygen Evolution Reaction.

Electrocatalytic water splitting is a feasible technology that can produce hydrogen from renewable sources. The oxygen evolution reaction (OER), which has a slower kinetics and higher overpotential than the hydrogen evolution reaction, is the bottleneck that limits the overall water splitting. It is essential to develop efficient OER catalysts to reduce the anode overpotential. Herein, Ni,Co,Yb-FeOOH nanorod arrays grown directly on a carbon cloth are synthesized by a simple one-step hydrothermal method. The doped Ni2+ and Co2+ can occupy Fe2+ and Fe3+ sites in FeOOH, increasing the concentration of oxygen vacancies (VO), and the doped Yb3+ with a larger ionic radius can occupy the interstitial sites, which leads to more edge dislocations. VO and edge dislocations greatly enrich the active sites in FeOOH/CC. In addition, density functional theory calculations confirm that doping of Ni2+, Co2+, and Yb3+ modulates the electronic structure of the main active Fe sites, bringing its d-band center closer to the Fermi level and reducing the Gibbs free energy change of the rate-determining step of the OER. When the current density reaches 10 mA cm-2, the overpotential of Ni,Co,Yb-FeOOH/CC is only 230.9 mV, and the Tafel slope is 22.7 mV dec-1. In particular, a mechanism of multi-cation doping synergistic interaction with the oxygen vacancy and edge dislocation to enhance the OER catalytic activity of the material is proposed.

New glass cathode materials for Li-ion battery: Ni-Co doping in Li-B-O based glass

Lithium-borate-based glass co-doped with nickel and cobalt ions was successfully fabricated by a two-step melt quenching method. The relationship between Ni and Co contents in the glasses was investigated, with a focus on their electrochemical properties and battery performance. Cyclic voltammetry was used to pre-investigate the electrochemical properties of the glass electrodes. It was found that the specific capacitance of all conditions was above 100 F/g. This preliminary study showed that the glass is feasible to use as a Li-ion battery cathode. The Co-rich content sample (NC11) exhibited the highest specific capacity of 380 mAh/g in the first cycle test. However, the specific capacity was dramatically decreased in subsequent cycles due to Li-ion trapping in the glass structure. Additionally, the higher amount of Ni ions in the co-doping Ni/Co-LBO glass enhanced the retention properties. This suggests that Ni-rich content could improve the release of free Li-ions from the host glass structure.

Structural transition and enhanced magnetic, optical and photocatalytic properties of novel Ce–Ni co-doped BiFeO3 nanoparticles

Bi1-xCexFe1-xNixO3 (x = 0%, 4%, 6% and 8%) samples were synthesized using sol-gel method to study strategically the influence of Ce–Ni co-doping on structural, vibrational, magnetic, optical and photocatalytic properties utilizing various techniques. XRD showed that whole samples crystallized in single-phase as well as revealed a huge lattice distortion with rising Ce–Ni co-substitution content. A structural phase change from rhombohedral to orthorhombic occurred at the co-substitution sample with x = 8%, confirmed by XRD and the Rietveld refinement as well as Raman analysis. EDS analysis evidenced the existence of Bi, Fe, Ce as well as Ni concentrations in the co-substitution samples with stoichiometric proportion. Crystallinity is noted to be raised when Ce–Ni is co-substitution in BiFeO3 (BFO). Ce–Ni co-doped in BiFeO3 significantly induced improvement of ferromagnetic property, which was shown by the drastic rising with a maximum saturation (Ms) magnetization values of 2.741 emu/g. The optical energy bandgap was sharply reduced with the Ce–Ni co-substitution concentration. It was found that Ce3+ and Ni2+ co-substitution enormously impacted the photocatalytic efficiency of undoped BFO. Furthermore, with the increase of Ce–Ni co-doping into BFO up to 6%, the photocatalytic efficiency was maximized. The photocatalytic feasibility mechanism of Ce–Ni co-substitution BFO was discussed in detail. We have noted in this work that the fascinating properties in co-substituted BiFeO3 give the feasibility of producing a novel functional device.

Facile Zn and Ni Co-Doped Hematite Nanorods for Efficient Photocatalytic Water Oxidation.

In this work, we report the effect of zinc (Zn) and nickel (Ni) co-doping of hydrothermally synthesized hematite nanorods prepared on fluorine-doped tin oxide (FTO) substrates for enhanced photoelectrochemical (PEC) water splitting. Seeded hematite nanorods (NRs) were facilely doped with a fixed concentration of 3 mM Zn and varied concentrations of 0, 3, 5, 7, and 9 mM Ni. The samples were observed to have a largely uniform morphology of vertically aligned NRs with slight inclinations. The samples showed high photon absorption within the visible spectrum due to their bandgaps, which ranged between 1.9–2.2 eV. The highest photocurrent density of 0.072 mA/cm2 at 1.5 V vs. a reversible hydrogen electrode (RHE) was realized for the 3 mM Zn/7 mM Ni NRs sample. This photocurrent was 279% higher compared to the value observed for pristine hematite NRs. The Mott–Schottky results reveal an increase in donor density values with increasing Ni dopant concentration. The 3 mM Zn/7 mM Ni NRs sample produced the highest donor concentration of 2.89 × 1019 (cm−3), which was 2.1 times higher than that of pristine hematite. This work demonstrates the role of Zn and Ni co-dopants in enhancing the photocatalytic water oxidation of hematite nanorods for the generation of hydrogen.