Band Gap Reduction Research Articles

NIR reflective yellow pigment derived from gadolinium phosphate by doping bismuth and vanadium

This paper investigates the novel series of Near-infrared (NIR) reflective pigments with the general formula Gd1-xBix(P1-yVyO4) prepared via the facile hydrothermal method [where, x=y=0, 0.05, 0.1, 0.2, and 0.5]. The synthesized compounds were examined by XRD, XPS, FTIR, UV-Vis DRS, SEM and TEM characterization techniques. Bismuth, vanadium co-doping in GdPO4 host lattice unaltered the phase structure up to x=y=0.1. At higher co-dopant concentrations, the distortion in the phase structure leads to the formation of the mixed phases. Among the individual Bi3+ and V5+ doped GdPO4, the vanadium-doped GdPO4 showed an effective band gap reduction because of the contribution of V3d orbital from dopant element which leads to the color changes. However, vanadium doping drastically reduced the reflectance property of the compound. On the other hand, by bismuth and vanadium co-doping, the band gap was tuned to give a bright yellow color with significant changes in reflectance property. From the prepared compounds, Gd0.9Bi0.1(P0.9V0.1O4) composition showed a hexagonal phase of gadolinium phosphate hydrate with b* value of 34.58 and a reflectance value of 72.92 %. The shape of the particles was identified as nanorod by HRTEM analysis with good chemical and thermal stability.

Enhanced photocatalytic degradation of Rhodamine B using polyaniline-coated XTiO3(X = Co, Ni) nanocomposites

In this study, novel polyaniline-coated perovskite nanocomposites (PANI@CoTiO3 and PANI@NiTiO3) were synthesized using an in situ oxidative polymerization method and evaluated for the photocatalytic degradation of Rhodamine B (RhB) a persistent organic pollutant. The nanocomposites displayed significantly enhanced photocatalytic efficiency compared to pure perovskites. The 1%wt PANI@NiTiO3 achieved an impressive 94% degradation of RhB under visible light after 180 min, while 1wt.% PANI@CoTiO3 reached 87% degradation under UV light in the same duration. X-ray diffraction (XRD) confirmed that the crystalline structures of CoTiO3 and NiTiO3 remained intact post-polymerization. At the same time, Fourier transform infrared spectroscopy (FTIR) verified the successful deposition of PANI through characteristic functional group vibrations. Diffuse reflectance spectroscopy (DRS) revealed reduced band gaps of 2.63 eV for 1wt.% PANI@NiTiO3 and 2.46 eV for 1wt.% PANI@CoTiO3, enhancing light absorption across UV and visible ranges. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis demonstrated the uniform distribution of PANI, ensuring consistent surface activity and efficient charge transfer. The photocatalytic test confirmed a pseudo-first-order degradation mechanism. The study elucidates the degradation mechanism through intermediate identification via HPLC-MS analysis, highlighting N-de-ethylation, aromatic ring cleavage and eventual mineralization into CO2 and H2O as critical pathways. Furthermore, the 1wt.%PANI@NiTiO3 nanocomposite demonstrated excellent stability and recyclability, maintaining its degradation efficiency over four consecutive cycles with minimal change. These findings highlight the potential of PANI@XTiO3 nanocomposites for sustainable and efficient wastewater treatment, addressing diverse environmental challenges by tailoring photocatalysts to specific light sources.

Cutting-edge Nano-therapeutics: silver nanoparticles loaded with ciprofloxacin for powerful antidiabetic, antioxidant, anti-inflammatory, and antibiotic action against resistant pathogenic bacteria

Abstract The rise of antibiotic resistance among pathogenic bacteria poses a critical challenge to global healthcare, necessitating innovative therapeutic strategies. This study addresses this gap by developing ciprofloxacin-loaded silver nanoparticles (CIP@Ag NPs), combining robust antibacterial efficacy with additional therapeutic benefits. CIP@Ag NPs were synthesized and characterized through UV–visible spectroscopy, revealing a distinct redshift to 401 nm and a reduced band gap of 2.24 eV, enhancing their photocatalytic and bioactive properties. Structural and morphological integrity was confirmed using XRD and SEM analyses. The nanoparticles exhibited remarkable multifunctionality, with 84% DPPH radical scavenging activity and a fourfold increase in total antioxidant capacity compared to bare Ag NPs. Anti-inflammatory activity was evidenced by 86.43% inhibition of egg albumin denaturation at 800 μg/ml. Additionally, CIP@Ag NPs demonstrated potent antidiabetic effects, achieving 73% α-amylase and 68% α-glucosidase inhibition at 60 μg/mL. Antibacterial assays of CIP@Ag NPs showed significant improvement, with inhibition zones of up to 34 mm against multidrug-resistant strains like Staphylococcus aureus and Escherichia coli, surpassing the efficacy of both Ag NPs and ciprofloxacin individually. These findings underscore the potential of CIP@Ag NPs as a multifunctional nanoplatform, offering a promising solution to combat antibiotic resistance while addressing inflammation, oxidative stress, and diabetes-related complications.

Enhanced optical properties of chitosan polymer doped with orange peel dye investigated via UV–Vis and FTIR analysis

The current research aims to determine the impact of orange peel dye (OPD), an eco-friendly addition, on the optical properties of biodegradable polymers. This study investigates the enhancement of optical properties in solid electrolytes based on chitosan (CS) and glycerol, with varying OPD concentrations. UV–Vis-NIR spectroscopy revealed significantly enhanced UV–visible light absorption in the 200–500 nm region and effective UV light blocking. FTIR analysis showed strong interactions between OPDs and the CS matrix, with functional groups such as O–H, C=O, and C=C. UV–Visible spectroscopy indicated a reduction in the optical band gap from 5.11 eV in pure CS to 2.93 eV and 2.84 eV with increasing OPD concentrations, reflecting alterations in the electronic structure and enhanced sub-bandgap states. The refractive index improved from 1.31 in pure CS to 1.54 and 1.62 in the doped electrolytes, attributed to increased optical density and light-harvesting capability. Optical basicity also increased from 1.01 to 1.32, enhancing donor properties. These results suggest that OPD-doped CS solid electrolytes offer enhanced optical properties, making them suitable for optoelectronic and UV-blocking applications due to their tunable band gap, improved polarizability, and enhanced light interaction.

Harnessing Hole Sites in 2D Monolayer C60 for Metal Cluster Anchoring.

Synthesis of 2D quasi-hexagonal phase C60 (qHP C60) has opened avenues for its application as a novel catalytic support. This study investigates the structure, stability, and anisotropic properties of Cu4 clusters anchored on the qHP C60 surface through density functional theory calculations. Our findings reveal that the Cu4 cluster preferentially occupies the intrinsic holes of the qHP C60 via one of its tetrahedral faces, resulting in enhanced stability and conductivity, with a significantly reduced band gap of 0.11 eV, compared to the semiconductor behavior of pristine qHP C60. The anisotropic mechanical properties are retained, affirming the robustness of the material under stress. Importantly, the interaction between qHP C60 and Cu4 not only modifies intramolecular bonding but also introduces additional active sites, thereby having a promising enhanced catalytic performance. This work underscores the potential of qHP C60 as an innovative support in catalysis, paving the way for further exploration of its capabilities in industrial applications.

Impact of the Acceptor Group on the Properties of Triphenylamine-Donor-Acceptor Dyes: An Experimental and Computational Study.

Three triphenylamine-Indane donor-acceptor dyes with different functional groups on the acceptor were studied to investigate how substitution would affect the optical properties. The dyes studied were IndCN, containing two malononitrile groups; InO, with two ketone groups; and InOCN, which features mixed functional groups. A combination of Raman spectroscopy, UV-vis absorption and emission spectroscopy, and density functional theory (DFT) calculations were employed for characterization. The dyes exhibited intramolecular charge transfer transitions with relatively high molar absorptivity (εabs) of ∼50 mM-1 cm-1 at 491-591 nm within the visible spectrum and emissions at 690-840 nm in dichloromethane. The malononitrile-containing dyes showed lower-energy absorption and emissions due to a reduced band gap compared to ketone-containing dyes. The bulkiness of the malononitrile group led to a bent geometry, increasing nonradiative decay and reducing the fluorescence quantum yield. The dyes exhibited fluorescence quantum yields less than 0.25 and lifetimes of ∼5 ns. Resonance Raman spectra and DFT calculations showed that the longer linker group (propen-1-ylidene linker) in these systems reduced the charge-transfer character of the optical transition. The emission intensities of the three dyes were temperature-sensitive, with ketone-containing dyes showing shifts in emission bands as well. This could be due to molecular stacking and intermolecular π-interactions.

K-Resolved Ultrafast Light-Induced Band Renormalization in Monolayer WS2 on Graphene.

Understanding and controlling the electronic properties of two-dimensional materials are crucial for their potential applications in nano- and optoelectronics. Monolayer transition metal dichalcogenides have garnered significant interest due to their strong light-matter interaction and extreme sensitivity of the band structure to the presence of photogenerated electron-hole pairs. In this study, we investigate the transient electronic structure of monolayer WS2 on a graphene substrate after resonant excitation of the A-exciton using time- and angle-resolved photoemission spectroscopy. We observe a pronounced band structure renormalization, including a substantial reduction of the transient band gap in good quantitative agreement with our ab initio theory, revealing the importance of both intrinsic WS2 and extrinsic substrate contributions. Our findings deepen the fundamental understanding of band structure dynamics in two-dimensional materials and offer valuable insights for the development of novel electronic and optoelectronic devices based on monolayer TMDs and their heterostructures with graphene.

Band structure and magnetism engineering of InSe monolayers through doping with IVA- and VA-group atoms: role of impurities.

In this work, we investigate the electronic and magnetic properties of the InSe monolayer enriched by doping with IVA-group (Si and Ge) and VA-group (P and As) atoms. Both In and Se sublattices are considered as doping sites to realize n- and p-type doping (XIn@InSe and XSe@InSe systems, X = Si, Ge, P, and As), respectively. The pristine InSe monolayer is an indirect gap semiconductor with a band gap of 1.41 eV. n-Doping processes preserve the monolayer's nonmagnetic nature. IVA-group impurities lead to monolayer metallization, while a considerable band gap reduction is induced by doping with VA-group atoms. The band gap also decreases considerably when realizing p-type doping with IVA-group atoms. In contrast, monolayer magnetization is achieved by p-type doping when replacing Se atoms with P and As atoms, leading to the formation of new 2D magnetic semiconductors. In these cases, VA-group impurities mainly produce the system's magnetism. Furthermore, our calculations also provide evidence for the emergence of magnetism in the InSe monolayer through doping with pair impurities (pX@InSe systems), where Si2/Ge2 (incorporated at the Se sublattice) and P1/As1 (incorporated at the In sublattice) dopant atoms play a key role in determining the electronic and magnetic properties of respective pair-atom-doped systems. Herein, the magnetic semiconductor nature of pSi@InSe and pGe@InSe systems is confirmed, while pAs@InSe is found to be a half-metallic system. Our results suggest the usefulness of doping with IVA- and VA-group atoms that can serve as an effective strategy to functionalize the InSe monolayer, providing insights into the role of impurities.

MXene-based composite photocatalysts for efficient degradation of antibiotics in wastewater

MXene-based (nano)materials have recently emerged as promising solutions for antibiotic photodegradation from aquatic environments, yet they are limited by scalability, stability, and selectivity challenges in practical settings. We formulated Fe2O3-SiO2/MXene ternary nano-photocomposites via coupled wet impregnation and sonochemistry approach for optimised tetracycline (TC) removal (the second most used antibiotic worldwide) from water using response surface methodology-central composite design (RSM-CCD). The photocatalysts containing various loading of Fe2O3/SiO2 (5–45 wt%) on the MXene with a range of calcination temperatures (300–600 °C) via RSM optimisation were synthesised, characterised regarding crystallinity properties, surface morphology, binding energy, and light absorption capability, and analysed for TC degradation efficiency. The 25FeS/MX-450 composite among all samples demonstrated a superior efficiency in TC photocatalytic removal (98%) under optimised conditions (TC degradation: 39.75 mg/L, time: 68.28 min, pH: 5.57, catalyst dosage: 0.75 g/L). The developed surface area, with a reduced band gap due to FeS nanoparticles incorporation with improved light absorption within the visible spectrum, played a crucial role in the 25FeS/MX-450 heterostructure matrix, enhancing photogenerated carriers’ separation and transportation capabilities. The tetracycline photoreduction mechanism involved electron transfer from FeS to the surface of MXene, engaging with O2 to produce •O2−, attributed to the high electron mobility of MXene. Our findings for such nano-photocomposites materials can underscore the considerable potential of MXene-based nanomaterials for pharmaceutical removal from waterways.

Comparison of essential physical properties between pristine armchair silicene nanoribbons and those doped with Ge and As

In this paper, some physical properties of pristine armchair silicene nanoribbons (ASiNR) and those doped with Ge (ASiGeNR) and As (ASiAsNR) using the VASP (Vienna ab initio simulation package) computational program, by using density functional theory. The results show significant differences in the structural and electronic properties between these systems. For ASiGeNR and ASiAsNR, structural parameters such as the distance between two nearest-neighbor atoms in the hexagonal ring, the distance between two farthest atoms, and the buckling height are all larger compared to ASiNR. While ASiNR and ASiGeNR have band gaps of approximately 0.262 eV and 0.2410 eV, respectively, opening at the Γ point, ASiAsNR does not have a band gap. The results indicate that ASiNR and ASiGeNR exhibit semiconductor properties, while ASiAsNR exhibits metallic properties. For ASiGeNR, the substitution of Ge leads to a reduction in bandgap and an increase in thermal conductivity, attributed to the energy level of Ge being close to that of Si. For ASiAsNR, the substitution with As increases the density of states at the top of the valence band, suggesting better electrical conductivity. ASiNR, with its wide bandgap, is suitable for applications in semiconductor devices such as MOSFETs and sensors. ASiGeNR is well-suited for optoelectronic applications such as solar cells or light-emitting diodes (LEDs), while ASiAsNR is appropriate for spintronics or high-speed electronic devices.

In Silico Detection and Conveyance Feasibility of Antifungal Prodrug Flucytosine on the Surface of Pristine and Germanium-Doped SiC Nanosheet.

The work describes a novel sensing and transportation feasibility of the well-established antifungal drug Flucytosine (5-FC) using a 2D Silicon carbide (SiC) and Germanium-doped Silicon carbide (Ge@SiC) nanosheet via PBE level of Density functional theory. The computational study revealed that the drug molecules adhere to SiC and Ge@SiC sheets, maintaining their structural properties through physisorption on SiC and chemisorption on Ge@SiC. The charge transfer process associated with the adsorption is observed by Lowdin charge analysis and both the SiC and Ge@SiC sheets are identified as a feasible oxidation-based nanosensor for the drug. The results of electronic property calculation revealed a reduction in bandgap by 48.2% and 44.8% on SiC and Ge@SiC sheets respectively on adsorption of the drug, highlighting SiC nanosheet to be used as a bandgap-based sensing device. Sensing response at room temperature and human body temperature suggested that, the SiC sheet has an excellent selectivity to Flucytosine drug. The drug's desorption efficiency from the carrier is analyzed using recovery time analysis at different temperatures and frequencies, suggesting the SiC nanosheet to be a better candidate. Together, the study highlights the potential sensing ability of SiC nanosheet for Flucytosine in contrast to the existing 0-D nanostructures.

Spherical Mg/Cu Co‐doped Na4Fe3(PO4)2P2O7 Cathode Materials with Mitigated Diffusion‐induced Stresses and Enhanced Cyclic Stability

Na4Fe3(PO4)2P2O7 (NFPP) has been regarded as the promising cathode material for sodium‐ion batteries (SIBs). However, the practical applications of NFPP are hindered by its high‐volume changes, poor intrinsic electron conductivity and sluggish Na+ ions diffusion kinetics. Herein, a spray‐drying and solid‐state reaction method have been utilized to fabricate the spherical trace amount Mg/Cu co‐doped Na4Fe3(PO4)2P2O7 (NFMCPP). The Mg/Cu co‐doping can effectively mitigate the lattice volume change and promote the electronic conductivity of NFMCPP by reducing band gap between the conduction and valence bands. While, the unique spherical structured NFMCPP with a carbon film even coated on its surface ensures rapid electron transport. Moreover, small NFMCPP particles with spherical geometry demonstrate an alleviated diffusion‐induced stress and enhanced structural stability, due to the high sphericity structure enables fluent Na+ extraction/insertion, leads to a low high‐stress concentration and uniform stress/strain distribution during extensive (de)sodiation process. Consequently, the optimized spherical NFMCPP cathode materials exhibit an excellent rate capability and cyclic stability.

Elastic limit and relaxation of GaAs/In(Al,Ga)As core/shell nanowires for near-infrared applications

In the GaAs/Inx(Al,Ga)1-xAs core/shell nanowire (CSNW) geometry, narrow cores exhibit significant bandgap reduction and enhanced electron mobility because of their ability to sustain extreme tensile elastic strain. In such an elastic state, the coherency limits and the resulting physical properties of the nanowires are governed by the strain field distribution and plastic relaxation mechanisms. Using atomic-resolution transmission electron microscopy, we determined the three-dimensional strain field, critical misfit, and plastic relaxation relative to the indium content of the shell, while maintaining constant core-shell dimensions. The strain was mapped experimentally in both coherent and plastically relaxed nanowires with a core radius of 10 nm and thick shells and was compared to atomistic and continuum calculations. Our findings reveal that, while axial strains remain uniform, elastic relaxation induces radial and tangential strain gradients. This is attributed to the strain concentration at the sharp interfaces, which persisted even after plastic relaxation. For the pertinent growth conditions, the maximum sustained elastic strain in the cores was observed for the GaAs/In0.5Al0.5As nanowires. The plastic relaxation of nanowires with shells of high indium content involved Frank partials delimiting horizontal intrinsic stacking faults (SFs), misfit dislocations gliding on inclined close-packed planes, and stair-rod dislocations along SF junction lines attributed to nanowire bending.Ab initiocalculations showed that the heterojunction remained type I even for the highest elastic strain, despite the existence of strain gradients at the core-shell interface. Our results elucidate the elastoplastic behaviour of CSNWs with narrow cores, offering new perspectives on growth strategies to further push their coherency limits.

Optimization of deposition time and temperature for high-quality PbS thin films via chemical bath deposition

In this study, lead sulfide (PbS) thin films were synthesized using chemical bath deposition (CBD) on glass substrates, employing lead nitrate and thiourea as source of Lead and Sulfur respectively, and triethanolamine was used as complexing agent. The research systematically examined the impact of two key parameters: deposition time (30-90 minutes) and bath temperature (55-90°C), revealing intricate relationships between deposition conditions and film characteristics. Deposition time analysis demonstrated a non-linear transmittance trend, with values changing from 20% at 30 minutes to 8% at 60 minutes, before recovering to 10% at 90 minutes. Additionally, the band gap changed from 2.00 eV at 30 minutes to 1.63 eV at 60 minutes and then increased to 1.70 eV at 90 minutes. Temperature variations showed a progressive decrease in transmittance from 23.75% at 55°C to 11% at 90°C, accompanied by a corresponding band gap reduction from 1.80 eV to 1.50 eV. The optimal conditions for producing high-quality PbS thin films suitable for p-type solar cell applications were determined to be a deposition time of 45 minutes and a bath temperature of 90°C, which effectively balance transmittance and band gap requirements. These findings provide crucial insights for enhancing PbS thin film performance in solar cell and infrared detection technologies, demonstrating the significance of precise parameter control in chemical bath deposition.

Influence of Sn2+ doping to improve the charge transport and light-emitting properties of CsPbCl3 perovskites

Doping B-site with metal ions is an emerging strategy to reduce lead toxicity and enhance the optoelectronic performance of lead halide perovskites. Also, the concentration of metal dopants plays an important role in achieving the desired electrical and optical properties of these halide perovskites. This work presents a simple chemical approach to synthesize pure and Sn2+doped CsPbCl3perovskites at room temperature. The dopant concentration was varied from 1 to 9 mol%. The structural, morphological, optical, thermal, and electrical properties of prepared perovskites are studied in order to check the optimal doping concentration along with to know the improvement in the optoelectronic properties required for LEDs and photovoltaic cells. It was observed that CsPbCl3perovskites exhibit high photoluminescence intensity, blue/violet emission, and high charge carrier mobility (up to 56.3 cm2V s-1) with a reduction in bandgap (up to 2.865 eV) after Sn2+doping.

Size and Crystallinity‐Dependent Photocatalytic Performance of MIL‐53(Fe) and MIL‐53(Fe)/g‐C3N4 Composite

ABSTRACTMIL‐53(Fe) is a novel photocatalytic material that has been developed over the past decade; however, significant efforts are still required to fully optimize its photocatalytic performance in order to meet the requirements of practical applications. In this paper, we investigated the effects of size and crystallinity on the photocatalytic performance of MIL‐53(Fe) and its composites x‐MIL‐53(Fe)/g‐C3N4 (x‐MIL‐Fe/CN). During the hydrothermal synthesis process, the control over particle size was achieved by adjusting the amount of acetic acid (HAc). Ball milling was utilized to manipulate both the size and crystallinity of MIL‐53(Fe). Photocatalytic experiments demonstrated that MIL‐53(Fe) and 15‐MIL‐Fe/CN, characterized by the smallest particle sizes and great crystallinity, exhibited the highest photocatalytic activity. This enhancement in photocatalytic activity can be attributed to the reduced band gap and lower recombination rate of photogenerated carriers. Notably, the hydrogen evolution rate for 15‐MIL‐Fe/CN reached up to 4950 μmol·g−1·h−1, but MIL‐53(Fe) achieved a 98% degradation of methyl orange within 60 min.

Efficacy of nickel doped graphitic carbon nitride as energy storage material

Abstract The current article reports the synthesis of graphitic carbon nitride (GCN), through simple thermal decomposition of urea at a moderate temperature of 550 °C and doping of as-developed material with transition element like nickel. The proper phase formation of the sample was confirmed by x-ray diffraction whereas electron microscopic images analyzed the sample morphologies. The successful doping was verified by x-ray photoelectron spectroscopy whereas thermogravimetric study predicted the stability of the material under elevated temperature. Fourier transformed infrared spectroscopy showed that after Ni doping there is a substantial change in the vibrational energy level of the sample. UV–vis reflectance spectra confirmed the reduction of optical bandgap after metal doping. The samples show promises towards supercapacitor application. Cyclic voltametric study shows that after metal doping the value of specific capacitance became 162 Fg−1 at scan rate 5 mV s−1 and when the same was calculated from galvanostatic charging–discharging characteristics the values came even higher. The energy and power density of both the samples was calculated and all these when compared with different reported results, confirmed the performance of Ni doped GCN is comparable and sometimes even far better along with the advantages of the easy, large scale and high yield synthesis approach.

Analytical study on the flexural wave band gaps of arbitrary periodic stiffened plates by using beam-plate coupling theory

In this paper, the flexural wave band gap characteristics of periodic stiffened plates are studied by using beam-plate coupling theory. A theoretical model of arbitrary periodic stiffened plate is established considering the coupling effect of Timoshenko beam and Kirchhoff plate. The flexural wave band structures of periodic stiffened plate are calculated by using plane wave expansion method and Bloch theorem. Numerical calculation and experimental tests were conducted to verify the proposed theoretical model. In addition, the parametric studies were performed to examine the effects of geometric parameters on both bandgap and vibration reduction characteristics of periodic stiffened plate. Results show that periodic stiffened plate can yield significant flexural wave band gaps and vibration isolation performance in a specific frequency range, which shows a good agreement with numerical simulation and experimental results. The geometrical parameters of stiffened plates have a significant influence on adjusting low-frequency flexural wave band gaps. These research findings offer a new technical approach for low frequency vibration and sound optimization of stiffened structures.

Mn-doped SrTiO3 perovskite: Synthesis and characterisation of a visible light-active semiconductor

This study focuses on the synthesis and characterisation of Mn-doped SrTiO3 using the citric method. As-prepared samples featured a non-porous microstructure with a mean particle size of approximately 5 μm, composed of sintered submicron crystallites. Manganese was successfully incorporated into the perovskite structure as Mn4+, with a homogeneous distribution across the Sr and Ti positions. The doping induced a distinctive dark brown hue, indicating significant visible light absorption. A pronounced band gap shift from 3.32 to 2.92 eV was revealed via Tauc analysis of the Kubelka-Munk function. Both the SrTiO3 and Mn-doped SrTiO3 samples demonstrated a high adsorption capacity exclusively for cationic dye (Methylene Blue) at pH 10, with the Mn-doped sample showing slightly enhanced removal efficiency, reaching a maximum adsorption capacity of 310.7 mg g−1. The selective adsorption at high pH can be attributed to electrostatic interactions between the perovskite surface and MB molecules. This combination of high adsorption capacity and a reduced band gap highlights the material’s potential for photocatalysis applications.

Enhanced photocatalytic H2 generation via in-situ grown CuO-decorated TiO2 nanotubes on Ti-Cu alloys: A synergistic thermo-electrochemical approach

In the present study, we developed a thermo-electrochemical strategy to grow CuO self-decorated TiO2 nanotubes (TiNTs) on Ti-xCu alloys (x = 0, 2, 4, 6, and 8 wt%). The Ti-xCu metastable solid solution alloys were prepared by rapid quenching after solid solution heat treatment. Based on microstructural analyses, unlike all other samples, which consist of the α-Ti phase, the microstructure of the Ti-8Cu sample is biphasic, consisting of α-Ti and the Ti2Cu intermetallic compound. Electrochemical anodization of the Ti-xCu samples results in the in-situ formation of CuO nanoparticles decorating the TiO2 nanotubes on substrates containing Cu. As the Cu concentration increases, the order and integrity of the nanotube arrays gradually decrease while the Cu concentration within the nanotubes increases; however, the Ti-6Cu sample presents a satisfactory structural order and a uniform distribution of Cu. Based on XPS analysis, it has been determined that CuO is the main species decorating the TiNTs. This results in a maximum reduction of the band gap by approximately 0.5 eV for the Ti-6Cu sample compared to the pure Ti sample (3.35 eV), leading to improved absorption of visible light. Furthermore, the CuO species extended the lifetime of charge carriers, as demonstrated by electrochemical impedance spectroscopy. This combination of band gap reduction and enhanced charge carrier separation in Ti-6Cu resulted in a photocatalytic H2 production rate of 35.8 µL/cm2·h, more than ten times higher than the pure Ti sample. These findings hold significant promise for developing efficient and sustainable energy production systems.