arXiv subjects

Dilip Sasmal

Publications and source records attributed to Dilip Sasmal.

8 recordsLinked to original sources

arXiv2025

Increased Covalence and V-center mediated Dark Fenton-Like Reactions in V-doped TiO2: Mechanisms of Enhanced Charge-Transfer

Tuning the valence state and electronic structure of catalytically active sites is crucial for improving Fenton and Fenton-like reactions, which rely on the efficient activation of the H2O2 molecule. Pure TiO2, however, has inadequate activity towards the H2O2 activation and is often constrained by the intrinsic electronic limitations of pristine TiO2. Herein, a rational approach has been demonstrated to improve the Fenton-like catalytic performance of TiO2 through multivalent vanadium (V) doping. A comprehensive characterization using X-Ray Diffraction (XRD), Raman spectroscopy, UV-Vis spectroscopy, X-Ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), and Density functional theory (DFT) reveals that V incorporation substantially alters the electronic structure of TiO2. The DFT results, supported by experimental data, indicate that V doping enhances Ti-O covalence and introduces mid-gap states, resulting in a reduced band gap and improved charge transfer. XPS confirms the coexistence of multiple oxidation states of V, which serve as active centres for activating H2O2 and generating OH radicals. As a result, V-doped TiO2 exhibits significantly enhanced dark-catalytic activity in degrading the organic dye Rhodamine B (RhB). Overall, this study provides fundamental insights into multivalent-cation-induced valence state and electronic structure modulation in TiO2, offering a promising strategy for designing high-performance catalysts via defect engineering for sustainable environmental remediation.

cond-mat.mtrl-sci↗

arXiv2025

Interfacial Synergy in Ag-Doped CuO-AgCl-g-C3N4 Composites for Efficient Charge Separation and Low-power Methylene Blue Degradation

An Ag-doped CuO-AgCl-g-C3N4 heterostructure has been designed to achieve rapid Methylene Blue (MB) degradation through a synergistic photo-Fenton mechanism driven by low-power UV illumination. The composite integrates narrow-bandgap CuO, plasmonic Ag/AgCl, and visible-responsive g-C3N4 into a dual Z-scheme configuration that promotes efficient interfacial charge transfer while preserving strong redox potentials. Diffuse reflectance UV-Vis spectra ascertained the bandgap positions of the composite corresponding to those of its constituents: 2.9 eV (g-C3N4) and 1.42 eV (Ag-doped CuO-AgCl), indicating enhanced absorption and efficient charge carrier generation. BET analysis confirmed the presence of mesoporosity and revealed an effective surface area, ensuring the availability of abundant adsorption and reaction sites. A commercial 11 W UV irradiation was used for the photocatalytic test. Almost complete degradation of MB occurred within 10 min, following pseudo-first-order kinetics with a high apparent rate constant of 0.45/min. The remarkable activity arises from the synergistic interplay of Fenton-like redox cycling and efficient photoinduced charge carrier generation and separation. In addition, it has been demonstrated that intentionally incorporated AgCl plays an active role as a plasmonic-semiconducting interface, strengthening charge separation and catalyst stability under neutral conditions, rather than acting as a passive chloride byproduct. Overall, by linking defect engineering, heterojunction design, and photo-Fenton synergy, this study establishes a low-power, catalytic platform offering a viable pathway towards sustainable dye wastewater remediation.

cond-mat.mtrl-sci↗

arXiv2025

Hexagonal polymorphism induced structural disorder and dielectric anomalies of Ca/Mn modified BaTiO3

This work involves the local structural investigation of the samples using Extended X-ray Absorption Spectra (EXAFS) analysis to investigate structural changes due to the Ca and Mn-modified BaTiO3. TEM investigation of the crystal structure reveals the coexistence of the tetragonal and hexagonal phases of BaTiO3. Band gap modification and Urbach tail variation in UV-DRS measurements reveal a reduction of band gap from UV to Visible range (3.2 eV to 2 eV). This band gap change is correlated with the valence band modification observed in PES measurements due to localised defects in the material, and supported by theoretical Density of States calculations. The electron localisation function calculation is used to analyse the changes in the localised electron density near the dopant atoms. It reveals the local expansion and contraction of the lattice surrounding the dopant atom. All these structural modifications lead to variations in the dielectric properties and diffusive nature of the phase transition. The defect-induced structural modifications, multiple phase coexistence, band gap variations and dielectric properties are explored and correlated.

cond-mat.mtrl-sci↗

arXiv2025

Estimating the Diffuseness for the Non-Relaxor Type Ferroelectric to Paraelectric Phase Transition in BaTiO3

The normal ferroelectric to paraelectric phase transition in model ferroelectric materials such as BaTiO3 is typically characterized by a sharp, well-defined dielectric constant peak at a specific transition temperature. However, under certain modifications of the parent material, this transition can become diffuse over a broad range of temperatures. This has garnered significant research attention over the past few decades, primarily because of its intriguing and not yet fully understood physical properties. The parameters developed to measure the diffuseness are also ambiguous. In this work, an investigation has been conducted to understand the transition dynamics of the non-relaxor ferroelectric systems in the temperature interval over which the diffuse phase transition occurs. This is achieved by modelling the dielectric response phenomenologically, using a distribution of local transition temperatures. Moreover, a temperature dependent differential analysis is introduced, enabling the clear demarcation of distinct dielectric regimes and providing enhanced insight into the evolution of the phase transition. It is strongly recommended that the degree of diffuseness is skeptical in many senses. Hence, following the establishment, a simple yet effective new measure of diffuseness is being proposed, offering a more accurate and physically meaningful estimation of the diffuse phase transition.

cond-mat.mtrl-sci↗

arXiv2024

Enhancing Fenton-like Photo-degradation and Electrocatalytic Oxygen Evolution Reaction (OER) in Fe-doped Copper Oxide (CuO) Catalysts

Although hydrogen generation by water electrolysis is the cheapest of all other available sources, water splitting still occurs with sluggish kinetics. It is a challenging barrier for H2 production on a large scale. Moreover, research is still underway to understand the oxygen evolution reaction (OER) and design the catalysts with improved OER performance. Herein, we report the synthesis, characterization, and OER performance of iron-doped copper oxide (CuO) as low-cost catalysts for water oxidation. The OER occurs at about 1.49 V versus the RHE with a Tafel slope of 69 mV/dec in a 1 M KOH solution. The overpotential of 338 mV at 10 mA/cm2 is among the lowest compared with other copper-based materials. The catalyst can deliver a stable current density of >10 mA/cm2 for more than 10 hours. Additionally, wastewater treatment, particularly synthetic dye wastewater, is vital for preventing water scarcity and adverse effects on human health and ecotoxicology. The as-synthesized catalysts are also utilized for Fenton-like photo-degradation under low-power visible household LED lights toward the most commonly industrially used simulated Methylene blue dye wastewater. Almost complete degradation of the MB dye has been achieved within 50 minutes of visible light irradiation with a first-order rate constant of 0.0973/min. This dual functionality feature can open new pathways as a non-noble, highly efficient, and robust catalyst for OER and wastewater treatments.

physics.app-ph↗

arXiv2024

Recent advances in hydrogen production using sulfide-based photocatalysts

Sulfide-based photocatalysts (PC) are promising materials for efficiently producing hydrogen (H2). This chapter aims to provide a detailed survey of the recent advancements in sulfide-based photocatalysts and emphasize their enhanced performance and pathways to efficient H2 production. A detailed summary has been given, including several metal sulfides, such as cadmium sulfide (CdS), zinc sulfide (ZnS), molybdenum disulfide (MoS2), tungsten disulfide (WS2), lead sulfide (PbS), nickel sulfides (NiS/NiS2), iron disulfide (FeS2), copper sulfides (CuS/Cu2S), cobalt sulfides (CoS/CoS2), tin disulfide (SnS2), indium sulfide (In2S3), bismuth sulfide (Bi2S3), zinc cadmium sulfide (ZnxCd1-xS), manganese cadmium sulfide (MnxCd1-xS), zinc indium sulfide (ZnIn2S4), and cadmium indium sulfide (CdIn2S4). This chapter will focus on the latest advancements in metal-sulfide-based materials for photocatalytic hydrogen evolution reactions (HER), taking its accelerated growth and excellent research into account. After briefly outlining the basic properties, the chapter will showcase the cutting-edge strategies and recent research progress, including the construction of heterojunctions, defect engineering, co-catalyst loading, elemental doping, and single-atom engineering, which improve the electronic structure and charge separation capabilities of metal sulfides for photocatalytic hydrogen production. A future perspective and outlook have been proposed, focusing on some key points and a standard protocol. With this knowledge, we hope sulfide-based photocatalysts can be modified and engineered to improve their efficiency and stability in future research.

cond-mat.mtrl-sci↗

arXiv2024

Effect of pH on photocatalytic degradation of Methylene Blue in water by facile hydrothermally grown TiO2 Nanoparticles under Natural Sunlight

Each year, the production of synthetic dye wastewater reaches a trillion tons, posing a significant challenge to addressing water scarcity on a global level. Hence, the treatment of wastewater to prevent water scarcity is of prime importance, and failing to do so will increase ecotoxicological risks and human health. Textile wastewater contains harmful dye. Photocatalytic degradation of such dye-contaminated wastewater is crucial to purifying the dye-contaminated water. However, this process takes time, uses high-power lamps, and is expensive. Here, we report the effect of the concentration of precursor on the size and surface morphology of TiO2 nanostructures prepared by facile hydrothermal synthesis and its ability to perform as a photocatalyst to degrade the most common industrial textile dye, methylene blue (MB), under natural sunlight. The impact of particle size on the photocatalytic activity and photocarrier migration rate was thoroughly examined. Also, the effect of pH on adsorption and photocatalytic degradation has been evaluated in detail. With several optimized conditions, almost complete dye degradation was achieved within 40 minutes under the direct illumination of natural sunlight. The enhanced photocatalytic performance can be correlated to the synergetic effect of a higher charge transfer mechanism, good catalytic active surface area availability (386 m2/g), and several optimized parameters that affect the reaction efficacy. Additionally, repeated use of NPs without sacrificing performance five times confirmed its stability and Sustainability as a promising candidate for large-scale industrial textile wastewater remedies.

cond-mat.mtrl-sci↗

arXiv2024

Unveiling the Direct Piezoelectric Effect on Piezo-phototronic Coupling in Ferroelectrics: First Principle Study Assisted Experimental Approach

A new study explores the distinct roles of spontaneous polarization and piezoelectric polarization in piezo-phototronic coupling. This investigation focuses on differences in photocatalytic and piezo-photocatalytic performance using sodium bismuth titanate (NBT), a key ferroelectric material. The research aims to identify which type of polarization has a greater influence on piezo-phototronic effects. A theoretical assessment complements the experimental findings, providing additional insights. This study explores the enhanced piezo-phototronic performance of electrospun nanofibers compared to sol-gel particles under different illumination conditions (11W UV, 250W UV, and natural sunlight). Electrospun nanofibers exhibited a rate constant (k) improvement of 2.5 to 3.75 times, whereas sol-gel particles showed only 1.3 to 1.4 times higher performance when ultrasonication was added to photocatalysis. Analysis using first-principle methods revealed that nanofibers had an elastic modulus (C33) about 2.15 times lower than sol-gel particles, indicating greater flexibility. The elongation of lattice along z-axis in the case of nanofibers reduced the covalency in the Bi-O and Ti-O bonds. These structural differences led to reduced spontaneous polarization and piezoelectric stress coefficients (e31 & e33). Despite having lower piezoelectric stress coefficients, higher flexibility in nanofibers led to a higher piezoelectric strain coefficient, 2.66 and 1.97 times greater than sol-gel particles, respectively. This improved the piezo-phototronic coupling for nanofibers.

cond-mat.mtrl-sci↗