Krishnendu Das

Bio: Krishnendu Das is an academic researcher from National Institute of Technology, Rourkela. The author has contributed to research in topics: Photocatalysis & Ternary operation. The author has an hindex of 7, co-authored 11 publications receiving 297 citations.

One pot synthesis of CdS/BiOBr/Bi2O2CO3: A novel ternary double Z-scheme heterostructure photocatalyst for efficient degradation of atrazine

Abstract: In this study, a simple one-step hydrothermal method was developed for morphology controlled synthesis of CdS/BiOBr/Bi2O2CO3 ternary heterostructure materials. The ternary system contained well dispersed CdS nanoparticles (50–80 nm) anchored over ultrathin BiOBr and Bi2O2CO3 nanoplates with high interfacial contact. A significant enhancement in visible light absorption, prolonged life time decay and improved charge carrier separation and migration property accounted for the excellent photocatalytic activity towards atrazine herbicide degradation (>95% in 30 min). A double Z-scheme electron transfer mechanism was proposed to explain the dramatic increase in photocatalytic activity which was deduced from photoelectrochemical measurements, scavenger and radical ( OH and O2 ‾) trapping experiments. MTT assay study revealed that the photo-catalytically treated atrazine solution showed significant reduction in cytotoxicity. This study provides an effective strategy for facile synthesis of bismuth based ternary heterostructures with potential applications in the field of environmental remediation.

Facile synthesis and photocatalytic efficacy of UiO-66/CdIn2S4 nanocomposites with flowerlike 3D-microspheres towards aqueous phase decontamination of triclosan and H2 evolution

Abstract: Construction of porous heterostructure photocatalyst material with improved surface and optoelectrical properties is a practical and effective strategy for mineralization of toxic organic pollutants and water splitting reaction under visible light irradiation. Herein, we have developed a facile hydrothermal route to prepare a series of novel UiO-66/CdIn2S4 heterojunction nanocomposite materials containing finely dispersed UiO-66 spherical nanoparticles (20−40 nm) anchored over high aspect ratio CdIn2S4 nanosheets. Comprehensive characterization of the UiO-66/CdIn2S4 nanocomposites revealed a hierarchical 3D microflower structure with enhanced surface reactive sites, better channelization of charge carriers, high resistance to charge recombination and a favorable band alignment between the two semiconductor components. The optimal photocatalyst (30UiO-66/CdIn2S4) showed improved photocatalytic efficiency towards triclosan degradation with rate constant (0.0094 min−1) twelve times higher than the pure CdIn2S4 (0.0007 min−1). The 30UiO-66/CdIn2S4 photocatalyst also exhibited higher H2 evolution rate (2.95 mmolg−1 h−1) with apparent conversion efficiency of 20.8 %.

A facile reflux method for in situ fabrication of a non-cytotoxic Bi2S3/β-Bi2O3/ZnIn2S4 ternary photocatalyst: a novel dual Z-scheme system with enhanced multifunctional photocatalytic activity

Abstract: In this study, we have developed a novel non-cytotoxic Bi2S3/β-Bi2O3/ZnIn2S4 ternary nanocomposite using a mild in situ reflux method for multimodal applications in the fields of waste water remediation, H2 energy production and microbial disinfection. Initially, the metastable β-Bi2O3 phase with nanoplate morphology was synthesized by thermal decomposition of Bi2O2CO3. The co-assembly of Bi2S3 and ZnIn2S4 with β-Bi2O3 is achieved by a tailor made in situ reflux route using thioacetamide as the sulfur source. Comprehensive characterization of the ternary composite revealed close microscopic contact between the semiconductors, fast electron channelization, enhanced charge carrier separation and a prolonged life time (11.25 ns) of the excited state. The ternary composite exhibits excellent visible light assisted photocatalytic activity for aqueous phase tetracycline (TCN) degradation and Cr(VI) reduction achieving 96.3% (Kapp = 0.0868 min−1) and 93.7% (Kapp = 0.2236 min−1) removal in a short reaction span of 40 min and 12 min, respectively. The ternary composite also afforded a H2 generation rate of 2243 μmol h−1 g−1 with an apparent conversion efficiency of 14.3%. A bacterial inactivation study conducted using Enterobacter cloacae suggested good visible light assisted bacterial degradation activity of the coupled semiconductor system. The MTT assay study confirms the non-cytotoxic nature of the photocatalyst as well as the treated TCN and Cr(VI) solutions. A synergistic dual Z-scheme electron migration mechanism is deduced from radical trapping experiments and the ESR study which accounts for the excellent photocatalytic activity of the ternary composite material.

In situ Irradiated XPS Investigation on S-Scheme TiO2@ZnIn2S4 Photocatalyst for Efficient Photocatalytic CO2 Reduction

Abstract: Reasonable design of efficient hierarchical photocatalysts has gained significant attention. Herein, a step-scheme (S-scheme) core-shell TiO2 @ZnIn2 S4 heterojunction is designed for photocatalytic CO2 reduction. The optimized sample exhibits much higher CO2 photoreduction conversion rates (the sum yield of CO, CH3 OH, and CH4 ) than the blank control, i.e., ZnIn2 S4 and TiO2 . The improved photocatalytic performance can be attributed to the inhibited recombination of photogenerated charge carriers induced by S-scheme heterojunction. The improvement is also attributed to the large specific surface areas and abundant active sites. Meanwhile, S-scheme photogenerated charge transfer mechanism is testified by in situ irradiated X-ray photoelectron spectroscopy, work function calculation, and electron paramagnetic resonance measurements. This work provides an effective strategy for designing highly efficient heterojunction photocatalysts for conversion of solar fuels.

Nanostructured CdS for efficient photocatalytic H 2 evolution: A review

Abstract: Cadmium sulfide (CdS)-based photocatalysts have attracted extensive attention owing to their strong visible light absorption, suitable band energy levels, and excellent electronic charge transportation properties. This review focuses on the recent progress related to the design, modification, and construction of CdS-based photocatalysts with excellent photocatalytic H2 evolution performances. First, the basic concepts and mechanisms of photocatalytic H2 evolution are briefly introduced. Thereafter, the fundamental properties, important advancements, and bottlenecks of CdS in photocatalytic H2 generation are presented in detail to provide an overview of the potential of this material. Subsequently, various modification strategies adopted for CdS-based photocatalysts to yield solar H2 are discussed, among which the effective approaches aim at generating more charge carriers, promoting efficient charge separation, boosting interfacial charge transfer, accelerating charge utilization, and suppressing charge-induced self-photocorrosion. The critical factors governing the performance of the photocatalyst and the feasibility of each modification strategy toward shaping future research directions are comprehensively discussed with examples. Finally, the prospects and challenges encountered in developing nanostructured CdS and CdS-based nanocomposites in photocatalytic H2 evolution are presented.

Photocatalytic reduction of CO2 on BiOX： Effect of halogen element type and surface oxygen vacancy mediated mechanism

Abstract: Photo-chemical conversion of CO2 into solar fuels by photocatalysts has attracted significant attention. However, poor reaction efficiency remains a huge obstacle. Deep insight into the reaction mechanism of CO2, especially the active site of photocatalyst could provide scientific basis for the development of more efficient photocatalyst. The high inertness of CO2 and the multi-electron reduction feature on a photocatalyst determine high complexity of the reaction for the study. Here, pure Bismuth oxyhalides (BiOX, where X = F, CI, Br, I) with the layered structure, which were synthesized by both hydrothermal method and chemical precipitation method, were selected as model photocatalysts. The photocatalytic behaviors of the samples were evaluated by the CO2 reduction with H2O without the additional photosensitizer and sacrificial agent. The as-prepared BiOBr was observed to exhibit the best CO2 photoreduction performance under the simulated sunlight. The evolution rates of CO and CH4 are 21.6 μmol g−1 h−1 and 1.2 μmol g−1 h−1, respectively. The effects of water dosage, light intensity and irradiation time on the efficiency of CO2 photoreduction were investigated systematically. Interestingly, the reduction selectivity of CO2 to CO almost reaches 100% in the case of high light intensity. By combination with isotopic tracing method, electron spin-paramagnetic resonance (ESR), in-situ Fourier transform infrared (FTIR) characterization, positron annihilation lifetime (PAL) spectra, and Density functional theory (DFT) calculation, the oxygen vacancy mediated mechanism of photoreduction CO2 was suggested for BiOX. This work provides new information and insights to deepen the understanding for defect photocatalysis on CO2 reduction of semiconductor.