DFT and experimental investigations on the photocatalytic activities of NiO nanobelts for removal of organic pollutants

NiO nanobelts synthesized using the hydrothermal method are explored for photocatalytic degradation of organic pollutants like RhB, MO, MB, and CV. The XPS analysis confirmed the formation of the stoichiometric NiO nanobelts. Few micrometer long cubic crystalline NiO nanobelts of the average thickness of ∼75 nm delivered a bandgap of 4.07 eV. The FTIR studies revealed that the mesoporous NiO nanobelts delivered stable photocatalytic activities after controlled irradiation under a xenon lamp. The kinetic studies showed the 79.1, 82.7, 76.7, and 89% degradation of MO, MB, CV, and RhB after 140 min at the rate constants (k) of 0.007, 0.008, 0.009, and 0.012 min−1, respectively. Complementary first-principles Density Functional Theory (DFT) and scavenging studies revealed the chemical picture and influence of the , and photogenerated from NiO nanobelts in the photocatalytic degradation of organic dyes. These studies corroborate the use of the NiO nanobelts in the stable and eco-friendly photocatalytic degradation activities of a wide range of organic pollutants

Implementing dopant-free hole-transporting layers and metal-incorporated CsPbI2Br for stable all-inorganic perovskite solar cells

Mixed-halide CsPbI2Br perovskite is promising for efficient and thermally stable all-inorganic solar cells; however, the use of conventional antisolvent methods and additives-based hole-transporting layers (HTLs) currently hampers progress. Here, we have employed hot-air-assisted perovskite deposition in ambient condition to obtain high-quality photoactive CsPbI2Br perovskite films and have extended stable device operation using metal cation doping and dopant-free hole-transporting materials. Density functional theory calculations are used to study the structural and optoelectronic properties of the CsPbI2Br perovskite when it is doped with metal cations Eu2+ and In3+. We experimentally incorporated Eu2+ and In3+ metal ions into CsPbI2Br films and applied dopant-free copper(I) thiocyanate (CuSCN) and poly(3-hexylthiophene) (P3HT)-based materials as low-cost hole transporting layers, leading to record-high power conversion efficiencies of 15.27% and 15.69%, respectively, and a retention of >95% of the initial efficiency over 1600 h at 85 °C thermal stress

Regulated electrochemical performance of manganese oxide cathode for potassium-ion batteries: A combined experimental and first-principles density functional theory (DFT) investigation

Potassium-ion batteries (KIBs) are promising energy storage devices owing to their low cost, environmental-friendly, and excellent K+ diffusion properties as a consequence of the small Stoke's radius. The evaluation of cathode materials for KIBs, which are perhaps the most favorable substitutes to lithium-ion batteries, is of exceptional importance. Manganese dioxide (α-MnO2) is distinguished by its tunnel structures and plenty of electroactive sites, which can host cations without causing fundamental structural breakdown. As a result of the satisfactory redox kinetics and diffusion pathways of K+ in the structure, α-MnO2 nanorods cathode prepared through hydrothermal method, reversibly stores K+ at a fast rate with a high capacity and stability. It has a first discharge capacity of 142 mAh/g at C/20, excellent rate execution up to 5C, and a long cycling performance with a demonstration of moderate capacity retention up to 100 cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations confirm that the K+ intercalation/deintercalation occurs through 0.46 K movement between MnIV/MnIII redox pairs. First-principles density functional theory (DFT) calculations predict a diffusion barrier of 0.31 eV for K+ through the 1D tunnel of α-MnO2 electrode, which is low enough to promote faster electrochemical kinetics. The nanorod structure of α-MnO2 facilitates electron conductive connection and provides a strong electrode–electrolyte interface for the cathode, resulting in a very consistent and prevalent execution cathode material for KIBs

Photocatalytic behavior of Ba(Sb/Ta)2O6 perovskite for reduction of organic pollutants: Experimental and DFT correlation

We have synthesized closely packed hexagonal 2D plates and clustered nanoparticle morphologies of Ba(Sb/Ta)2O6 (BSTO) perovskite via the polymerizable complex method for photocatalytic dye degradation activities. The BSTO crystallized in a hexagonal structure. The presence of Ba2+, Sb5+, Ta5+, and O2− chemical states identified from XPS confirmed the formation of mixed Ba(Sb/Ta)2O6 phase accompanied with a minor amount of TaOx. Furthermore, BSTO showed excellent photocatalytic activity for the degradation of various organic dyes. The kinetic studies revealed 65.9%, 77.3%, 89.8%, and 84.2%, of Crystal Violet (CV), Methylene Blue (MB), Rhodamine blue (RhB), and Methylene Orange (MO), respectively, after irradiation of 180 min without using a cocatalyst. The formation of and OH−surface radicals, which are believed to facilitate the degradation of the dyes, are unveiled through first-principles Density Functional Theory (DFT) calculations and scavenging studies. Our results suggest that BSTO holds promise as an excellent photocatalyst with better degradation efficiency for various organic dyes

Ternary Cu2SnS3: synthesis, structure, photoelectrochemical activity, and heterojunction band offset and alignment

Ternary Cu2SnS3 (CTS) is an attractive nontoxic and earth-abundant absorber material with suitable optoelectronic properties for cost-effective photoelectrochemical applications. Herein, we report the synthesis of high-quality CTS nanoparticles (NPs) using a low-cost facile hot injection route, which is a very simple and nontoxic synthesis method. The structural, morphological, optoelectronic, and photoelectrochemical (PEC) properties and heterojunction band alignment of the as-synthesized CTS NPs have been systematically characterized using various state-of-the-art experimental techniques and atomistic first-principles density functional theory (DFT) calculations. The phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses have an optical band gap of 1.1 eV and exhibit a random distribution of uniform spherical particles with size of approximately 15–25 nm as determined from high-resolution transmission electron microscopy (HR-TEM) images. The CTS photocathode exhibits excellent photoelectrochemical properties with PCE of 0.55% (fill factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent density of −3.95 mA/cm2 under AM 1.5 illumination (100 mW/cm2). Additionally, the PEC activities of CdS and ZnS NPs are investigated as possible photoanodes to create a heterojunction with CTS to enhance the PEC activity. CdS is demonstrated to exhibit a higher current density than ZnS, indicating that it is a better photoanode material to form a heterojunction with CTS. Consistently, we predict a staggered type-II band alignment at the CTS/CdS interface with a small conduction band offset (CBO) of 0.08 eV compared to a straddling type-I band alignment at the CTS/ZnS interface with a CBO of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS interface points to efficient charge carrier separation and transport across the interface, which are necessary to achieve enhanced PEC activity. The facile CTS synthesis, PEC measurements, and heterojunction band alignment results provide a promising approach for fabricating next-generation Cu-based light-absorbing materials for efficient photoelectrochemical applications

Solution-processed Cd-substituted CZTS nanocrystals for sensitized liquid junction solar cells

The Earth-abundant kesterite Cu2ZnSnS4 (CZTS) exhibits outstanding structural, optical, and electronic properties for a wide range of optoelectronic applications. However, the efficiency of CZTS thin-film solar cells is limited due to range of factors, including electronic disorder, secondary phases, and the presence of anti-site defects, which is key factor limiting the Voc. The complete substitution of Zn lattice sites in CZTS nanocrystals (NCs) with Cd atoms offers a promising approach to overcome several of these intrinsic limitations. Herein, we investigate the effects of substitution of Cd2+ into Zn2+ lattice sites in CZTS NCs through a facile solution-based method. The structural, morphological, optoelectronic, and power conversion efficiencies (PCEs) of the NCs synthesized have been systematically characterized using various experimental techniques, and the results are corroborated by first-principles density functional theory (DFT) calculations. The successful substitution of Zn by Cd is demonstrated to induce a structural transformation from the kesterite phase to the stannite phase, which results in the bandgap reducing from 1.51 eV (kesterite) to 1.1 eV (stannite), which is closer to the optimum bandgap value for outdoor photovoltaic applications. Furthermore, the PCE of the novel Cd-substituted liquid junction solar cell underwent a four-fold increase, reaching 1.1%. These results highlight the importance of substitutional doping strategies in optimizing existing CZTS-based materials to achieve improved device characteristics

Structural and morphological properties of electrochemically deposited CdTe thin films

In present report, p-type CdTe semiconductor thin films were grown directly on transparent conductive Fluorine-doped SnO2-coated (FTO) glass substrates using three-electrode electrodeposition technique. The whole work carried out at ambient condition. Structural studies reveal that films are possessing cubic zinc blend crystal structure. The growth mechanism of CdTe nanostructures is revealed by investigating the cyclic voltammetry analysis. Morphological characterization demonstrates high-purity, uniform and well covered CdTe thin film over FTO glass substrate. The Hot probe experiment confirmed the p-type semiconducting behavior of CdTe thin films. The current investigation provides a novel approach in synthesis of p-type CdTe nanostructure, without any post annealing or surface treatment, for the direct fabrication of semiconductor sensitized solar cells

Structural and morphological properties of electrochemically deposited CdTe thin films

In present report, p-type CdTe semiconductor thin films were grown directly on transparent conductive Fluorine-doped SnO2-coated (FTO) glass substrates using three-electrode electrodeposition technique. The whole work carried out at ambient condition. Structural studies reveal that films are possessing cubic zinc blend crystal structure. The growth mechanism of CdTe nanostructures is revealed by investigating the cyclic voltammetry analysis. Morphological characterization demonstrates high-purity, uniform and well covered CdTe thin film over FTO glass substrate. The Hot probe experiment confirmed the p-type semiconducting behavior of CdTe thin films. The current investigation provides a novel approach in synthesis of p-type CdTe nanostructure, without any post annealing or surface treatment, for the direct fabrication of semiconductor sensitized solar cells

Film thickness effects on morphology, optical and structural properties of chemical bath deposition grown CdS thin films for solar cell applications

CdS thin films of varying thickness were deposited on the glass substrate by chemical bath deposition (CBD) using Cadmium Chloride (CdCl2) and Thiourea ((NH2)2CS) as Cd and S sources respectively with ammonia as a complexing agent. The synthesized CdS thin films have been characterized using X-ray diffractometer (XRD), Raman spectroscopy, UV-Vis-NIR spectrophotometer, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersion X-ray analysis (EDAX). From XRD analysis it is inferred that the obtained CdS films have highly orientated hexagonal structure with the preferential orientation along (002) plane. The optical characterization raveled that the films are highly transparent (60%–80%) in the visible region. From TEM analysis it has been observed that the inter planner spacing for CdS thin film is ∼0.31 nm and average crystallite size is 7–8 nm. The EDAX data revealed nearly stoichiometric characteristics of the CdS thin films. The SEM analysis showed that CdS thin films are smooth, homogeneous and uniform without cracks with randomly oriented spherical nanocrystallites. The CdS thin films have very high transmission in the range 600–1200 nm with the band gap >2.54 eV. The purpose of the present study is to develop window/buffer layer for CZTS solar cells

Electrochemical synthesis of p-Cu2O/n-ZnO nanorods hetero-junction for photovoltaic application

Development of high performance visible light responsive solar cell materials has attracted wide interest due to their potential applications in the energy industries. In this work, ZnO nanorods films were successfully prepared on the ITO coated glass substrates via simple three electrode electrochemical deposition route. The Cu2O nanoparticles were then electrodeposited on the surface of ZnO nanorods to form p-Cu2O/n-ZnO core-shell hetero-structure. The synthesized ZnO, Cu2O films and p-Cu2O/n-ZnO hetero-structure were characterized by low angle x-ray diffraction, scanning electron microscopy, and UV-Visible spectrophotometer. Due to the hierarchical morphologies and core-shell structure, p-Cu2O/n-ZnO hetero-structure shows a prominent visible-light-driven photocatalytic performance under the low intensity light irradiation. The obtained results suggest that it is possible to synthesize ZnO nanorods, Cu2O films and p-Cu2O/n-ZnO core-shell hetero-structure by a simple, cost effective and environment friendly electrodeposition process which can be useful for water splitting and solar cell device fabrication