Applications In Energy Devices Research Articles

First principle study of strain tunable electronic and optical properties of half-Heusler alloys XCoGe (X=V, Nb, Ta)

Half-Heusler alloys are gaining considerable attention for designing novel optoelectronic and renewable energy device applications. In the present work, we performed the first principle study of structural, electronic, and optical properties of XCoGe(X=V,Nb,andTa) half-Heusler alloys under external strain (0–8%). All compounds exhibit cubic crystal structures with an F-43m space group. The lattice constant and bond length increase (decrease) with increasing tensile (compressive) strain. The calculated formation energy of XCoGe systems is negative and increases (decreases) with varying the tensile (compressive) strain from 0 to 8%, indicating the stability of these systems. All XCoGe compounds possess an indirect band gap nature and are retained under strain. The band gap reduces under tensile strain and considerably widens by external compressive strain. The X-s state and Co-s state mainly contribute to the valence band maximum and conduction band minimum in XCoGe systems. Interestingly, the optical absorption spectra reveal maximum absorption in the visible energy range for both unstrained and strained systems. Interestingly, the red- and blue-shift under tensile and compressive strain in XCoGe make them good candidates for optoelectronic applications. The results pave the path for the practical utilization of XCoGe compounds for optoelectronic and light detection applications.

Effective construction of a CuCo MOF@graphene functional electrocatalyst for hydrogen evolution reaction.

Electrochemical water splitting is considered a green and sustainable method of producing hydrogen energy. Herein, to pursue a highly efficient hydrogen evolution reaction, we fabricated high-performance electrocatalysts, by utilizing a bimetallic (Cu and Co) metal-organic framework to modify rGO through a one-step in situ approach. The synthesized CuCoOC@rGO presents a highly ordered structure with a defect-rich porous surface for the hydrogen evolution reaction (HER). Specifically, the appropriate adjustment of metal (Cu and Co), 1,3,5-benzenetricarboxylic acid (H3BTC), and rGO ratios leads to a well-defined morphology, which creates a defect-rich porous surface. Characterized by XRD, SEM, EDS, FT-IR spectroscopy, Raman spectroscopy, XPS, and BET, the morphology exposes more active sites, strong evidence for the promotion of electrocatalytic efficiency. Upon the analysis of the experimental data, the obtained CuCoOC@rGO catalyst exhibits excellent activity in alkaline media with a low overpotential of 120 mV at a current density of 10 mA cm-2, and a Tafel slope of 124 mV dec-1 for the hydrogen evolution reaction (HER). Guided by the structure-activity relationship, the superior HER activity of CuCoOC@rGO in alkaline electrolyte could originate from many sources, including: (1) as a self-supported substrate, CuCoOC@rGO not only leads to profitable electrical contact and mechanical stability but also firmly roots into the rGO without extra binders. (2) The highly ordered structure provides smooth ion and electron transport channels, which are conducive to electrolyte infiltration and gas release. (3) The abundance of defective pores on the surface of the nanoarrays, which offers more active sites for the catalytic process. This study provides new prospects for the rational design and fabrication of advanced hierarchical functional electrocatalysts for application in electrochemical energy devices.

Characterization and Modelling of Nanomaterials Synthesized by Chemical Vapor Deposition

In recent years, Chemical Vapor Deposition (CVD) has emerged as a pivotal technique for the synthesis of high-quality nanomaterials, owing to its ability to produce uniform and scalable thin films with controlled properties. This study presents a comprehensive characterization and modelling of nanomaterials synthesized via CVD, elucidating the intricate relationship between process parameters and the resultant material properties. Utilizing advanced characterization techniques, including Transmission Electron Microscopy (TEM), XPS, and Raman Spectroscopy, we have discerned the morphological, compositional, and structural attributes of the synthesized nanomaterials. The experimental data were subsequently employed to develop a predictive model, leveraging machine learning algorithms, to forecast the properties of nanomaterials based on CVD parameters. The model exhibited high accuracy and can serve as a robust tool for optimizing CVD processes in real-time. Our findings underscore the potential of CVD in tailoring nanomaterial properties for specific applications and provide a foundational framework for researchers and industries aiming to harness the full potential of nanomaterials synthesized via CVD. This work not only advances our understanding of CVD-synthesized nanomaterials but also paves the way for their application in next-generation electronic, photonic, and energy devices.

Transitional trimetallic alloy embedded polyacrylamide hydrogel derived nitrogen-doped carbon air-cathode for bioenergy generation in microbial fuel cell

Heterometallic carbons are popular materials for application in energy devices due to their high oxygen reduction reaction (ORR) activity and good catalytic stability. Particularly in microbial fuel cells (MFCs), Fe group metal alloys are efficient ORR catalysts. This work has embedded different metallic alloy nanoparticles in polyacrylamide hydrogel derived in-situ nitrogen-doped carbon. All the catalysts (Fe@NC, FeCo@NC, FeNi@NC, and FeCoNi@NC) are used as air cathodes and examined for power generation in single chamber MFCs. Trimetallic composite (FeCoNi@NC) performed better than Pt/C. FeCoNi@NC exhibited superior electrocatalytic activity with an oxygen reduction peak at 0.394 V (vs RHE) and a corresponding peak current density of −0.159 mA. FeCoNi@NC records maximum power output of 963.5 mW m−2 at 2483.2 mA m−2, 3.287 and 1.136 times higher than NC and 10 wt% Pt/C, respectively. This could be due to the uniformly distributed alloy nanoparticles, abundant pyridinic-N, and M−Nx sites that enhance the durability, charge transfer, and power generation in MFCs. These findings suggest that the trimetallic transition metal-carbon (MNC) electrodes could be promising ORR catalysts, justifying their application for energy devices.

Towards Sustainable Fuel Cells and Batteries with an AI Perspective

With growing environmental and ecological concerns, innovative energy storage systems are urgently required to develop smart grids and electric vehicles (EVs). Since their invention in the 1970s, rechargeable lithium-ion batteries (LIBs) have risen as a revolutionary innovation due to their superior benefits of high operating potential and energy density. Similarly, fuel cells, especially Proton Exchange Membrane Fuel Cells (PEMFC) and Solid-Oxide Fuel Cells (SOFC), have been developed as an energy storage system for EVs due to their compactness and high-temperature stability, respectively. Various attempts have been made to explore novel materials to enhance existing energy storage technologies. Materials design and development are significantly based on trial-and-error techniques and require substantial human effort and time. Additionally, researchers work on individual materials for specific applications. As a viewpoint, we present the available sustainable routes for electrochemical energy storage, highlighting the use of (i) green materials and processes, (ii) renewables, (iii) the circular economy approach, (iv) regulatory policies, and (v) the data driven approach to find the best materials from several databases with minimal human involvement and time. Finally, we provide an example of a high throughput and machine learning assisted approach for optimizing the properties of several sustainable carbon materials and applying them to energy storage devices. This study can prompt researchers to think, advance, and develop opportunities for future sustainable materials selection, optimization, and application in various electrochemical energy devices utilizing ML.

Nanomaterials for supercapacitors as energy storage application: Focus on its characteristics and limitations

Demand for energy is steadily increasing due to the ever-increasing population growth, changing lifestyle as well as the depleting natural resources. The result is the increase in the cost of conventional energy devices. Nanotechnology via the application of tailor-made nanomaterials has brought in revolutionary changes in the design and fabrication of various energy storage devices. There have been reports of increased efficiency, decreased cost because of which there has been an enhanced market growth of the energy storage devices. Immense research activities are focused on the fabrication of electrode materials having precise nano-dimensions and morphologies, fabrication of cost-effective storage devices and methods to enhance efficiency. Composite materials based on carbon, metal oxide and polymer-based nanomaterials have been used for fabrication of electrode materials. Nanosized particles in such composites have brought about enhanced material properties as compared to their bulk counterparts, which in turn has contributed to their improved energy storage efficiency. But despite the success attained due to nanotechnological interventions, some of the limiting factors identified that have put a restraint in the demand and market growth of applied nanomaterials for energy capture are related to toxic processes involved during the synthesis of nanomaterials and during the application process.An overview of different nanomaterials used till date for fabrication of electrodes (with special focus on supercapacitors) will be addressed in this study. While the focus is in addressing the advantages of the use of nanomaterials and their composites, the study will also highlight the challenges associated during the fabrication and application in energy devices. It is expected that an update of such literature will benefit those undergoing research on nanotechnology and renewable energy technology.

Bandgap tuning and thermoelectric characteristics of Sc-based double halide perovskites K2ScAgZ6 (Z = Cl, Br, I) for solar cells applications

Using the full-potential linearized augmented plane wave plus local orbitals method within the frame work of density functional theory, the Sc-based double halide perovskites K2ScAgZ6 (Z = Cl, Br, I) are investigated for determining their physical properties. To investigate the structural and thermodynamic stability of these Sc-based double halide perovskites we calculate tolerance factor, formation energy, and phonon dispersion curve using GGA-PBEsol approximation. The calculated values of lattice parameters using GGA-PBEsol are found to be consistent with the available data. Subsequently, the Tran-Blaha modified Becke-Johnson (mBJ-LDA) potential is used for electronic properties. Implementation of TB-mBJ potential is clearly shows that K2ScAgZ6 have indirect bandgap, which is consistent with the literature. To evaluate these double perovskites and reveal their potential use in optical devices, several optical parameters are computed for an incident photon energy range of 0–8 eV. The BoltzTraP code is also employed to investigate temperature dependent electrical characteristic of these compounds in the temperature range of 200–600 K. Investigated halide double-perovskites have been shown to display excellent physical properties for solar cells and renewable energy device applications.

Proton-Ion Conductivity in Hexagonal Wurtzite-Nanostructured ZnO Particles When Exposed to a Reducing Atmosphere

Zinc oxide (ZnO), a direct wide band gap semiconductor (≥3.30 eV), has widespread potential for applications in energy devices and related industries. The initial physical demonstration of ZnO in ceramic fuel cells (CFCs) gave a new view of developing high ionic conductivity for multifunctional semiconductor technology. However, in the present work, we successfully synthesized highly textured nanoparticles of ZnO using a hydrothermal method followed by sintering in a reducing atmosphere. The resultant ZnO materials as electrolytes showed efficient ionic conductivity (5.28 × 10−2 S cm−1) and an excellent power density of 520 mW cm−2 ± 5% at 550 °C for low-temperature ceramic fuel cells (LT-CFCs). The achievement of enhanced ionic conductivity without any external ions or cation doping in the CFC was anticipated, since there was a rare possibility of vacancies in the bulk ZnO structure to conduct oxygen ions or protons. Therefore, we found that laterally the surfaces of the ZnO nanoparticles could be textured to become oxygen-deficient when sintered in an H2 atmosphere, which suggests a special mechanism for effective ionic transport. Furthermore, experimental analyses such as SEM, XPS, UV–visible, and EIS methods were performed to analyze the changes in the structural properties and mechanism of ionic transport in ZnO nanoparticles. The presented work provides insights into a novel approach for developing high ionic conductivity in electrolytes in low-cost semiconductor oxides such as ZnO for energy storage and conversion devices.

Defect Engineering in A2 BO4 Thin Films via Surface-Reconstructed LaSrAlO4 Substrates.

Ruddlesden-Popper oxides (A2 BO4 ) have attracted significant attention regarding their potential application in novel electronic and energy devices. However, practical uses of A2 BO4 thin films have been limited by extended defects such as out-of-phase boundaries (OPBs). OPBs disrupt the layered structure of A2 BO4 , which restricts functionality. OPBs are ubiquitous in A2 BO4 thin films but inhomogeneous interfaces make them difficult to suppress. Here, OPBs in A2 BO4 thin films are suppressed using a novel method to control the substrate surface termination. To demonstrate the technique, epitaxial thin films of cuprate superconductor La2- x Srx CuO4 (x= 0.15) are grown on surface-reconstructed LaSrAlO4 substrates, which are terminated with self-limited perovskite double layers. To date, La2- x Srx CuO4 thin films are grown on LaSrAlO4 substrates with mixed-termination and exhibit multiple interfacial structures resulting in many OPBs. In contrast, La2- x Srx CuO4 thin films grown on surface-reconstructed LaSrAlO4 substrates energetically favor only one interfacial structure, thus inhibiting OPB formation. OPB-suppressed La2- x Srx CuO4 thin films exhibit significantly enhanced superconducting properties compared with OPB-containing La2- x Srx CuO4 thin films. Defect engineering in A2 BO4 thin films will allow for the elimination of various types of defects in other complex oxides and facilitate next-generation quantum device applications.

Electrochemical Conversion of Natural Graphite into Carbon Nanostructures for Energy Storage Applications

Natural graphite minerals with global reserves greater than 320 million tones can be considered as low-cost and highly available precursors for the preparation of high-quality carbon nanostructures with potential applications in energy devices and related areas. Here, the electrochemical conversion of natural graphite minerals into carbon nanostructures, comprising onion-like carbon nanoparticles and multiwall carbon nanotubes (MWCNTs) in high-temperature molten salts are studied. The galvanostatic polarization of electrodes made of such minerals is conducted in molten LiCl and LiCl-NaCl at various current densities, leading to the exfoliation of the minerals into carbon nanostructures. The influence of non-carbon impurities present in the natural graphite mineral, and the current density applied on the characteristics of the resultant nanocarbons are investigated. Moreover, the structural and microstructural properties of the nanocarbons fabricated using natural graphite minerals are compared with those produced using commercially pure graphite electrodes. It is found that the electrochemical nanostructuring of the mineral in molten salt not only increases the surface area of the material, but also increases its electrical conductivity. The high-yield conversion of the mineral into carbon nanostructures is realized at the cathode current density of around 1 A cm-2. The Li- and Na- ion storage performances of this sample are evaluated. The Li-ion storage capacity of the sample is found to be remarkable at around 460 mAh g-1 after 500 charge/discharge cycles at the current density of 200 mA g-1. The green molten salt preparation and the electrochemical performance of nanocarbons is discussed here.

Proficient One-Step Heat-Up Synthesis of Manganese Sulfide Quantum Dots for Solar Cell Applications.

The necessity to develop renewable energy resources that are highly durable and flexible with superior energy density and capacitance ability has attracted considerable interest in the field of solar cell research. Semiconducting compound materials that are easily available, hazard-free and cost-effective are emerging as potential solutions to tackle this challenge. Herein, we present multiple molecular precursors used to grow manganese sulfide nanoparticles through a proficient one-step heat-up approach. For all of the tested samples, the X-ray diffraction peaks correspond to a γ-MnS hexagonal wurtzite structure. UV-Vis spectroscopy yielded absorption wavelengths of 359–420 nm and band-gap energies of 3.78–4.0 eV. Photoluminescence analysis shows characteristics of red and blue shift from 451–602 nm. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) reveal a narrow size distribution with nanosticks and large contact areas, which are critical for improved catalytic performance. The current study provides an improved pathway to a well-grown and uniform nanocrystal structure for applications in energy devices.

Spin-Polarized Study of the Structural, Optoelectronic, and Thermoelectric Properties of the Melilite-Type Gd2Be2GeO7 Compound

The present work is a theoretical study of the structural and spin-polarized dependent optoelectronic thermoelectric properties of the melilite-typeGd2Be2GeO7 compound, using the full potential linearized augmented plane wave approach in the framework of density functional theory. The predicted structural parameters are in good accordance with the measured counterparts. It is found that the title compound is more stable in the ferromagnetic order than in the non-magnetic order. The calculated band structure using the modified Becke–Johnson potential reveals that the studied compound has a wide bandgap of 3.78 eV. The frequency-dependent linear optical spectra are studied in an energy range expanding from 0 to 30 eV. Finally, the semi classical Boltzmann theory as incorporated in the Boltztrap code is used to study the spin-polarized dependent transport properties. The obtained results show that Gd2Be2GeO7 is a potential candidate for conversion energy device applications.

Cation Defect Engineering of Transition Metal Electrocatalysts for Oxygen Evolution Reaction

AbstractThe rational design and development of highly efficient oxygen evolution reaction (OER) electrocatalysts is vital for the application of renewable energy devices. Recently, the strategy of defect engineering draws much attention due to its positive effect on regulating the electronic structure, and thus, promoting the electrocatalytic performance of various materials. In this review, the main focus is on the cation vacancy defects of transition metal‐based electrocatalysts; the latest progress in cation vacancy defect engineering for the electrocatalytic OER is summarized. The different effects of cation vacancy defects on OER are well discussed together with the reaction mechanism, mainly including improving the conductivity, optimizing the adsorption of key intermediates, guiding the surface reconstruction to form active species, and enhancing the long‐term stability. Then, methods to construct cation vacancy defects on different electrocatalysts and the characterization of cation vacancies are systematically introduced. Finally, the remaining challenges and future prospects of cation vacancy defect engineering for promoting OER performance are further proposed.

First-principle investigation of thermoelectric and optoelectronic properties of Rb2KScI6 and Cs2KScI6 double perovskite for solar cell devices

Double perovskite (DP) halides are a reliable source of renewable energy that plays a vital role to fulfill the requirements of energy crunch. Therefore, the analysis of these perovskite halides have promising uses for thermoelectric and optoelectronics purposes. We investigated the thermoelectric and optoelectronics properties of Rb2KScI6 and Cs2KScI6 halides for use in renewable energy devices by using FP-LAPW + lo approach based on DFT. The calculated Goldsmith's tolerance factor and enthalpy of the formation of studied halides reveal that these are structurally and thermodynamically stable in cubic phase. Moreover, the analyzed value of Poisson and Pugh ratio reveals ductile nature of these materials. Further, we computed the bandgaps by analyzing electronic characteristics. For bandgap calculations of Rb2KScI6 (Eg = 2.75 eV) and Cs2KScI6 (Eg = 2.65 eV), we employed mBJ potentials to obtain precise values as comparison to experimental values. The complex dielectric function used to reveal the optical properties of the analyzed materials. The calculated optical results clearly show the maximum absorption of light in infrared (IR) region revealed that the analyzed materials are appropriate for optoelectronic purposes. The thermoelectric behavior was examined as to figure of merit (ZT), electrical-conductivity (EC), the Seebeck-coefficient (S) as well as thermal-conductivity. Animatedly in future, the analyzed consequences would be supportive to experimental investigation of Rb2KScI6 and Cs2KScI6 for renewable energy device applications.

Current Progress in 2D Metal–Organic Frameworks for Electrocatalysis

The 2D nanosheets of metal–organic frameworks (MOFs) have recently emerged as a promising material that makes them valuable in widespread electrocatalytic fields due to their atomic‐level thickness, abundant active sites, and large surface area. Efficient electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting are highly desired with low overpotentials to promote the industrial applications of energy conversion and devices. 2D MOF nanostructures provide long‐term stability and high electrical conductivity to enhance catalyst activity and durability. This review briefly summarizes the synthesis and electrocatalytic applications of 2D MOF for HER/OER/water splitting. More attention is focused on the synthetic strategies of 2D MOF and their derivatives. The catalytic performance and superior properties of these materials are highlighted. The outperformance of these materials originates from the rational design, myriad of abundant active sites, and atomic‐level thickness. The current and future challenges in this field and the scientific perspectives to overcome these challenges are highlighted. It is suggested that the construction of 2D MOF nanostructures can develop a state‐of‐the‐art electrocatalyst in energy and environmental division.

Features and applications of energy devices for prone robot-assisted minimally invasive esophagectomy: a narrative review.

Background and ObjectiveRobot-assisted surgery is particularly useful in esophagectomy for esophageal cancer because robotic systems have high-resolution three-dimensional imaging, tremor filtering, and articulated instruments. This review article focuses on the applications and limitations of surgical devices in robot-assisted minimally invasive esophagectomy (RAMIE).MethodsA narrative search of Medline was performed for articles published using the keywords “robot-assisted esophagectomy”, “technique”, “postoperative complication”, and “short-term outcomes”.Key Contents and FindingsMonopolar scissors: these devices with a sharp tip have an articulating function that allows for fast, sharp dissection without an electrical source. However, scissor-type devices cannot compress the organ, and their hemostatic ability is rather weak. Maryland bipolar forceps: the device has a very thin tip that allows for accurate dissection as well as stronger hemostatic ability by closing the forceps to compress tissues and applying electric current. The disadvantage is longer operation time because the forceps need to be constantly closed and reopened. Long Maryland bipolar grasper: the tip of the long Maryland bipolar grasper is slightly blunt and has the advantage of versatility because it can grip the tissue more delicately. Ultrasonic scalpel: the device can transect tissues speedily without bleeding, shortening operation time, but lacks articulating function. Although thermal spread to the surroundings is relatively narrow, activation time increases with the amount of tissue to be grasped; this raises the temperature above that of the vessel sealer. Vessel sealer: the device is one of the most powerful hemostatic energy devices, based on bipolar electrodes. The articulating jaws on both sides are more suited for sharp transection rather than meticulous dissection because of its powerful hemostatic force and blunt tip. It is also important to note that the vessel sealer produces widespread high-temperature steam. SynchroSeal: the device offers fast activation time, and due to the tip of the device being finely divided, which requires relatively precise manipulation.ConclusionsRobot-assisted surgery reduces the limitations of conventional endoscopic surgery by offering stable high-resolution three-dimensional imaging, tremor filtering, and articulated instruments. It is important to understand and exploit the advantages of energy devices suitable for RAMIE.

Interface-engineered MoS2/CoS/NF bifunctional catalysts for highly-efficient water electrolysis

The utilization of non-noble metal catalysts with robust and highly efficient electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are extremely important for the large-scale implementation of renewable energy devices. Integration of bifunctional electrocatalysts on both anode and cathode electrodes remains a significant challenge. Herein, we report on a novel and facile strategy to construct the ordered and aligned MoS2 nanosheet-encapsulated metal–organic frameworks (MOFs) derived hollow CoS polyhedron, in-situ grown on a nickel foam (NF). The starfish-like MoS2/CoS/NF heterojunctions were formed due to the ordered growth of the material caused by NF substrate. The optimized 2-MoS2/CoS/NF heterojunction exhibits robust bifunctional electrocatalytic activity with a low overpotential of 67 and 207 mV toward the HER and OER at 10 mA cm−2, and the long-term stability, which exceeds most of the reported bifunctional electrocatalysts. Such high electrocatalytic performance arises due to the synergistic effect between the MoS2 and CoS phases across the interface, the abundant active sites, as well as the hierarchical pore framework, which collectively enhance the mass and electron transfer during the reactions. The work provides a promising approach to fabricating bifunctional catalysts with custom-designed heterojunctions and remarkable performance for applications in electrochemical energy devices and related areas.

Study of MC:DN-Based Biopolymer Blend Electrolytes with Inserted Zn-Metal Complex for Energy Storage Devices with Improved Electrochemical Performance.

Stable and ionic conducting electrolytes are needed to make supercapacitors more feasible, because liquid electrolytes have leakage problems and easily undergo solvent evaporation. Polymer-based electrolytes meet the criteria, yet they lack good efficiency due to limited segmental motion. Since metal complexes have crosslinking centers that can be coordinated with the polymer segments, they are regarded as an adequate method to improve the performance of the polymer-based electrolytes. To prepare plasticized proton conducting polymer composite (PPC), a simple and successful process was used. Using a solution casting process, methylcellulose and dextran were blended and impregnated with ammonium thiocyanate and zinc metal complex. A range of electrochemical techniques were used to analyze the PPC, including transference number measurement (TNM), linear sweep voltammetry (LSV), cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The ionic conductivity of the prepared system was found to be 3.59 × 10−3 S/cm using the EIS method. The use of glycerol plasticizer improves the transport characteristics, according to the findings. The carrier species is found to have ionic mobility of 5.77 × 10−5 cm2 V−1 s−1 and diffusion coefficient of 1.48 × 10−6 cm2 s−1 for the carrier density 3.4 × 1020 cm−3. The TNM revealed that anions and cations were the predominant carriers in electrolyte systems, with an ionic transference value of 0.972. The LSV approach demonstrated that, up to 2.05 V, the film was stable, which is sufficient for energy device applications. The prepared PPC was used to create an electrical double-layer capacitor (EDLC) device. The CV plot exhibited the absence of Faradaic peaks in the CV plot, making it practically have a rectangular form. Using the GCD experiment, the EDLC exhibited low equivalence series resistance of only 65 Ω at the first cycle. The average energy density, power density, and specific capacitance values were determined to be 15 Wh/kg, 350 W/kg, and 128 F/g, respectively.

First-principles investigations of metal chalcogenides Tl2Hg3X4(X=S,Se,Te) for advanced optoelectronic and thermoelectric applications

The crystalline metal chalcogenides materials have got great attraction due to their narrow bandgap materials for renewable energy applications. In the present work, we have broadly explored the optoelectronic and thermoelectric properties of Tl2Hg3X4(X ​= ​S, Se, Te) using first-principle calculations. The Tl2Hg3S4, Tl2Hg3Se4, and Tl2Hg3Te4 have a monoclinic crystal structure and exhibit semiconducting nature with band gaps of 2.0 ​eV, 1.5 ​eV, and 0.8 ​eV, respectively. In the visible region, a minimum absorption occurred for the S dopant, but as we replace S with Se/Te a halted absorption is seen in the visible region that confirming their nominal employment in optoelectronic applications (solar cells). Optical absorption of Se and Te dopant in Tl2Hg3X4 is found in I.R and the visible region of the radiation, making them promising candidates for optoelectronics. Further, the thermoelectric parameters versus carrier concentration are studied for these materials using the BoltzTraP code. The drifts of thermoelectric parameters for the Te dopant diverge from the tendencies of S and Se dopants at specific temperatures i.e., at 300, 500, and 700 ​K. The power factor (PF) of Tl2Hg3S4 and Tl2Hg3Se4 (Tl2Hg3Te4) favor n-type (p-type) doping, indicating higher mobility of electrons(holes) as compared with the holes (electrons). These findings suggest the practical realization of these compounds for emerging optoelectronic and renewable energy device applications.

Research progress of Fe-N-C catalysts for the electrocatalytic oxygen reduction reaction

The oxygen reduction reaction (ORR) is an important half-reaction for various energy devices, such as fuel cells and metal-air batteries. The sluggish kinetics of the four-electron ORR needs the development of electrocatalysts with high efficiency and activity to replace precious metal platinum. Alternatively, metal-nitrogen-carbon catalysts, particularly Fe-N-C, are considered the most promising candidates because their rich active sites can reduce the energy barrier of oxygenic intermediates. In this review, the recent research breakthroughs of Fe-N-C catalysts in theoretical and experimental studies are summarized in detail. First, the mechanistic understanding of the electrocatalytic ORR based on Fe-N-C catalysts is outlined. Then, the design strategies of Fe-N-C catalysts and classifications of active sites are expounded, after which the connection between the active site and catalytic performance is discussed. Subsequently, the application status of Fe-N-C catalysts in polymer membrane fuel cells and zinc-air batteries is described. Finally, the challenges and opportunities of Fe-N-C catalysts regarding controllable synthesis, mechanism, and applications in energy devices are further proposed.