Materials For Energy Conversion Research Articles

Analytical parametrization for magnetization of Gadolinium based on scaling hypothesis

Gadolinium, which has a Curie temperature of 293 K, has been served as the reference material for the room-temperature magnetic energy conversion. Using the scaling hypothesis and university class of phase transition, we propose an analytical parametrization of Gd magnetization (M(T,H)) for fields up to 5 T and temperatures between 250 and 340 K. The key step is to fit the single-variable scaling function, beyond the leading divergent term, that well describes the entire two-variable M(T,H) near the Curie temperature. Constraints of the scaling function are derived and are used to construct the parametrization form. A stable fitting algorithm based on separating the length scale is introduced. The final expression is analytical, well defined at Curie temperature, and is validated by comparing to experiments including the magnetization and the specific heat. The proposed parametrization turns the knowledge of scaling hypothesis into an efficient and accurate scheme that quantitatively describes the material near the second-order transition. This advantage can become significant when considering realistic applications.

Self-supporting honeycomb-like porous nickel phosphide microsphere with high atomic percentage of phosphorus for high performance supercapacitor

Transition metal phosphides (TMPs), especially those with high atomic percentages of phosphorus in TMPs, are attracting extensive attention in novel electrode materials for energy conversion and storage due to their metallization properties, desired electrical conductivity together with superior redox activity, and high theoretical capacity. Unfortunately, their inherent low surface electroactivity and poor structural integrity result in unsatisfactory capacity rates and low cycling stability. Herein, we propose a facile hydrothermal and subsequent low-temperature phosphating strategy to construct a self-supporting honeycomb-like porous Ni5P4 microsphere with a high atomic percentage of phosphorus. Benefiting from the unique porous structural peculiarities in the microsphere to reduce ion/electron diffusion paths and increased the accessible area of the electrolyte, as well as provide significant durability, the Ni5P4 microsphere provides a high specific capacity of 450.1 C g−1 at 1 A g−1 (about 6 times than corresponding NiO microsphere) and good rate capability. Moreover, an asymmetric supercapacitor assembled based on Ni5P4 microsphere and activated carbon (AC) electrodes delivers a high specific energy of 43.5 Wh kg−1 at the specific power of 820 W kg−1, and good cycling stability with 88 % capacity retention after 5000 cycles.

Two-Dimensional Mesoporous Materials for Energy Storage and Conversion: Current Status, Chemical Synthesis and Challenging Perspectives

Two-Dimensional Mesoporous Materials for Energy Storage and Conversion: Current Status, Chemical Synthesis and Challenging Perspectives

Recent Developments and Perspectives of Cobalt Sulfide-Based Composite Materials in Photocatalysis

Photocatalysis, as an inexpensive and safe technology to convert solar energy, is essential for the efficient utilization of sustainable renewable energy sources. Earth-abundant cobalt sulfide-based composites have generated great interest in the field of solar fuel conversion because of their cheap, diverse structures and facile preparation. Over the past 10 years, the number of reports on cobalt sulfide-based photocatalysts has increased year by year, and more than 500 publications on the application of cobalt sulfide groups in photocatalysis can be found in the last three years. In this review, we initially summarize the four common strategies for preparing cobalt sulfide-based composite materials. Then, the multiple roles of cobalt sulfide-based cocatalysts in photocatalysis have been discussed. After that, we present the latest progress of cobalt sulfide in four fields of photocatalysis application, including photocatalytic hydrogen production, carbon dioxide reduction, nitrogen fixation, and photocatalytic degradation of pollutants. Finally, the development prospects and challenges of cobalt sulfide-based photocatalysts are discussed. This review is expected to provide useful reference for the construction of high-performance cobalt sulfide-based composite photocatalytic materials for sustainable solar-chemical energy conversion.

Near Field Scattering Optical Model-Based Catalyst Design for Artificial Photoredox Transformation

The sun offers a clean and renewable energy cornucopia, whereas how to utilize this inexhaustible yet decentralized energy with the assistance of appropriate media is an enduring topic. Plasmonic metal-based nanostructures (mainly Au and Ag) represent a class of fascinating materials for solar energy conversion due to their exclusive surface plasmon resonance (SPR)-enabled light-harvesting capability. In contrast to these plasmonic metals with characteristic SPR peaks, modulating the optical absorption peaks of nonplasmonic metals (e.g., small Pt nanoparticles) in the visible region but without size alteration is a grand challenge. Until recently, we demonstrated a near field scattering (NFS) optical model to manipulate the absorption peaks of Pt nanoparticles by adjusting their dielectric environment, sowing the seeds for tuning the optical absorption property of other metal nanoparticles and even semiconductor quantum dots. It is the purpose of the present Perspective to retrospect the history of NFS optical model and guide the function-oriented design of NFS-based nanostructures for artificial photoredox transformation.

Solution-Processed Cu2S Nanostructures for Solar Hydrogen Production.

Cu2S is a promising solar energy conversion material due to its suitable optical properties, high elemental earth abundance, and nontoxicity. In addition to the challenge of multiple stable secondary phases, the short minority carrier diffusion length poses an obstacle to its practical application. This work addresses the issue by synthesizing nanostructured Cu2S thin films, which enables increased charge carrier collection. A simple solution-processing method involving the preparation of CuCl and CuCl2 molecular inks in a thiol-amine solvent mixture followed by spin coating and low-temperature annealing was used to obtain phase-pure nanostructured (nanoplate and nanoparticle) Cu2S thin films. The photocathode based on the nanoplate Cu2S (FTO/Au/Cu2S/CdS/TiO2/RuO x ) reveals enhanced charge carrier collection and improved photoelectrochemical water-splitting performance compared to the photocathode based on the non-nanostructured Cu2S thin film reported previously. A photocurrent density of 3.0 mA cm-2 at -0.2 versus a reversible hydrogen electrode (V RHE) with only 100 nm thickness of a nanoplate Cu2S layer and an onset potential of 0.43 V RHE were obtained. This work provides a simple, cost-effective, and high-throughput method to prepare phase-pure nanostructured Cu2S thin films for scalable solar hydrogen production.

Electrochemical Behavior of Morphology-Controlled Copper (II) Hydroxide Nitrate Nanostructures

Nanostructure control is an important issue when using electroactive materials in energy conversion and storage devices. In this study, we report various methods of synthesis of nanostructured copper (II) hydroxide nitrate (Cu2(OH)3NO3) with a layered hydroxide salt (LHS) structure using various synthesis methods and investigate the correlation between nanostructure, morphology, and their pseudocapacitive electrochemical behavior. The variations in nanostructure size and morphology were comprehensively explored by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the electrochemical activity was characterized using cyclic voltammetry. We demonstrate that Cu2(OH)3NO3–LHS nanostructured submicron particles produced by alkaline precipitation with 88% of the copper cations can cycle with a two-electron redox process. Unfortunately, the electroactivity decreases rapidly from the first cycle due to the occurrence of structural transformations and subsequent electrochemical grinding. However, samples obtained by ultrasonication and microwave synthesis, two original synthesis methods for LHS materials, formed of nanosized crystalline domains agglomerated in micron-sized particles, represent a good compromise between capacity and cyclability. Moreover, by using pair distribution function analysis on electrode materials after repeated cycling, we were able to follow the chemical and structural changes occurring in Cu2(OH)3NO3 materials during electrochemical cycling with first a quick transformation to Cu2O and then the appearance of Cu metal and copper acetate Cu(II)2(O2CCH3)4·2H2O.

Interdependence between structural and magnetic properties of transition metal doped multiferroic perovskite ferroelectric ceramics and its sustainable applications: Review

Multiferroic perovskite materials are considered brilliant & suitable materials for power storage and electrical energy conversion because of their excessive power efficiency, temperature stability, and occasional dielectric loss. The electric houses of such multiferroic substances are modify-made through ferroelectric and ferromagnetic parts and feature unfolded first-rate avenues in an electrochemical supercapacitor, photovoltaic, and optical tool applications. Dopants significantly optimize such materials' magnetic and structural properties owing to suitable applications like capacitors, multi-aspect capacitors (MLCs), and strength capability gadgets. This survey features the logical progressions announced in transition metal doped barium titanate multiferroic ferroelectric ceramics for energy applications by optimizing their magnetic properties. This paper begins off evolved with a quick advent of Barium titanate and a dialogue at the outcomes of diverse dopants with the aid of using extraordinary synthesis techniques, and their outcomes on structural and magnetic homes also are depicted. Ultimately, this assessment summarizes the diverse doping outcomes, which paves the manner for destiny studies in this multiferroic substantial for sustainable tool applications.

Hydrogen-bonded organic frameworks and their derived materials for electrochemical energy storage and conversion

Hydrogen-bonded organic frameworks and their derived materials for electrochemical energy storage and conversion

Electronic Modulation of the 3D Architectured Ni/Fe Oxyhydroxide Anchored N-Doped Carbon Aerogel with Much Improved OER Activity.

It remains a big challenge to develop non-precious metal catalysts for oxygen evolution reaction (OER) in energy storage and conversion systems. Herein, a facile and cost-effective strategy is employed to in situ prepare the Ni/Fe oxyhydroxide anchored on nitrogen-doped carbon aerogel (NiFeOx(OH)y@NCA) for OER electrocatalysis. The as-prepared electrocatalyst displays a typical aerogel porous structure composed of interconnected nanoparticles with a large BET specific surface area of 231.16 m2·g-1. In addition, the resulting NiFeOx(OH)y@NCA exhibits excellent OER performance with a low overpotential of 304 mV at 10 mA·cm-2, a small Tafel slope of 72 mV·dec-1, and excellent stability after 2000 CV cycles, which is superior to the commercial RuO2 catalyst. The much enhanced OER performance is mainly derived from the abundant active sites, the high electrical conductivity of the Ni/Fe oxyhydroxide, and the efficient electronic transfer of the NCA structure. Density functional theory (DFT) calculations reveal that the introduction of the NCA regulates the surface electronic structure of Ni/Fe oxyhydroxide and increases the binding energy of intermediates as indicated by the d-band center theory. This work provides a new method for the construction of advanced aerogel-based materials for energy conversion and storage.

Carbon Confined Mesoporous Catkin-like SnPS3 Nanostructure for Lithium Storage with Great Superiority

Metal phosphosulfides (MPSs) are members of a category of emerging energy storage and conversion materials, particularly having significant potentials in lithium storage due to their phosphorus and sulfur dual anion centers and unique two-dimensional channels. Nevertheless, it is still very challenging for the controllable design and synthesis of MPSs nanomaterials with complex-element components. Herein, a distinctive carbon confined mesoporous catkin-like SnPS3 nanostructure (SnPS3@C) is controllably synthesized and fabricated based on the partial volatilization of the reduced tin and the following bottom-up phosphosulfuration by a chemical vapor deposition method. As the anode material of lithium ion batteries, the catkin-like SnPS3@C offers multiple active centers for lithium insertion, complete carbon shell to protect inner active materials, interlaced fibrous networks for efficient electron transfer as well as abundant inner mesopores for Li+ diffusion and volume buffer, thus showing prominent structure advantages in lithium storage. The catkin-like SnPS3@C electrode demonstrated superior electrochemical capability with a very high reversible capacity (1302 mAh g–1 at 300 mA g–1), excellent rate property (630 mAh g–1 at 8000 mA g–1) and distinguished cycling stability (1030 mAh g–1 after 1000 cycles at 1000 mA g–1). This work offers a new avenue to develop high-performance MPSs materials for advanced lithium ion batteries.

High-Entropy Perovskites for Energy Conversion and Storage: Design, Synthesis, and Potential Applications.

Perovskites have shown tremendous promise as functional materials for several energy conversion and storage technologies, including rechargeable batteries, (electro)catalysts, fuel cells, and solar cells. Due to their excellent operational stability and performance, high-entropy perovskites (HEPs) have emerged as a new type of perovskite framework. Herein, this work reviews the recent progress in the development of HEPs, including synthesis methods and applications. Effective strategies for the design of HEPs through atomistic computations are also surveyed. Finally, an outlook of this field provides guidance for the development of new and improved HEPs.

Exciton Ground State Fine Structure and Excited States Landscape in Layered Halide Perovskites from Combined BSE Simulations and Symmetry Analysis

AbstractLayered halide perovskites are solution‐processed natural heterostructures where quantum and dielectric confinement down to the nanoscale strongly influence the optical properties, leading to stabilization of bound excitons. Detailed understanding of the exciton properties is crucial to boost the exploitation of these materials in energy conversion and light emission applications, with on‐going debate related to the energy order of the four components of the most stable exciton. To provide theoretical feedback and solve among contrasting literature reports, this work performs ab initio solution of the Bethe–Salpeter equation (BSE) for symmetrized reference Cs2PbX4 (X = I and Br) models, with detailed interpretation of the spectroscopic observables based on group‐theory analysis. Simulations predict the following Edark < Ein‐plane < Eout‐of‐plane fine‐structure assignment, consistent with recent magneto‐absorption experiments and obtain similar increase in dark/bright splitting when going from lead‐iodide to a lead‐bromide composition as found experimentally. The authors further suggest that polar distortions may lead to stabilization of the in‐plane component and end‐up in a bright lowest exciton component, discuss exciton landscape over a broad energy range and clarify the exciton spin‐character, when large spin‐orbit coupling is in play, to rationalize the potential of halide perovskites as triplet sensitizers in combination with organic dyes.

Defect Engineering of Carbons for Energy Conversion and Storage Applications

Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future carbon. To this end, carbon materials with attractive features, such as tunable pore architecture, good electrical conductivity, outstanding physicochemical stability, abundant resource, and low cost, have used as promising electrode materials for energy conversion and storage. Defect engineering could modulate the structures of carbon materials, thereby affecting their electronic properties. The presence of defects on carbons may lead to asymmetric charge distribution, change in geometrical configuration, and distortion of the electronic structure that may result in unexpected electrochemical performances. In this review, recent advances in defects of carbons used for energy conversion and storage were examined in terms of types, regulation strategies, and fine characterization means of defects. The applications of such carbons in supercapacitors, rechargeable batteries, and electrocatalysis were also discussed. The perspectives toward the development of defect engineering carbons were proposed. In all, novel insights related to improvement in high‐performance carbon materials for future energy conversion and storage applications were provided.

Novel 2D sulfur-doped V2O5 flakes and their applications in photoelectrochemical water oxidation and high-performance energy storage supercapacitors

Development of high-performance energy storage devices with exceptional and consistent performance is of immense significance due to ecological concerns to meet the growing demands for high-performance energy conversion and storage. V2O5 materials have attracted particular attention for energy storage owing to their excellent Faradaic performance, several oxidation valences, inexpensive, ease of synthesis, and non-toxic, all of which make them favorable materials for both energy conversion and storage applications. In this investigation, an efforts has been made to synthesize the novel 2D S-doped V2O5 flakes via a facile hydrothermal procedure. The materials developed were utilized in photoelectrochemical (PEC) water oxidation as well as electrochemical energy storage supercapacitors. XRD analysis confirmed that V2O5 crystal structure is orthorhombic, and doping of the sulfur ions into V2O5 lattice, which has considerably narrowed the band gap from 2.17 eV to 2.02 eV. Nyquist plots revealed that the doped electrode showed reduced inner resistance (RS) and charge transmission resistance (RCT) compared to that of naked electrode. Density functional theory (DFT) calculations illustrate that sulfur-ion doping in the two-dimensional V2O5 monolayer remarkably enhances the electrical properties of the materials. Furthermore, the doping of S into the host matrix causes a positive influence on its structure, electrical conductivity and ion diffusion. Doped V2O5 2D flakes exhibited a specific capacitance of 749F/g at 1 A/g with excellent stability after 3000 cycles at 2.5 A/g compared to the undoped sample. Furthermore, 2D S-doped V2O5 flakes showed ∼ 4.7 folds improvement in photocurrent density and reduced charge resistance than the undoped sample, indicating that doped V2O5 has excellent photoelectrochemical (PEC) water oxidation properties. The fabricated 2D nanostructured materials can be the potential materials for constructing inexpensive and high-performance energy conversion (e.g., hydrogen production, green energy generation), and energy storage devices.

Dynamic Lone Pair Expression as Chemical Bonding Origin of Giant Phonon Anharmonicity in Thermoelectric InTe

AbstractLoosely bonded (“rattling”) atoms withs2lone pair electrons are usually associated with strong anharmonicity and unexpectedly low thermal conductivity, yet their detailed correlation remains largely unknown. Here we resolve this correlation in thermoelectric InTe by combining chemical bonding analysis, inelastic X‐ray and neutron scattering, and first principles phonon calculations. We successfully probe soft low‐lying transverse phonons dominated by large In1+z‐axis motions, and their giant anharmonicity. We show that the highly anharmonic phonons arise from the dynamic lone pair expression with unstable occupied antibonding states induced by the covalency between delocalized In1+5s2lone pair electrons and Te 5pstates. This work pinpoints the microscopic origin of strong anharmonicity driven by rattling atoms with stereochemical lone pair activity, important for designing efficient materials for thermoelectric energy conversion.

Dynamic Lone Pair Expression as Chemical Bonding Origin of Giant Phonon Anharmonicity in Thermoelectric InTe.

Loosely bonded ("rattling") atoms with s2 lone pair electrons are usually associated with strong anharmonicity and unexpectedly low thermal conductivity, yet their detailed correlation remains largely unknown. Here we resolve this correlation in thermoelectric InTe by combining chemical bonding analysis, inelastic X-ray and neutron scattering, and first principles phonon calculations. We successfully probe soft low-lying transverse phonons dominated by large In1+ z-axis motions, and their giant anharmonicity. We show that the highly anharmonic phonons arise from the dynamic lone pair expression with unstable occupied antibonding states induced by the covalency between delocalized In1+ 5s2 lone pair electrons and Te 5p states. This work pinpoints the microscopic origin of strong anharmonicity driven by rattling atoms with stereochemical lone pair activity, important for designing efficient materials for thermoelectric energy conversion.

Designing Black Phosphorus and Heptazine-Based Crystalline Carbon Nitride Composites for Photocatalytic Water Splitting

Black phosphorus (BP) and heptazine-based crystalline carbon nitride (KPHI) composite photocatalysts were synthesized by molten salt and ultrasound-assisted liquid phase exfoliation methods. The structure, morphology and optical properties of the as-prepared BP/KPHI composites were evaluated by various characterization techniques. In addition, the photocatalytic performance of BP/KPHI composites for hydrogen production was investigated. The photocatalytic activity of BP/KPHI composite catalysts could be modulated by changing the loading mass ratio of BP. The BP/KPHI composite photocatalyst with a mass ratio of 10% exhibited the highest photocatalytic activity with the hydrogen production rate of 4.3 mmol g−1 h−1, about three times higher than that of pristine KPHI. Benefiting from the advantages of simplicity, rapidity, high yield and good controllability, this nanocomposite photocatalyst has the potential to serve as an excellent photocatalytic material for solar energy conversion.

Optically triggered cascade heat releasing from leakage-proof hydrate salt for intelligent thermal energy storage

Hydrate salts are promising phase change materials for energy storage and conversion due to their safety, large latent heat and low cost. However, leakage during melting and supercooling in solidification are two main obstacles limiting their practical application. Herein, sodium sulfate decahydrate (SSD) was encapsulated with silica shell and further modified to be highly hydrophobic thus to achieve leakage-proof. Furthermore, azobenzene was introduced with delicate design to conduct isomerization under light illumination, the heat of which triggered solidification of supercooled SSD thus forming a cascade heat release process. The encapsulated SSD possesses high latent heat (123 J/g) and energy storage efficiency (80 %), and maintains shape-stable at 25 °C above SSD's m.p. More importantly, introduction of Azo can release heat stored in SSD promptly with temperature increased by 12 °C. This study paves the way for designing an intelligent thermal energy storage method by optically triggering cascade heat releasing from a stably stored phase change materials composite.

Elucidation of a Photothermal Energy Conversion Mechanism in Hydrogenated Molybdenum Suboxide: Interplay of Trapped Charges and Their Dielectric Interactions

Hydrogenated molybdenum suboxide (HxMoO3-y) is a promising photothermal energy conversion (PEC) material. However, its charge carrier dynamics and underlying mechanisms remain unclear. Utilizing flash-photolysis time-resolved microwave conductivity, we investigated charge carrier-dielectric interactions in the Pt/HxMoO3-y composite. The charge recombination of H2-reduced Pt/HxMoO3-y was 2-3 orders of magnitude faster than that of Pt/MoO3, indicating efficient PEC. A complex photoconductivity study revealed that Pt/HxMoO3-y has two types of trapping mechanisms, Drude-Zener (DZ) and negative permittivity effect (NPE) modes, depending on the reduction temperature. Pt/HxMoO3-y reduced at 100 °C exhibited a dominant NPE owing to the electrical interaction of trapped charges with the surrounding ions and/or OH base. This polaronic trapped state retarded the PEC process. We found Pt/HxMoO3-y reduced at 200 °C to be optimal owing to the balanced suppression of the NPE and charge diffusion. This is the first report revealing the charge dynamics in hydrogenated metal oxides and their impacts on PEC processes.