Energy Conversion Applications Research Articles

Advancements in printed components for proton exchange membrane fuel cells: A comprehensive review

Proton Exchange Membranes (PEM) are a promising technology for fuel cells and electrolyzer cells, in line with societal goals for clean and sustainable fuel conversion and generation, respectively, in a vast field of applications. PEM fuel cell (PEMFC) technology has an important advantage for energy conversion applications, because it requires a lower operating temperature and is lighter and more compact than other technologies, which makes it ideal for portable and transportation applications. However, open issues remain to be addressed for PEMFC that hinder their widespread adoption, both on the technical side, such as too high operational temperature range, cell efficiency, and long-term stability, as well as on the industrial side with implementation issues, material and device component availability, and cost. PEM technology research usually focuses on the synthesis of novel materials such as non-noble metal catalysts and non-halogenated membranes. In parallel, developing high-throughput and cost-effective manufacturing methods for components, in particular Membrane Electrode Assembly (MEA), can also lift an important barrier to their mass production, thus contributing to the same goals and securing industrial provision. From this perspective, printing technologies such as spray coating, inkjet printing, and screen printing have emerged as promising approaches with the required precision and scalability. This review covers recent advancements and developments in advanced PEMFC technology manufacturing, with a focus on 2D printing methodologies to fabricate some or all of the MEA components. Leveraging these techniques as simplified large-area manufacturing methods for PEM technology can become a more viable and industrially attractive solution. This work presents a comparison study addressing the key progress indicators both in process and in characterization to build a working framework in which both scientists, engineers and manufacturers can collaborate toward the industrial implementation of this emergent field.

Magnetic Hyperporous Elastic Material with Excellent Fatigue Resistance and Oil Retention for Oil-Water Separation.

Oily wastewater has caused serious threats to the environment; thus, high-performance absorbing materials for effective oil-water separation technology have attracted increasing attention. Herein, we develop a magnetic, hydrophobic, and lipophilic hyperporous elastic material (HEM) templated by high internal phase emulsions (HIPE), in which free-radical polymerization of butyl acrylate (BA) and divinylbenzene (DVB) is employed in the presence of poly(dimethylsiloxane) (PDMS), lecithin surfactant, and modified Fe3O4 nanoparticles. The adoption of the emulsion template with nanoparticles as both stabilizers and cross-linkers endows the HEM with biomimetic hierarchical open-cell micropores and elastic cross-linked networks, generating an oil absorbent with outstanding mechanical stability. Compressive fatigue resistance of the HEM is demonstrated to endure 2000 mechanical cycles without plastic deformation or strength degradation. By exploiting the synergistic effect of hierarchical structures and low-surface-energy components, the resulting HEM also possesses excellent and robust hydrophobicity (water contact angle of 164°) and good oil absorption capacity, in which Fe3O4 nanoparticles lead to convenient magnetically controlled oil recyclability as well. Notably, the unique biomimetic microporous structure demonstrates superior oil retention capacity (>95% at 1000 rpm and >60% at 10,000 rpm) over the state-of-the-art porous materials for a diverse variety of oils to reduce the risk of secondary oil leakage, along with good recoverability by squeezing owing to the excellent compression resilience. These excellent performances of our HEM provide broad prospects for practical applications in oil-water separation, energy conversion, and smart soft robotics.

BaCoO2 with Tetrahedral Cobalt Coordination: The Missing Element to Understand Energy Storage and Conversion Applications in BaCoO3-δ-Based Materials.

Barium-cobaltate-based perovskite (BaCoO3-δ) and barium-cobaltate-based nanocomposites have been intensively studied in energy storage and conversion devices mainly due to flexible oxygen stoichiometry and tunable nonprecious transition metal oxidation states. Although a rich and complex family of structural polymorphs has already been reported for these perovskites in the literature, the potential structural evolution that may occur during the oxygen reduction reaction and the oxygen evolution reaction has not been investigated so far. In this study, we synthesized and characterized the lowest Co-oxidation state possible in the compound, BaCoO2, which exhibits a quartz-derived, trigonal structure with a helicoidally corner-sharing, CoO4-tetrahedral-framework as already proposed by Spitsbergen et al. Oxygen can reversibly be inserted in such a crystal structure to form BaCoO3-δ, i.e., with 0 ≤ δ ≤ 1, based on the results of an in situ coupled thermogravimetric - neutron diffraction study and which presents therefore giant oxygen capacity storage due to the extreme tunability of the electronic configuration of the cobalt cations which defines the fundamental origins of the materials performance. The reversible conversion of BaCoO2 to BaCoO3-δ associated with a similar electronic conductivity above 900 K permits to clarify the high potential of BaCoO3-δ-based energy storage and conversion devices.

Hydroxide-Derived Nanostructures: Scalable Synthesis, Characterization, Properties, and Potential Applications.

Metal oxide nanostructures have received an increasing attention owing to their unique chemical and physical properties along with their widespread applications in various fields. This article provides an overview of the recent discovery - christened Hydroxides-Derived Nanostructures, or HDNs - in which hydroxide aqueous solutions (mostly tetramethylammonium hydroxide, TMAH) are reacted at temperatures < 100°C and under atmospheric pressure with various metal-containing precursors to scalably prepare novel metal oxide nanostructures. In one case, a dozen commercial and earth abundant Ti-containing powders such as binary carbides, nitrides, borides, among others, are converted into new, 1D TiO2-based lepidocrocite (1DL) nanofilaments (NFs). Application-wise, the 1DLs show outstanding performance in a number of energy, environmental, and biomedical fields such as photo- and electrocatalysis, water splitting, lithium-sulfur and lithium-ion batteries, water purification, dye degradation, cancer therapy, and polymer composites. In addition to 1DL, the HDNs family encompasses other metal oxides nanostructures including magnetic Fe3O4 nanoparticles and MnO2 birnessite-based crystalline 2D flakes. The latter showed promise in electrochemical energy conversion and storage applications. The developed recipe provides a new vista in the molecular self-assembly synthesis of nanomaterials that can advance the field with a library of novel nanostructures with substantial implications in a multitude of fields.

Oxygen evolution reaction kinetics and photoluminescence studies of zinc stannate (ZnSnO3/Zn2SnO4) nanoparticles synthesized via [formula omitted] mediated route

A groundbreaking method utilizing Aloebarbadensismiller gel to synthesize novel zinc stannate nanoparticles in two distinct phases, followed by calcination at 600 °C, has been developed. Structural, optical, and electrochemical analyses were meticulously conducted to explore the impact of phase variation. X-ray diffraction confirmed the formation of face-centered perovskite and inverse spinel cubic structures for ZnSnO3 and Zn2SnO4 nanoparticles respectively, with irregular sizes and shapes observed in both phases. Energy-dispersive X-ray spectroscopy confirmed their purity. Tauc’s plot revealed direct energy band gaps of 3.45 eV and 3.4 eV for ZnSnO3 and Zn2SnO4 respectively, with photoluminescence emission spectra displaying distinct peaks at 646 nm and 647 nm. The study identified higher defect levels in the inverse spinel structure. Notably, the synthesized nanoparticles exhibited promising characteristics for light-emitting diodes and display technology, with color-correlated temperatures (6810 and 6695 K) suggesting their potential application. Furthermore, the nanoparticles demonstrated remarkable performance in oxygen evolution reaction (OER) studies, with low overpotentials (η10) in the range of 269 mV and 273 mV along with a minimal Tafel slope of 76 mV dec−1 and stable electrochemical behavior over 45 h at a current density of 20 mA/cm2, indicating their efficacy as electrocatalysts. The current work unveils the novel synthesis of zinc stannate nanoparticles through an Aloebarbadensismiller gel, a method that stands out for its eco-friendly and cost-effective nature. We delve into uncharted territory by investigating these nanoparticles’ oxygen evolution reaction kinetics and photoluminescence properties, shedding light on their potential applications in energy conversion and sensing technologies. This pioneering study contributes to the understanding of zinc stannate nanoparticles’ behavior, paving the way for transformative advancements in various fields.

Post-treatment induced anisotropic growth of MOF-derived surface modified heterogeneous catalyst for efficient oxygen evolution reaction

The advancement of electrocatalysts exhibiting outstanding performance in the oxygen evolution reaction (OER), crucial for hydrogen production, holds immense significance in addressing energy shortages and mitigating environmental pollution. In this study, a novel approach to synthesizing Co-MOF (Metal-Organic Framework) directly immobilized onto a Ni foam substrate through hydrothermal synthesis is presented. In contrast to conventional methods employing powder-based synthesis with binders, our direct attachment method offers a unique and efficient means of creating robust Co-MOF at Ni foam (Co-MOF@NF) hybrid catalysts. Subsequently, a chemical reduction approach utilizing sodium borohydride was employed to introduce surface modification into the Co-MOF structure. The resulting material, sodium borohydride treated Co-MOF@NF (Red. 1 h Co-MOF@NF), exhibited a remarkable enhancement in OER activity compared to the pristine Co-MOF@NF sample. Notably, Red.1 h Co-MOF@NF demonstrated a substantially reduced overpotential of 235 mV to achieve a current density of 10 mA cm⁻2, in contrast to the 300 mV overpotential required by the pristine Co-MOF@NF under the same conditions. Furthermore, the Red.1 h Co-MOF@NF catalyst displayed exceptional stability, sustaining a current density of 50 mA cm⁻2 for over 48 h, highlighting its promising potential for practical applications. The synergistic effects of direct hydrothermal attachment, surface modification, and improved OER performance make this study a significant contribution to the advancement of efficient and stable electrocatalysts for energy conversion applications.

First-principles study of Na2AgAsZ6 (Z = F, Cl, Br, I) of structural, elastic, optoelectronic, and transport properties of lead-free halide double perovskites for energy conversion applications

In this article, density functional theory (DFT) is used to investigate the physical aspects of the halide double perovskites Na2AgAsZ6 (Z = F, Cl, Br, I). These substances have a cubic arrangement and are classified under space group Fm3m (225) based on their octahedral and tolerance factors values. All the perovskites are determined to be thermodynamically stable, as indicated by their negative formation energy. These double perovskite materials are semiconductors based on their electronic band structure. The energy band gaps of Na2AgAsF6, Na2AgAsCl6, Na2AgAsBr6, and Na2AgAsI6 were determined to be 2.96 eV, 1.93 eV, 1.28 eV, and 0.68 eV, respectively. We also calculated and examined the optical properties of these substances in the photon energy range of 0–8 eV. Our results indicate that the majority of the absorption occurs in the visible-ultraviolet spectrum, which makes the materials well-suited for solar systems. We employed the BoltzTraP algorithm to compute the thermoelectric properties of the materials and establish their thermoelectric behavior. These materials demonstrated figures of merit values of 0.55, 0.71, 0.74, and 0.75, respectively. Thus, these materials are appropriate for application in photovoltaic and thermoelectric devices.

Ternary Eu3+ crystalline complexes with photoluminescence and triboluminescence for dynamic stress visualization

Investigation of photoluminescence (PL) and fracture-induced triboluminescence (TL) is necessary for the development of both fundamental theories and practical applications in mechanical energy conversion; however, most known PL/TL-emitting materials are confined to inorganic systems. In this study, a novel lanthanide-based crystalline complex (LnCC), Eu(DBM)3DETA was synthesized via the synergistic coordination of Eu3+ with DBM (Dibenzoylmethane) and DETA (Diethylenetriamine) units, leading to the formation of brighter LnCC with bright red emission, high PL quantum yields (57.19 %) and unique TL characteristics. The key to success in obtaining Eu(DBM)3DETA is the utilization of DETA molecule as synergistic ligand, presenting block crystals with higher coordination number of Eu3+ ions via recrystallization. Due to the dense accumulation of cross-linked three-dimensional frameworks through van der Waals interactions, the fracture-induced piezoelectric effect results in charge separation and excitation through the resultant electric field and discharge, triggering a fast TL response of Eu(DBM)3DETA and expanding the possibilities of the quantitative stress sensing. Importantly, amorphous powders can still recover to their original PL and TL emission intensities after recrystallization in cyclic crystal-to-amorphous phase transitions. The unique PL and TL characteristics of Eu(DBM)3DETA provide promising opportunities to display stress visualization differences of electronic signatures under different forces.

Magnetic analysis of permeability configurable nanocrystalline flake ribbons for medium frequency energy conversion applications

The novel permeability configurable nanocrystalline flake ribbons (NFR) utilizing Fe-based nanocrystalline material has been increasingly adopted in diverse energy conversion applications. However, the application-oriented magnetic properties are rarely examined. In this paper, the flexible NFR materials with different permeabilities are measured while the influence of permeability configuration is analyzed regarding the initial and amplitude permeabilities, B–H curves, and core losses. A measurement method using a full bridge inverter and LCL compensation is designed to test the magnetic material under various flux densities and in the frequency range between 50 kHz–150 kHz. In addition, ferrite materials with similar permeabilities are also tested for comparison. Results reveal that the NFR materials exhibit superior stability in terms of amplitude permeability changes and saturation capability compared with ferrites. Core loss grows with increased crushing, but permeability becomes more stable at higher frequencies. Hence, NFR materials can be matched to various applications based on their characteristics with different permeabilities. Additionally, the NFR materials have shown lower loss densities than their ferrite counterparts at high flux density conditions. Hence, the NFR material can be beneficial to achieve higher power density. Through analysis and experiments, this paper provides measurement optimization bases for practical energy conversion applications.

Highly Stable MOF-Type Lead Halide Luminescent Ferroelectrics.

Lead halide molecular ferroelectrics represent an important class of luminescent ferroelectrics, distinguished by their high chemical and structural tunability, excellent processability and distinctive luminescent characteristics. However, their inherent instability, prone to decomposition upon exposure to moisture and light, hinders their broader ferroelectric applications. Herein, for the first time, we present a series of isoreticular metal-organic framework (MOF)-type lead halide luminescent ferroelectrics, demonstrating exceptional robustness under ambient conditions for at least 15 months and even when subjected to aqueous boiling conditions. Unlike conventional metal-oxo secondary building units (SBUs) in MOFs adopting highly centrosymmetric structure with limited structural distortion, our lead halide-based MOFs occupy structurally deformable [Pb2X]+ (X=Cl-/Br-/I-) SBUs that facilitate a c-axis-biased displacement of Pb2+ centers and substantially contribute to thermoinducible structural transformation. Importantly, this class of MOF-type lead halide ferroelectrics undergo ferroelectric-to-paraelectric phase transitions with remarkably high Curie temperature of up to 505 K, superior to most of molecular ferroelectrics. Moreover, the covalent bonding between phosphorescent organic component and the light-harvesting inorganic component achieves efficient spin-orbit coupling and intersystem crossing, resulting in long-lived afterglow emission. The compelling combination of high stability, ferroelectricity and afterglow emission exhibited by lead halide MOFs opens up many potential opportunities in energy-conversion applications.

Hierarchical porous carbon materials for lithium storage: Preparation, modification, and applications.

Secondary battery as an efficient energy conversion device have been highly attractive for alleviating the energy crisis and environmental pollution. Hierarchical porous carbon materials with multiple sizes pore channels are considered as promising materials for energy conversion and storage applications, due to their high specific surface area and excellent electrical conductivity. Although many reviews have reported on carbon materials for different fields, systematic summaries about hierarchical porous carbon materials for lithium storage are still rare. In this review, we fist summarize the main preparation methods of hierarchical porous carbon materials, including hard template method, soft template method, and template-free method. The modification methods including porosity and morphology tuning, heteroatom doping, and multiphase composites are introduced systematically. Then, the recent advances in hierarchical porous carbon materials on lithium storage are summarized. Finally, we outline the challenges and future perspectives for the application of hierarchical porous carbon materials in lithium storage.

Organic Electrode Materials for Energy Storage and Conversion: Mechanism, Characteristics, and Applications.

ConspectusLithium ion batteries (LIBs) with inorganic intercalation compounds as electrode active materials have become an indispensable part of human life. However, the rapid increase in their annual production raises concerns about limited mineral reserves and related environmental issues. Therefore, organic electrode materials (OEMs) for rechargeable batteries have once again come into the focus of researchers because of their design flexibility, sustainability, and environmental compatibility. Compared with conventional inorganic cathode materials for Li ion batteries, OEMs possess some unique characteristics including flexible molecular structure, weak intermolecular interaction, being highly soluble in electrolytes, and moderate electrochemical potentials. These unique characteristics make OEMs suitable for applications in multivalent ion batteries, low-temperature batteries, redox flow batteries, and decoupled water electrolysis. Specifically, the flexible molecular structure and weak intermolecular interaction of OEMs make multivalent ions easily accessible to the redox sites of OEMs and facilitate the desolvation process on the redox site, thus improving the low-temperature performance, while the highly soluble nature enables OEMs as redox couples for aqueous redox flow batteries. Finally, the moderate electrochemical potential and reversible proton storage and release of OEMs make them suitable as redox mediators for water electrolysis. Over the past ten years, although various new OEMs have been developed for Li-organic batteries, Na-organic batteries, Zn-organic batteries, and other battery systems, batteries with OEMs still face many challenges, such as poor cycle stability, inferior energy density, and limited rate capability. Therefore, previous reviews of OEMs mainly focused on organic molecular design for organic batteries or strategies to improve the electrochemical performance of OEMs. A comprehensive review to explore the characteristics of OEMs and establish the correlation between these characteristics and their specific application in energy storage and conversion is still lacking.In this Account, we initially provide an overview of the sustainability and environmental friendliness of OEMs for energy storage and conversion. Subsequently, we summarize the charge storage mechanisms of the different types of OEMs. Thereafter, we explore the characteristics of OEMs in comparison with conventional inorganic intercalation compounds including their structural flexibility, high solubility in the electrolyte, and appropriate electrochemical potential in order to establish the correlations between their characteristics and potential applications. Unlike previous reviews that mainly introduce the electrochemical performance progress of different organic batteries, this Account specifically focuses on some exceptional applications of OEMs corresponding to the characteristics of organic electrode materials in energy storage and conversion, as previously published by our groups. These applications include monovalent ion batteries, multivalent ion batteries, low-temperature batteries, redox flow batteries with soluble OEMs, and decoupled water electrolysis employing organic electrodes as redox mediators. We hope that this Account will make an invaluable contribution to the development of organic electrode materials for next-generation batteries and help to unlock a world of potential energy storage applications.

Selective Covalent Basal Plane Modification as a Probe of Hydroxide Ion Conduction Pathways in Magnesium Aluminum Layered Double Hydroxides.

Understanding ionic conduction in layered double hydroxides (LDHs) is a crucial step towards utilizing them as solid, hydroxide ion-conducting electrolytes in energy conversion applications. We selectively modified the interlayer and external surfaces of MgAl LDHs with tris(hydroxymethyl)aminomethane (TRIS) ligands. By adjusting the concentration of the TRIS surface modifier, the LDH basal plane surfaces could be functionalized everywhere (internally and externally) or only externally. External modification resulted in loss of OH-conductivity compared to pristine LDHs, confirming that external platelet surfaces are the primary ion conduction pathway.

Optimizing photocatalytic and supercapacitive performance by β-Bi2O3@BiFeO3 modification with PVDF polymer based nanocomposites

The PVDF (Poly-Vinyl-difloride) membrane modified with Bismuth oxide (β-Bi2O3)/Bismuth Ferrite (BiFeO3) p-n heterojunction synthesized via hydrothermal process to explore its energy storage and conversion applications. The PVDF-Bi2O3/BiFeO3 nanocomposites (NCs) prepared in this study were subjected to analysis using PXRD, FTIR, UV-Vis DRS, FE-SEM with EDX, TEM, and transient photocurrent response techniques, individually. The as-prepared materials were evaluated for their photocatalytic performance in the visible light-induced degradation of Methylene Blue (MB) and Rhodamine-B (RhB) dyes. The photocatalytic performance demonstrates degradation efficiencies of 95% for MB dye and 83% for RhB dye when utilizing the PVDF-β-Bi2O3@BiFeO3 nanocatalyst. The enhancement in the photocatalytic performance of the PVDF-Bi2O3/BiFeO3 heterojunction was a result of improved visible light absorption, suppression of photogenerated electron-hole pair recombination, accelerated separation and migration of photogenerated charges. The capacitance behavior of PVDF-β-Bi2O3@BiFeO3 is significantly higher than β-Bi2O3@BiFeO3 in 3 M KOH solution which has specific capacitance of 300 F g−1at 1 A g−1 of current density and fabricated a symmetric device has10.08 Wh kg−1 and 999.39 W kg−1 specific energy and specific power at 0.5 A g−1 of current density with the 88.7% of capacitance retention and 94.12% of coulombic efficiency up to 10000 cycles.

First-principle simulation of inorganic Na2CuSbX6 (X = Cl, Br, I) halides for photovoltaic and energy conversion applications

The exceptional flexibility of optoelectronic attributes exhibited by inorganic Na2CuSbX6 (X = Cl, Br, I) halides has sparked significant interest in recent research. Our approach involves the utilization of Wien2k and BoltzTrap coding to scrutinize the mechanical, thermoelectric and optoelectronic attributes of studied halides. Structural stability have been investigated through Born stability criteria employing generalized gradient approximation (GGA-PBEsol). In addition, negative formation energy (−2.15 eV for Cl-halide, −1.88 eV for Br-halide and −1.68 eV for I-halide) indicate all halides are thermo-dynamical stable. For accurate calculation of optoelectronic properties, modified Becke and Johnson (mBJ) potential has been employed. Band structure indicate all halides are semiconductor with indirect bandgap nature having bandgap values 1.7 eV for Cl-halide, 1.34 eV for Br-halide and 0.85 eV for I-halide respectively. Substituting Cl-halide with Br and I-halide results in enhanced optical absorption predominantly in the visible region, causing a shift in the absorption edge from visible light to IR. Further, electronic thermoelectric properties are discussed against temperature 300 K to 800 K. The computed higher Seebeck coefficient observed in Na2CuSbI6 suggests that a narrower band gap is more suitable for thermoelectric applications in comparison to Na2CuSbBr6 and Na2CuSbCl6. In a broader context, the computational analysis of thermoelectric and optical properties indicates that Li2CuSbX6 halides is generally well suited for use in solar cell devices and energy conversion applications.

Biopolymer Materials in Triboelectric Nanogenerators: A Review.

In advancing the transition of the energy sector toward heightened sustainability and environmental friendliness, biopolymers have emerged as key elements in the construction of triboelectric nanogenerators (TENGs) due to their renewable sources and excellent biodegradability. The development of these TENG devices is of significant importance to the next generation of renewable and sustainable energy technologies based on carbon-neutral materials. This paper introduces the working principles, material sources, and wide-ranging applications of biopolymer-based triboelectric nanogenerators (BP-TENGs). It focuses on the various categories of biopolymers, ranging from natural sources to microbial and chemical synthesis, showcasing their significant potential in enhancing TENG performance and expanding their application scope, while emphasizing their notable advantages in biocompatibility and environmental sustainability. To gain deeper insights into future trends, we discuss the practical applications of BP-TENG in different fields, categorizing them into energy harvesting, healthcare, and environmental monitoring. Finally, the paper reveals the shortcomings, challenges, and possible solutions of BP-TENG, aiming to promote the advancement and application of biopolymer-based TENG technology. We hope this review will inspire the further development of BP-TENG towards more efficient energy conversion and broader applications.

Hot-Injection Synthesis of Cesium Lead Halide Perovskite Nanowires with Tunable Optical Properties.

Metal halide perovskite semiconductors have emerged as promising materials for various optoelectronic applications due to their unique crystal structure and outstanding properties. Among different forms, perovskite nanowires (NWs) offer distinct advantages, including a high aspect ratio, superior crystallinity, excellent light absorption, and carrier transport properties, as well as unique anisotropic luminescence properties. Understanding the formation mechanism and structure-property relationship of perovskite NWs is crucial for exploring their potential in optoelectronic devices. In this study, we successfully synthesized all-inorganic halide perovskite NWs with high aspect ratios and an orthorhombic crystal phase using the hot-injection method with controlled reaction conditions and surface ligands. These NWs exhibit excellent optical and electrical properties. Moreover, precise control over the halogen composition through a simple anion exchange process enables the tuning of the bandgap, leading to fluorescence emission, covering a wide range of colors across the visible spectrum. Consequently, these perovskite NWs hold great potential for efficient energy conversion and catalytic applications in photoelectrocatalysis.

Exploring the Influence of Cation and Halide Substitution in the Structure and Optical Properties of CH3NH3NiCl3 Perovskite.

This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.

Nano tumbleweed-like tungsten disulfide as a viable surrogate for platinum counter electrodes in dye-sensitized solar cells

Tungsten disulfide (WS2), a notable member of the transition metal dichalcogenides family, has emerged as a promising candidate for energy storage and conversion applications. In this study, WS2 was synthesized via a hydrothermal method using sodium tungstate and thiourea as precursor materials, with hydroxylamine hydrochloride as the reducing agent and cetyl trimethyl ammonium bromide as a surfactant. The primary objective was to develop a cost-effective, easily synthesized, and scalable material capable of replacing platinum (Pt) in dye-sensitized solar cells (DSSCs), where Pt is both prohibitively expensive and scarce. Characterization of the synthesized WS2 was conducted through a range of physical analyses, including SEM, TEM, XRD, EDAX, FTIR, and Raman spectroscopy, which provided compelling evidence for the formation of a unique nano-tumbleweed-like structure of WS2. When used as a counter electrode (CE), the synthesized WS2 exhibited exceptional photocatalytic activity, resulting in a commendable power conversion efficiency (PCE) of 12.06 % when coupled with fluorine-doped tin oxide (FTO) plates coated with TiO2 as the photoanode, N719 as the dye, and Iˉ/I3ˉ as the liquid electrolyte. Additionally, the fabricated device underwent comprehensive electrical characterization, including cyclic voltammetry (CV), current-voltage (IV) measurements, electrochemical impedance spectroscopy (EIS), and Tafel analysis, revealing properties similar to those of Pt counter electrodes. Notably, WS2 demonstrated an open-circuit potential of 852 mV and a short-circuit current density of 28 mA/cm2, accompanied by a fill factor of 0.43 and a commendable lifetime of 15.92 ms.

Nonconjugated Polymers Enabled Solar Water Oxidation.

Wholly distinct from conjugated polymers which are featured by generic charge transfer capability stemming from a conjugated molecular structure, solid nonconjugated polymers mediated charge transport has long been deemed as theoretically impossible because of the deficiency of π electrons along the molecular skeleton, thereby retarding their widespread applications in solar energy conversion. Herein, we first conceptually unveil that intact encapsulation of metal oxides (e.g., TiO2, WO3, Fe2O3, and ZnO) with an ultrathin nonconjugated polyelectrolyte of branched polyethylenimine (BPEI) can unexpectedly accelerate the unidirectional charge transfer to the active sites and foster the defect generation, which contributes to the boosted charge separation and prolonged charge lifetime, ultimately resulting in considerably improved photoelectrochemical (PEC) water oxidation activities. The interfacial charge transport origins endowed by BPEI adornment are elucidated, which include acting as a hole-withdrawing mediator, promoting vacancy generation, and stimulating the directional charge flow route. We additionally ascertain that such charge transport characteristics of BPEI are universal. This work would unlock the charge transfer capability of nonconjugated polymers for solar water oxidation. The nonconjugated insulating polymer was utilized as a charge transport mediator for boosting charge migration and separation over metal oxides toward solar water oxidation.