Nanoporous Morphology Research Articles

Design and Optimization of Nanoporous Materials as Catalysts for Oxygen Evolution Reaction—A Review

With the growing demand for new energy sources, electrochemical water splitting for hydrogen production is a technology that must be vigorously promoted. Therefore, to improve the efficiency of the oxygen evolution reaction (OER) at the anode, high-performance OER catalysts are essential. Given their advantages in electrocatalysis, nanoporous materials have garnered considerable attention in previous studies for OER applications. This review provides a comprehensive overview of various strategies to optimize active site utilization in nanoporous materials. These strategies include regulating pore size and porosity, constructing hierarchical nanoporous structures, and enhancing material conductivity. Additionally, it covers approaches to boost the intrinsic OER activity of nanoporous materials, such as tuning the composition of anions and cations, creating vacancies, constructing interfaces, and forming boundary active sites. While nanoporous materials offer significant potential for advancing OER, challenges remain, including difficulties in quantifying activity within nanopores, the unclear impact of nanoporous material morphology, challenges in accessing nanopore interiors with in situ techniques, and a lack of theoretical calculations on pore structure. However, these challenges also present opportunities, and we hope this review provides a fresh perspective to inspire future research.

High-temperature anodization route to nanoporous niobium oxides with enhanced supercapacitive properties in aqueous electrolytes

Relatively little work has been done on Nb2O5 pseudocapacitive behaviors in aqueous solutions. Here, the galvanostatic anodization of niobium in K2HPO4-containing glycerol electrolyte at high temperature is fully explored. The anodically grown films on niobium have ordered nanoporous morphology and are composed of a low-crystalline orthorhombic Nb2O5, which can be directly employed as supercapacitor electrodes without any posttreatment process. To further improve their supercapacitive performances, a facile technique to generate Fe-doped Nb2O5 films is developed, where the as-anodized films are treated by an electrochemical doping in FeCl3 ethylene glycol solution. The Fe-doped Nb2O5 films show a wider potential window and higher capacitance than that of the as-anodized films in aqueous electrolytes. They present a maximum areal capacitance of 168.1 mF cm−2 at 1 mV s−1 and excellent cycling stability with 85.8 % capacitance retention after 10,000 cycles. The charge storage in the Fe-doped Nb2O5 is believed to occur by the incorporation of Li+ ions with concomitant reduction of Nb5+ to Nb4+ in aqueous lithium-containing solutions. Unlike nonaqueous media, Li+ intercalation/deintercalation in aqueous media is a diffusion-controlled process, leading to the comparatively slower pseudocapacitive processes. Nevertheless, in terms of an industrial applicability the Fe-doped Nb2O5 films deserve special attention.

Molecular dynamics of quantitative evaluation of confined fluid behavior in nanopores media and the influencing mechanism: Pore size and pore geometry

Understanding the potential mechanisms of reservoir fluid storage, transport, and oil recovery in shale matrices requires an accurate and quantitative evaluation of the fluid behavior and phase state characteristics of the confined fluid in nanopores as well as the elucidation of the mechanisms within complex pore structures. The research to date has preliminary focused on the fluid behavior and its influencing factors within a single nanopore morphology, with limited attention of the role of pore structures in controlling fluid behavior and a lack of quantitative methods for characterizing the phase state of fluids. To address this gap, we utilize molecular dynamics simulations to examine the phase state characteristics of confined fluids across various pore sizes and geometries, revealing the mechanisms by which wall boundary conditions influence fluid behavior. We use the simulation results to validate the accuracy and applicability of the quantitative characterization model for fluid phase state properties. Our findings show that the phase state features of fluids differ significantly between slit-like and cylindrical pores, with lower absorption limits in pore sizes of 2.8 and 7 nm, respectively. Based on pore sizes, we identified three regions of confined fluid phases and determined that the influence of the adsorbed state fraction on fluid phase state cannot be ignored for pores smaller than approximately 85 nm. Additionally, cylindrical pores interact with the internal fluids about 1.8 times stronger than slit-like pores.

From Waste to Sensor: Facile Synthesis of a Copper‐Doped Hydroxyapatite Nanocomposite as a Colorimetric Sensing Platform for Uric Acid

AbstractUric acid serves as a vital diagnostic marker for diseases like arthritis, gout, etc. Accurate quantification of UA is crucial for diagnosis. The hydroxyapatite (HAp), being catalytic in nature, was used as a template for copper nanoparticles (CuNPs) synthesis and for providing surface area for chemical reactions needed for sensing uric acid. HAp was synthesized from waste chicken bones, followed by doping with copper metal salt through calcination. The synthesis of copper hydroxyapatite (Cu‐HAp) nanocomposite was confirmed using different techniques. SEM displayed the nanoporous morphology of the material. The hexagonal crystal structure of HAp was revealed by X‐ray diffraction analysis, and energy dispersive X‐ray analysis showed the successful doping of Cu on HAp. The Cu‐HAp nanocomposite and 3,3′,5,5′‐tetramethylbenzidine (TMB) dye were employed as a new colorimetric sensing platform for uric acid sensing. The fabricated sensing platform detected uric acid with excellent sensitivity (LOD, 0.24 μM) and a wide linear range (1–270 μM). Optimization experiments demonstrated that the proposed sensor performs best at 4 mg of Cu‐HAp nanocomposite, pH 6, with a response time of 100 s. Furthermore, TMB and H2O2 concentrations of 12 and 8 mM were used, respectively. The proposed sensor successfully detected uric acid in physiological samples.

Hierarchically Porous Vanadium-Based Cathode Materials for High-Performance Na-Ion Batteries

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) in sectors requiring extensive energy storage. The abundant availability of sodium at a low cost addresses concerns associated with lithium, such as environmental contamination and limited availability. However, SIBs exhibit lower energy density and cyclic stability compared to LIBs. One of the key challenges in improving the performance of SIBs lies in the electrochemical properties of the cathode materials. Among the various cathodes utilized in SIBs, sodium vanadium phosphates (NVPs) and sodium vanadium fluorophosphates (NVPFs) are particularly advantageous. These vanadium-based cathodes offer high theoretical capacity and are cost-effective. Commercialization of SIBs with NVPF cathodes has already begun. However, the poor conductivity of these cathode materials leads to a short cycle life and inferior rate performance. Various synthesis methods have been explored to enhance the conductivity, including heteroatom doping (N, S, and Co), surface modification, the fabrication of porous nanostructures, and composite formation with conductive carbon materials. In particular, cathodes with interconnected hierarchical micro- and nano-porous morphologies have shown promise. This review focuses on the diverse synthesis methods reported for preparing hierarchically porous cathodes. With increased attention, particular emphasis has been placed on carbon composites of NVPs and NVPFs. Additionally, the synthesis of vanadium pentoxide-based cathodes is also discussed.

Template assisted fabrication of nanoporous titanium dioxide coating on 316 L stainless steel for orthopaedic applications

BackgroundSurface modified metallic implants with nanoporous morphology finds extensive application as functional implant material as it mimics the biological conditions as well as matches the mechanical characteristics of the bone. The current study involves synthesis of nano-titania coating by the employment of PMMA as a templating agent and compared with widely used PEG 400. MethodThe titania coatings were synthesized by sol-gel methodology and deposited on 316 L SS by dip coating method. The coating morphology was characterized by Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), Scanning electron microscopy - energy dispersive X-ray analysis (SEM-EDX) and Atomic force microscopy (AFM). The bioactive nature of the coatings were evaluated by in vitro bioactivity study in simulated body fluid (SBF). The toxicity and cell adhesion of the coatings were analyzed by MTT assay. The ability of the coatings to resist corrosion was studied with potentiodynamic polarization and electrochemical impedance spectroscopy. Significant findingsThe changes in the cell adhesion behavior are observed for the different coatings. The TiO2 coatings exhibited excellent corrosion resistance. Besides, the nanoporous coating developed with PMMA as the templating agent revealed excellent bioactivity as well as higher corrosion resistance.

Novel nanoporous amorphous/nanocrystalline composite structured RuNiFeCo multicomponent alloys with exceptional catalytic activity for ammonia borane hydrolytic dehydrogenation

The pursuit of high-efficient and cost-effective catalysts for hydrogen generation is imperative to address the energy crisis. Herein, nanoporous RuNiFeCo alloys (np-RuNiFeCo) with high catalytic activity for ammonia borane (AB) hydrolytic dehydrogenation have been prepared by dealloying Fe25NixCo40-xRu5B30 (x = 0–40) high-entropy amorphous alloys with low Ru content. The np-RuNiFeCo are composed of an amorphous/hexagonal close-packed Ru nanocrystalline dual-phase structure and exhibit a uniform nanopore/ligament bicontinuous architecture. The morphology, composition, and AB hydrolysis catalytic properties of the np-RuNiFeCo can be regulated by varying the Ni/Co content in the precursors, and the best catalytic activity with a high turnover frequency value of 148.2 molH2molRu‐1min‐1 and a low apparent activation energy of 25.3 kJmol‐1 was obtained when x = 30. Density functional theory simulations indicate that the presence of Ni, synergizing with Fe and Co, promotes electron transfer to Ru and enhances the adsorption energies of both AB and H2O molecules while reducing the activation barrier for cleaving the H2O molecule, leading to enhanced intrinsic catalytic activity of the alloy. The exceptional catalytic performance of the np-RuNiFeCo arises from the synergy of multiple principal elements, nanoporous morphology, and amorphous/nanocrystalline heterogeneous interface. In addition, the mechanisms of dealloying and nanoporous structure formation have been discussed based on surface diffusion.

Exploring the spectroscopic and I‑V‑T characteristics advancements of cadmium zinc tungsten phosphate diode

This research accomplished the growth of cadmium zinc tungsten phosphate (CZWP) thin films on both glass and p-Si substrates, employing the sol–gel spin coating method. The sol–gel technique offers a versatile and controlled approach for fabricating nanomaterials with tailored properties. The structural and morphological analyses, conducted through XRD and FE-SEM, provided comprehensive insights into the nature of the films. The optical properties, absorbance behavior, energy gap, refractive indices, dielectric, conductivity, and electronegativity, underwent meticulous examination through UV–Vis spectroscopy. The X-ray diffraction analysis of the zinc cadmium tungsten phosphate diode reveals diffraction lines indicative of a nanostructure featuring a monoclinic-phase Zn2P2O7 and Cd3P6O28. Furthermore, SEM analysis confirms a nanoporous morphology with a nanograpes-like structure in the successful crystalline structure of the cadmium zinc tungsten phosphate nanostructure. The optical absorption studies, covering a wavelength range from 190 to 1500 nm, unveiled both direct and indirect energy band gaps, measuring 4.14 and 3.77 eV, respectively. A rigorous analysis of the I-V-T characteristics for the CZNP/p-Si junction in dark mode led to the identification of key parameters, including the transport ideality factor, barrier height, and series resistance.

Porous Morphology of High Grafting Density Mixed Polyelectrolyte Brushes Grown from a Y-Inimer Coating.

Mixed A/B polyelectrolyte (PE) brushes of opposite charges are grown from a Y-shaped initiator-bearing coating to facilitate intimate mixing of the A and B polyelectrolytes in a 1:1 grafting ratio. The design of the Y-shaped inimer includes both ATRP and NMP initiators attached to a common Y-junction. A copolymer of a Y-shaped inimer with glycidyl methacrylate is cross-linked to the substrate resulting in a stable ultrathin coating decorated with Y-shaped initiators. Weak PE A/B mixed brushes based on poly(methacrylic acid)/poly(2-vinylpyridine) (PMAA/P2VP) with a high grafting density of ∼1 chain/nm2 are grown by surface-initiated ATRP and NMP, respectively. Detailed morphological characterization of the PMAA/P2VP brushes in response to pH changes reveals a nanoporous morphology under conditions that maximize complex coacervate formation between oppositely charged brushes. The charge ratio between the A and B brushes is varied via the composition of the brushes to further study the morphology evolution. The effect of intimate contact between the A and B brushes on the morphology is probed by comparing with a mixed A/B PE system with random fluctuations in grafting composition. A quantitative and qualitative study of the pore evolution with pH as well as charge composition is presented using a combination of atomic force microscopy, water contact angle measurement, and image analysis using Gwyddion software. These studies demonstrate that the porous morphology is enhanced and most uniform when the brushes are grown from the Y-inimer, indicating that a 1:1 grafting ratio and intimate contact between A and B brushes are essential.

Side chain-engineered pseudocapacitive semiconducting polymer electrodes for symmetrical supercapacitors operable at wide potentials

Pseudocapacitive electrodes based on inorganic metal oxides exhibit superior capacitance. However, they suffer from limited operational voltage, resulting in low energy and power densities. To address these issues, redox semiconducting polymer (SP)-based pseudocapacitive electrodes, integrating electron donor and acceptor functionalities, offer a promising solution. In this study, we introduce two novel pseudocapacitive SP electrodes composed of highly planar electron-donating building blocks 4,8-bis ((5-octylthiophen-2-yl)ethynyl)benzo[1,2-b:4,5-b'] dithiophene (TBDT) with an electron-accepting building blocks benzo[c][1,2,5]thiadiazole (BT) and its side chain manipulated counterpart, i.e., OBT, denoted as SP1 and SP2, respectively. Among them, SP2 demonstrates a maximum specific capacitance of 117 F/g at 1 A/g. Furthermore, a symmetric supercapacitor fabricated for full-cell applications exhibits a significant energy density, reaching 29.1 Wh kg−1, and a maximum power density of 12.4 kW kg−1 within the wide operating potential window of 2.5 V. The exceptional performance of the pseudocapacitive electrode can be attributed to its highly planar backbone, nanoporous morphology, low crystallinity, and low lowest unoccupied molecular orbital levels. Overall, this new class of pseudocapacitive polymer electrode holds great potential for diverse sustainable energy storage technologies, addressing the limitations of traditional inorganic metal oxide-based electrodes by offering wide potentials window.

Deep reinforcement learning for microstructural optimisation of silica aerogels

Silica aerogels are being extensively studied for aerospace and transportation applications due to their diverse multifunctional properties. While their microstructural features dictate their thermal, mechanical, and acoustic properties, their accurate characterisation remains challenging due to their nanoporous morphology and the stochastic nature of gelation. In this work, a deep reinforcement learning (DRL) framework is presented to optimise silica aerogel microstructures modelled with the diffusion-limited cluster–cluster aggregation (DLCA) algorithm. For faster computations, two environments consisting of DLCA surrogate models are tested with the DRL framework for inverse microstructure design. The DRL framework is shown to effectively optimise the microstructure morphology, wherein the error of the material properties achieved is dependent upon the complexity of the environment. However, in all cases, with adequate training of the DRL agent, material microstructures with desired properties can be achieved by the framework. Thus, the methodology provides a resource-efficient means to design aerogels, offering computational advantages over experimental iterations or direct numerical solutions.

SepT, a novel protein specific to multicellular cyanobacteria, influences peptidoglycan growth and septal nanopore formation in Anabaena sp. PCC 7120.

Multicellular organization is a requirement for the development of complex organisms, and filamentous cyanobacteria such as Anabaena represent a paradigmatic case of bacterial multicellularity. The Anabaena filament can include hundreds of communicated cells that exchange nutrients and regulators and, depending on environmental conditions, can include different cell types specialized in distinct biological functions. Hence, the specific features of the Anabaena filament and how they are propagated during cell division represent outstanding biological issues. Here, we studied SepT, a novel coiled-coil-rich protein of Anabaena that is located in the intercellular septa and influences the formation of the septal specialized structures that allow communication between neighboring cells along the filament, a fundamental trait for the performance of Anabaena as a multicellular organism.

Application of Anodic Titanium Oxide Modified with Silver Nanoparticles as a Substrate for Surface-Enhanced Raman Spectroscopy.

The formation of nanostructured anodic titanium oxide (ATO) layers was explored on pure titanium by conventional anodizing under two different operating conditions to form nanotube and nanopore morphologies. The ATO layers were successfully developed and showed optimal structural integrity after the annealing process conducted in the air atmosphere at 450 °C. The ATO nanopore film was thinner (1.2 +/- 0.3 μm) than the ATO nanotube layer (3.3 +/- 0.6 μm). Differences in internal pore diameter were also noticeable, i.e., 88 +/- 9 nm and 64 +/- 7 nm for ATO nanopore and nanotube morphology, respectively. The silver deposition on ATO was successfully carried out on both ATO morphologies by silver electrodeposition and Ag colloid deposition. The most homogeneous silver deposit was prepared by Ag electrodeposition on the ATO nanopores. Therefore, these samples were selected as potential surface-enhanced Raman spectroscopy (SERS) substrate, and evaluation using pyridine (aq.) as a testing analyte was conducted. The results revealed that the most intense SERS signal was registered for nanopore ATO/Ag substrate obtained by electrodeposition of silver on ATO by 2.5 min at 1 V from 0.05M AgNO3 (aq.) (analytical enhancement factor, AEF ~5.3 × 104) and 0.025 M AgNO3 (aq.) (AEF ~2.7 × 102). The current findings reveal a low-complexity and inexpensive synthesis of efficient SERS substrates, which allows modification of the substrate morphology by selecting the parameters of the synthesis process.

Development of highly sensitive relative humidity sensor based on nanoporous PCPDTBT thin film

A novel type of capacitive humidity sensor with surface-type electrode geometry is presented in the present study. The high sensitivity and significantly high bandwidth associated with this planar-type humidity sensor (Al/PCPDTBT/Al) allow the facile and reliable estimation of ambient humidity. The use of a polymer sensing material Poly[2,6-(4,4-bis-(2-ethylhexyl)− 4 H-cyclopenta[2,1-b;3,4-b՛]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) with hierarchical nanoporous surface morphology and large surface/volume ratio ensures the sensor’s stable performance coupled with swift response to ambient humidity changes. Specifically, at a relatively lower frequency bias signal (i.e., 1 kHz), a fairly higher order of humidity sensitivity has been observed, i.e., 415.07 pF/%RH. While, sensitivities at significantly higher AC signal frequencies (i.e., 10 and 100 kHz) have been experimentally determined to be 345.18 pF/%RH and 154.72 pF/%RH, respectively. Likewise, the resistive sensitivity of the humidity sensor has been estimated to be − 3624.88 kΩ/%RH, − 2381.11 kΩ/%RH and − 1338.14 kΩ/%RH, at 1, 10 and 100 kHz test frequencies, respectively. The operating mechanism of the capacitive humidity sensor relies on an increase in the dielectric constant of the PCPDTBT active sensing layer accompanied by the rise in the ambient humidity levels. In addition to enhanced bandwidth and improved capacitive and resistive sensitivity, the mean response & recovery time of the fabricated device have been recorded to be ∼ 4 min, 17 s and ∼8 min, 43 s, respectively.

Nanoporous Coral Cluster‐Like Copper Metal‐Organic Framework as an Efficient Anode for Lithium‐Ion Batteries

AbstractOwing to the rich redox functionalities and numerous pore structure, metal‐organic frameworks (MOFs) are directly emerging as prospective electrode materials with special properties. In the present study, exotic and unique nanomaterials of copper‐based metal‐organic framework (Cu‐MOF‐74) were successfully prepared by coordination assembly of Cu (II) and 2,5‐dihydroxyterephthalic acid (DHTA) through the solvothermal route and served as anode materials for lithium‐ion batteries for the first time. The Cu MOF has a coral cluster‐like nanoporous morphology composed of hexagonal columns with a length of 3.0 μm and a radius of 132 nm. When tested as anode, it achieved a high reversible capability of 870.3 mA h g−1 at 100 mA g−1, remarkable rate performance (up to 1000 mA h g−1) and a long service life (300 cycles) in the dis‐/charge process. Such outstanding properties of the MOF anode may be mainly ascribed to the conjugated ligand moiety and the particular microstructural features. The results of this study provided insights for the rational design of primitive MOFs for advanced lithium storage.

A data-driven modeling approach to quantify morphology effects on transport properties in nanostructured NMC particles

We present a data-driven modeling approach to quantify morphology effects on transport properties in nanostructured materials. Our approach is based on the combination of stochastic modeling of the 3D nanostructure and numerical modeling of effective transport properties, which is used to investigate process-structure–property relationships of hierarchically structured cathode materials for lithium-ion batteries. We focus on nanostructured LiNi1/3Mn1/3Co1/3O2 (NMC) particles, the nanoporous morphology of which has a crucial impact on their effective transport properties (i.e, effective ionic and electric conductivity) and thus on the performance of the cell. First, we develop a parametric stochastic model for the 3D morphology of the nanostructured NMC particles based on excursion sets of so-called χ2-fields. This model, which has only two parameters, is then fitted to FIB-SEM image data of the NMC particles manufactured with different calcination temperatures and different particle sizes. This way it is possible to generate digital twins of the NMC particles. In a second step, measured 3D image data and corresponding digital twins are used as input for the numerical simulation of effective transport properties. Based on the results obtained by these simulations, we can quantify process-structure–property relationships. Overall, we present a methodological framework that allows for an efficient optimization of the fabrication process of nanostructured NMC particles.

Single-crystal nanoporous high-entropy (oxy)hydroxides nanosheets for electrocatalysis: Structure and electronic dual enhancement

High-entropy materials are new-fashioned electrocatalysts due to their interesting “cocktail effect”. However, it is still a great challenge to synthesize single-crystal high-entropy nanomaterials such as (oxy)hydroxides due to the different crystal growth mode for different elements. Herein, we design a dynamic crystal growth strategy by multi-cation exchange to fabricate single-crystal high-entropy (oxy)hydroxides nanosheets. Nanoporous morphology can be achieved by incorporating Al ion into the multicomponent (oxy)hydroxides system after a reversible Al insertion-dissolution process. When adopted as potential electrocatalysts for oxygen evolution reaction (OER), we find that the seven-component ZnVNiCoFeAlRu-OHs single-crystal nanoporous nanosheets display a significantly improved OER performance with a low overpotential of 229 mV at 10 mA cm−2 and a shallow Tafel slope of 39.3 mV dec−1. Both XPS and DFT calculation reveal that Ru acted an electron dedicator could effectively moderate the overall electronic structures for better OER performance. This work develops an entropy and enthalpy driven multi-cation exchange strategy for synthesizing a library of single-crystal high-entropy (oxy)hydroxides for various applications.

CuCo2O4 supported graphene quantum dots as a new and promising catalyst for methanol oxidation reaction

Recently, the design of an active electrocatalyst with a unitary structure and high electrocatalytic performance as an efficient and low-cost electrode material has received enormous attention in improving the performance of energy and storage devices. In this study, flower-like CuCo2O4 nanorods are synthesized through the hydrothermal method followed by calcination. Then, CuCo2O4 is hybridized with graphene quantum dots (GQDs) prepared by the pyrolysis method. The structure and morphology of the synthesized electrocatalysts are analyzed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction methods. The electrochemical performance of the prepared materials supported on a glassy carbon electrode is investigated by cyclic voltammetry at different methanol concentrations and various scan rates. Also, chronoamperometry and electrochemical impedance spectroscopy techniques are performed for the evaluation of stability and conductivity. The GQD/CuCo2O4 exhibits a good electrochemical surface area of 19.25 cm2 in 1 M KOH and 4 M methanol. Also, GQD/CuCo2O4 shows a higher current density for methanol oxidation reaction (MOR) than CuCo2O4. The superior electrochemical performance of the GQD/CuCo2O4 can be attributed to the strengthening of the CuCo2O4 nanoparticle structure by a large electrochemically active surface associated with nanoporous morphology in the presence of GQDs. Besides, GQDs enhance the catalyst's performance by increasing electrical conductivity and specific surface area.

High Performance Photorechargeable Li‐Ion Batteries Based on Nanoporous Fe2O3 Photocathodes

AbstractIn recent years, photorechargeable Li‐ion batteries (Li‐PRBs) are investigated as potential energy devices to supply continuous power to remote IoT or electronic devices. These Li‐PRBs, due to their lightweight and low‐cost, offers various advantages compared to conventional combination of solar cells and a battery. Single active material‐based PRBs have gained attention due to the use of multifunctional materials which perform both solar energy harvesting and storage, however most of the PRBs studied so far are based on ion intercalation. Herein, the use of conversion type active material α‐Fe2O3 for efficient and stable operation of Li‐PRBs is demonstrated. Cost‐effective solution processing method is used to synthesize α‐Fe2O3 nanorods (NRs), which form nanoporous morphology when blended with Multi‐walled carbon nanotubes / Phenyl‐C61 butyric acid methyl ester (MWCNT/PCBM) conducting additives to form photocathodes. α‐Fe2O3 NRs shown simultaneous solar energy harvesting in visible region of spectra, owing to its energy bandgap Eg ≈ 2.1 eV, and efficient Li‐ion storage via conversion reaction mechanism. Li‐PRB has shown photoconversion and storage efficiency of ≈1.988% when illuminated with blue LED (λex ≈ 470 nm) for large voltage window (0.8–2.57 V). The use of conversion type material like Fe2O3 in PRBs opens up new pathways to explore new materials and mechanisms for these emerging devices.

Low-temperature synthesis of nano-porous high entropy spinel oxides with high grain boundary density for oxygen evolution reaction

Recently, high entropy spinel oxides have become a hotspot for oxygen evolution electrocatalysts. However, high temperature preparation method offers limited control over their morphology and size, leading to unsatisfactory OER catalytic activity. It is worth noting that low temperature can prevent grain coarsening and increase the grain boundary density of catalysts, effectively promoting the OER catalytic activity. However, low temperature preparation of nano-porous high-entropy spinel oxides catalysts has rarely been reported. In this paper, a nano-porous high-entropy oxide catalyst with high grain boundary density (Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)3O4 was first prepared by low temperature solution combustion method. Benefiting from the nano-porous morphology and high grain boundary density, it shows the enhanced OER activity with the overpotential of 275 mV at a current density of 10 mA cm−2, and the Tafel slope is 50.27 mVdec−1. Importantly, it also presents an outstanding long-term stability due to its high structural stability caused by high entropy, and its overpotential has almost no obvious attenuation at a current density of 10 mA cm−2 for 60 h and at a current density of 250 mA cm−2 for 40 h. This work provides a novel strategy to prepare high-performance nanostructured high entropy spinel oxides catalysts.