Search Results (44)

The oxygen evolution reaction (OER) plays a central role as an anode in electrocatalytic processes such as energy conversion and storage and the generation of molecular oxygen from the electrolysis of water. Currently, precious metal oxides such as IrO₂ and RuO₂ are recognized as reference OER electrocatalysts with reasonably high activity; however, their widespread use in practical devices has been severely hindered by their high cost and scarcity. It is essential to design alternative OER electrocatalysts made of low-cost and abundant earth elements with significant activity and robustness. We report four new nanocellulose-derived Fe–zeolite nanocomposites, namely Fe/Zeolite@CCNC (1), Fe/Zeolite@CCNF (2), Fe/Zeolite/CNT@CCNC (3), and Fe/Zeolite/CNT@CCNF (4). Two different types of nanocellulose were investigated: nanocellulose nanofibrils and nanocellulose nanocrystals. Characterization with TEM, SEM-EDS, PXRD, and XPS is reported. The nanocomposites exhibited electrocatalytic activity for OER that varies based on the origin of biocarbon and the composition content. The effect of adding carbon nanotubes to the nanocomposites was studied, and an improvement in OER catalysis was observed. The electrochemical double-layer capacitance and electrochemical impedance spectroscopy of the nanocomposites are reported. The nanocomposite 3 exhibited the highest performance, with an onset potential value of 1.654 V and an overpotential of 551 mV, which exceeds the activity of RuO₂ for OER catalysis at 10 mA/cm² in the glassy carbon electrode. A 24 h chronoamperometry study revealed that the catalyst is active for ~2 h under continuous operating conditions. BET surface analysis showed that the crystalline nanocellulose-derived composite exhibited 301.47 m²/g, and the fibril nanocellulose-derived composite exhibited 120.39 m²/g, indicating that the increased nanoporosity of the former contributes to the increase in OER catalysis. Full article

Solid oxide fuel cells (SOFCs) have been considered as alternative energy conversion devices because of their high energy conversion efficiency, fuel flexibility, and cost efficiency without precious metal catalysts. In current SOFCs, the cermet anode consists of nickel and ion-conducting ceramic materials, and solid oxide electrolytes and ceramic cathodes have been used. SOFCs normally operate at high temperatures because of the lower ion conductivity of ceramic components at low temperatures, and they have weaknesses in terms of mechanical strength and durability against thermal shock originating from the properties of ceramic materials. To solve these problems, metal-supported solid oxide fuel cells (MS-SOFCs) have been designed. SOFCs using metal substrates, such as Ni-based and Cr-based alloys, provide significant advantages, such as a low material cost, ruggedness, and tolerance to rapid thermal cycling. In this article, SOFCs are introduced briefly, and the types of metal substrate used in MS-SOFCs, as well as the advantages and disadvantages of each metal support, are reviewed. Full article

Zirconium, a critical rare metal with exceptional corrosion resistance and nuclear applications, is conventionally produced via the energy-intensive Kroll process. The electrolysis of ZrC_xO_y soluble anodes has been extensively investigated due to its advantages in having a short process flow and resulting in high-quality products. In particular, during the electrolysis of zirconium oxycarbide with a C:O molar ratio of 1:1, gaseous CO can be released, and no residual anodes are generated, which is extremely appealing. In this regard, this paper explores the feasibility of preparing zirconium metal through high-temperature vacuum reduction to produce zirconium oxycarbide using ZrO₂ as the raw material, followed by direct molten-salt electrolysis. Firstly, the reduction products were characterized using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The results showed that under a vacuum of <10 Pa at 1750 °C, the reduction products mainly consisted of ZrC_xO_y and a small amount of ZrO₂, and they exhibited good electrical conductivity (0.0169 Ω·cm). Subsequently, the cyclic voltammetry test results of the reduction products revealed the reversible redox behavior of ZrC_xO_y. There were characteristic oxidation peaks at −0.53 V and −0.01 V (vs. Pt), corresponding to the formation of Zr²⁺ and Zr⁴⁺, respectively, and a reduction peak at −1.51 V, indicating the conversion from Zr²⁺ to Zr. Finally, β-zirconium metal with a purity of 99.2 ± 0.3 wt.% was obtained through potentiostatic electrolysis, and its quality met the R60704 grade specified in ASTM B551-12 (2021). This study offers a novel approach for the short-flow preparation of zirconium metal, which is conducive to expanding its applications. Full article

In this research work, two distinct types of three-dimensional (3D) capacitors were successfully fabricated, each with its own unique features and advantages. The first type of capacitor is centered around a 3D nanoporous structure. This structure is formed on a nickel substrate through anodic oxidation. After undergoing high-temperature thermal oxidation, a monolithic Ni-NiO-Pt metal–insulator–metal (MIM) capacitor with a nanoporous dielectric architecture is achieved. Structurally, this innovative design brings about several remarkable benefits. Due to the nanoporous structure, it has a significantly increased surface area, which can effectively store more charges. As a result, it exhibits an equivalent capacitance density of 69.95 nF/cm², which is approximately 18 times higher than that of its planar, non-porous counterpart. This high capacitance density enables it to store more electrical energy in a given volume, making it highly suitable for applications where miniaturization and high energy storage in a small space is crucial. The second type of capacitor makes use of Through-Glass Via (TGV) technology. This technology is employed to create an interdigitated blind-via array within a glass substrate, attaining an impressively high aspect ratio of 22.5:1 (with a via diameter of 20 μm and a depth of 450 μm). By integrating atomic layer deposition (ALD), a conformal interdigital electrode structure is realized. Glass, as a key material in this capacitor, has outstanding insulating properties. This characteristic endows the capacitor with a high breakdown field strength exceeding 8.2 MV/cm, corresponding to a withstand voltage of 5000 V. High breakdown field strength and withstand voltage mean that the capacitor can handle high-voltage applications without breaking down easily, which is essential for power-intensive systems like high-voltage power supplies and some high-power pulse-generating equipment. Moreover, due to the low-loss property of glass, the capacitor can achieve an energy conversion efficiency of up to 95%. Such a high energy conversion efficiency ensures that less energy is wasted during the charge–discharge process, which is highly beneficial for energy-saving applications and systems that require high-efficiency energy utilization. Full article

Tin dioxide (SnO₂) is a low-cost and high-capacity anode material for lithium-ion batteries, but the fast capacity fading significantly limits its practical applications. Current research efforts have focused on preparing sophisticated composite structures or optimizing functional binders, both of which increase material manufacturing costs. Herein, we utilize pristine and commercially available SnO₂ nanopowders and enhance their cycling performance by simply narrowing the potential range and optimizing electrolytes. Specifically, a narrower potential range (0–1 V) mitigates the capacity fading associated with the conversion reaction, whereas an ether-based electrolyte further suppresses the volume expansion related to the alloy reaction. Consequently, this SnO₂ anode delivers a promising battery performance, with a high capacity of ~650 mAhg⁻¹ and stable cycling for 100 cycles. Our work provides an alternative approach to developing high-capacity and long-cycling metal oxide anode materials. Full article

Nitrobenzene liquid-phase catalytic hydrogenation is commonly regarded as one of the most effective technologies for aniline production. The traditional granular catalysts have the disadvantages that the reactor bed pressure drop is large and the mass transfer efficiency between gas and liquid phases is low. In this study, a novel structured mesh-type Pd/γ-Al₂O₃/Al catalyst was prepared by anodic oxidation and pore structures of γ-Al₂O₃/Al supports were constructed by acid pore-widening treatments. The results showed that acid pore-widening treatments can improve the pore size of γ-Al₂O₃/Al supports; the support with HNO₃ pore-widening treatment exhibited the largest pore size, being enlarged from 3.7 nm to 4.6 nm. The Pd/γ-Al₂O₃/Al catalysts prepared with different acid pore-widening treatment supports contribute to the increased active metal Pd loading, more Pd⁰ content, and better dispersion of the Pd particles. The catalyst prepared with HNO₃ pore-widening treatment support exhibited the largest active metal Pd loading, enlarging from 1.82% to 1.95%, the largest Pd⁰ content being enlarged from 52.1% to 58.5% and the smallest Pd particle size being reduced from 103 nm to 41 nm, resulting in the highest nitrobenzene conversion, increasing from 67.2% to 74.3%. Eventually, we calculated that the pressure drop of structured catalysts was 1/72 of that of granular catalysts, resulting in a better diffusion of the H₂ through nitrobenzene solution to active sites on the catalyst surface and a significant increase in the catalytic activity. Full article

The application of electrochemical hydrogen evolution reaction (HER) for renewable energy conversion contributes to the ultimate goal of a zero-carbon emission society. Metal phosphides have been considered as promising HER catalysts in the alkaline environment, which, unfortunately, is still limited owing to the weak adsorption of H* and easy dissolution during operation. Herein, a bimetallic NiCoP-2/NF phosphide is constructed on nickel foam (NF), requiring rather low overpotentials of 150 mV and 169 mV to meet the current densities of 500 and 1000 mA cm⁻², respectively, and able to operate stably for 100 h without detectable activity decay. The excellent HER performance is obtained thanks to the synergetic catalytic effect between Ni and Co, among which Ni is introduced to enhance the intrinsic activity and Co increases the electrochemically active area. Meanwhile, the protection of the externally generated amorphous phosphorus oxide layer improves the stability of NiCoP/NF. An electrolyser using NiCoP-2/NF as both cathode and anode catalysts in an alkaline solution can produce hydrogen with low electric consumption (overpotential of 270 mV at 500 mA cm⁻²). Full article

Electron and hole transporting layers play a major role in high-performance and stable organic-based optoelectronic devices. This paper demonstrates detailed device engineering of multi-junction organic photovoltaics built on two different metal oxide-based electron and hole transport (buffer) layers prepared by thermal or solution-processed methods. The main focus is on the device processing parameters as well as practical details of preparation of buffer layers to give the research community a clear, step-by-step recipe to successfully replicate and build series and parallel connected multi-junction solution-based organic solar cells for their needs. Here, the recipes and deposition conditions of two metal oxide buffer layers are presented in detail, based on basic commercially available materials and tools, to achieve well-engineered tandem (multi-junction) solution-processed organic solar cells. The buffer layers have appropriate energy levels for electrical selectivity of anode and cathode electrodes, and they are highly stable and chemically compatible with processing of solution-based polymer solar cells. To demonstrate the engineering steps of multi-junction devices, the PCE10:PC70BM blend is used as the active layer for all subcells. Then, to improve the power conversion efficiency of the single-junction photovoltaic device, PCE10:PC70BM blend is used in combination with DPPx:PC70BM with different absorption spectra for bottom and top subcell active layers. An optimized series tandem device with 10.6% power conversion efficiency is demonstrated. Generally, the device structures reported here can also be used for other types of optoelectronic devices, such as light emitting diodes and photodetectors. Full article

This study focuses on the synthesis of mixed metal oxide anodes (MMOs) with the composition Ti/RuO₂Sb₂O₄Pt_x (where x = 0, 5, 10 mol) using hybrid microwave irradiation heating. The synthesized electrodes were characterized using scanning electron microscopy, X-ray energy-dispersive analysis, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. These electrodes were then evaluated in both bulk electrolytic and fuel cell tests within a reversible chloralkaline electrochemical cell. The configurations using the electrodes Ti/(RuO₂)_0.7-(Sb₂O₄)_0.3 and Ti/(RuO₂)_66.5-(Sb2O₄)_28.5-Pt₅ presented lower onset potential for oxygen and chlorine evolution reactions and reduced resistance to charge transfer compared to the Ti/(RuO₂)₆₃-(Sb₂O₄)₂₇-Pt₁₀ variant. These electrodes demonstrated notable performance in reversible electrochemical cells, achieving Coulombic efficiencies of up to 60% when operating in the electrolytic mode at current densities of 150 mA cm⁻². They also reached maximum power densities of 1.2 mW cm⁻² in the fuel cell. In both scenarios, the presence of platinum in the MMO coating positively influenced the process. Furthermore, a significant challenge encountered was crossover through the membranes, primarily associated with gaseous Cl₂. This study advances our understanding of reversible electrochemical cells and presents possibilities for further exploration and refinement. It demonstrated that the synergy of innovative electrode synthesis strategies and electrochemical engineering can lead to promising and sustainable technologies for energy conversion. Full article

The current commercially used anode material, graphite, has a theoretical capacity of only 372 mAh/g, leading to a relatively low energy density. Lithium (Li) metal is a promising candidate as an anode for enhancing energy density; however, challenges related to safety and performance arise due to Li’s dendritic growth, which needs to be addressed. Owing to these critical issues in Li metal batteries, all-solid-state lithium-ion batteries (ASSLIBs) have attracted considerable interest due to their superior energy density and enhanced safety features. Among the key components of ASSLIBs, solid-state electrolytes (SSEs) play a vital role in determining their overall performance. Various types of SSEs, including sulfides, oxides, and polymers, have been extensively investigated for Li metal anodes. Sulfide SSEs have demonstrated high ion conductivity; however, dendrite formation and a limited electrochemical window hinder the commercialization of ASSLIBs due to safety concerns. Conversely, oxide SSEs exhibit a wide electrochemical window, but compatibility issues with Li metal lead to interfacial resistance problems. Polymer SSEs have the advantage of flexibility; however their limited ion conductivity poses challenges for commercialization. This review aims to provide an overview of the distinctive characteristics and inherent challenges associated with each SSE type for Li metal anodes while also proposing potential pathways for future enhancements based on prior research findings. Full article

In this work, the performances of nickel iron layered double hydroxides (LDH) with the nitrate anion at the interlayer (NiFe-NO₃) for the manufacture of anodes for lithium-ion batteries have been tested before and after its sintering at different temperatures. After synthesis, the material was thermally analyzed in a range 30–1250 °C, showing a mass loss occurring in three different consecutive steps leading to a total mass decrease of ~30 mass%. Following thermogravimetric analysis (TGA), four samples were prepared by annealing at four different temperatures: one of the four did not undergo a thermal treatment (NiFe-0), while the remaining three were annealed at 250 °C, 360 °C, and 560 °C for 6 h (NiFe-250, NiFe-360, and NiFe-560). All materials where completely characterized via FE-SEM, PXRD, and FT-IR. The pristine LDH material showed some structural and compositional changes for growing temperatures, starting from the typical turbostratic hexagonal structure through a mixture of amorphous metal oxides and finally to the stoichiometric oxides FeNi₂O₄ and NiO. The as-obtained materials were mixed with carbon black (C65) and sodium alginate and tested as electrodes in Swagelok half cells in LP30 vs. metallic Li to perform CV and GCPL analysis. The electrochemical tests showed that the performances of NiFe-0, both in terms of stability and specific capacity, are not so different from the one of the NiFe-560, even if the Ni mass% in the former is lower than in the NiFe-560. This phenomenon could be explained by assuming a combined mechanism of reaction involving both intercalation and conversion. Full article

Various iron oxides have been proven to be promising anode materials for metal-ion batteries due to their natural abundance, high theoretical capacity, ease of preparation, and environmental friendliness. However, the synthesis of iron oxide-based composites requires complex approaches, especially when it comes to composites with intrinsically conductive polymers. In this work, we propose a one-step microplasma synthesis of polyaniline-coated urchin-like FeOOH nanoparticles (FeOOH/PANI) for applications as anodes in lithium-ion batteries. The material shows excellent electrochemical properties, providing an initial capacity of ca. 1600 mA∙h∙g⁻¹ at 0.05 A∙g⁻¹ and 900 mA∙g⁻¹ at 1.2 A∙g⁻¹. Further cycling led to a capacity decrease to 150 mA∙h∙g⁻¹ by the 60th cycle, followed by a recovery that maintained the capacity at 767 mA∙h∙g⁻¹ after 2000 cycles at 1.2 A∙g⁻¹ and restored the full initial capacity of 1600 mA∙h∙g⁻¹ at a low current density of 0.05 A∙g⁻¹. Electrochemical milling—the phenomenon we confirmed via a combination of physico-chemical and electrochemical techniques—caused the material to exhibit interesting behavior. The anodes also exhibited high performance in a full cell with NMC532, which provided an energy density of 224 Wh∙kg⁻¹, comparable to the reference cell with a graphite anode (264 Wh∙kg⁻¹). Full article

Cathodic protection is widely used for metal corrosion protection. To improve their performance, it is necessary and urgent to study the influence of metal oxides on the microstructure and performance of aluminum alloy sacrificial anodes. Taking an Al-Ga-In sacrificial anode as the research object, the dissolution morphology and current efficiency characteristics were studied by means of electrochemical testing and microstructural observation, and the influence of varying Pb and Bi contents on the performance of an aluminum alloy sacrificial anode was investigated. The test results reveal that: (1) The Al-Ga-In sacrificial anode with 4% Pb and 1% Bi contents exhibits the best sacrificial anode performance. (2) The inclusion of an appropriate Bi element content shifts the open-circuit potential in a negative direction and promotes activation dissolution. Conversely, excessive Bi content leads to uneven dissolution, resulting in the shedding of anode grains and greatly reducing the current efficiency. (3) During the activation dissolution of the aluminum alloy, the second phase preferentially dissolves, and the activation point destroys the oxide film, resulting in the dissolution of the exposed aluminum matrix. Consequently, the concentration of dissolved metal ions is reduced and deposited back on the surface of the anode sample, promoting the continuous dissolution of the anode. Full article

The photoelectrochemical cells (PECs) performing high-efficiency conversions of solar energy into both electricity and high value-added chemicals are highly desirable but rather challenging. Herein, we demonstrate that a PEC using the oxidatively electropolymerized film of a heteroleptic Ru(II) complex of [Ru(bpy)(L)₂](PF₆)₂ Ru1 {bpy and L stand for 2,2′-bipyridine and 1-phenyl-2-(4-vinylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline respectively}, polyRu1, as a working electrode performed both efficient in situ synthesis of hydrogen peroxide and photocurrent generation/switching. Specifically, when biased at −0.4 V vs. saturated calomel electrode and illuminated with 100 mW·cm⁻² white light, the PEC showed a significant cathodic photocurrent density of 9.64 μA·cm⁻². Furthermore, an increase in the concentrations of quinhydrone in the electrolyte solution enabled the photocurrent polarity to switch from cathodic to anodic, and the anodic photocurrent density reached as high as 11.4 μA·cm⁻². Interestingly, in this single-compartment PEC, the hydrogen peroxide yield reached 2.63 μmol·cm⁻² in the neutral electrolyte solution. This study will serve as a guide for the design of high-efficiency metal-complex-based molecular systems performing photoelectric conversion/switching and photoelectrochemical oxygen reduction to hydrogen peroxide. Full article

The electrocatalytic conversion of biomass into high-value-added chemicals is one of the effective methods of green chemistry. Conventional metal catalysts have disadvantages, such as low atomic utilization and small surface areas. Catalyst materials derived from metal–organic frameworks (MOFs) have received much attention due to their unique physicochemical properties. Here, an MOF-derived non-precious metal Co_xNi_yS electrocatalyst was applied to the oxidation of biomass-derivative 5-hydroxymethylfurfural (HMF). The HMF oxidation reaction activities were modulated by regulating the content of Co and Ni bimetals, showing a volcano curve with an increasing proportion of Co. When the Co:Ni ratio was 2:1, the HMF conversion rate reached 84.5%, and the yield of the main product, 2,5-furandicarboxylic acid (FDCA), was 54%. The XPS results showed that the presence of high-valent nickel species after electrolysis, which further proved the existence and reactivity of NiOOH, as well as the synergistic effect of Co and Ni promoted the conversion of HMF. Increasing the content of Ni could increase the activity of HMF electrochemical oxidation, and increasing the content of Co could reduce the increase in the anodic current. This study has important significance for designing better HMF electrochemical catalysts in the future. Full article