Energy advances最新文献

In the present work, colloidal systems of sodium lignosulfonate (lignin) and its carbonized form (C-lignin) in H₂O and polyethylene glycol (PEG) were synthesized and used for solar-thermal conversion. PEG and H₂O play the role of a dispersant of the suspended particles as the base fluids and an environment for transferring heat. Based on the results, PEG performs better as the base fluid than water. All the synthesized microfluids (MFs) were stable at an optimum concentration of 0.2 g/60 ml. The comparative studies show that the C-lignin/PEG has the best light-to-heat conversion efficiency. The C-lignin/PEG was used at high light intensities and for several heating/cooling cycles without losing its performance in heat generation. All the calculated thermo-physical parameters indicated that C-lignin/PEG is more eligible than lignin/PEG in photo-thermal conversion. The prepared C-lignin/PEG has several advantages: green, inexpensive and simplicity of the preparation procedure, not using a dispersant, high photo-thermal durability and heat-generation efficiency, and excellent ability to generate heat from sunlight.

The major issues that determine the efficiency of photocatalyst composite materials for solar hydrogen production, with or without a sacrificial agent, are efficient visible light harvesting properties, efficient separation of charge carriers and their utilization of redox sites, and stability. Thus, significant efforts have been devoted in the past few decades to modify the above characteristics by integrating constituent components of composites using different approaches. In the present review, we aim to summarize the recent advances, predominantly, in the area of TiO₂-based photocatalyst composites for solar hydrogen production. Firstly, we present the recent progress in material integration aspects by discussing the integration of TiO₂ with different categories of materials, including noble/3d metals, metal oxides/sulphides/selenides, other low bandgap semiconductors, C-based materials, and dye sensitizers. Furthermore, we discuss how material integration helps in tailoring the electronic and optical properties for activity tuning in solar H₂ production. Subsequently, critical changes in the physico-chemical and electronic properties of composites with respect to their preparation methods, morphology, crystallographic facets, particle size, dopant, calcination temperature, and structure–activity relationship to solar hydrogen production are addressed in detail. Moreover, we discuss the importance of fabricating a photocatalyst in a thin film form and performing solar hydrogen production in different reactor set-ups for enhancing its photocatalytic performance, while addressing device scalability. Despite the significant advancements made in this field, solar-to-hydrogen conversion efficiency still needs to be improved to realise the practical application of solar hydrogen production. In this case, the direct conversion of water to hydrogen via overall water splitting and renewable H₂ production from wastewater or biomass components by employing suitable photocatalysts are some possible ways to improve the energy efficiency, and continuous research in the above directions is highly desirable.

In this work, the suitability of the spinel material ZnFe₂O₄, which has already been widely investigated in the context of its magnetic and photocatalytic properties, for use as active material for the cathode side in zinc ion batteries is presented. In addition to pure ZnFe₂O₄, part of the Fe³⁺ was doped with Ti⁴⁺ to achieve stabilization of Zn vacancies in the material and increase ionic conductivity as indicated by previous modelling results. Ceramic samples with the composition ZnFe_2−xTi_xO₄ (x = 0 to 0.25) were prepared via a Pechini synthesis route and investigated regarding their optical, structural and electrochemical characteristics. It has been successfully demonstrated that both pure and Ti doped ZnFe₂O₄ can be used as active material in the positive electrodes of zinc metal batteries or in an “anode-free” setup with Sn metal. Cells with calcined ZnFe_2xTi_xO₄ (x = 0.09)|0.5 M zinc triflate in acetonitrile|Zn showed a stable cycling behavior over 1000 cycles and an average initial specific capacity of 55 mA h g⁻¹.

Lithium-ion batteries produce a vast amount of gases during decomposition reactions and thermal runaway. While the amount and composition of these gases has been investigated in the past, little is known about their impact on thermal transport inside the battery cell. Especially for pouch cells, which do not have a rigid housing, this becomes even more important in multi-cell scenarios since thermal propagation is governed by heat transfer. In this work, a simulation framework is presented that enhances the chemical single cell model by accounting for these thermal transport changes in gas producing pouch cells. It is validated by performing two battery cell propagation experiments in an autoclave. Besides the temperature measurement, the propagation time between the cells and the gas composition are analyzed and compared between simulation and experiment. Further, it is investigated how the application of an external pressing force impacts the heat transfer and thus the propagation behavior. In the given setup, the propagation time decreased from 37.2 s to 16.8 s with increasing pressing force.

With the increasing interest in incorporating redox-active organic molecules as potential materials in energy storage systems, we envisaged a chemical design of a naturally occurring redox-active flavin moiety. Herein, we report the fabrication and characterization of asymmetric supercapacitors (ASCs) based on modified flavins as cathode materials. Notably, subtle chemical modification with the incorporation of a carboxylic functionality around the flavin core (cFl) was found to impart superior ion-storage properties compared to a simple flavin derivative (Fl). As determined, the specific capacitance (SC) for cFl and Fl as individual electrodes was found to be 170 and 62 F g⁻¹, respectively, whereas in a two electrode ASC with activated carbon serving as the anode, the SC was found to be 107 and 29 F g⁻¹, respectively, at a current density of 1.25 A g⁻¹. With better cycling stability (retaining 87% of its initial SC in the case of cFl) and significantly higher energy density (38 W h kg⁻¹ for cFl) as compared to most of the known organic material-based electrodes, the modified flavin derivatives serve as better organic electrode alternatives for practical energy storage applications.

α-Pinene and isobutene/isobutane can undergo hybrid alkylation under acid catalysis, resulting in C₁₄ and C₂₀ product fractions with favorable bio-based high-energy-density fuel properties after hydrogenation. In this study, the catalytic performance of zeolite molecular sieves, such as Hβ, HY, HZSM-5, HZSM-35, HSAPO-11, was investigated for the alkylation of α-pinene and Isobut-5 (a mixture of isobutene/isobutane with a mass ratio of 1 : 5) given the acidic sites and specific pore structures with shape-selective abilities of zeolite catalysts. Various characterization techniques, including temperature-programmed desorption of ammonia (NH₃-TPD), Fourier transform infrared spectroscopy with pyridine adsorption (Py-IR), N₂ adsorption/desorption, X-ray fluorescence spectrum (XRF), and particle size analysis, were conducted to analyze the acidic properties, pore characteristics, silica–aluminum ratio, and grain size of the zeolites, and their influence on the alkylation of α-pinene and Isobut-5. Moreover, the recycling performance of the favorite Hβ-25n catalyst and an effective regeneration method were investigated using temperature-programmed oxidation (TPO) analysis. This study provides essential research data for the preparation of α-pinene-based high-energy-density fuels.

Biogas upgrading by selective adsorption of CO₂ using vacuum pressure swing adsorption (VPSA) is a technology that can enable the utilization of the isolated biomethane as a direct replacement for natural gas. In this work, we report for the first time the investigation of LTA and SAPO-34 macroscopic beads with hierarchical porosity as CO₂ adsorbents in a VPSA setup. While a binder is generally required to shape zeolites and zeotypes into the macroscopic format (e.g. beads, pellets) needed for application in a VPSA column, in this work binderless LTA and SAPO-34 beads were studied and compared with commercial binder-containing zeolite 4A beads. Binary breakthrough experiments were conducted with a gas mixture mimicking biogas (i.e. 40 vol% CO₂ and 60 vol% CH₄) in a single adsorption column up to 4 bar. The SAPO-34 beads displayed a slightly steeper breakthrough with less significant tailing compared to the LTA beads, which was ascribed to faster intra-crystalline diffusion due to the different framework structure and the lower adsorption strength of CO₂ on SAPO-34 compared to LTA. Notably, both the binderless LTA and SAPO-34 beads displayed a slightly sharper breakthrough and less significant tailing compared to commercial 4A beads. This was attributed to the open and accessible hierarchical pore structure of the binderless beads. The CO₂ adsorption capacity for the SAPO-34 beads was relatively stable over 5 cycles, while the LTA and commercial 4A beads displayed a significant decrease in adsorption capacity from the first to the second cycle. For the SAPO-34 beads, a cyclic adsorption capacity at breakthrough around 2 mmol g⁻¹ and a CO₂ productivity > 3 mol kg⁻¹ h⁻¹ were achieved. These values are significantly higher than those of the LTA and commercial 4A beads, making the SAPO-34 beads a promising candidate for industrial application in VPSA.

Thin film CdTe-based photovoltaic devices have achieved high efficiency above 22%. However, the device performance is limited by large open circuit voltage deficit. One of the primary reasons is non-ohmic back contacts. In this work, nickel oxide is used as a back buffer layer to form an ohmic back contact. We comprehensively investigate oxygen effects during sputtering on film properties and device performance. Increased oxygen in the deposition environment led to darker films, increased carrier concentration, decreased mobility and decreased resistivity. X-ray photoelectron spectroscopy showed peak shifts favouring Ni³⁺ over Ni²⁺, and X-ray diffraction demonstrated that crystallinity hit a peak at around 5% oxygen input. The NiO back buffer layer improves device performance by reducing barrier height at the gold back contact and improving valence band offset at the CdTe/NiO interface. The NiO layer deposited without oxygen improved the V_oc to 710 mV, from a baseline of 585 mV. At 5% and 20% oxygen content during deposition, efficiency improved relative to the reference due to an increase in open circuit voltage (V_oc) and short circuit current (J_sc). V_oc increase is due to improved valence band offset between CdTe and NiO. The large conduction band offset also reflects minority carriers away from the CdTe/NiO interface and reduces interface recombination. SCAPS simulations demonstrated that an increase in valence band offset has shown pronounced effects of both s-kinks and rollover.

Lithium metal batteries are a significant promise for next-generation energy storage due to their high energy density. However, challenges persist in their commercialization stemming from issues during the lithium deposition/dissolution processes, such as low Coulombic efficiency, dendrite formation, and dead-lithium formation. Addressing these challenges requires careful electrolyte design to enhance the reversibility of the lithium metal negative electrode by modifying solvation structures and engineering interfaces. The Coulombic efficiency of lithium deposition/dissolution is one of the most crucial factors in evaluating the performance of electrolytes toward lithium metal, although this is influenced by various factors. In this study, a separator-free cell is adopted to minimize extraneous influences and focus on assessing the intrinsic effects of electrolytes on lithium deposition/dissolution. 48 different electrolytes based on three salts of Li[PF₆], Li[FSA] and Li[TFSA] varying in solvents were investigated with or without additives. Moreover, Raman spectroscopy and X-ray photon spectroscopy enhance the discussion by revealing variations in the major species of solid electrolyte interphase components under different electrolyte conditions.

Moving the fabrication of electronics from the conventional 2D orientation to 3D space, necessitates the use of sophisticated additive manufacturing processes which are capable to deliver multifunctional materials and devices with exceptional spatial resolution. In this study, it is reported the nozzle-guided 3D-printing of highly conductive, epoxy-dispersed, single-walled carbon nanotube (SWCNT) architectures with embedded thermoelectric (TE) properties, capable to exploit significant waste thermal energy from the environment. In order to achieve high-resolution and continuous printing with the SWCNT-based paste through a confined nozzle geometry, i.e. without agglomeration and nozzle clogging, a homogeneous epoxy resin-dispersed SWCNT paste was produced. As a result, various 3D-printed structures with high SWCNT concentration (10 wt%) were obtained via shear-mixing processes. The 3D printed p- and n-type epoxy-dispersed SWCNT-based thermoelements exhibit high power factors of 102 and 75 μW mK⁻², respectively. The manufactured 3D carbon-based thermoelectric generator (3D-CTEG) has the ability to stably operate at temperatures up to 180 °C in ambient conditions (1 atm, relative humidity: 50 ± 5% RH), obtaining TE values of an open-circuit voltage V_OC = 13.6 mV, short-circuit current I_SC = 1204 μA, internal resistance R_TEG = 11.3 Ohm, and a generated power output P_max = 4.1 μW at ΔT = 100 K (with T_Cold = 70 °C). The approach and methodology described in this study aims to increase the flexibility of integration and additive manufacturing processes for advanced 3D-printed conceptual devices and the development of multifunctional materials.