Energy Conversion Devices Research Articles

The influence of lattice anharmonicity on the thermal transport properties of two-dimensional MgF2

Abstract Graphene research has ignited interest in two-dimensional (2D) materials. In addition to their unique electronic, mechanical, and optical properties, 2D materials exhibit distinctive thermal transport characteristics. A profound understanding of the microscopic mechanisms underlying the thermal transport properties of 2D materials is crucial for applications in energy conversion and storage devices. However, current studies lack insights into the influence of higher-order lattice anharmonicity on the transport behavior of 2D materials. Thus, this paper focuses on the 2D 1T phase MgF2, analyzing its microscopic thermal transport properties through an anharmonic lattice dynamics approach. Our methodology comprehensively accounts for the effects of quartic anharmonicity and four-phonon scattering on the thermal transport properties of 2D materials.

Biomass-derived materials for energy storage and electrocatalysis: recent advances and future perspectives

AbstractOver the last decade, there has been significant effort dedicated to both fundamental research and practical applications of biomass-derived materials, including electrocatalytic energy conversion and various functional energy storage devices. Beyond their sustainability, eco-friendliness, structural diversity, and biodegradability, biomass-derived materials provide additional benefits, including naturally organized hierarchical structures, rich surface properties, and an abundance of heteroatoms. These characteristics make them appealing candidates for effective energy storage and electrocatalytic energy conversion applications. This review explores the recent advancements in biomass-derived materials for energy storage system (ESS), including supercapacitors and electrocatalytic reactions. We also address the scientific and technical hurdles associated with these materials and outline potential avenues for future research on biomass-based energy conversion applications. By emphasizing the significance of controllable structural designs and modifications, we highlight their crucial roles in advancing this field. Graphical Abstract

Polymeric Materials in Energy Conversion and Storage

Energy conversion and storage devices based on polymeric materials are emerging as a promising avenue for renewable power sources [...]

Effect of N-Doped Carbon on the Morphology and Oxygen Reduction Reaction (ORR) Activity of a Xerogel-Derived Mn(II)O Electrocatalyst

This work synthesizes a xerogel from a sol–gel synthesis strategy and supports it on N-doped carbon support from spent coffee biomass (Mn(II)O/N-CC, hereafter MnO) as an efficient oxygen reduction reaction (ORR) catalyst in alkaline electrolytes. The effects of N-CC carbon content on MnO nanoparticle size, dispersion, distribution, morphology, and electrochemistry on ORR are discussed. The SEM and TEM measurements show that increasing the N-CC content during the MnO gelation reaction improved MnO dispersion and particle size during thermal treatment, increasing the ORR’s electrochemical active surface area. Several physiochemical and electrochemical characterizations show a clear relationship between N-CC catalysts and ORR activities. The best catalyst, MnO/N-CC-5, had an even distribution of 27 nm MnO nanoparticles on the N-CC support. The MnO/N-CC-5 catalyst had almost identical ORR kinetics and stability to those of the state-of-the-art Pt/C catalyst in 0.1 M KOH electrolytes, losing only 10 mV in half-wave potential after 5000 potential cycles and retaining 96% of current for over 10 h of continuous chronoamperometric stability. By measuring the electrochemical active surface areas of various catalysts by cyclic voltammetry at different scan rates and measuring the double layer capacitance (Cdl) and ECSA, MnO/N-CC-5 catalysts were shown to have enhanced ORR activity. The XPS analysis explains the ORR activity in terms of the Mn3+/Mn4+ ratio, and a mechanism was proposed. These findings suggest that the MnO/N-CC-5 catalyst could be a cathode catalyst in fuel cells, biofuel cells, metal–air batteries, and other energy conversion devices.

Strain-Induced Tunable Enhancement of Piezoelectricity in a Novel Molecular Multiferroic Material.

Multiferroics are appealing because of application potentials in data storage devices, sensors, transducers, and energy harvesters. Molecular multiferroics emerge as a promising alternative to inorganic multiferroics due to flexibility, light weight, low toxicity, solution processing, structural diversity, and chemical tunability. While researches have predominantly focused on perovskite structures, studies on molecular ionic multiferroics remain relatively limited. It is urgent to creatively build a novel platform for studying and developing the coupling and interaction between the stress, electricity, and magnetism. Knowing this, the work focuses on a novel organic-inorganic hybrid multiferroic N-ethyl-N-(fluoromethyl)-N-methylethylammonium tetrabromoferrate (III) showing coexisting magnetic and electric orderings. It undergoes antiferromagnetic, ferroelectric, and ferroelastic transitions. Notably, under a strain of 2.0%, the piezoelectric response increases tenfold, and the coercive field of ferroelectric polarization is reduced by half. The strain-induced enhancement of piezoelectricity is rarely reported in molecular multiferroics. Density functional theory is employed to predict that the mechanism of the large piezoelectric response under strain engineering is related to the cation rotation and phase switching between the stable phase and an energetically competitive metastable phase. This study creates a new paradigm to develop molecular multiferroics and future microelectronic devices for energy conversion.

Deep Eutectic Solvent and Molten Salt-Assisted Construction of Wheat Straw-Derived N/O Co-Doped Porous Carbon for Flexible Zinc-Air Batteries.

As a common biomass resource, wheat straw is gradually being derived as carbon materials for oxygen reduction reaction (ORR) in zinc-air batteries (ZABs). Herein, the wheat straw-derived carbon was prepared by ball milling and pyrolysis using deep eutectic solvent (DES) as the medium, which avoided the cumbersome procedures. The hydrogen bond of DES was utilized to reconstructed into a hydrogen bond network structure between DES and lignin/cellulose/hemicellulose of wheat straw. The hydrogen bond network structure was converted into N/O co-doped porous carbon (N/O-WSPC) with abundant N/O co-doped sites after high-temperature pyrolysis. Meanwhile, KHCO3 was employed to further generate hierarchical pore structures and increase the specific surface area of the N/O-WSPC. The N/O co-doped sites provided intrinsic ORR activity, while the porous structure facilitates the mass transfer effect. Therefore, the N/O-WSPC exhibited a half-wave potential of 0.87 V (vs. RHE) and a limiting current density of 5.98 mA cm-2 for ORR. The N/O-WSPC-based flexible ZAB displayed an energy density of 652.23 Wh kg-1 and a charging-discharging cycle duration for over 19 h. The DES-assisted strategy facilitates the sustainable and efficient application of wheat straw-derived carbon materials in energy storage and conversion devices.

Novel N-doped carbon nanotubes impregnated Mn spheres with polydopamine coating as an efficient polysulfide immobilizer for Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage and conversion devices due to the high theoretical capacity and cost-effectiveness of sulfur. However, they still suffer from sluggish redox kinetics and the shuttle effect caused by complex polysulfides. In this work, graphitic carbon nitride (g-C3N4) is utilized as a template and further hydrothermally treated with an Mn source and glucose. The pyrolysis of g-C3N4 gives rise to N-doped carbon nanotubes, producing abundant sites for physical confinement and chemical adsorption of polysulfides, while glucose carbonization brings forth amorphous carbon and Mn source produces metal spheres. Afterward, polydopamine (PDA) induces N-doped carbon coating and promotes interface connection as well as electron immigration. This synergistic design possesses a high surface area of micropores and mesopores to aggregate sulfur and accelerate redox kinetics. As a result, the N-doped carbon nanotube with Mn spheres and PDA coating@sulfur (CN/Mn-PDA@S) exhibits a high reversible capacity of 813.5 mAh g−1 at 1 C with a decay rate of 0.064% per cycle and remarkable capacity retention at 2 C with rate performance up to 4 C. Therefore, the novel design of N-doped carbon nanotubes with Mn spheres and PDA coating serves as an efficient polysulfide immobilizer for Li-S batteries.

Enhanced bifunctional electrocatalysis of Co5.47N nanocrystals in porous carbon nanofibers for high-efficiency zinc-air batteries

As a promising energy conversion and storage device, recently, rechargeable zinc-air batteries (ZABs) have developed rapidly, and the exploitation of excellent electrode catalysts to improve the energy efficiency and long-term performance of ZABs has become a focus of current research. Herein, the Co5.47N nanocrystals embedded in porous carbon nanofibers (Co5.47N PCNFs) were designed to act as a bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and iodide oxidation reaction (IOR), which occur on the electrode in the charging-discharging process of ZABs. The electrochemistry results showed that the ORR activity of Co5.47N PCNFs is comparable to the commercial Pt/C electrocatalyst, and the IOR activity and stability are higher than those of the Pt/C electrocatalyst. Importantly, Co5.47N PCNFs electrocatalyst endows ZABs with a low charge–discharge voltage difference (0.49 V), a high round-trip energy efficiency (72.1 %), as well as a large specific capacity (791.5 mAh gZn−1), surpassing the performance of Pt/C electrocatalyst. Density functional theory calculation demonstrates that Co5.47N PCNFs have lower Gibbs free energy for the formation of IOR intermediate species, thereby displaying outstanding IOR catalytic performance compared to that of Pt/C electrocatalyst. These findings offer crucial insights into the rational design of cobalt nitride-based electrocatalysts for application in ZABs with high energy efficiency.

Reducing Non-Radiative Energy Losses in Non-fullerene Organic Solar Cells.

With the rapid advancement of non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed the 20% threshold, highlighting their considerable potential as next-generation energy conversion devices. In comparison to inorganic or perovskite solar cells, the open-circuit voltage (Voc) of OSCs is constrained by substantial non-radiative energy losses (ΔEnr), leading to values notably below those anticipated by the Shockley-Queisser limit. In OSCs, non-radiative energy losses are intimately associated with the electroluminescent quantum efficiency (EQEEL) of charge transfer states, which is in turn directly affected by the photoluminescence quantum yield (PLQY) of acceptor materials. Consequently, enhancing the PLQY of low-bandgap acceptor materials has emerged as a pivotal strategy to effectively mitigate ΔEnr. This review article delves into the intrinsic correlation between molecular structure and PLQY from the vantage point of acceptor material design. It further explores methodologies for designing acceptor materials exhibiting high PLQY, with the ultimate goal of realizing OSCs that combine high efficiency with minimal ΔEnr.

Breaking the Limitations of Activity and Stability in Powdered Materials for Oxygen Evolution Reaction: The Critical Role of Catalyst-Inducing Seeds

Powdered catalysts are extensively employed in industrial-scale energy conversion devices but struggle with weak powder-substrate adhesion and inherent instability in gas-evolving and highly oxidative oxygen evolution reactions (OER). This work introduces an innovative strategy in which powdered materials serve a critical role as catalyst-inducing seeds to break these limitations. Specifically, powdered Ti2CTx MXene with anchored cobalt single atoms (Co-SAs) shows negligible catalytic activity on its own but serves as catalyst-inducing seeds, significantly enhancing the catalytic activity of the conductive FeNi substrate. Mechanistic studies demonstrate that Co-SAs accelerate the oxidation rate of Ti2CTx, leading to the micro-battery corrosion behavior between oxidized Co/Ti2CTx and FeNi alloy, which generates highly OER-active corrosion products tightly bonded to FeNi alloy, thereby enhancing catalytic activity and ensuring stability. The prepared porous electrode shows a low overpotential of 303mV to deliver an ultra-high current density of 1000mAcm-2 and maintains activity for 1200hours under high current density conditions, rivaling advanced self-supporting electrodes. Moreover, replacing Co in Co/Ti2CTx with metals like Fe, Ni or Mn, yields comparable effects, suggesting the scalability of catalyst-inducing seeds. This approach breaks traditional limitations of powdered materials in OER, offering an effective pathway to engineer advanced catalytic electrodes.

Bacterial film-based degradable triboelectric nanogenerator for both contact and non-contact sensing

As an emerging environmentally friendly energy conversion device, degradable triboelectric nanogenerators (TENGs) play an important role in self-powered sensing, health care and human–machine interaction. However, traditional degradable materials used in TENGs often suffer from limited material sources and complex preparation processes, restricting large-scale production for widespread applications. Here, we propose a simple and efficient way to prepare degradable TENGs with inactivated bacterial film, taking advantage of wide source, self-proliferation and easy culture properties of bacteria. The prepared bacterial film-based TENG (BF-TENG) has stable electrical output, good durability and fatigue resistance, along with superior capabilities in both contact and non-contact sensing. In contact mode, the BF-TENG can generate a peak voltage of up to 83.3 V, which is employed for accurate Morse code transmission. In non-contact mode, the BF-TENG is capable of effectively perceiving the target polymer at a distance of 150 cm. The non-contact LED control circuit and a sensing array based on BF-TENG further demonstrate its practical potential for gesture recognition and spatial position perception. Furthermore, the fully degradable nature of BF-TENG ensures effortless disposal after use without environmental impact, serving as a promising solution for the new generation of eco-friendly and sustainable sensing devices.

Mechanically Exfoliated InP Thin Films for Solar Energy Conversion Devices

III‐V semiconductors are favoured photo absorber materials for solar energy conversion due to their ideal bandgap, yet their high‐cost hinders widespread adoption. Utilizing thin films of these semiconductors presents a viable way to address the cost‐related challenges. Here, a novel mechanical exfoliation technique is demonstrated, also known as controlled spalling, as a cost‐effective and facile way to obtain thin films of III‐V semiconductors. As a proof of concept, 15 μm thick InP films are successfully exfoliated from their original wafers. Thorough characterization using cathodoluminescence and photoluminescence spectroscopy confirms that the opto‐electronic properties of the exfoliated InP films remain unaffected. Utilizing these InP thin films, InP thin‐film heterojunction solar cells with efficiencies exceeding 13% are demonstrated. Additionally, InP photoanodes are fabricated by integrating NiFeOOH catalyst onto these InP thin‐film solar cells, achieving an impressive photocurrent density of 19.3 mA cm−2 at 1.23 V versus reversible hydrogen electrode, along with an applied bias photon‐to‐current efficiency of ≈4%. Overall, this study showcases the efficacy of controlled spalling in advancing economically viable and efficient III‐V semiconductor‐based solar energy conversion devices.

Graphene-Based Materials in Energy Storage and Conversion Devices

Global energy demand and environmental concerns have grown increasingly over the years. To solve these problems, advanced energy storage and conversion technologies are essential. This work explores the applications of graphene-based materials to enhance the performance of lithium-ion batteries, supercapacitors, and solar cells. In lithium-ion batteries, graphene significantly improves electrical conductivity, mechanical stability, and energy capacity, thereby improving battery performance. Likewise, in supercapacitors, graphene-based electrodes exhibit excellent specific capacitance and energy density, which are crucial for high-power applications. In solar cells, graphene improves photoelectric conversion efficiency and stability, especially in perovskite and ZnO/Si heterojunction solar cells. However, the high cost and complexity of producing graphene limit its widespread use. Future research should focus on developing cost-effective production methods, optimizing graphene properties through doping, exploring composite materials, and expanding graphene applications in sustainable energy and environmental fields. This work provides an overview of current progress and suggests directions for future research in this area.

Solar Selectivity of Silver Nanoparticles Modified Copper Oxide Nanocomposite Thin Films Prepared by Facile Chemical Oxidation Method

AbstractSilver nanoparticles modified copper oxide nanocomposite thin films (Ag‐CuO NC TFs) and pristine CuO TF were successfully synthesized on copper substrates using a chemical oxidation route. X‐ray diffractometry (XRD) characterization of Ag‐CuO NC TFs revealed the formation of monoclinic crystal structured CuO. Scanning electron microscopy (SEM) images showed a star‐like grain morphology of the Ag‐CuO NC TFs. Energy dispersive X‐ray spectroscopy (EDX) analysis ascertained the presence of anticipated elements without impurities. Fourier transform infrared spectroscopy (FTIR) investigation confirmed the presence of Ag NPs on CuO in the Ag‐CuO NC TFs. Raman spectroscopy examination indicated the presence of a spinel structure with vibrational and tetrahedral sites. UV‐Vis‐NIR reflectance analysis demonstrated that Ag‐CuO NC TFs with 2.0 wt.% Ag NPs exhibited solar absorptance of 72.39 %, thermal emittance of 4.3 %, and a highest solar selectivity of 16.83 among the prepared thin films. These results suggest that the Ag‐CuO NC TFs could be promising candidates for use as solar selective absorbers in solar thermal energy conversion devices.

Suppressing Se Vacancies in Sb2Se3 Photocathode by In Situ Annealing with Moderate Se Vapor Pressure for Efficient Photoelectrochemical Water Splitting.

Sb2Se3 emerges as a promising material for solar energy conversion devices. Unfortunately, the common deep-level defect VSe (selenium vacancy) in Sb2Se3 results in a low solar conversion efficiency. The post selenization process has been widely adopted for suppressing VSe. However, the effect of selenization on suppressing VSe is often compromised and even more VSe are induced due to defect-correlation. Herein, high-quality Sb2Se3 films are prepared using an unconventional selenization process, with precisely regulating in situ annealing Se vapor pressure. It is found that moderate Se vapor pressure annealing can efficiently suppress VSe by overcoming defect-correlation, as well as promotes grain growth and forms a better heterojunction band alignment. Consequently, the Sb2Se3 photocathode shows a high-level photocurrent of 19.5 mA cm-2 at 0 VRHE, an onset potential of 0.40 VRHE and a half-cell solar-to-hydrogen conversion efficiency of 1.9%, owing to the inhibited charge recombination, excellent charge transport and interface charge extraction. This work provides a significant insight to suppress deep-level defect VSe by adjusting Se vapor pressure for efficient Sb2Se3 photocathode.

Environmentally Friendly Biological Activated Carbon Derived from Sugarcane Waste as a Promising Carbon Source for Efficient and Robust Rechargeable Zinc–Air Battery

China is one of the largest sugarcane industrial countries in the world, and the annual output of bagasse waste is abundant. Classical incineration, landfill, and other treatment methods are inefficient and seriously harmful to the environment, so it is urgent to develop a new comprehensive utilization of agricultural waste. In this work, the sugarcane waste residue is converted to biological activated carbon (BAC) through a simple pre-carbonization and KOH activation process, which is then mixed with perovskite oxide BaCo0.5Fe0.5O3−δ (BCF) to form BAC/BCF composite air electrode. BAC/BCF assembled rechargeable zinc–air battery (ZAB) exhibits a relatively good output maximum power density of 96 mW·cm−2 and considerable long-term charge–discharge cycle stability over 250 h operation. These results indicate that the BAC derived from sugarcane waste is a promising potential carbon material candidate for ZAB application, which can realize the high-value utilization of agricultural waste in the field of efficient and durable energy storage and conversion devices.

Hierarchical exsolution in vertically aligned heterostructures

Metal nanoparticle exsolution from metal oxide hosts has recently garnered great attention to improve the performance of energy conversion and storage devices. In this study, the nickel exsolution mechanisms in a vertically aligned nanostructure (VAN) thin film of heteroepitaxial (Sr0.9Pr0.1)0.9Ti0.9Ni0.1O3−δ-Ce0.9Gd0.1O1.95 with a columnar architecture was investigated for the first time. Experimental results and Density Functional Theory (DFT) calculations reveal that the multiple vertical interphases in a VAN with a hierarchical arrangement provide faster and more selective Ni diffusion pathways to the surface than traditional bulk diffusion in epitaxial films. Kinetic studies conducted at different temperatures and times indicate that the nucleation process of the exsolved metal nanoparticles primarily takes place at the surface through the phase boundaries of the columns. The vertical strain is crucial in preserving the film’s microstructure, yielding a robust heteroepitaxial architecture after reduction. This innovative heteromaterial opens up new possibilities for designing efficient devices through advanced structural engineering to achieve controlled nanoparticle formation.

Current trends in micro‐supercapacitor devices

AbstractRecently, efforts have been made to design miniaturized energy storage devices according to custom requirements. The application of micro‐electronic equipment has increased significantly in information technology and biotechnology. Microelectromechanical systems, nanoelectromechanical systems, maintenance‐free wireless sensor networks, implantable medical devices, micro‐robots, and integrating energy conversion devices require micropower sources in small dimensions. Conventional supercapacitor devices cannot fulfill such high‐power demand, but miniaturization within the microscale helps enhance the working efficiency due to the shortening of diffusion path length. Micro‐supercapacitors (MSCs) in the micron to centimeter dimension range integrated with circuits and microelectronic components have gained great interest due to their high‐power density, high‐frequency response, and long cycling stability. Research on the design and fabrication of MSCs has progressed enormously. Integrating MSCs with other electronic units helps to achieve a highly efficient self‐powered system. This review presents a critical summary of the recent progress of novel materials for MSCs, fabrication methods, advanced design, and challenges in the MSCs industry.

Optical Applications of CuInSe2 Colloidal Quantum Dots.

The distinctive chemical, physical, electrical, and optical properties of semiconductor quantum dots (QDs) make them a highly fascinating nanomaterial that has been extensively studied. The CuInSe2 (CIS) QDs demonstrates great potential as a nontoxic alternative to CdSe and PbSe QDs for realizing high-performance solution-processed semiconductor devices. The CIS QDs show strong light absorption and bright emission across the visible and infrared spectrum and have been designed to exhibit optical gain. The special characteristics of these properties are of great significance in the fields of solar energy conversion, display, and electronic devices. Here, we present a comprehensive overview of the potential applications of colloidal CIS QDs in various fields, with a particular focus on solar energy conversion (such as QD solar cells, QD-sensitized solar cells, and QD luminescence solar concentrators), solar-to-hydrogen production (such as photocatalytic and photoelectrochemical H2 production), and QD electronics (such as QD transistors, QD light-emitting diodes, and QD photodetectors). Furthermore, we offer our insights into the current challenges and future opportunities associated with CIS QDs for further research.

Integration of 2D borophene into semiconducting N, P, S, and F-doped 1D carbon for energy storage and conversion devices

Innovative energy storage and high-performing conversion devices are urgently required to meet global energy issues. In this study, we synthesized and characterized a nitrogen, phosphorus, sulfur, and fluorine-doped one-dimensional carbon (NPSF@C) integrated with two-dimensional borophene (Bph) nanosheets, forming a nanocomposite (NPSF@C/Bph). The physicochemical and structural characterization confirmed borophene’s successful doping and integration into the NPSF@C matrix. Density Functional Theory (DFT) analysis indicated that the doping of heteroatoms and the integration of Bph increased the number of conduction bands in NPSF@C/Bph, effectively reducing the band gap of the material from 1.99 eV (MWCNT) and 1.43 eV (Bph) to 0.067 eV. This transformation was attributed to the introduction of localized states near the Fermi level and an enhanced density of states, resulting in a metal-like behavior for the NPSF@C/Bph composite. The NPSF@C/Bph composite demonstrated a specific surface area of 1962.78 m2/g and a pore volume of 1.2423 cm3/g, significantly enhancing its electrochemical performance. The composite showed a high specific capacitance of 837F/g at a current density of 1 A/g and retained 92.72 % of its initial capacitance after 10,000 cycles. It also exhibited a high energy density of 78.28 Wh/kg and a power density of 4545 W/kg in a symmetric supercapacitor device. Additionally, electrochemical tests revealed that the NPSF@C/Bph composite exhibited a lower overpotential and higher current density for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to its counterparts. Specifically, the overpotential for OER is 283 eV, and HER is 73 mV at a current density of 10 mA/cm2. The Tafel slopes were 63 mV/dec for OER and 67 mV/dec for HER, indicating superior reaction kinetics.