Materials For Energy Conversion Research Articles

(Nanocarbons Division Poster Award, 3rd Place) Investigating the Impact of Reaction and Carbonization Variables on ZIF-67 and Its Energy Storage Properties

Metal-organic frameworks (MOFs), with their exceptional properties such as high surface area, well-defined pores, and diverse chemical functionalities, have garnered widespread attention in scientific and industrial domains [1-2]. Among these, zeolitic imidazolate frameworks (ZIFs), known for their chemical and thermal stability, are extensively explored for applications ranging from catalysis and gas adsorption to electronic devices and sensors.By employing a novel hydrothermal method in aqueous solutions at room temperature, ZIF-67 nanocrystals were successfully synthesized, eliminating the need for toxic organic solvents and reducing overall costs. The resulting materials demonstrated notable efficiency in energy storage. To address the increasing demand for scalable synthesis methods, the study investigated the impact of reaction scale, reaction time, and reaction mixture dilution on the yield, morphology, and molecular structure of ZIF-67. The optimized conditions increased the production yield to 83%, surpassing the reported 75%. The subsequent carbonization process under three different regimes (800 °C, 800 °C with 3h ramp, 900 °C) resulted in materials exhibiting promising energy storage capabilities, with capacitance values reaching 81 F g−1 at a low sweep rate of 5 mV s−1. The carbonization yield showed a decrease with increasing carbonization time and temperature, and capacitance values were influenced by the presence of cobalt in the material.A slightly higher specific surface area of sample C-800 is reflected in the slightly higher capacitance values over all sweep rates indicating that specific surface area plays a role in the behavior of here synthesized materials. Capacitance is invariant at higher sweep rates (above 20mV s-1) which can be an indication that a part of the material surface, at macro- and mesopores, is highly responsive and highly conductive. At lower sweep rates micropores become available, due to prolonged time for ion insertion, which increases the capacitance that is unavailable at higher sweep rates. The highest percentage rise in capacitance is also seen in sample C-800 as its micropore volume, 40% of its total volume, is the highest among the samples investigated.Specifically, considering only the carbon part, the specific capacitance reached 176 F g−1, comparable to literature values for MOF-derived carbons [3]. The study suggests that dissolution of cobalt could enhance the material's capacitance behavior, opening avenues for further improvement in energy storage applications. This transformative approach addresses challenges associated with escalating energy demands and showcases the potential of ZIF-67-derived materials in electrochemical applications.AcknowledgementThis research was supported by the Science Fund of the Republic of Serbia, grant number 7750219, Advanced Conducting Polymer-Based Materials for Electrochemical Energy Conversion and Storage, Sensors and Environmental Protection-AdConPolyMat (IDEAS programme)

(Invited) In Situ x-Ray Spectroscopy for Energy Materials

In response to the worldwide surge in energy demand, the materials scientists devote themselves to the search for clean and sustainable energy. Without the development of cutting-edge renewable energy materials, going green has never been simple. The zero-emission future requires a multifaceted approach. Advanced functional materials for more effective energy conversion, storage, and conservation are the universal focus of energy research. Although the ideas for increasing the efficiency of current energy materials in terms of energy conversion, storage, or conservation are clear and straightforward, they are technically challenging. It is difficult to better engineer materials in an efficient manner for a practical use without knowing the fundamental atomic and electronic structures, particularly how they respond under operating conditions. Synchrotron x-ray spectroscopies, including x-ray absorption and emission spectroscopies are powerful tools to study the local unoccupied and occupied electronic states. In addition, employing the in situ technique permits us to monitor the atomic and electronic structure modulations of the energy material at work. An emerging x-ray spectro-microscopic technique, scanning transmission x-ray microscopy, which provides spatially resolved x-ray spectroscopy. The significance of utilizing x-ray spectroscopy for the atomic and electronic structure characterization of several significant energy material systems, such as advanced nanocatalysts, artificial photosynthesis materials, and smart materials, will be discussed in this presentation. Recent developments of in situ technique, a number of recent studies, and energy science-related Tamkang University (TKU) end-stations at the BL45A and BL27A of TPS will also be presented.

(Invited) Tailored Electrochemical Interfaces for Renewable Fuels Production

Tailoring the structure of the electrified interface and the electrocatalytically active sites at the atomic and molecular levels is key to elucidating the design principles to develop advanced materials for sustainable energy conversion and storage. This talk will focus on recent strategies to tune the structure-activity-selectivity relationships for oxygen, carbon dioxide/carbon monoxide and methane electrocatalysis to produce renewable fuels.First, I will present our work toward understanding and tuning the structure-property relations for oxygen evolution for the production of green hydrogen in proton exchange membrane water electrolysers. Then, I will show our model studies on well-defined Cu-based surfaces to understand structure-properties relations for the electrochemcial CO2 reduction reaction. We have investigated the effect of electrolyte, pH, and potential dependence for CO reduction on Cu single crystals as well as methods to evaluate the facet distribution on Cu-based catalysts. Finally, I will discuss some strategies for selective oxidation reactions such as partial oxidation of methane to produce liquid fuels such as methanol.

(Invited) Two-Dimensional Layered Materials and Their Mixed-Dimensional Hybrids for Electrochemical Applications

Compared with their 3D counterparts, two-dimensional (2D) van der Waals (vdW) materials exhibit quantum confinement where charge carriers are spatially confined at the physical boundaries. Particularly, when mixing 2D materials with other low-dimensional (LD) materials, they exhibit enormous potential in electrochemical energy applications due to the unique properties arising from reduced dimensionality and, more importantly, material integration synergy.In this work, 2D transition metal dichalcogenides (MoS2) and their mixed low-dimensional hybrids (MLDHs) are introduced with an emphasis on the hybrid structure construction using the one-step solvothermal synthesis technique and their electrochemical applications. Fundamental insight into the synergistic effect of the MLDHs integration in terms of active site exposure, surface area enlargement, electrical conductivity improvement, and structural phase engineering for advancing the development of Li-ion batteries (LIBs) and electrocatalytic hydrogen evolution reaction (HER) will also be discussed. Specifically, in the case of LIBs, 2D-based binary hybrids (i.e., MoS2/MXene) deliver a Li-ion storage capacity of 540 mA h g−1 at 100 mA g−1 and a stable cycle performance up to 300 cycles. In sharp contrast, the 2D-based ternary MLDHs (i.e., MoS2/MXene/CNT) exhibit a higher Li-ion storage capacity (1500 mAh g−1 at 100 mA g−1), outstanding cycle stability (up to 300 cycles) and excellent rate capability (500 mAh g−1 at 4000 mA g−1) as an anode of LIBs. In the case of HER, the MLDH heterostructures show an overpotential of 169 mV with a low Tafel slope of 51 mV/dec and can be cycled to 1000 cycles. Leveraging the unique microreactor platform based on the 2D vdW platform, a mechanistic understanding of charge transport dynamics at the electrified electrode and current collector interface will be highlighted.The knowledge gained on how mixed-dimensional physics and chemistry will shed light on the design principle of the electrode materials for electrochemical energy storage and conversion and deepen the understanding of the process-structural-property-performance (PSPP) relationship of the vdW-based hybrid structures.

(Invited) Probing Electrochemical Interfaces in Catalytic and Energy Materials and Process Using Operando Soft X-Ray Spectroscopy

Advanced energy technology arises from the understanding in fundamental science, thus rest in large on in-situ/operando characterization tools for observing the physical and chemical interfacial processes. Synchrotron based X-ray spectroscopic techniques offers unique characterization in many important energy materials of energy conversion, energy storage and catalysis in regards to the functionality, complexity of material architecture, chemistry and interactions among constituents within. However, it is challenging to reveal the real mechanism of the chemical processes.In the operando soft X-ray spectroscopy characterization of interfacial phenomena in energy materials and devices, it has been found that the microstructure and composition of materials as well as the microstructure evolution process have a great influence on performances in a variety of fields, e.g., energy conversion and energy storage materials, chemical and catalytic processes. This presentation will show how to best use the in-situ/operando soft X-ray spectroscopy characterization techniques, including soft x-ray absorption spectroscopy (XAS) and resonant inelastic soft X-ray scattering (RIXS) to investigate the real electrochemical mechanism during the operation. The experimental results show how in-situ/operando soft X-ray spectra characterization techniques uncover the phase conversion, chemical and environmental change of elements and other very important information of solid/gas and solid/liquid interfaces in real time, thus further enhance the understanding of real reaction mechanism.

Regulation of Electron Delocalization Region in 2D Heteroligand-Based Copper-Organic Framework to Enhance Charge Storage.

The rechargeable aqueous ammonium ion battery shows great potential in low-cost energy storage system because of its long life and environmental friendliness. However, most inorganic host materials used in ammonium ion batteries are still limited by slow diffusion kinetics. Herein, it is identified that a 2D heteroligand-based copper-organic framework featuring numerous ammonium ion adsorption site in the π-conjugated periodic skeleton supplies multiple accessible redox-active sites for high-performance ammonium storage. Benefitting from the effective regulation of electron delocalization by heteroligand and the inherent hydrogen bond cage mechanism between ammonium ions, the resultant full battery delivers a large specific energy density of 211.84Whkg-1, and it can be stably operated for 12000 cycles at 5Ag-1 for over 80 days. This explanatory understanding provides a new idea for the rational design of high-performance MOF-based ammonium ion battery cathode materials for efficient energy storage and conversion in the future.

Revealing vibrational, elastic, electro-optic, and thermoelectric aspects of double perovskites Na2ScCuX6 (X=Cl, Br) for energy harvesting applications by implementing DFT approach

Currently, the novel combination of double perovskites Na2ScCuX6 (X = Cl, Br) is being investigated as a potential solution to fulfil the energy requirements. For this purpose, the stability, vibrational, mechanical, electro-optic, and transport properties are addressed systematically. The tolerance factor and Born mechanical criteria ensure structural and mechanical stabilities. The calculated formation and Gibbs free energies ensure the thermal stabilities. Thermodynamic properties against temperature and pressure are explored by discussing entropy, thermal expansion, and Debye temperature. The elastic characteristics have provided insight into anisotropy and mechanical strength. Meanwhile, ductile nature is characterized by the Poisson ratio and Pugh's ratio. The electronic aspects have estimated the band gaps of Na2ScCuCl6 and Na2ScCuBr6, which yielded values of 1.63 and 1.58 eV, respectively. The materials demonstrated substantial light absorption (order of 105 cm−1) and minimal reflectivity (below 25 %) in the visible range. The thermoelectric performance has been evaluated in the temperature range of 100–600K using the Seebeck effect, conductivities, and figure of merit. Lastly, the superior figure of merit (ZT) values ranging between 0.78 and 0.84 demonstrate the suitability of materials for thermal energy conversion. Therefore, Na2ScCuCl6 and Na2ScCuBr6 have the potential to be considered feasible candidates for energy harvesting applications.

Heterostructure Fe7S8/Mn(OH)2 of incomplete sulfurization induces Mn atoms with high density of states for enhancing oxygen evolution reaction and supercapacitor electrochemical performance

Heterostructures and the introduction of heterogeneous elements have been regarded as effective strategies to promote electrochemical performance. Herein, sulfur species are introduced by a simple hydrothermal vulcanization method, which constructs the open heterostructure Fe7S8/Mn(OH)2 as a bifunctional material. The open cordyceps-like morphology can make the material contact more sufficiently with the electrolyte, exposing a large number of reaction sites. Furthermore, the introduction of the heterogeneous element S successfully constructs a heterogeneous interface, the interface-modulated composite material consists of Mn atoms contributing the main density of states (DOS) near the Fermi energy level from the density functional theory (DFT) calculations, which optimizes the adsorption energy of oxygen-containing intermediates during the oxygen evolution reaction (OER) process and reduces the reaction energy barrier, being conducive to the improvement of the material’s electrochemical properties. As predicted, the Fe7S8/Mn(OH)2 material exhibits remarkable electrochemical properties, such as an overpotential of 202 mV at 10 mA cm−2 for the oxygen evolution reaction and even a specific capacitance of 2198 F g−1 at 1 A g−1. This work provides new insights into the role of introducing sulfur species and controlling the structure of the material, and exemplifies novel design ideas for developing bifunctional materials for energy storage and conversion.

Functional organic materials for energy storage and conversion: recent developments and future perspectives

Functional organic materials for energy storage and conversion: recent developments and future perspectives

Manipulation of Oxidation States on Phase Boundary via Surface Layer Modification for Enhanced Alkaline Hydrogen Electrocatalysis.

In alkaline water electrolysis and anion exchange membrane water electrolysis technologies, the hydrogen evolution reaction (HER) at the cathode is significantly constrained by a high energy barrier during the water dissociation step. This study employs a phase engineering strategy to construct heterostructures composed of crystalline Ni4W and amorphous WOx aiming to enhance catalytic performance in the HER under alkaline conditions. This work systematically modulates the oxidation states of W within the amorphous WOx of the heterostructure to adjust the electronic states of the phase boundary, the energy barriers associated with the water dissociation step, and the adsorption/desorption properties of intermediates during the alkaline HER process. The optimized catalyst, Ni4W/WOx-2, with a quasi-metallic state of W coordinated by a low oxygen content in amorphous WOx, demonstrates exceptional catalytic performance (22 mV@10mA cm-2), outperforming commercial Pt/C (30 mV@10mA cm-2). Furthermore, the operando X-ray absorption spectroscopy analysis and theoretical calculations reveal that the optimized W atoms in amorphous WOx serve as active sites for water dissociation and the nearby Ni atoms in crystalline Ni4W facilitated the release of H2. These findings provide valuable insights into designing efficient heterostructured materials for energy conversion.

Enhancing thermoelectric effect with BaTiO3-doped ZrO2 tapes and ferromagnetic nanostructures

The Anomalous Nernst Effect (ANE) emerges as a promising candidate for converting heat into electricity through magnetic nanostructures. However, the substrate plays a central role in optimizing this phenomenon for future technological applications. Tapes of ZrO2 and BaTiO3-doped ZrO2, manufactured by tape casting, possess characteristic flexibility in the green state, which makes them suitable for use as coverings on virtually any curved surface. Moreover, BaTiO3 ceramic materials present piezoelectric properties, which, when combined with thermoelectric properties, can generate interesting heterostructures with simultaneous thermal and vibrational power conversion capabilities. This study explores the combination of tape casting and magnetron sputtering to improve the functionalization of ceramic tapes with ferromagnetic nanostructures. Specifically, it investigates the quasi-static and thermoelectric properties of heterostructures created by depositing NiFe thin films onto sintered ZrO2 and BaTiO3-doped ZrO2 tapes using magnetron sputtering. The results indicate a 71 % increase in the effective thermoelectric coefficient as the amount of BaTiO3 in the ceramic substrate increases. These findings suggest a new approach to integrating these techniques for the production of multifunctional materials for thermoelectric energy conversion.

Porous Thermoelectric Materials for Energy Conversion by Thermoelectrocatalysis

Novel uses of thermoelectric (TE) materials as catalyst and catalyst promoters have been reported recently for a variety of applications such as environmental gas mitigation, battery, and photoreduction of nuclear wastewater. TE Seebeck voltage is found to increase the catalytic activities by tens to hundreds of times, and this effect is termed thermoelectrocatalysis. In these uses, the TE materials are in an open‐circuit configuration, which is different from the usual closed‐circuit configuration in the TE energy generation and cooling devices. A new figure of merit defined as the Seebeck voltage per unit heat loss is proposed for the application of thermoelectrocatalysis. Techniques such as dense bulk porous surface and increased thickness of the TE materials are used for the optimization of the thermoelectrocatalysis of the oxyselenide BiCuSeO for the carbon dioxide hydrogenation reactions.

Carbonized wood fiber-supported S, N-codoped carbon layer-coated multinary metal sulfide nanoarchitecture for efficient oxygen evolution reaction at ampere-level current density

Multinary metal sulfides (MMSs) are highly suitable candidates for the application of electrocatalysis as they offer numerous parameters for optimizing the electronic structure and catalytic sites. Herein, a stable nanoarchitecture consisting of MMSs ((NiCoCrMnFe)Sx) nanoparticles embedded in S, N-codoped carbon (SNC) layers derived from metal organic framework (MOF) and supported on carbonized wood fibers (CWF) was fabricated by directly carbonization. Benefiting from this carbon-coated configuration, along with the synergistic effects within multinary metal systems, (NiCoCrMnFe)Sx@SNC/CWF delivers an exceptionally low overpotential of 260 mV at a high current density of 1000 mA cm−2, a small Tafel slope of 48.5 mV dec−1, and robust electrocatalytic stability. Furthermore, the (NiCoCrMnFe)Sx@SNC/CWF used as the cathode of rechargeable Zn-air batteries demonstrates higher power density and remarkable durability, surpassing that of commercial RuO2. Thus, we showcase the feasibility and advantages of employing highly efficient and durable MMSs materials for low-cost and sustainable energy conversion.

Wood derived carbon embedded with shell-core CoP@CoFe for efficient oxygen evolution

Development of hybrid materials with specific architecture, interface, and multicomponent interactions demonstrates effective paradigm for pursuing high-performance energy conversion materials. Herein, using renewable and inexpensive wood-derived carbon as host, the shell-core CoP@CoFe particles are embedded on walls of carbonized wood channels (termed as CoP@CoFe/CW) to fabricate composite catalyst for electrocatalysis oxygen evolution reaction (OER). With benefits of the well distribution of CoP@CoFe particles, high conductivity of CW with channels, and good integration between them, highly exposed catalysis surface as well as rapid charge/mass transfer are achieved. The interface effect of shell-core hybrid activates the intrinsic OER efficiency of CoP@CoFe. Thus, the designed CoP@CoFe/CW yields excellent OER performance with ultralow overpotential of 120 mV (10 mA cm−2). This strategy of catalyst design based on eco-friendliness and renewable CW host may offer promising reference to explore composite materials with high conductivity and fast mass transfer for water electrolysis and other energy storage/conversion systems.

Van der Waals gap engineering in 2D materials for energy storage and conversion

Van der Waals gap engineering in 2D materials for energy storage and conversion

II-Scheme Heterojunction Frameworks Based on Covalent Organic Frameworks and HKUST-1 for Boosting Photocatalytic Hydrogen Evolution.

Covalent organic frameworks (COFs) are one type of promising polymer semiconductors in solar-driven hydrogen production, but majority of COFs-based photocatalytic systems show low photocatalytic efficiency owing to lack of metal active sites. Herein, we reported II-Scheme heterojunction frameworks based on COF (TpPa-1) and metal-organic framework (HKUST-1) for highly efficient hydrogen production. The coordination bonding directed self-assembly of HKUST-1 on the surface of TpPa-1 endows the heterojunction frameworks (HKUST-1/TpPa-1) with strong interface interaction, optimized electronic structures and abundant redox active sites, thus remarkably boosting photocatalytic hydrogen evolution. The hydrogen evolution rate for optimal HKUST-1/TpPa-1 is as high as 10.50 mmol g-1 h-1, which is significantly enhanced when compared with that of their physical mixture (4.13 mmol g-1 h-1), TpPa-1 (0.013 mmol g-1 h-1) and Pt-based counterpart (6.70 mmol g-1 h-1). This work offers a facile approach to the construction of noble-metal-free II-Scheme heterojunctions based on framework materials for efficient solar energy conversion.

Nanoporous Carbon Materials Derived from Biomass Precursors: Sustainable Materials for Energy Conversion and Storage

Nanoporous Carbon Materials Derived from Biomass Precursors: Sustainable Materials for Energy Conversion and Storage

Synthesis of Cs3Cu2I5 Nanocrystals in a Continuous Flow System.

Achieving the goal of generating all of the world's energy via renewable sources and significantly reducing the energy usage will require the development of novel, abundant, nontoxic energy conversion materials. Here, a cost-efficient and scalable continuous flow synthesis of Cs3Cu2I5 nanocrystals is developed as a basis for the rapid advancement of novel nanomaterials. Ideal precursor solutions are obtained through a novel batch synthesis, whose product served as a benchmark for the subsequent flow synthesis. Realizing this setup enabled a reproducible fabrication of Cs3Cu2I5 nanocrystals. The effect of volumetric flow rate and temperature on the final product's morphology and optical properties are determined, obtaining 21% quantum yield with the optimal configuration. Consequently, the size and morphology of the nanocrystals can be tuned with far more precision and in a much broader range than previously achievable. The flow setup is readily applicable to other relevant nanomaterials. It should enable a rapid determination of a material's potential and subsequently optimize its desired properties for renewable energy generation or efficient optoelectronics.

Precursor engineering for soft selective synthesis of phase pure metal-rich digenite (Cu9S5) and djurleite (Cu31S16) nanocrystals and investigation of their photo-switching characteristics.

Copper sulfide nanostructures have evolved as one of the most technologically important materials for energy conversion and storage owing to their economic and non-toxic nature and superior performances. This paper presents a direct, scalable synthetic route aided by a single source molecular precursor (SSP) approach to access copper sulfide nanomaterials. Two SSPs, CuX(dmpymSH)(PPh3)2 (where X = Cl or I), were synthesized in quantitative yields and thermolyzed under appropriate conditions to afford the nanostructures. The analysis of the nanostructures through pXRD, EDS and XPS suggested that phase pure digenite (Cu9S5) and djurleite (Cu31S16) nanostructures were isolated from -Cl and -I substituted SSPs, respectively. The morphologies of the as-synthesized nanomaterials were investigated using electron microscopy techniques (SEM and TEM). DRS studies on pristine materials revealed blue shifted optical band gaps, which were found to be optimum for photoelectrochemical application. A prototype photoelectrochemical cell fabricated using the pristine nanostructures exhibited a stable photo-switching property, which presents these materials as suitable economic and environmentally friendly photon absorber materials.

Energy Storage Application of CaO/Graphite Nanocomposite Powder Obtained from Waste Eggshells and Used Lithium-Ion Batteries as a Sustainable Development Approach.

The reuse of waste materials has recently become appealing due to pollution and cost reduction factors. Using waste materials can reduce environmental pollution and product costs, thus promoting sustainability. Approximately 95% of calcium carbonate-containing waste eggshells end up in landfills, unused. These eggshells, a form of bio-waste, can be repurposed as catalytic electrode material for various applications, including supercapacitors, after being converted into CaO. Similarly, used waste battery electrode materials pose environmental hazards if not properly recycled. Various types of batteries, particularly lithium-ion batteries, are extensively used worldwide. The recycling of used lithium-ion batteries has become less important considering its low economic benefits. This necessitates finding alternative methods to recover and reuse the graphite rods of spent batteries. Therefore, this study reports the conversion of waste eggshell into calcium oxide by high-temperature calcination and extraction of nanographite from spent batteries for application in energy storage fields. Both CaO and CaO/graphite were characterized for their structural, morphological, and chemical compositions using XRD, SEM, TEM, and XPS techniques. The prepared CaO/graphite nanocomposite material was evaluated for its efficiency in electrochemical supercapacitor applications. CaO and its composite with graphite powder obtained from used lithium-ion batteries demonstrated improved performance compared to CaO alone for energy storage applications. Using these waste materials for electrochemical energy storage and conversion devices results in cheaper, greener, and sustainable processes. This approach not only aids in energy storage but also promotes sustainability through waste management by reducing landfills.