Field Of Energy Conversion Research Articles

Steady and transient state behavior of a gasification process under fixed-bed downdraft configuration

Gasification is a thermochemical process that has gained significant interest in the field of biomass energy conversion. Despite the level of technological maturity of the process, the dynamic variation of the process as a result of changes in both the properties of the gasifying agent and biomass has not been analysed in sufficient depth. Therefore, the present study characterizes the process dynamically as a function of step-type changes in rice husk biomass moisture content and gasifying airflow. To identify stability conditions and the range for inducing disturbances, steady-state tests were carried out using a 32-factorial design. The experimental results demonstrate that within the tested range of airflow, the gasification process operates in the oxygen-limited zone. Despite increasing the airflow from 20 to 40 standard liters per minute (SLPM) and driving the reaction towards the combustion zone, the high temperatures achieved resulted in the gas reaching a peak Lower Heating Value (LHV) of 2.6 MJ/Nm3 and a gas power of 2.6 kW, with a Cold Gas Efficiency (CGE) of 62%. In contrast, the effect of biomass moisture content was negligible due to the thermal inertia of the reactor and the natural variation of the process. Dynamic evaluation revealed that the oxidation temperature and gas concentration were the variables that took the longest to return to stability after air disturbances. It took approximately 1200 s for the hydrogen (H2) concentration to stabilize, while the gas power required about 300 s. No clear results were observed regarding the impact of the dynamic disturbance in moisture content, which varied between 12.3% w.t and 21.5% w.t.

High In-Plane Thermoelectric Performance of Layered Bi4O4SeCl2.

The van der Waals semiconductor Bi4O4SeCl2 has recently attracted great interest due to its extremely small lattice thermal conductivity, which may find possible application in the field of energy conversion. Herein, we accurately predict the thermoelectric transport properties of Bi4O4SeCl2 using first-principles calculations and Boltzmann transport theory, where the carrier relaxation time is obtained by fully considering the electron-phonon coupling. It is found that a maximum p-type ZT value of 3.1 can be reached at 1100 K along the in-plane direction, which originates from increased Seebeck coefficient induced by multivalley band structure, as well as enhanced electrical conductivity caused by relatively stronger intralayer bonding. Besides, it is interesting to note that comparable p- and n-type ZT values can be realized in certain temperature regions, which is very desirable in the fabrication of thermoelectric modules.

Porous GaP/g‐C3N4 Photoanode for Enhanced Hydrogen Production

AbstractThe g‐C3N4 decorated porous gallium phosphide have been fabricated by a facile electrophoretic deposition (EPD) process. The morphology, element composition and light absorption of the GaP/g‐C3N4 photoanode were observed using field‐emission scanning electron microscopy, X‐ray photoelectron spectroscopy, ultraviolet and visible spectrophotometer, respectively. When acting as photoanode, porous GaP/g‐C3N4 serves as a direct Z‐scheme system, where photogenerated holes in GaP are expended by electrons generated from the g‐C3N4, inhibiting the corrosion of GaP. Therefore, the porous GaP/g‐C3N4 showed a larger photocurrent density, which is 2.1 times as large as that of the porous GaP without g‐C3N4, and a more stable photocurrent density for over 10000 s (at 0 V vs RHE). Thus, this work delivers a practical way to improve the photoelectrochemical stability and property of III–V semiconductor materials, which could be used in solar energy conversion fields.

Advances and Challenges in Interfacial Binding Forces for Electrocatalysts.

As a practical chemical energy conversion technology, electrocatalysis could be used in fields of energy conversion and environmental protection. In recent years, significant research efforts have been devoted to the design and development of high-performance electrocatalysts because the rational design of catalysts is crucial for enhancing electrocatalytic performance. Creating electrocatalysts by forming interactions between different components at the interface is an important means of controlling and improving performance. Therefore, several common interfacial binding forces used for synthesizing electrocatalysts was systematically summarized in this review for the first time. The discussion revolves around the crucial roles these binding forces play in various electrocatalytic reaction processes. Various characterization techniques capable of proving the existence of these interfacial binding forces was also involved in the review. Finally, some prospects and challenges for designing and researching materials through the utilization of interfacial binding forces were presented.

The Preparation of N, P-Doped NiSe Nanorod Electrode Materials on Nickel Foam Using the Microwave Method for High-Performance Supercapacitors.

Transition metal selenides have the leading position in the field of energy storage and conversion due to their high theoretical capacity, good electrical conductivity, and cycling stability. Nickel is widely used for the construction of positive electrodes in devices due to its good conductivity, variable valence state, and ideal redox activity. NiSe materials have high internal resistance and are prone to volume change during charging and discharging, thus affecting the practical application of this electrode material, and the reported NiSe materials have not achieved a more desirable capacity value. Therefore, in this study, N, P-NiSe nanoelectrode materials were prepared using nickel foam as the nickel source and hexachlorocyclotriphonitrile as the nitrogen and phosphorus dopant using an efficient, energy-saving, and simple microwave method. It was also characterised by XRD and XPS to confirm the successful preparation of N, P-NiSe materials. In addition, the material yielded a high capacitance value (3184 F g-1) and good cycling stability (72% of the initial capacitance value was retained after 4000 cycles) in electrochemical tests. To demonstrate its excellent suitability for practical applications, an asymmetric supercapacitor was assembled using N, P-NiSe as the anode and activated carbon as the cathode. At an operating voltage of 1.6 V, the device achieved an energy density of 289.06 Wh kg-1 and a power density of 799.26 W kg-1 and retained 80% of its initial capacity after 20,000 cycles.

Improving the Oxygen Evolution Reaction Kinetics in Zn-Air Battery by Iodide Oxidation Reaction.

Zinc-air batteries (ZABs) have garnered considerable attention as a highly promising contender in the field of energy storage and conversion. Nevertheless, their performance is considerably impeded by the proliferation of dendrites on the Zinc anode and the slow kinetics of the redox reaction on the air cathode. Herein, taking Ag30%@LaCoO3 (Ag30%@LCO) heterojunction catalyst as the cathode, it is demonstrated that adding KI additives to the alkaline electrolyte can not only enhance the oxygen electrocatalytic reaction but also inhibit the formation of zinc anode dendrites, thereby achieving a comprehensive improvement in the performance of ZABs. Under the action of the KI additive, the optimized Ag30%@LCO catalyst shows a decreased overpotential from 460 to 220mV at j = 10mA cm-2, while the assembled ZAB shows reduced charging potential (1.8V), and long cycle stability (180h). Furthermore, the morphology characterization results indicate a reduction in dendrites on the Zn anode. Both experimental and calculated results indicate that the presence of I- as a reaction modifier alters the trajectory of the conventional oxygen evolution reaction, resulting in a more thermodynamically favorable pathway. The introduction of KI additives as electrolytes provides a straightforward approach to developing comprehensively improved ZABs.

Biomass Energy Gasification Technology and Application

Globally, the dual challenges of energy crisis and environmental pollution encourage people to seek sustainable energy solutions. Biomass energy, with its renewable and environmentally friendly characteristics, has gradually become an important choice to replace the traditional energy. Biomass gasification technology, as an advanced thermochemical process to convert biomass energy into combustible gas, not only improves the efficiency of energy utilization, but also shows great potential in the field of energy conversion and environmental protection due to its cleanliness and operability. In this paper, we deeply analyze the basic principles of biomass gasification technology, including the key steps such as pyrolysis, gasification and gas purification, and explore the application strategies of this technology in biomass energy conversion. In particular, the paper details the innovative practice of Shanghai Diyan Environmental Protection Technology Co., Ltd. in the field of biomass gasification, including its technological breakthrough in printing and dyeing sludge treatment, as well as the national utility model patent obtained. The successful cases of the company not only show the advantages of biomass gasification technology in practical industrial applications, but also provide valuable experience and inspiration for the same industry. Through these studies and practices, this paper aims to provide theoretical basis and technical support for the efficient and environmental protection utilization of biomass energy, in order to promote the further development and application of biomass energy gasification technology.

Nanotubes from Transition Metal Dichalcogenides: Recent Progress in the Synthesis, Characterization and Electrooptical Properties.

Inorganic layered compounds (2D-materials), particularlytransition metal dichalcogenide (TMDC), are the focus of intensive research in recent years. Shortly after the discovery of carbon nanotubes (CNTs) in 1991, it was hypothesized that nanostructures of 2D-materials can also fold and seam forming, thereby nanotubes (NTs). Indeed, nanotubes (and fullerene-like nanoparticles) of WS2 and subsequently from MoS2 were reported shortly after CNT. However, TMDC nanotubes received much less attention than CNT until recently, likely because they cannot be easily produced as single wall nanotubes with well-defined chiral angles. Nonetheless, NTs from inorganic layered compounds have become a fertile field of research in recent years. Much progress has been achieved in the high-temperature synthesis of TMDC nanotubes of different kinds, as well as their characterization and the study of their properties and potential applications. Their multiwall structure is found to be a blessing rather than a curse, leading to intriguing observations. This concise minireview is dedicated to the recent progress in the research of TMDC nanotubes. After reviewing the progress in their synthesis and structural characterization, their contributions to the research fields of energy conversion and storage, polymer nanocomposites, andunique optoelectronic devices are being reviewed. These studies suggest numerous potential applications for TMDC nanotubes in various technologies, which are briefly discussed.

Twist Proximity-Endowed Large Figure of Merit in a Band-Modulated CrI3/1T-MoS2 Moiré Superlattice.

Moiré superlattices with a robust twist proximity effect in the low-dimensional regime can facilitate nanoscale thermoelectric devices. In pristine systems, the low efficiency and lack of proficient control of thermoelectric properties impede desirable advancements in the field of energy conversion. In the present study, we demonstrate remarkable macroscopic thermoelectric response as a consequence of microscopic band structure modulation via the twist proximity in an engineered CrI3/1T-MoS2 moiré superlattice. The local twist effect, which leads to the microscopic phenomena of electron localization, results in a comprehensive electronic structure modulation. Consequently, these local effects convolute the macroscopic thermoelectric effect. Additionally, flat bands and angle-dependent metallic to semiconducting transitions are observed at 10.89, 23.41, and 30° twist angles. We correlate the observed phenomenon with the augmented spin-charge transport and interconversion via the twist proximity effect in its semiconducting phase. The estimated ultralow electronic and lattice thermal conductivities further corroborate with the observed large figure of merit and Seebeck coefficient. The maximum values of the Seebeck coefficient and figure of merit are estimated to be ∼413 μV/K and ∼4.3 at 200 K for 30° under the constant time relaxation approach. The twist-endowed outstanding thermoelectric effect in moiré superlattices with band modulation unveils a distinctive approach to establish efficient thermoelectric devices.

Piezocatalysts and Piezo‐Photocatalysts: From Material Design to Diverse Applications

AbstractPiezocatalysis and piezo‐photocatalysis technology is a continuously developing catalytic technology based on the piezoelectric effect of catalysts, which breaks the barrier between mechanical and chemical energy. The piezoelectric polarization field formed by the mechanical deformation of piezoelectric materials is proven to effectively manipulate band structures, improve the separation of electron‐hole pairs and enhance the catalytic activity, thus alleviating energy crises and environmental issues. Herein, this review first introduces the technology of piezocatalysis and piezo‐photocatalysis, comprehensively summarizes the synthesis methods of piezo(photo)catalysis materials, and analyzes and discusses the measures to optimize the performance of piezo(photo)catalysts. The following systematically summarizes the characteristics and development of the current main piezo(photo)catalytic systems, and discusses the application of first principles calculations in piezo(photo)catalysis in combination with practical researches. Subsequently, the main application progress of piezo(photo)catalysis in environmental remediation, energy conversion, and biomedical therapy fields is presented. In the end, the current challenges, development direction, and future prospects are prospected.

Formation of core-shell structure MnCo2O4 microspheres and as a bifunctional catalyst for zinc-air batteries

Efficient and stable bifunctional catalysts, facilitating oxygen reduction and oxygen evolution, play a pivotal role in energy conversion and storage fields. In this paper, four core-shell MnCo2O4 catalyst samples are prepared by controlling different solvent heating time, which are 0.5 h, 2 h, 6 h, and 12 h, respectively. The subsequent tests indicate that the sample with a 6 h not only has an ideal core-shell structure, but also exhibits favorable performance. The unique core-shell structure and favorable electrochemical performance are mainly attributed to the prepared precursor spheres. The microspheres have an inherent core-shell structure. Detailed studies of the morphological variations of MnCo2O4 catalysts with the different solvent heating time are performed using transmission electron microscopy and field emission scanning electron microscopy. Furthermore, we analyze the potential formation mechanism of the core-shell structure MnCo2O4 catalyst. The obtained core-shell structured MnCo2O4 catalysts provide a new way for the preparation of cathode catalyst for zinc-air batteries.

Mild formation of Ni(OH)2 dense nanosheets array for ultra-efficient electrocatalytic hydrogen evolution

Synthesizing high performance and affordable nickel-based electrocatalysts has been one of the research hotspots in the field of clean energy conversion. Herein, facile electroless plating accompanied with mild impregnation method is explored to synthesize petal-like Ni(OH)2 flakes on carbon cloth (CC) for electrocatalytic alkaline hydrogen evolution reaction (HER). Notably, the optimal Ni(OH)2/CC electrode has outstanding HER activity requiring only 24.6 mV vs. RHE of overpotential to reach 25 mA cm−2 of current density, and only 101.5 mV vs. RHE of overpotential to reach 100 mA cm−2. Meanwhile, the 25-h stability test results performed well. This is primarily due to its plentiful interfacial contact, favorable surface morphology of ultrathin and dense nanosheets array, and rapid electron transport. Overall, this study provides a viable approach for the development of efficient, low-cost, hydrophilic nickel-based catalysts for electrocatalytic water splitting applications.

Nanoarchitectonics of Laser Induced MAX 3D‐Printed Electrode for Photo‐Electrocatalysis and Energy Storage Application with Long Cyclic Durability of 100 000 Cycles

Abstract3D printing, a rapidly expanding domain of additive manufacturing, enables the fabrication of intricate 3D structures with adjustable fabrication parameters and scalability. Nonetheless, post‐fabrication, 3D‐printed materials often require an activation step to eliminate non‐conductive polymers, a process traditionally achieved through chemical, thermal, or electrochemical methods. These conventional activation techniques, however, suffer from inefficiency and inconsistent results. In this study, a novel chemical‐free activation method employing laser treatment is introduced. This innovative technique effectively activates 3D‐printed electrodes, which are then evaluated for their photo and electrochemical performance against traditional solvent‐activated counterparts. The method not only precisely ablates surplus non‐conductive polymers but also exposes and activates the underlying electroactive materials. The 3D‐printed electrodes, processed with this single‐step laser approach, exhibit a notably low overpotential of ≈505 mV at a current density of −10 mA cm−2 under an illumination wavelength of 365 nm. These electrodes also demonstrate exceptional durability, maintaining stability through >100 000 cycles in energy storage applications. By amalgamating 3D printing with laser processing, the creation of electrodes with complex structures and customizable properties is enabled. This synergy paves the way for streamlined production of such devices in the field of energy conversion and storage.

Recent progress of metal halide perovskite materials in heterogeneous photocatalytic organic reactions.

Photocatalytic technology is widely regarded as an important way to utilize solar energy and achieve carbon neutrality, which has attracted considerable attentions in various fields over the past decades. Metal halide perovskites (MHPs) are recognized as "superstar" materials due to their exceptional photoelectric properties, readily accessible and tunable structure, which made them intensively studied in solar cells, light-emitting diodes, and solar energy conversion fields. Since 2018, increased attention has been focused on applying the MHPs as a heterogeneous visible light photocatalyst in catalyzing organic synthesis reactions. In this review, we present an overview of photocatalytic technology and principles of heterogeneous photocatalysis before delving into the structural characteristics, stability, and classifications of MHPs. We then focus on recent developments of MHPs in photocatalyzing various organic synthesis reactions, such as oxidation, cyclization, C-C coupling etc., based on their classifications and reported reaction types. Finally, we discuss the main limitations and prospects regarding the application of metal halide perovskites in organic synthesis.

Tough and elastic hydrogel thermocells for heat energy utilization

Hydrogel thermocells possess great potential in the energy conversion field as they directly absorb waste heat from the environment to drive redox reactions for continuous electricity generation. However, achieving high toughness and good elasticity simultaneously in hydrogel thermocells remains a challenge because of the inherent contradiction of energy dissipation mechanisms, severely limiting their practical applications and lifespan. To address this, a skin-like hydrogel network with a highly dense interwoven network is developed to construct hydrogel thermocells with good elasticity and high toughness. The dense network structure can effectively disperse the stress and hinder crack propagation, thus breaking the contradiction between high toughness and good elasticity. The thermocell realizes a toughness of 460 J m−2 while reaching an elastic limit strain of 350 %, far exceeding the elasticity of previous stretchable hydrogel thermocells. Meanwhile, it exhibits ultra-low hysteresis and excellent fatigue resistance under tensile and compressive cyclic loads. Moreover, the thermocell can work stably over long periods, enabling stable voltage output even under compression, bending, and stretching. In addition, the thermocell can power the LED lamp and calculator, and can also be connected in series to form large arrays, thus rendering it an ideal power source for wearable devices.

Waste heat management in electric motors using thermoelectric generator integrated with phase change material and metal foam-embedded heat sink

The waste heat management process from various thermal sources is associated with promising results in the energy conversion field. Thermoelectric generators integrated with phase change materials containing metal foams are useful means for recovering waste heat and converting it into electrical energy. Installing these hybrid cases on common heat sources and providing a practical strategy for waste heat management addresses a significant research gap in this field. The aim of this study is to manage waste heat from a three-phase asynchronous electric motor of a milling machine for the first time using a novel prototype thermoelectric system. Four thermoelectric modules (connected electrically in series) with zero-cooling energy phase change material and copper foam heat sink were embedded on the motor body. Hence, continuous and fluctuating loads were imposed on the motor, starting from ambient temperature. This caused the motor body to heat up and transfer the wasted heat to the module and the environment. The results of this study show that the proposed system was successfully started via the waste heat of the motor body. Thermal energy was absorbed from the hot side of the module, and the hybrid heat sink controlled the temperature of the cold side. Moreover, an appropriate temperature difference was provided across the module, and the system produced electricity for a long time during milling operation. The maximum output voltage in constant and periodic loads, with on/off durations of 180 s and 360 s, was recorded as 960 mV, 1280 mV, and 1440 mV, respectively. The mentioned hybrid thermoelectric system provides a unique solution for waste heat management in industrial applications, improving economic savings.

Comprehensive review and analysis of photovoltaic energy conversion topologies

Energy conversion is a pivotal process with widespread applications, spanning renewable energy systems, electric vehicles, and industrial power grids. Selecting the right energy conversion topology is critical for optimizing system performance, efficiency, and reliability. This comprehensive review paper provides a thorough overview of energy conversion topologies used in photovoltaic (PV) panel systems, as well as their applicability in diverse domains. Furthermore, the paper conducts a detailed analysis of commonly employed energy conversion topologies. Each topology is meticulously examined based on its operating principles, advantages, drawbacks, and typical use cases. This comprehensive review serves as an invaluable resource for researchers, engineers, and practitioners engaged in the dynamic field of energy conversion, offering insights into both wind energy and photovoltaic panel systems.

Sonication-Induced Boladipeptide-Based Metallogel as an Efficient Electrocatalyst for the Oxygen Evolution Reaction.

Bioinspired, self-assembled hybrid materials show great potential in the field of energy conversion. Here, we have prepared a sonication-induced boladipeptide (HO-YF-AA-FY-OH (PBFY); AA = Adipic acid, F = l-phenylalanine, and Y = l-tyrosine) and an anchored, self-assembled nickel-based coordinated polymeric nanohybrid hydrogel (Ni-PBFY). The morphological studies of hydrogels PBFY and Ni-PBFY exhibit nanofibrillar network structures. XPS analysis has been used to study the self-assembled coordinated polymeric hydrogel Ni-PBFY-3, with the aim of identifying its chemical makeup and electronic state. XANES and EXAFS analyses have been used to examine the local electronic structure and coordination environment of Ni-PBFY-3. The xerogel of Ni-PBFY was used to fabricate the electrodes and is utilized in the OER (oxygen evolution reaction). The native hydrogel (PBFY) contains a gelator boladipeptide of 15.33 mg (20 mmol L-1) in a final volume of 1 mL. The metallo-hydrogel (Ni-PBFY-3) is prepared by combining 15.33 mg (20 mmol L-1) of boladipeptide (PBFY) with 3 mg (13 mmol L-1) of NiCl2·6H2O metal in a final volume of 1 mL. It displays an ultralow Tafel slope of 74 mV dec-1 and a lower overpotential of 164 mV at a 10 mA cm-2 current density in a 1 M KOH electrolyte, compared to other electrocatalysts under the same experimental conditions. Furthermore, the Ni-PBFY-3 electrocatalyst has been witnessed to be highly stable during 100 h of chronopotentiometry performance. To explore the OER mechanism in an alkaline medium, a theoretical calculation was carried out by employing the first-principles-based density functional theory (DFT) method. The computed results obtained by the DFT method further confirm that the Ni-PBFY-3 electrocatalyst has a high intrinsic activity toward the OER, and the value of overpotential obtained from the present experiment agrees well with the computed value of the overpotential. The biomolecule-assisted electrocatalytic results provide a new approach for designing efficient electrocatalysts, which could have significant implications in the field of green energy conversion.

Comprehensive analysis on three-phase imbalance management technology of low-voltage distribution network

Energy production and use is one of the major sources of global greenhouse gas emissions. To combat climate change, many countries and organizations are pushing to reduce the use of fossil fuels, and the use of renewable energy sources such as solar, wind, and hydro is growing rapidly. The conversion of these renewable energy into electricity requires a large amount of power electronics. Power electronics have higher energy conversion efficiency, greater adjustability and control, and smaller size and weight than traditional generators. These characteristics make power electronic equipment have a wide range of application prospects in the field of energy conversion and power control. There may be cost, reliability, debugging, and three-phase imbalance issues. Based on the harm of three-phase imbalance to the economic operation and safe and stable operation of distribution network, the importance of three-phase imbalance in low-voltage distribution network is expounded, and the relationship between three-phase unbalance current and power factor is elaborated on the construction of three-phase imbalance. Reduce the harm of three-phase imbalance to the distribution network and reduce the loss of distribution network lines.

Defect-rich CoRu alloy embedded in the porous carbon serving as highly-efficient and bifunctional electrocatalyst for overall water splitting over a wide pH range

Exploring highly-efficient and pH-universal overall water splitting electrocatalysts are critical but keep challenging. Herein, a highly-efficient, dual-function and pH-universal electrocatalyst consisting of CoRu alloy nanoparticles embedded in the carbon matrix (CoRu/C) was successfully synthesized through an acid etching-pyrolysis conversion process using ZIF-67 as a precursor. Benefiting from the rich crystal defects created during the alloy formation process that could serve as active catalytic sites and the optimized electronic structure, the as-obtained CoRu/C electrocatalyst required overpotentials of only 18 and 37 mV to reach a current density of 10 mA cm−2 for hydrogen evolution reaction (HER) and 184 and 170 mV for oxygen evolution reaction (OER) in 1.0 M KOH and 0.5 M H2SO4 aqueous solution, respectively. For practical application, the CoRu/C catalyst only needs a cell voltage of 1.49 and 1.45 V in a two-electrode overall water splitting system to achieve a current density of 10 mA cm−2 in alkaline and acidic medium, respectively. The present work paves a new way for the design and construction of efficient bifunctional electrocatalyst for overall water splitting, and would inspire widespread research interest in the field of energy storage and conversion.