Renewable Energy Storage Technologies Research Articles

Porous activated carbon electrodes derived from Eleusine coracana biowaste in electric double layer capacitors: Nanoarchitectonics and performance

The development of high-performance supercapacitors from biowaste is crucial for advancing sustainable and renewable energy storage technologies. In this study, we report the fabrication of electrodes for high-performance supercapacitors using porous carbon derived from red millet (Eleusine coracana) straw. Porous carbon was synthesized via a two-step chemical activation process using KOH, resulting in a hierarchical pore structure comprising macro-, meso-, and micropores. The red millet-based porous carbon electrodes, assembled in a two-electrode symmetrical supercapacitor, exhibited a specific capacitance of 68 Fg⁻1 at a current density of 0.5 Ag⁻1 in a 1 M Na₂SO₄ aqueous electrolyte. At a mass loading of 5 mg per electrode, the system demonstrated a specific capacitance of 300 Fg⁻1 at 1 Ag⁻1, with an energy density of 9.1 Whkg⁻1 and a power density of 1.86 kWkg⁻1, as determined from galvanostatic charge-discharge measurements. Additionally, the supercapacitor showed excellent cyclic stability, retaining 98.78% of its initial capacitance after 5000 cycles at 10 Ag⁻1. These findings highlight the potential of porous carbon derived from agricultural biowaste for scalable applications in electric double-layer capacitors.

New approach for quality function development based on cooperative game-based consensus mechanism and three-way decision method

Quality function deployment (QFD) is a team-based product development approach for identifying critical engineering characteristics according to customer requirements to improve customer satisfaction. Nonetheless, there are some limitations in the current QFD methods when used in real-world situations. For example, most of them cannot handle experts’ conflict opinions regarding the correlation evaluations between customer requirements and engineering characteristics, and only focus on how to acquire a complete importance ranking of engineering characteristics which is unnecessary in many realistic cases. In this study, we aim to develop a new QFD approach by using the cooperative game consensus reaching process and three-way decision theory. First, the cooperative game-based consensus mechanism is applied to help experts reach a consensus on the correlation assessments between customer requirements and engineering characteristics. Then, an extended three-way decision method is adopted to obtain the importance classifications of engineering characteristics and identify the critical ones for product improvement. Finally, the proposed QFD approach is illustrated with a case study regarding renewable energy storage technology improvement, and its efficiency and advantages are verified via comparative analysis and simulation analysis.

Solar Flow Battery for Grid Innovation: Exploring Novel Cell Designs and Osmotically Balanced Neutral pH Electrolytes

The demand for clean and efficient energy with low carbon emissions has been increased continuously. In 2022, 29.9% of global electricity production came from renewable energy sources, and the UK contributed a relatively high percentage of 41.5%. However, it appears to lag behind the Nordic countries, showing an impressive 81.2% of its electricity from renewable sources. The primary hurdle to expanding the share of renewable energy is intermittency. There is a crucial need for research and development in energy storage systems to enhance this aspect. Among various renewable energy storage technologies, redox flow battery (RFB) has recently come into the spotlight because of its scalability, long-term storage capability, and fast kinetics. However, the highly concentrated acidic condition and high voltage of the conventional RFB electrolytes make applying this technology for the integration of Photovoltaic cells difficult. Here, we report a, efficient solar-rechargeable redox flow battery (SRFB) with significantly enhanced safety and stability. Particularly, we introduce a competitive osmotically-balanced neutral pH aqueous Iodine/Bromine electrolyte combination, which has not been used for solar-to-electricity storage technologies. The present work holds great potential for safe and reliable charging/discharging operations to existing photovoltaic-assisted battery technologies. These results promote the utilization of existing solar cell facilities and are a cornerstone for the development of SFBs for practical and efficient energy storage devices.

A comprehensive review of innovative approaches in renewable energy storage

As the world confronts the challenges of climate change and strives to transition towards sustainable energy systems, the integration of renewable energy sources into the power grid has become paramount. However, the inherently intermittent nature of renewables necessitates effective and reliable energy storage solutions to ensure a stable and resilient energy supply. This paper presents a thorough and comprehensive review of the innovative approaches undertaken in the field of renewable energy storage. The exploration begins with a detailed analysis of various renewable energy sources, including solar, wind, geothermal, and hydro, outlining their unique contributions to the global energy landscape. Emphasis is placed on the challenges associated with intermittency and the critical role that advanced energy storage technologies play in mitigating these challenges. The review encompasses an in-depth examination of existing energy storage technologies, ranging from well-established solutions such as lithium-ion batteries and pumped hydro storage to newer developments like sodium-ion batteries and flywheel energy storage. Each technology is scrutinized for its advantages, limitations, and current deployment scenarios. Furthermore, the paper delves into cutting-edge innovations, including the latest advancements in battery technologies such as solid-state batteries and organic flow batteries. Additionally, it explores emerging approaches like thermal energy storage and gravity-based energy storage, providing a holistic understanding of the evolving landscape. Through a critical analysis of economic considerations, environmental impacts, and the regulatory landscape, the review highlights the complex interplay between technology, policy, and market forces in shaping the future of renewable energy storage. The paper concludes with insights into potential integration strategies, recommendations for future research directions, and the role of policy and industry initiatives in fostering a sustainable and resilient energy storage ecosystem. This comprehensive review aims to contribute to the ongoing discourse on advancing renewable energy storage technologies and fostering a transition towards a more sustainable and reliable energy future. Keywords: Innovative, Renewable, Energy, Storage, Review.

Assessing the Feasibility of Implementing Porous Carbon Foam Electrodes Derived from Coal in Redox Flow Batteries

The feasibility of carbon foam electrodes derived from coal for the vanadium redox flow battery (VFB) is assessed as a pathway to repurpose mining waste for use in renewable energy storage technologies. Three-electrode, half-cell, and full-cell measurements provide proof-of-concept for coal foam as an electrode material for VFBs. Similarities in physical and chemical properties between the coal foam used here and other VFB electrode materials is characterised via SEM, micro-CT, XPS, MRI, and Raman spectroscopy. We show that significant improvement in electrochemical performance of the coal foam electrodes can be achieved via simple techniques to improve material wetting and remove impurities. The overall characteristics and electrochemical behaviour indicate that coal-derived foam can be feasibly utilised as an electrode material, and with further electrode activation, may provide a competitive solution to both cost-efficient VFBs and waste reduction.

Electrochemically decoupled reduction of CO2 to formate over a dispersed heterogeneous bismuth catalyst enabled via redox mediators.

Electrochemical CO2 reduction is a topic of major interest in contemporary research as an approach to use renewably-derived electricity to synthesise useful hydrocarbons from waste CO2. Various strategies have been developed to optimise this challenging reaction at electrode interfaces, but to-date, decoupled electrolysis has not been demonstrated for the reduction of CO2. Decoupled electrolysis aims to use electrochemically-derived charged redox mediators - electrical charge and potential vectors - to separate catalytic product formation from the electrode surface. Utilising an electrochemically generated highly reducing redox mediator; chromium propanediamine tetraacetate, we report the first successful application of decoupled electrolysis to electrochemical CO2 reduction. A study of metals and metal composites found formate to be the most accessible product, with bismuth metal giving the highest selectivity. Copper, tin, gold, nickel and molybdenum carbide heterogeneous catalysts were also investigated, in which cases H2 was found to be the major product, with minor yields of two-electron CO2 reduction products. Subsequent optimisation of the bismuth catalyst achieved a high formate selectivity of 85%. This method represents a radical new approach to CO2 electrolysis, which may be coupled directly with renewable energy storage technology and green electricity.

Nano-graphitic crystallites effect on the improved K-ion intercalation properties of Kigelia Africana fruit-derived hard carbon for potassium-ion batteries

The development of intermittent renewable energy storage technology is essential for building a sustainable, low-carbon society. Potassium-ion (K-ion) batteries are being extensively explored as alternate energy storage devices due to their closest redox potential and similarities to Lithium (Li) and Sodium (Na) batteries. Identifying alternate carbonaceous materials is, therefore, crucial to overcome the shortcomings of graphite. In this context, hard carbon derived from cellulose-rich Kigelia Africana fruit (KAP) was pyrolyzed at 1000 °C and 1100 °C and characterized using various techniques. The employed facile direct carbonization retains the inherent oxygen atoms (6.6 %). It restricts the growth of graphitic crystallites in the ab plane, thereby reducing the d-spacing revealed by X-ray Diffraction (XRD) and Raman Spectral analysis. The enhanced K-ion storage through insertion, as corroborated by Cyclic Voltammetry (CV) through the increased kinetics at the low potential < 0.5 V vs K/K+. The Galvanostatic Charge-Discharge (GCD) analysis further substantiates the role of graphitic nanocrystallites combined with the adsorption of O-atoms through the improved rate capability of KAP-1100 (110 mAh/g at 200 mA/g). On the other hand, KAP-1000 provides 10 mAh/g at 200 mA/g, which is almost ten times lower. Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) analysis further prove the efficient diffusion coefficient (1.5 × 10-8 cm2/s) of K-ions in the hard carbon and low charge transfer resistance (Rct). This study reveals the effect of local structure and the inherently available heteroatom for developing better anodes for K-ion batteries.

Preparation of Ni and NiCu/Yttria‐Stabilized Zirconia Model Electrodes with Optimized Triple‐Phase Boundary Geometry for Fundamental Operando Spectroscopic Studies

Solid oxide cell technologies play a pivotal role in the realm of renewable energy storage, guiding us through the journey toward decarbonization. Understanding how electrocatalytic materials behave under high‐temperature conditions is an absolute necessity to push these technologies forward. Operando spectroscopic investigations, such as near‐ambient pressure X‐ray photoelectron spectroscopy (NAP–XPS), offer insights into the chemical nature of active working electrodes, including the dynamic response of redox states and adsorbate chemistry to changing electrochemical conditions. Mixed ceramic–metallic electrodes exhibit a limited region with electrochemically active triple‐phase‐boundary (TPB) sites, which are located close to the electrolyte/electrode interface. To monitor this specific region spectroscopically, metallic (Ni) and bimetallic (NiCu) network‐like structures are synthesized on a yttria‐stabilized zirconia electrolyte and the electrochemical state and performance are studied by using operando NAP–XPS. In the experiments, the surface oxidation states under different polarizations are revealed, the gas composition dependent Nernst shift is confirmed, electrocatalytic activities are unraveled, and hydrogen evolution is correlated with the applied potential. The findings demonstrate, the effectiveness of thin‐film model cells with spectroscopically accessible TPB regions for probing interfacial states and electrochemical processes. The obtained fundamental knowledge can provide valuable insights for the advancement of renewable energy storage technologies.

Cost effective Cr-doped Co(OH)2 nano-flower assemblies exhibiting excellent electrochemical performance for supercapacitors

Chromium doping along with topology, the nano-flowers exhibit exceptional electrochemical performance. By systematically characterizing the prepared samples of pristine Co(OH)2 and Cr doped Co(OH)2 using a comprehensive series of analytical techniques, including XRD, SEM, TEM, EDX, FTIR, and PL, a profound understanding of their structural and morphological features is achieved. Paving the path for significant advancements in renewable energy storage technology exploration for prime and cost-effective electrode materials for supercapacitors is a major challenge. This paper presents an innovative study on Cr doped Co(OH)2 based nano-flowers. The synergistic role of the average size of fibrous structures comprising nano-flowers is in the range of 20 nm showing high surface area of the prepared sample. Electrochemical performance was acquired in 2 M KOH electrolyte by CV, GCD and EIS. To understand the rate of ion transport within the sample, diffusion coefficient has been calculated. The discernible improvement in redox behavior, maximize the capacitance of 3 % Cr-Co(OH)2 to 1252 Fg−1 and diffusion coefficient to 1.509 × 10−5 cm2s−1. Furthermore, the power law unveils the pseudocapacitive nature of 3 % Cr-Co(OH)2 electrode material and unprecedented cyclic stability by possessing retention rate of 93 % even after 5000 cycles. All these calculated properties exhibit the immense potential of doped nano-flowers as a reliable source of high-energy electrode material.

Covalent Organic Framework-based Solid-State Electrolytes, Electrode Materials, and Separators for Lithium-ion Batteries.

The increasing global energy consumption has led to the rapid development of renewable energy storage technologies. Lithium-ion batteries (LIBs) have been extensively studied and utilized for reliable, efficient, and sustainable energy storage. Nevertheless, designing new materials for LIB applications with high capacity and long-term stability is highly desired but remains a challenging task. Recently, covalent organic frameworks (COFs) have emerged as superior candidates for LIB applications due to their high porosity, well-defined pores, highly customizable structure, and tunable functionalities. These merits enable the preparation of tailored COFs with predesigned redox-active moieties and suitable porous channels that can improve the lithium-ion storage and transportation. This review summarizes the recent progress in the development of COFs and their composites for a variety of LIB applications, including (quasi) solid-state electrolytes, electrode materials, and separators. Finally, the challenges and potential future directions of employing COFs for LIBs are also briefly discussed, further promoting the foundation of this class of exciting materials for future advances in energy-related applications.

Development of Lithium/Sodium-Ion Battery Electrodes Based on Solvent Engineered Tin(II) Oxide Nanomaterials

With the global economy pushing towards a greener and cleaner energy future for the world, renewable energy storage technologies must continue to develop and improve to allow for a seamless transition from the ways of the past to a carbon neutral future. To this end, renewable battery technology and in particular the capacity of the anode must be improved. Furthermore this improvement must be made across various battery technologies (Lithium/Sodium-ion) and be cost-effective to allow for its widespread implementation and use worldwide.In this work, Tin(II) Oxide (SnO)/single wall carbon nanotube (SWCNT) composite electrodes are analysed as a possible alternative dual anode material for both lithium (LIB) and sodium-ion batteries (NIB). The LIB is limited by the current commercial anode material of graphite with a relatively low theoretical capacity of 372 mAh g-1 whilst NIBs use hard carbon with a capacity of roughly 300 mAh g-1. Alloy/de-alloy materials are envisioned to be a suitable candidate for next generation LIBs/NIBs due to their large specific capacities (875mAh g-1/ 847 mAh g-1 for SnO respectively) although major drawbacks concern the poor cycling life associated with the volume change and the associated irreversible capacity. To overcome such issues the downsizing of materials and the fabrication of composites which incorporate both lithium active and inactive material are viewed as promising solutions. Nanostructured metal oxides, forming an inactive oxide matrix are appealing candidates.Through the implementation of a solvent engineered wet chemistry synthesis, various layered SnO microparticles are produced with several morphologies well-suited to energy storage applications. This synthesis method is facile, scalable and is favourable in comparison to hydrothermal synthesese normally used to synthesise nanomaterials. While SWCNTs are themselves not suited towards energy storage applications, their incorporation in the electrodes allows them to act as a conductive additive at a lower weight loading than other conventional carbon sources (carbon black/graphite), presenting a more effective strategy to form an effective electrical percolation network while also removing the need for polymer binders/copper current collector.The optimised morphology of SnO produces a high capacity, high rate and stable anode for LIB technology. An initial coloumbic efficiency (ICE) in excess of 80% is recorded and a stable cycling capacity of 815 mAh g-1 at 0.5C after 300 cycles is also achieved, demonstrating its long term stability. A maximum capacity of 980 mAh g-1 is recorded at 0.1C, whilst high rate capacities of 775, 671 and 364 mAh g-1 are recorded at 1,2 and 5C respectively. Furthermore a full-cell is composed with a NMC cathode to demonstrate a potential full-cell real world device. As an NIB anode, a maximum capacity of 568 mAh g-1 was recorded at 0.05C, whilst a low ICE of 50% proves an issue under further investigation. Furthermore a cycling capacity of 595 mAh g-1 is recorded after 50 cycles at 0.1C, dropping to 360 mAh g-1 at 100 cycles which is still in excess of that recorded for hard carbon in NIBs.A high capacity, scalable and cost effective anode has been developed that is interchangeable between LIBs/NIBs and exceeds the performance of the current commercial anodes. Reference s : [1] S. Jaśkaniec, S. R. Kavanagh, S. Ryan, J. Coelho, C. Hobbs, A. Walsh, D. O. Scanlon and V. Nicolosi, npj 2D Mater. Appl., 2021, 5, 27. [2] J. H. Shin and J. Y. Song, Nano Converg., 2016, 3(1), 9. [3] F. Zhang, J. Zhu, D. Zhang, U. Schwingenschlögl and H. N. Alshareef, Nano Lett., 2017, 17, 1302–1311.

On using unstabilized compressed earth blocks as suspended weights in gravity energy storages

Gravity Energy Storage (GES) is an emerging renewable energy storage technology that uses suspended solid weights to store and release energy. This study is the first to investigate the feasibility of using unstabilized Compressed Earth Blocks (uCEBs) as a cost-effective and sustainable alternative for weight manufacturing in GES systems. The analysis demonstrates that uCEBs offer competitive advantages over conventional materials in terms of density and cost. The relatively low strength requirements of weights allow for CEB production without stabilizers, reducing manufacturing time and capital costs. The study highlights potential of uCEBs for GES and describes the manufacturing method. Overall, uCEBs represent a promising option to enhance GES efficiency and affordability.

Assessment of inlet mixing during charge and discharge of a large-scale water pit heat storage

Pit thermal energy storage (PTES) is an efficient renewable energy storage technology widely used in large-scale solar district heating systems. Accurate modeling of mixing in a PTES due to inlet flow is key in calculating heat storage performance. However, the commonly used one-dimensional PTES models fail to consider inlet mixing due to the three-dimensional nature of the mixing flow. This research adopts a three-dimensional model to analyze the dynamic behavior of inlet mixing inside the PTES. The model is validated against measurements of the Dronninglund PTES. To quantify the inlet mixing impact, two performance indicators (i.e., the penetration height (Z) and the energy distribution ratio (ηj)) are proposed. The parametric analysis revealed that Z is more dependent on the Reynold (Re) number than the Froude (Fr) number, while both the Re and Fr numbers influence ηj. According to the dimensional theory, the penetration height Z shows a power-law relation with time. For the energy distribution ratio ηj, a power-law relation with time is seen, although an asymptotic formula is needed in the region of a negative buoyancy jet. Finally, the inflow mixing inside the PTES is characterized under various operating conditions by empirical correlations. The results of this study could be used to improve the current one-dimensional heat storage models in terms of inlet mixing.

Dynamic response and safety performance of an anode-supported solid oxide electrolysis cell operating under electrical transients

Solid oxide electrolysis cells have emerged as a promising technology for renewable energy storage. The intermittent operation, however, could jeopardize durability. Understanding the transient response characteristics of the solid oxide electrolysis cell under diverse electrical inputs is crucial to comprehend the dynamic durability of the electrolysis cell. Yet, the electrochemical and temperature dynamic responses are challenging to be in-situ measured. In this study, a three-dimensional electrochemical-mass-heat coupled dynamic model of the solid oxide electrolysis cell is established and validated by the experimental I–V curve and electrochemical impedance spectroscopy data. The current and voltage manipulations on the transient responses are evaluated and the cause of voltage overshoot during current control is analyzed. The effects of amplitude and switching time of current upward manipulation on the electrochemical and thermal responses are also investigated. It is discovered that 40% current upward (60% power upward) slightly exceeds the upper limit of the temperature gradient of 8 K/cm and approaches the FU limit of 90%. On the other hand, the influence of switching time on safety performance is negligible.

Comparative techno-economic analysis of large-scale renewable energy storage technologies

Energy storage is an effective way to address the instability of renewable energy generation modes, such as wind and solar, which are projected to play an important role in the sustainable and low-carbon society. Economics and carbon emissions are important indicators that should be thoroughly considered for evaluating the feasibility of energy storage technologies (ESTs). In this study, we study two promising routes for large-scale renewable energy storage, electrochemical energy storage (EES) and hydrogen energy storage (HES), via technical analysis of the ESTs. The levelized cost of storage (LCOS), carbon emissions and uncertainty assessments for EESs and HESs over the life cycle are conducted with full consideration of the critical links for these routes. In order to reduce the evaluation error, we use the Monte Carlo method to derive a large number of data for estimating the economy and carbon emission level of ESTs based on the collected data. The results show that lithium ion (Li-ion) batteries show the lowest LCOS and carbon emissions, at 0.314 US$ kWh-1 and 72.76 gCO2e kWh-1, compared with other batteries for EES. Different HES routes, meaning different combinations of hydrogen production, delivery and refueling methods, show substantial differences in economics, and the lowest LCOS and carbon emissions, at 0.227 US$ kWh-1 and 61.63 gCO2e kWh-1, are achieved using HES routes that involve hydrogen production by alkaline electrolyzer (AE), delivery by hydrogen pipeline and corresponding refueling. The findings of this study suggest that HES and EES have comparable levels of economics and carbon emissions that should be both considered for large-scale renewable energy storage to achieve future decarbonization goals.

A Magnetic Binder‐Linked Air Electrode with Anti‐Pulverization Behavior for Rechargeable and Recyclable Zn‐Air Batteries

AbstractThe increasing demand for energy, coupled with the continuing deterioration of the environment, has heightened people's desire for renewable energy storage technologies, such as rechargeable zinc‐air batteries (ZABs). However, the race for the developing ZABs usually focuses on the search for new materials, with less emphasis on electrode engineering and recycling. Herein, for the first time, a simple, scalable, and inexpensive electrode engineering and recycling strategy for ZABs is proposed based on the magnetic binder engineering of the cobalt‐implanted electrocatalysts. By manipulating the electrode with magnets, the ZAB can cycle for 1200 h (7200 cycles), and its anti‐pulverization behavior is revealed through in situ observation of a visual cell with an air electrode in the charged state. Moreover, the cobalt‐implanted electrocatalysts can be recycled from the spent ZABs using a magnetic force‐separation method. Additionally, the ZAB with the recycled electrocatalyst exhibits considerably prolonged cycling stability for over 500 h (ΔE = 0.86 V). This study not only enables the design of magnetic force‐engineered electrodes with improved battery performance but also provides sustainable solutions for recycling electrocatalysts for many possible applications beyond ZABs.

Comparative energy, economic, and environmental analyses of power-to-gas systems integrating SOECs in steam-electrolysis and co-electrolysis and methanation

The integration of solid oxide electrolysis cells (SOEC) and methanation as a power-to-gas system is a promising technology for renewable energy storage and CO2 utilization. SOEC can operate in both modes: water electrolysis for hydrogen production and water/carbon dioxide co-electrolysis for syngas production. The operating conditions and performance of the integrated systems between the methanation and SOECs with both modes are different. To study the direct and indirect utilization of CO2 in the methanation integrating SOEC with both modes, this study focuses on the comparative analysis of two integrated systems between the methanation and SOECs with water electrolysis mode and co-electrolysis mode for green natural gas production from fermentation waste in all aspects such as energy and economic analyses. Additionally, heat integration of both integrated systems with pinch analysis is studied. Results indicate that the methane yield of mixed CO and CO2 methanation is higher than that of CO2 methanation. The integrated system between the methanation and SOEC with co-electrolysis mode achieves a higher system efficiency, compared to that of a system using SOEC with water electrolysis mode. The efficiency of both systems can be improved by heat integration which increases by 4.60–6.09%. Moreover, the levelized cost of the product in the system using SOEC with water electrolysis of 201.35–211.86 $/MWh is lower than that of the system using SOEC with co-electrolysis mode. The CO2 emission intensities of the system using SOEC with co-electrolysis mode by power consumption sources from the wind turbine are the lowest about 1.37 kgCO2,e/kWh.

Realizing Renewable Energy Storage Potential in Municipalities: Identifying the Factors that Matter

Abstract The share of renewable energy in heat and power generation is expected to increase significantly and reach record levels in the coming decades. As a result, emerging energy storage technologies will be key elements in balancing the energy system. To compensate the variability and non-controllability of seasonally generated renewable energy (RES) (daily fluctuations in solar radiation intensity, wind speed, etc.) development of sufficient energy storage infrastructure in the regions will play a major role in transforming RES supply potential into reality. However, local public authorities that are responsible for creating an enabling policy environment for RES infrastructure development in regions encounter numerous challenges and uncertainties in deploying sufficient energy accumulation that often remain unanswered due to a lack of knowledge and on-site capacity, which in turn significantly hinders the regional path to climate neutrality. In this study, the PESLTE analytical framework and composite index methodology is applied to examine the multidimensional factors that influence the deployment of renewable energy storage technologies in municipalities: political, economic, social, legal, technological, and environmental. Developed model is approbated in a case study in a Latvian municipality where four different alternative energy storage technologies are compared: batteries for electricity storage, thermal energy storage, energy storage in a form of hydrogen, and energy storage in a form of biomethane.

Accurate combination forecasting of wave energy based on multiobjective optimization and fuzzy information granulation

Wave energy forecasting modeling is critical for promoting renewable energy storage technology as well as for energy sustainability and global carbon neutrality goals. However, due to the irregular volatility and complexity in wave energy data, all the effective information cannot be fully utilized by a traditional forecasting model; moreover, the point forecasting results cannot be used to effectively analyze the uncertainty of the time series. To overcome these shortcomings, a multistep point-interval combined significant wave height forecasting system based on the multiobjective grasshopper optimization algorithm and the fuzzy information granulation strategy is proposed to forecast the half-hour actual wave height at different buoy locations. Applying this system, Pareto optimal weights can be obtained to integrate the respective advantages of deep learning and neural network models in the combined forecasting module, achieve the best point and interval forecasting accuracy and accurately analyze the uncertainty of point forecasting results. Among the combined models, the proposed system has a more comprehensive and scientific prediction performance than other models (MAPE = 4.9866 for Site 1, MAPE = 4.9138 for Site 2, and MAPE = 3.9572 for Site 3). The forecasting outcomes indicate that the developed system significantly improves forecasting accuracy and stability, which provides reliable technical support for the sustainable development of wave power generation.

Interface engineering of Fe2P@CoMnP4 heterostructured nanoarrays for efficient and stable overall water splitting

Electrocatalytic water splitting to generate high-quality hydrogen is an attractive renewable energy storage technology; however, it is still far from becoming a real-world application. In this study, we developed an effective and stable nickel foam-supported Fe2P@CoMnP4 heterostructure electrocatalyst for overall water splitting. As expected, the as-obtained Fe2P@CoMnP4/NF electrocatalyst exhibits superb bifunctional catalytic activity and only requires extremely low overpotentials of 53 and 249 mV to achieve a current density of 10 mA cm−2 for the hydrogen and oxygen evolution reactions, respectively. Moreover, a two-electrode electrolyzer assembled using Fe2P@CoMnP4/NF as electrodes operates at the low cell voltage of 1.54 V at 10 mA cm−2, showing excellent long-term stability for 140 h. Theoretical calculations indicate that the surface electronic structure is effectively adjusted by the generated heterointerfaces between the Fe2P and CoMnP4 in a two-phase matrix, resulting in a Gibbs free energy of hydrogen adsorption close to zero and high intrinsic activity. This innovative strategy is a valuable route for producing low-cost high-performance bifunctional electrocatalysts for water splitting.