Nitrogen-doped graphene:Synthesis,characterizations and energy applications

Nitrogen-doped（N-doped） graphene has attracted increasing attentions because of the significantly enhanced properties in physic, chemistry, biology and material science, as compared with those of pristine graphene. By date, N-doped graphene has opened up an exciting new field in the science and technology of two-dimensional materials. From the viewpoints of chemistry and materials, this article presents an overview on the recent progress of N-doped graphene, including the typical synthesis methods, characterization techniques, and various applications in energy fields. The challenges and perspective of Ndoped graphene are also discussed. We expect that this review will provide new insights into the further development and practical applications of N-doped graphene.

Laser-assisted growth of hierarchically architectured 2D MoS2 crystals on metal substrate for potential energy applications

Recently, there has been substantial interest in the large-scale synthesis of hierarchically architectured transition metal dichalcogenides and designing electrodes for energy conversion and storage applications such as electrocatalysis, rechargeable batteries, and supercapacitors. Here we report a novel hybrid laser-assisted micro/nanopatterning and sulfurization method for rapid manufacturing of hierarchically architectured molybdenum disulfide (MoS2) layers directly on molybdenum sheets. This laser surface structuring not only provides the ability to design specific micro/nanostructured patterns but also significantly enhances the crystal growth kinetics. Micro and nanoscale characterization methods are employed to study the morphological, structural, and atomistic characteristics of the formed crystals at various laser processing and crystal growth conditions. To compare the performance characteristics of the laser-structured and unstructured samples, Li-ion battery cells are fabricated and their energy storage capacity is measured. The hierarchically architectured MoS2 crystals show higher performance with specific capacities of about 10 mAh cm-2, at a current rate of 0.1 mA cm-2. This rapid laser patterning and growth of 2D materials directly on conductive sheets may enable the future large-scale and roll-to-roll manufacturing of energy and sensing devices.

Special Section on Energy-Efficient Technologies--Crowd Energy Applications

Digital transformation generally refers to the process of change in business and society,based on the omnipresence of sensors,networks,information,andcommunication technology.Ever shorter development and innovation cycles are a characteristic feature of this process,which is currently influencing all industries and all areas of life,be it industrial

Guest Editorial Special Section on Energy-Efficient Technologies--Crowd Energy Applications

Since decades, the global electricity demand shows only one direction： a considerable constant increase every year. But the unlimited growth in energy consumption is discussed increasingly critical, not only primarily in terms of limitations but also in terms of more efficient, more intelligent, and more sustainable usage of energy. Energy-efficient technologies （EET） and renewable energy technologies are already in a competitive position in different markets, and they are also actively embedded in scientific research. Meanwhile,

Guest Editorial：Special Issue on Energy-Efficient Technologies--Crowd Energy Applications

The disruption of digital technologies has been a reality in many different industrial sectors for many years.The digital transformation is now having an increasing impact on the energy sector as well as the so-called"smart environments",e.g. bottom-to-bottom energy provision models (crowd energy) are no longer just

Preface to Special Issue on Carbon Materials for Energy Application

The rising cost and limited availability of fossil fuels, and the increasing concerns related to their role on global pollution and greenhouse effect have pushed considerably the need to accelerate the transition to a more sustainable use of energy based largely on renewable energy sources. Nanocarbon materials play a critical role in this transition, as they are the key materials for components of different devices necessary in enabling this transition （batteries, fuel cells, solar cells, etc.）. This issue collects 22 contributions, including one perspective and six review papers on the topic of carbon materials for energy applications, written by well-known experts in this field. It is really an exciting special issue that gives a very updated view of this topic, as well as trends and outlooks in this breakthrough research area. The initial perspective paper introduces the different possibilities offered from the growing level of knowledge in this area, testified from the exponentially rising number of publications. It also discusses the basie concepts for a rational design of these nanomaterials. The lk）llowing six reviews address different specific aspects of synthesis, characterization and use of carbon nanomaterials, from fuel cells to composite electrodes, supercapacitors and photoelectrochemical devices for CO2 conversion. These reviews represent an unique opportunity for the readers to be updated on the latest developments of new carbon families such as fullerene, grapbene, and carbon nanotube, and their derived nanocarbon materials （from carbon quantum dots to nanohorn, nanofiber, nano ribbon, etc.）. Second generation nanocarbons, including modification of these nanocarbons by surface functionalization or doping with heteroatoms to create specific tailored properties, and nanoarchitectured supramolecular hybrids, are also discussed. Finally, 1 communication and 14 full articles discuss several aspects of the use of these nanocarbon materials to develop new catalysts for a range of applications （from biomass conversion to Fisher-Tropsch reaction and electrochemical devices） and new materials for energy storage and conversion （adsorption pumps, Li-ion and Li-S batteries, electrodes for electrochemical uses）. We thus believe that this special issue dedicated to the use and development of carbon materials for energy applications represents a unique occasion for young and experienced researchers as well as for managers in the field of sustainable energy to have an updated view on this enabling topic for the future of our society. We thus invite all to have this special issue as a privileged component of your bookshelf.

Energy Storage Systems Technologies, Evolution and Applications

Energy in its varied forms and applications has become the main driver of today’s modern society. However, recent changes in power demand and climatic changes (decarbonization policy) has awakened the need to rethink through the current energy generating and distribution system. This led to the exploration of other energy sources of which renewable energy (like thermal, solar and wind energy) is fast becoming an integral part of most energy system. However, this innovative and promising energy source is highly unreliable in maintaining a constant peak power that matches demand. Energy storage systems have thus been highlighted as a solution in managing such imbalances and maintaining the stability of supply. Energy storage technologies absorb and store energy, and release it on demand. This includes gravitational potential energy (pumped hydroelectric), chemical energy (batteries), kinetic energy (flywheels or compressed air), and energy in the form of electrical (capacitors) and magnetic fields. This paper provides a detailed and comprehensive overview of some of the state-of-the-art energy storage technologies, its evolution, classification, and comparison along with various area of applications. Also highlighted in this paper is a plethora of power electronic Interface technologies that plays a significant role in enabling optimum performance and utilization of energy storage systems in different areas of application.

Atomic design of carbon-based dual-metal site catalysts for energy applications

Carbon-based dual-metal sites catalysts(DMSCs)have emerged as a new frontier in the field of sustainable energy due to their unique coordination environments,electronic structure,the maximized atom utilization.The reasonable utilization of carbonbased DMSCs provides new possibilities to achieve the outstanding catalytic performance,remarkable selectivity,recyclability in energy-related catalysis.Based on this,this review intends to summarize the recent breakthroughs in carbonbased DMSCs for the energy catalysis.Firstly,the definition and classifications of DMSCs are proposed,mainly dividing into three types(isolated dual-metal site pairs,binuclear homologous dual-metal sites pairs,binuclear heterologous dual-metal sites pairs).Subsequently,we discuss the potential of DMSCs targeting on energy conversion reactions,such as electrocatalytic hydrogen evolution reaction(HER),oxygen evolution reaction(OER),oxygen reduction reaction(ORR),CO_(2)reduction reaction(CO_(2)RR),N_(2) reduction reaction(NRR).Finally,we predict the remaining challenges and possible opportunities on the unique carbon-based DMSCs for energy applications in the future.

Single-atom site catalysts supported on two-dimensional materials for energy applications

Single-atom site catalysts(SACs) and two-dimensional materials(2DM) have gradually become two hot topics in catalysis over the past decades. Their combination with each other can further endow the derived SACs with extraordinary properties such as high loading, identical active sites, uniform coordination environment, distinctive metal-support interaction, and enhanced catalytic activities. In this review, we highlight the recent development in this specific research topic according to the types of substrates and focus on their applications in energy conversion field. Additionally, we also make a brief introduction to the synthesis and characterization methods for SACs supported on 2DM(SACs/2DM). Finally, the challenges and perspectives are summarized based on the current development status. It is believed that this work will make contributions to the rational design and fabrication of novel SACs/2DM, promoting their practical energy applications in the future.

On the Use of Nanofluids in Solar Energy Applications

Renewable energy technologies are in the centre of interest to narrow the gap between fossil fuels and clean energy systems.The dominant role of solar energy systems among the alternatives is beyond question owing to being associated with an infinite energy source,well-documented theory,simplicity,eco-friendly structure and notably higher energy and exergy efficiency range compared to other renewables.However,in solar energy systems,conventional working fluids with poor thermophysical properties are still utilised.In other words,further improvements are still available in the said systems by the use of unique nanoparticles with superior thermal,electrical,optical and mechanical properties.Within the scope of this research,the applications of nanofluids in various solar energy systems such as tracking and non-tracking solar collectors,photovoltaic/thermal systems,solar thermoelectric devices,solar stills,solar thermal energy storage systems,solar greenhouses and solar ponds are comprehensively analysed.Relevant comparisons and discussions are proposed for the potential impacts of various nanofluids on coefficient of performance(COP)and thermodynamic performance figures of solar energy systems such as energy and exergy efficiency,effectiveness and productivity.Some challenges of nanofluids are also addressed which need to be resolved in further works.

Advances on Theory and Experiments of the Energy Applications in Graphdiyne

After years of development,graphdiyne(GDY)has demonstrated the characteristics of transformative materials in many fields and has promoted great progress in fundamental and applied research.In practice,some important new concepts have been proposed,such as natural surface charge distribution inhomogeneity,multicavity space limiting effect,incomplete charge transfer effect on the atomic level,alkyne-alkene conversion of a chemical bond,in situ induction of constrained growth,reversible transition from high to low valence state,and so on.These characteristics originating from the special electronic structure and chemical structure of GDY have rapidly promoted the development of GDY science in recent years and produced many exciting results in fundamental and applied science.Therefore,we systematically introduce the recent theoretical and experimental progress of GDY in terms of its new structural,electronic,mechanical,thermal,and optical properties and its promising applications in the energy fields of membrane sciences,catalysis,energy storage,and conversion.Specifically,the great breakthrough of GDY zero-valence atomic catalysts,quantum dots catalysts,and heterostructure catalysts for catalytic applications are discussed in detail.We believe this review will provide some significant guidelines for the design and development of GDYbased high-performance materials and devices in energy fields.

Metal cyanamides: Open-framework structure and energy conversion/storage applications

Metal cyanamides are an emerging class of functional materials with potential applications in sustainable energy conversion and storage technologies such as catalysis,supercapacitors,photoluminescence and next-gen batteries.The[NCN]^(2-)as the anion,which is isolobal with[O]^(2-)endows metal cyanamides with similar physicochemical properties as oxides and chalcogenides.Whereas the unique quasI-linear structure and electronic resonance between[N=C=N]^(2-)and[N-C≡N]^(2-)of[NCN]entity bring out superior properties beyond oxides and chalcogenides.In this review,we present research status,challenges,and the recent striking progress on the metal cyanamides in the synthesis and applications.Specifically,the characteristic structures,physicochemical properties,synthetic methods with corresponding merits/demerits and latest applications in energy conversion and storage of cyanamides are summarized.The detailed outlooks for the new compounds design,morphology manipulation and potential applications are also exhibited.

A survey of Digital Twin techniques in smart manufacturing and management of energy applications

With the continuous advancement and exploration of science and technology,the future trend of energy technology will be the deep integration of digitization,networking,intelligence with energy applications.The increasing maturity of digital technologies,such as the Internet of Things,big data,and cloud computing,has given rise to the creation and use of a potential technology–Digital Twin.Currently,research on Digital Twin has produced many concepts and outcomes that have been applied in many fields.In the energy sector,while some relevant ideas and case studies of Digital Twin have been generated,there are still many gaps to be explored.As a potential technology with advantages in many aspects,Digital Twin is bound to generate more promotion and applications in the energy fields.This paper systematically reviews the existing Digital Twin approaches and their possible applications in the energy fields.In addition,this paper attempts to analyze Digital Twin from different perspectives,such as definitions,classifications,main features,case studies and key technologies.Finally,the directions and challenges of possible future applications of Digital Twin in the energy fields have been presented.

Finite Set-Model Predictive Current Control of Three-Phase Voltage Source Inverter for RES （Renewable Energy Systems） Applications

This paper focuses on a combination of three-phase VSI （voltage source inverter） with a predictive current control to provide an optimized system for three-phase inverters that control the load current. A FS-MPC （finite set-model predictive control） strategy for a three-phase VSI for RES （renewable energy systems） applications is implemented. The renewable energy systems model is used in this paper to investigate the system performance when power is supplied to resistive-inductive load. With three different cases, the evaluation of the system is done. Firstly, the robustness of control strategy under variable DC-Link is done in terms of the THD （total harmonic distortion）. Secondly, with one prediction step, the system performance is tested using different sampling time, and lastly, the dynamic response of the system with step change in the amplitude of the reference is investigated. The simulations and result analyses are carried out using Matlab/Simulink to test the effectiveness and robustness of FS-MPC for two-level VSI with AC filter for resistive-inductive load supplied by a renewable energy system.

Magnesium research and applications: Past, present and future

As the lightest structural metal and one of the most abundant metallic elements on earth, magnesium(Mg) has been used as an "industrial metal" for lightweighting in the transportation and electronics industries, in addition to other traditional applications in aluminum alloying,steel desulfurization and protective anodes. In recent years, research has shown significant potential for Mg to become a "technology metal"in a variety of new applications from energy storage/battery to biomedical products. However, global Mg production has shown steady but moderate growth in the last three decades. Mg applications as an industry metal are still limited due to some sustainability concerns of primary Mg production, as well as a number of technical issues related to the structural and corrosion performance of commercial Mg alloys.New Mg applications as an industrial or technology metal face tremendous technical challenges, which have been reflected in the intensified global research efforts in the last twenty years. This paper will review some past and present applications, and discuss future opportunities and challenges for Mg research and applications for the global Mg community.

Current trends on the use of deep learning methods for image analysis in energy applications

Deep learning methods for image analysis are attracting increasing interest for application in a wide range of different research fields.Here we aim to systematically analyze and discuss the most relevant examples for the energy sector.To this,we perform a comprehensive literature screening on applications of deep learning methods for image analysis,classify the results in application macro-areas,and discuss the emerging trends on the available energy-related cases.The results of the analysis show that,while the exploitation of these methods for energy applications still appears to be at an early stage,the interest during the last years,in terms of number of published works,has considerably grown.To provide a systematic overview on the available energy-related examples,we present a schematic correlation chart mapping algorithms,tasks,and applications.The reported analysis is intended to provide an up-to-date overview on the current application trends and potential developments for energy applications in the next future.

Advances and challenges in DFT-based energy materials design

The growing worldwide energy needs call for developing novel materials for energy applications.Ab initio density functional theory(DFT)calculations allow the understanding and prediction of material properties at the atomic scale,thus,play an important role in energy materials design.Due to the fast progress of computer power and development of calculation methodologies,DFT-based calculations have greatly improved their predictive power,and are now leading to a paradigm shift towards theory-driven materials design.The aim of this perspective is to introduce the advances in DFT calculations which accelerate energy materials design.We first present state-of-the-art DFT methods for accurate simulation of various key properties of energy materials.Then we show examples of how these advances lead to the discovery of new energy materials for photovoltaic,photocatalytic,thermoelectric,and battery applications.The challenges and future research directions in computational design of energy materials are highlighted at the end.

Advanced yolk-shell nanoparticles as nanoreactors for energy conversion

Yolk‐shell structured nanoparticles are of immense scientific and technological interests because of their unique architecture and myriad of applications.This review summarizes recent progresses in the use of yolk‐shell structured nanoparticles as nanoreactors for various chemical reactions.A very brief overview of synthetic strategies is provided with emphasis on recent research progress in the last five years.Catalytic applications of these yolk‐shell structured nanoreactors are then discussed by covering photocatalysis,methane reforming and electrochemical conversion.The state of the art research and perspective in future development are also highlighted.

Energy Storage and Multi-Source System for Reduction Energy Costs in the Consumer-Side

The objective of this work is to reduce energy costs for a consumer with multiple available energy resources and with an energy storage system. To achieve this, it is developed a methodology with a multi-criterion analysis that considers the demand side, the real-time prices, and the availability of the energy resources. In other words, the developed methodology manages the multi-source system, allowing savings for a consumer. In addition to the presentation of the methodology, it is made an application in a case study. It is considered and modeled a real consumer that has three different energy resources, including energy storage by battery. The situation comprehends solar generation, diesel generator and the electrical power grid. There are simulations and the results comprehend the savings for this consumer, considering the methodology application. The main result is a reduction in energy costs by 33.3%, considering the situation without this methodology. For the purpose of indicating the use of the storage system, it is presented the battery’s state of charge along the simulation. Also, there is a verification of the methodology’s robustness, through another simulation, using theoretical data for the consumer. In this case, the consumer has energy storage system, solar generation, biogas generator and the electrical power grid. In this situation, there is a reduction in energy costs by 30.2%, considering the situation without this methodology. In conclusion, the results show that the developed methodology is effective. In the two case studies presented there are significant savings for the consumer.

Uncover the Aesthetic Simplicity Associated with Mass Transfer in Energy Materials

Aesthetics,referred frequently to as a philosophical term,has played a starring role in forming and evolving a number of aspects of human society,including arts,politics,economics,ethics,etc.Indeed,exploring and investigating the aesthetic phenomena in the scientific field have aroused insightful research findings,which in turn has stimulated research interests in such a science-aesthetics field.In particular,better-evaluated aesthetic aspects of the materials field are expected to be uncovered upon the exceedingly-exposed fundamental breakthroughs in researching the basic structure and functionality of materials.In this report,we glimpse into the aesthetic simplicity of energy materials and comprehend specifically the mass transfer functionalities of key categories of energy materials through an intuitive and bottom-up approach.Our effort aspires to shed new lights on the functionality understanding and manipulation of functional materials in general.