Shenyang University of Technology

Graphene oxide is highly desired for printing electronics, catalysis, energy storage, separation membranes, biomedicine, and composites. However, the present synthesis methods depend on the reactions of graphite with mixed strong oxidants, which suffer from explosion risk, serious environmental pollution, and long-reaction time up to hundreds of hours. Here, we report a scalable, safe and green method to synthesize graphene oxide with a high yield based on water electrolytic oxidation of graphite. The graphite lattice is fully oxidized within a few seconds in our electrochemical oxidation reaction, and the graphene oxide obtained is similar to those achieved by the present methods. We also discuss the synthesis mechanism and demonstrate continuous and controlled synthesis of graphene oxide and its use for transparent conductive films, strong papers, and ultra-light elastic aerogels.

Hydrogen is the energy carrier with the highest energy density and is critical to the development of renewable energy. Efficient hydrogen storage is essential to realize the transition to renewable energy sources. Electrochemical hydrogen storage technology has a promising application due to its mild hydrogen storage conditions. However, research on the most efficient electrochemical hydrogen storage materials that satisfy the goals of the U.S. Department of Energy remain open questions. All of the above require strategies for designing new hydrogen storage materials. This review provides a brief overview of hydrogen preparation, hydrogen storage, and details the development of electrochemical hydrogen storage materials. We summarize the electrochemical hydrogen storage capabilities of alloys and metal compounds, carbonaceous materials, metal oxides, mixed metal oxides, metal–organic frameworks, MXenes, and polymer-based materials. It was observed that mixed metal oxides exhibit superior discharge capacity and cycling stability. The review indicates that it is vital to create novel materials with large surface area, active-conductive profiles, and low cost. We describe the challenges, gaps, and future perspectives of electrochemical hydrogen storage materials, and hope that the review could draw more attention to the development of electrochemical hydrogen storage materials with high hydrogen storage capacity, high safety, high cycle stability, and low cost and promoting their practical applications.

Oxygen vacancies (OVs) play a crucial role in the catalytic activity of metal-based catalysts; however, their activation mechanism toward peroxydisulfate (PDS) still lacks reasonable explanation. In this study, by taking bismuth bromide (BiOBr) as an example, we report an OV-mediated PDS activation process for degradation of bisphenol A (BPA) employing singlet oxygen (1O2) as the main reactive species under alkaline conditions. The experimental results show that the removal efficiency of BPA is proportional to the number of OVs and is highly related to the dosage of PDS and the catalyst. The surface OVs of BiOBr provide ideal sites for the inclusion of hydroxyl ions (HO–) to form BiIII–OH species, which are regarded as the major active sites for the adsorption and activation of PDS. Unexpectedly, the activation of PDS occurs through a nonradical mechanism mediated by 1O2, which is generated via multistep reactions, involving the formation of an intermediate superoxide radical (O2•–) and the redox cycle of Bi(III)/Bi(IV). This work is dedicated to the in-depth mechanism study into PDS activation over OV-rich BiOBr samples and provides a novel perspective for the activation of peroxides by defective materials in the absence of additional energy supply or aqueous transition metal ions.

Excited state characters and components play a decisive role in photoluminescence (PL) and electroluminescence (EL) properties of organic light‐emitting materials (OLEDS). Charge‐transfer (CT) state is beneficial to enhance the singlet exciton utilizations in fluorescent OLEDs by an activated reverse intersystem crossing process, due to the minimized singlet and triplet energy splitting in CT excitons. However, the dominant CT component in the emissive state significantly reduces the PL efficiency in such materials. Here, the strategy is to carry out a fine excited state modulation, aiming to reach a golden combination of the high PL efficiency locally emissive (LE) component and the high exciton utilizing CT component in one excited state. As a result, a quasi‐equivalent hybridization of LE and CT components is obtained in the emissive state upon the addition of only an extra phenyl ring in the newly synthesized material 4‐[2‐(4′‐diphenylamino‐biphenyl‐4‐yl)‐phenanthro[9,10‐d]imidazol‐1‐yl]‐benzonitrile (TBPMCN), and the nondoped OLED of TBPMCN exhibited a record‐setting performance: a pure blue emission with a Commission Internationale de L'Eclairage coordinate of (0.16, 0.16), a high external quantum efficiency of 7.8%, and a high yield of singlet exciton of 97% without delayed fluorescence phenomenon. The excited state modulation could be a practical way to design low‐cost, high‐efficiency fluorescent OLED materials.

Abstract The search for new two-dimensional monolayers with diverse electronic properties has attracted growing interest in recent years. Here, we present an approach to construct MA 2 Z 4 monolayers with a septuple-atomic-layer structure, that is, intercalating a MoS 2 -type monolayer MZ 2 into an InSe-type monolayer A 2 Z 2 . We illustrate this unique strategy by means of first-principles calculations, which not only reproduce the structures of MoSi 2 N 4 and MnBi 2 Te 4 that were already experimentally synthesized, but also predict 72 compounds that are thermodynamically and dynamically stable. Such an intercalated architecture significantly reconstructs the band structures of the constituents MZ 2 and A 2 Z 2 , leading to diverse electronic properties for MA 2 Z 4 , which can be classified according to the total number of valence electrons. The systems with 32 and 34 valence electrons are mostly semiconductors. Whereas, those with 33 valence electrons can be nonmagnetic metals or ferromagnetic semiconductors. In particular, we find that, among the predicted compounds, (Ca,Sr)Ga 2 Te 4 are topologically nontrivial by both the standard density functional theory and hybrid functional calculations. While VSi 2 P 4 is a ferromagnetic semiconductor and TaSi 2 N 4 is a type-I Ising superconductor. Moreover, WSi 2 P 4 is a direct gap semiconductor with peculiar spin-valley properties, which are robust against interlayer interactions. Our study thus provides an effective way of designing septuple-atomic-layer MA 2 Z 4 with unusual electronic properties to draw immediate experimental interest.

Abstract Electronic skins (e-skins) are devices that can respond to mechanical stimuli and enable robots to perceive their surroundings. A great challenge for existing e-skins is that they may easily fail under extreme mechanical conditions due to their multilayered architecture with mechanical mismatch and weak adhesion between the interlayers. Here we report a flexible pressure sensor with tough interfaces enabled by two strategies: quasi-homogeneous composition that ensures mechanical match of interlayers, and interlinked microconed interface that results in a high interfacial toughness of 390 J·m −2 . The tough interface endows the sensor with exceptional signal stability determined by performing 100,000 cycles of rubbing, and fixing the sensor on a car tread and driving 2.6 km on an asphalt road. The topological interlinks can be further extended to soft robot-sensor integration, enabling a seamless interface between the sensor and robot for highly stable sensing performance during manipulation tasks under complicated mechanical conditions.

Today, the use of renewable energy is increasing day by day due to its advantages, to solve existing challenges such as the increase in power demand. Microgrids (MGs) which have AC, DC, and DC/AC types, have received much attention due to their many advantages. MGs can be a suitable solution for supplying power to remote and sensitive areas and they can also increase the reliability of the system. Like all systems, MGs need a reliable control system to provide proper operation. There are many control methods such as robust control and adaptive control and control structures can be divided into two types: centralized and decentralized. This paper provides an overview of different decentralized control methods for MGs, based on recently published research. The methods used in each study are fully described, along with their results. Also, several research questions have been suggested for future research that can be used.

Mobile robots, including ground robots, underwater robots, and unmanned aerial vehicles, play an increasingly important role in people’s work and lives. Path planning and obstacle avoidance are the core technologies for achieving autonomy in mobile robots, and they will determine the application prospects of mobile robots. This paper introduces path planning and obstacle avoidance methods for mobile robots to provide a reference for researchers in this field. In addition, it comprehensively summarizes the recent progress and breakthroughs of mobile robots in the field of path planning and discusses future directions worthy of research in this field. We focus on the path planning algorithm of a mobile robot. We divide the path planning methods of mobile robots into the following categories: graph-based search, heuristic intelligence, local obstacle avoidance, artificial intelligence, sampling-based, planner-based, constraint problem satisfaction-based, and other algorithms. In addition, we review a path planning algorithm for multi-robot systems and different robots. We describe the basic principles of each method and highlight the most relevant studies. We also provide an in-depth discussion and comparison of path planning algorithms. Finally, we propose potential research directions in this field that are worth studying in the future.

In recent years, domestic and international researchers have been committed to the research of lithium-ion batteries. As the key to further improving the performance of the battery, the quality of the cathode material directly affects the performance indicators of the lithium battery; thus, the cathode material occupies the core position in the lithium-ion battery. LiFePO4 is a relatively excellent material for lithium-ion batteries, which has many advantages of low cost, high capacity, and environmental friendliness. However, as a result of the low conductivity of lithium iron phosphate and the slow diffusion rate of lithium ion, the development of lithium iron phosphate in the power battery industry is restricted. As a power battery applied in real life, there is still a lot of research space in energy density, consistency, and low-temperature performance. After years of efforts, researchers continue to explore the charging and discharging principle of lithium iron phosphate, to optimize the synthesis route, and to try coating, doping modification, and other methods to improve the performance of the material. This paper analyzes and summarizes the defects of lithium iron phosphate cathode materials and modification methods and provides an outlook on the future research direction of lithium iron phosphate.

This study presents an overview of the current status of hydrogen production in relation to the global requirement for energy and resources. Subsequently, it symmetrically outlines the advantages and disadvantages of various production routes including fossil fuel/biomass conversion, water electrolysis, microbial fermentation, and photocatalysis (PC), in terms of their technologies, economy, energy consumption, and costs. Considering the characteristics of hydrogen energy and the current infrastructure issues, it highlights that onsite production is indispensable and convenient for some special occasions. Finally, it briefly summarizes the current industrialization situation and presents future development and research directions, such as theoretical research strengthening, renewable raw material development, process coupling, and sustainable energy use.

Abstract It is crucial to align two-dimensional nanosheets to form a highly compact layered structure for many applications, such as electronics, optoelectronics, thermal management, energy storage, separation membranes, and composites. Here we show that continuous centrifugal casting is a universal, scalable and efficient method to produce highly aligned and compact two-dimensional nanosheets films with record performances. The synthesis mechanism, structure control and property dependence of alignment and compaction of the films are discussed. Significantly, 10-μm-thick graphene oxide films can be synthesized within 1 min, and scalable synthesis of meter-scale films is demonstrated. The reduced graphene oxide films show super-high strength (~660 MPa) and conductivity (~650 S cm −1 ). The reduced graphene oxide/carbon nanotube hybrid-film-based all-solid-state flexible supercapacitors exhibit ultrahigh volumetric capacitance (407 F cm −3 ) and energy density (~10 mWh cm −3 ) comparable to that of thin-film lithium batteries. We also demonstrate the production of highly anisotropic graphene nanocomposites as well as aligned, compact films and vertical heterostructures of various nanosheets.

Abstract Providing sufficient driving force for charge separation and transfer (CST) is a critical issue in photoelectrochemical (PEC) energy conversion. Normally, the driving force is derived mainly from band bending at the photoelectrode/electrolyte interface but negligible in the bulk. To boost the bulky driving force, we report a rational strategy to create effective electric field via controllable lattice distortion in the bulk of a semiconductor film. This concept is verified by the lithiation of a classic TiO 2 (Li-TiO 2 ) photoelectrode, which leads to significant distortion of the TiO 6 unit cells in the bulk with well-aligned dipole moment. A remarkable internal built-in electric field of ~2.1 × 10 2 V m −1 throughout the Li-TiO 2 film is created to provide strong driving force for bulky CST. The photoelectrode demonstrates an over 750% improvement of photocurrent density and 100 mV negative shift of onset potential upon the lithiation compared to that of pristine TiO 2 film.

The electrochemical performance of the as-synthesized mesoporous NiCo₂O₄flower-like products as electrode materials for battery-type supercapacitors is systematically investigated in detail.

This article studies the robust trajectory tracking control problem of a quadrotor unmanned aerial vehicle (UAV). In order to guarantee the desired trajectory tracking performance in the presence of external disturbances and model uncertainties, the design process of the quadrotor UAV controller is divided into two steps. First, by decomposing the attitude dynamic system into two serial-connected subsystems, a cascade active disturbance rejection control scheme is applied to the attitude subsystem. Second, by introducing an additional high-gain design parameter, a novel backstepping sliding-mode control scheme for position subsystem is constructed. Moreover, the Lyapunov stability analysis is provided to show that the trajectory tracking error can converge to an arbitrarily small residual set. Numerical results illustrate the effectiveness of the designed control method and its robustness to the external disturbances and model uncertainties. Finally, the proposed method is implemented on a quadrotor UAV to demonstrate its feasibility in practical application.

Shear thickening fluids (STFs) are a new type of nanosuspension, which are formed by dispersing micro and nanoparticles in a dispersant. STFs are easily deformed under the action of a low shear rate. However, they instantly transform into a hard solid-like state at a high shear rate. After the removal of the impact force, STFs revert to their original liquid state. During this process, STFs absorb a significant amount of impact energy. Hence, they can be employed as a buffer and for vibration reduction. In this study, a comprehensive review of existing literature on STFs is presented. First, the basic properties, classification, and rheological mechanism evolution of STFs are discussed. The factors influencing the shear thickening behavior of these fluids are then reviewed. Subsequently, several computational models of the STF are discussed because the underlying mechanism of STF is still unclear, and to date, there is a paucity of good computational models. Finally, the research progress of composites based on STF in the fields of stab and spike resistance and low- and high-velocity impacts, and the use of STF as a new energy dissipation medium in the fields of explosion resistance, vibration control, adaptive structure, and industrial polishing are summarized.

For electrical machine designers, core loss data are usually provided in the form of tables or curves of total loss versus flux density or frequency. These can be used to extract the loss coefficients of the core loss formulas. In this paper, three currently available formulas are discussed and compared with the loss data supplied by lamination steel manufacturers. It is found that the dynamic hysteresis loop plays an important role in the total loss calculation, especially at high flux densities and high frequencies, and the loss coefficients should change with frequency. A new modified formula is proposed to represent the coefficient changes. The new curve is applied to the measured manufacturer's data, with acceptable accuracy.

Abstract Metal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure–performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt 3 clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt 3 cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level. The as-prepared fully exposed Pt 3 cluster catalyst shows higher conversion (35.4%) and remarkable alkene selectivity (99.0%) for n-butane direct DDH reaction at 450 °C, compared to typical Pt NP and Pt SA catalysts supported on ND@G. Density functional theory calculation (DFT) reveal that the fully exposed Pt 3 clusters possess favorable dehydrogenation activation barrier of n-butane and reasonable desorption barrier of butene in the DDH reaction.

In order to solve the problems of excessive carbon emissions and environmental pollution caused by the current carbon trading policy, this paper breaks the traditional annual carbon trading mechanism and proposes an integrated energy system (IES) optimal dispatching method considering the seasonal carbon trading mechanism. Firstly, in order to ensure the dynamic balance of the multi-energy flow in the IES, the carbon flow equivalent to the electricity-gas-heat energy flow is introduced into the energy hub model, and the multi-energy flow energy hub model is established. Secondly, an optimized-stepped carbon trading mechanism is formulated to ensure internal carbon balance and restrain carbon emissions to prevent the annual carbon emissions settlement of the IES from exceeding the standard. Finally, according to the energy supply demand of the IES in different seasons, a seasonal carbon trading mechanism is formulated, which comprehensively considers carbon emissions and economics to optimize dispatch. The impact of the optimized-stepped carbon price and seasonal dispatch on carbon emissions and economics is compared. The cost of using the optimized-stepped carbon price is reduced by at least 14.50%, and carbon emissions are reduced by at least 2.54%. Under guaranteeing the same carbon emission quota, the IES net-benefit is increased by 6.8%.

Abstract Organic fluorescent emitters with narrowband emissions are highly desirable for high‐resolution organic light‐emitting diode (OLED) display technology. In principle, this can be achieved by specifically controlling the intrinsic structural relaxation and vibronic coupling in the excited state. Here, a design strategy to realize narrowband emission of organic fluorescent emitters is proposed by significantly enhancing the low‐frequency vibronic coupling strength ( Λ ) while simultaneously reducing the high‐frequency Λ of the commonly involved stretching modes. The quinolino‐[3,2,1‐ de ]acridine‐5,9‐dione (QAO) species is found to be directly associated with this design principle. By introducing single bond‐linked peripheral moieties into the QAO core, the constructed QAO derivatives are shown to exhibit better performance, by achieving a full width at half‐maximum of 23 nm/0.13 eV in toluene for the narrowest band as well as 27 nm/0.15 eV in doped devices, with negligible dependence on the doping concentrations. The maximum external quantum efficiency of the fabricated blue OLED is 17.5%.

Battery energy storage system (BESS) plays an important role in solving problems in which the intermittency has to be considered while operating distribution network (DN) penetrated with renewable energy. Aiming at this problem, this paper proposes a global centralized dispatch model that applies BESS technology to DN with renewable energy source (RES). The method proposed in this paper aims to minimize the power purchase cost considering network active loss cost as well as voltage deviation penalty cost. Later, second-order cone programming (SOCP) method as well as big M method are applied to make the problem tractable. Last, the method illustrated in this paper is applied and validated on a modified IEEE 33-bus benchmark system to verify the effectiveness of the proposed scheduling model.