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With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors will play a key role in revolutionizing modern day electronic and electrical devices. Among the popular dielectric materials, anti-ferroelectrics (AFE) display evidence of being a strong contender for future ceramic capacitors. AFE materials possess low dielectric loss, low coercive field, low remnant polarization, high energy density, high material efficiency, and fast discharge rates; all of these characteristics makes AFE materials a lucrative research direction. However, despite the evident advantages, there have only been limited attempts to develop this area. This article attempts to provide a focus to this area by presenting a timely review on the topic, on the relevant scientific advancements that have been made with respect to utilization and development of anti-ferroelectric materials for electric energy storage applications. The article begins with a general introduction discussing the need for high energy density capacitors, the present solutions being used to address this problem, and a brief discussion of various advantages of anti-ferroelectric materials for high energy storage applications. This is followed by a general description of anti-ferroelectricity and important anti-ferroelectric materials. The remainder of the paper is divided into two subsections, the first of which presents various physical routes for enhancing the energy storage density while the latter section describes chemical routes for enhanced storage density. This is followed by conclusions and future prospects and challenges which need to be addressed in this particular field.

Large scale Density Functional Theory (DFT) based electronic structure calculations are highly time consuming and scale poorly with system size. While semi-empirical approximations to DFT result in a reduction in computational time versus ab initio DFT, creating such approximations involves significant manual intervention and is highly inefficient for high-throughput electronic structure screening calculations. In this letter, we propose the use of machine-learning for prediction of DFT Hamiltonians. Using suitable representations of atomic neighborhoods and Kernel Ridge Regression, we show that an accurate and transferable prediction of DFT Hamiltonians for a variety of material environments can be achieved. Electronic structure properties such as ballistic transmission and band structure computed using predicted Hamiltonians compare accurately with their DFT counterparts. The method is independent of the specifics of the DFT basis or material system used and can easily be automated and scaled for predicting Hamiltonians of any material system of interest.

HighlightsThis review focuses on the differences and similarities of photocatalysis and electrocatalysis in the latest 2D nanomaterials.Strategies and traps for performance enhancement of 2D nanocatalysts are highlighted.Challenges, future directions and applications for new photocatalysis and electrocatalysis exploiting 2D nanomaterials are suggested.Photocatalysis and electrocatalysis have been essential parts of electrochemical processes for over half a century. Recent progress in the controllable synthesis of 2D nanomaterials has exhibited enhanced catalytic performance compared to bulk materials. This has led to significant interest in the exploitation of 2D nanomaterials for catalysis. There have been a variety of excellent reviews on 2D nanomaterials for catalysis, but related issues of differences and similarities between photocatalysis and electrocatalysis in 2D nanomaterials are still vacant. Here, we provide a comprehensive overview on the differences and similarities of photocatalysis and electrocatalysis in the latest 2D nanomaterials. Strategies and traps for performance enhancement of 2D nanocatalysts are highlighted, which point out the differences and similarities of series issues for photocatalysis and electrocatalysis. In addition, 2D nanocatalysts and their catalytic applications are discussed. Finally, opportunities, challenges and development directions for 2D nanocatalysts are described. The intention of this review is to inspire and direct interest in this research realm for the creation of future 2D nanomaterials for photocatalysis and electrocatalysis.

HighlightsThis review focuses on recent development of the piezo-electro-chemical coupling multiple systems based on various piezoelectric materials.Comparison of operating conditions and their electro-chemical performance is provided.Challenges, potential future directions, and applications for the development of piezo-electro-chemical hybrid systems are described.Piezoelectric materials have been analyzed for over 100 years, due to their ability to convert mechanical vibrations into electric charge or electric fields into a mechanical strain for sensor, energy harvesting, and actuator applications. A more recent development is the coupling of piezoelectricity and electro-chemistry, termed piezo-electro-chemistry, whereby the piezoelectrically induced electric charge or voltage under a mechanical stress can influence electro-chemical reactions. There is growing interest in such coupled systems, with a corresponding growth in the number of associated publications and patents. This review focuses on recent development of the piezo-electro-chemical coupling multiple systems based on various piezoelectric materials. It provides an overview of the basic characteristics of piezoelectric materials and comparison of operating conditions and their overall electro-chemical performance. The reported piezo-electro-chemical mechanisms are examined in detail. Comparisons are made between the ranges of material morphologies employed, and typical operating conditions are discussed. In addition, potential future directions and applications for the development of piezo-electro-chemical hybrid systems are described. This review provides a comprehensive overview of recent studies on how piezoelectric materials and devices have been applied to control electro-chemical processes, with an aim to inspire and direct future efforts in this emerging research field.

The growing need to process a diverse range of data has ignited effort in developing new multifunctional logic gate devices. In this article, we report a new form of all‐in‐one logic gate system that exploits the photoresponsivity of a self‐powered multifunctional BiFeO3 (BFO) sensor material. The BFO sensor can not only detect both light intensity and temperature, but it can also execute three common logic gates of “AND”, “OR”, and “NOT” by converting optical and thermal inputs into electrical output. The diverse functionality of the BFO logic gate sensor array utilizes the unique light‐and temperature‐controlled energy band structure and carrier behavior of the BFO material. To demonstrate the potential, a 3 × 3 logic gate sensor matrix is developed, which successfully detected light and temperature distributions, and accurately produced the three basic logic gate operations. This work provides a new route to construct highly integrated multifunctional electronic devices for the advancement of large sensing, communication, and computing operations. A self‐powered multifunctional BiFeO3 sensor material possesses a unique light‐and temperature‐controlled energy band structure and carrier behavior. The BFO sensor can not only detect both light intensity and temperature, but it can also execute three common logic gates of “AND”, “OR”, and “NOT” by converting a combination of optical and thermal inputs into electrical output.

HighlightsThe tactile performance of ultralight multifunctional sensors can reach the level of human tactile perception.An individual sensor can provide multiple tactile sensations: pressure, temperature, materials recognition, and 3D location. Therefore, it is no longer necessary to integrate multiple sensing modules with different functions, which greatly simplifies system complexity and reduces energy loss.The tactile system with multimodal learning algorithms has universality and can accommodate object recognition tasks in various application scenarios (e.g., Mars and Kitchen).Humans can perceive our complex world through multi-sensory fusion. Under limited visual conditions, people can sense a variety of tactile signals to identify objects accurately and rapidly. However, replicating this unique capability in robots remains a significant challenge. Here, we present a new form of ultralight multifunctional tactile nano-layered carbon aerogel sensor that provides pressure, temperature, material recognition and 3D location capabilities, which is combined with multimodal supervised learning algorithms for object recognition. The sensor exhibits human-like pressure (0.04–100 kPa) and temperature (21.5–66.2 °C) detection, millisecond response times (11 ms), a pressure sensitivity of 92.22 kPa−1 and triboelectric durability of over 6000 cycles. The devised algorithm has universality and can accommodate a range of application scenarios. The tactile system can identify common foods in a kitchen scene with 94.63% accuracy and explore the topographic and geomorphic features of a Mars scene with 100% accuracy. This sensing approach empowers robots with versatile tactile perception to advance future society toward heightened sensing, recognition and intelligence.

Bistable system exhibiting complex dynamic behavior has been viewed as an efficient method to overcome the issue of linear energy harvester only performing well near the resonant frequency. Moreover, performance enhancement strategies of bistable energy harvesters have been extensively discussed mainly for systems with perfectly symmetric potentials. Due to the presence of imperfections as a result of non-uniform manufacturing of the harvesters, eccentricity of the buckling or magnetic force and uneven gravity, the dynamic characteristics and performance enhancement of asymmetric potential energy harvesting remain an open issue. Therefore, this paper investigates the influence mechanism and performance enhancement of a cantilever-based bistable energy harvesting system with asymmetric potentials. Bifurcation diagrams of the dimensionless electromechanical equations are employed to discover the effect of asymmetric potentials on the output response. Based on the numerical results, a performance enhancement method is proposed by compensating the asymmetric potentials with an appropriate bias of the system to decrease the negative impact of asymmetric potentials on bistable energy harvesting. The optimum bias angle is derived and numerical simulations under constant and sweep frequency excitations demonstrate that the performance of the asymmetric potential bistable energy harvesters is enhanced in a certain bias angle range around the optimum value. Two bistable energy harvesters with different asymmetric potential energy functions are investigated in the experiments and results verify the effectiveness of the proposed method for improving the energy harvesting performance.

HighlightsAn introduction to the range of 2D nanomaterials and their advantages for energy scavenging applications.A variety of methods are presented for converting solar, mechanical, thermal, and chemical energies into electrical energy.A discussion of exclusive applications that exploit 2D nanomaterials for self-powered sensor devices.The development of a nation is deeply related to its energy consumption. 2D nanomaterials have become a spotlight for energy harvesting applications from the small-scale of low-power electronics to a large-scale for industry-level applications, such as self-powered sensor devices, environmental monitoring, and large-scale power generation. Scientists from around the world are working to utilize their engrossing properties to overcome the challenges in material selection and fabrication technologies for compact energy scavenging devices to replace batteries and traditional power sources. In this review, the variety of techniques for scavenging energies from sustainable sources such as solar, air, waste heat, and surrounding mechanical forces are discussed that exploit the fascinating properties of 2D nanomaterials. In addition, practical applications of these fabricated power generating devices and their performance as an alternative to conventional power supplies are discussed with the future pertinence to solve the energy problems in various fields and applications.

The coupling of photovoltaic and pyroelectric effects is a common phenomenon in ferroelectric films and often results in coupling enhancements. Although the coupling effects of a variety of ferroelectric films have been examined in terms of improved performance, they have yet to be quantitatively ranked and assessed. Here, by taking the charge coupling factor, the Yang’s charge, and output energy as metrics to evaluate the coupling performance, a methodology is developed for evaluating the performance of a range ferroelectric films when the pyroelectric and photovoltaic effects are coupled. By experimentally measuring and quantitatively ranking the evaluation metrics, the influence of coupling effects on the output charge and the energy harvesting capabilities of various ferroelectric films can be readily visualized. In addition, the analysis of the underlying reasons for the coupling enhancement enables optimization of the methods to quantify the charge coupling factor. This work provides a unique reference for the selection of materials, optimization of performance, and energy harvesting for coupled ferroelectric film-based generators. The Yang’s charge is proposed as a metric for evaluating the coupling performance in this study. Compared to the conventional charge coupling factor which only considers the relative performance change, the Yang’s charge also considers the absolute performance of the device.

Researchers in different disciplines from all around the world are constantly working on the development of new technologies for harvesting energy from sustainable sources. Among the various alternatives, wind is one of the most abundant resources. Traditionally, wind energy has been harvested to produce electrical energy using various types of wind turbines, including onshore or offshore wind turbines, horizontal or vertical axis wind turbines and micro-wind turbines; or, less traditionally, using wind pumps, or windmills, on sailing boats, and through some sports activities (such as kiteboarding, windsurfing and kitesurfing). In this context, wind energy harvesting using triboelectric nanogenerators (TENGs) has unique characteristics able to challenge the existing wind energy harvesting technologies. Wind-driven TENGs are in fact characterized by simple structures, reduced size and weight, easy installation, flexibility and low-cost operation. Here, starting from a detailed comparison with conventional wind turbine systems, we introduce the technological advancement of wind-driven TENGs. Device structures, materials, fabrication processes and performance characteristics in terms of costs and applications are outlined. Open issues and challenges to be addressed towards the development and industrialization of commercial products are also presented.Wind-driven triboelectric nanogenerators have the potential to revolutionize wind energy harvesting technologies. This Review analyses developments, costs and challenges of wind-driven triboelectric nanogenerators and evaluates research directions towards industrial applications.