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Abstract 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.

ABSTRACT Tactile sensors are a potential solution for material identification. However, current potential tactile sensors for material identification are pressed, expensive, and applications‐confined. Here we report a clamped‐on pyroelectric tactile sensor on the basis of a ferroelectric Bi0.5Na0.5TiO3 material to identify different film materials. The fabricated device exhibits different heat absorption capacities while in contact with different materials, leading to a different temperature change in the ferroelectric material under the same illumination. As a result, the device can recognize different materials by comparing the pyroelectric charge via integrating the obtained current under the same irradiation of 365 nm light‐emitting diode. The clamped‐on pyroelectric tactile sensor can identify six individual materials with a high accuracy of 98.8% and a fast response of 40 ms. All of the above processes can be accomplished with an intelligent material identification system. The device provides a new solution for material identification and lays a foundation for smart factories and laboratories.

Ferroelectric film materials have attracted significant interest due to their potential for harvesting various forms of clean energy from natural environmental sources. However, the photoelectric performance of these materials is frequently constrained by heat generation during light absorption, resulting in significant thermal losses. Most of ferroelectric films produce photocurrent and thermocurrent with opposite polarity, thus weakening the coupled photo-thermoelectric output of the devices. Here we report on a LaNiO3/BiMn2O5(BMO)/ITO ferroelectric film to produce photocurrent and thermocurrent with the same polarity. The polarity of the photocurrent generated by the BMO film is shown to be determined solely by the direction of spontaneous polarization, overcoming the detrimental effect of Schottky barrier for energy harvesting in device. We propose a new strategy to enhance the coupling factor, thereby offering valuable new insights for optimizing the utilization of ferroelectric materials in both light and heat energy applications.

The encapsulation of metal-based phase change materials using ceramics can realize safe and effective storage of high-temperature thermal energy. However, the use of a low toughness ceramic shell around the microcapsules cannot ensure the provision of a high latent heat and thermal cyclic stability. Here, we provide a new and effective design strategy for preparing biomimetic Al–Si microcapsules that are based on a sea-shell corrugated structure and a nano-scale corundum-mullite composite shell. The latent heat of the microcapsules was over 400 J/g, much greater than other metal-based microcapsules reported to date. The unique biomimetic-corrugated structure microcapsules obtained by a heat treatment at 1000 °C exhibited excellent thermal stability, achieving near zero heat loss after 5000 thermal cycles, whose latent heat of absorption and release reached up to 448.3 J/g and 451.8 J/g respectively. Furthermore, the microcapsules possessed a giant heat storage density of 945.8 J/g within 300–700 °C, and the performance figure of merit was 6384.2 × 106 J2·K−1·s−1·m−4, approximately 15 times higher than that of commercial solar salt. This new approach provides a pathway the practical application of Al–Si alloys as thermal storage materials for renewable energy applications.

Highlights The 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).

Abstract Optoelectronic logic gates have emerged as one of the key candidates for the creation of next generation logic devices. However, current optoelectronic logic gates can provide only one or two logic gates, severely limiting their applications. Here we report a self‐powered and mechanically flexible device based on a BaTiO3 ferroelectric film to produce multi‐modal logic gates. By exploiting the photo‐induced photovoltaic and pyroelectric effects of a Schottky junction which is created between BaTiO3 and LaNiO3, the device is able to provide five different optoelectronic logic gates, which can be operated using input lasers of different wavelength (405 or 785 nm). The mode of operation of the logic gate can be switched by controlling the wavelength and intensity of the input laser, where the switching process is both lossless and reversible. A logic gate array was designed to conduct the five logic operations, with 100% accuracy, thereby providing application potential for the Internet of Things, big data, and secure solutions for data processing and transmission.

Abstract Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light, mechanical and thermal energy and achieve a stable direct current output. Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage, while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics. Here, we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO3 ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies. This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3% energy enhancement to achieve a multi-dimensional "1 + 1 > 2" coupling enhancement in terms of current, charge and energy. This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.

Abstract We report the scalable fabrication of CdS/ZnS 1D/2D heterojunctions under ambient air conditions (i.e., room temperature and atmospheric pressure) in which ZnS nanoparticles are anchored on the surface of CdS nanosheets. The as‐formed heterojunctions exhibit a significantly enhanced photocatalytic H2 evolution rate of 14.02 mmol h−1 g−1 when irradiated with visible light, which is ~10 and 85 times higher than those of pristine CdS nanosheets and CdS nanoparticles, respectively, and superior to most of the CdS‐based photocatalysts reported to date. Furthermore, they provide robust photocatalytic performance with demonstratable stability over 58 h, indicating their potential for practical applications. The formation of 1D/2D heterojunctions not only provides improved exposed active sites that respond to illumination but also provides a rapid pathway to generate photogenerated carriers for efficient separation and transfer through the matrix of single‐crystalline CdS nanosheets. In addition, first‐principles simulations demonstrate that the existence of rich Zn vacancies increases the energy level of the ZnS valence band maximum to construct type‐II and Z‐scheme mixed heterojunctions, which plays a critical role in suppressing the recombination of carriers with limited photocorrosion of CdS to enhance photocatalytic behavior.

Abstract 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.

Abstract 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.

Abstract 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.

Abstract 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.

Summary: Wearable electronics are becoming increasingly important for medical applications as they have revolutionized the way physiological parameters are monitored. Ferroelectric materials show spontaneous polarization below the Curie temperature, which changes with electric field, temperature, and mechanical deformation. Therefore, they have been widely used in sensor and actuator applications. In addition, these materials can be used for conversion of human-body energy into electricity for powering wearable electronics. In this paper, we review the recent advances in flexible ferroelectric materials for wearable human energy harvesting and sensing. To meet the performance requirements for medical applications, the most suitable materials and manufacturing techniques are reviewed. The approaches used to enhance performance and achieve long-term sustainability and multi-functionality by integrating other active sensing mechanisms (e.g. triboelectric and piezoresistive effects) are discussed. Data processing and transmission as well as the contribution of wearable piezoelectric devices in early disease detection and monitoring vital signs are reviewed.

Summary: As the world's demand for alternative energy increases, the development of green energy harvesters becomes ever more important. As a result, the creation of triboelectric (TENG), piezoelectric (PENG), and pyroelectric nanogenerators, electromagnetic generators (EMG), solar cells, and electrochemical cells is attracting interest in an effort to convert mechanical, thermal, magnetic, solar, and chemical energy into electricity. In order to take advantage of the ambient energies from our surrounding environment, the design of hybridized generator units that can simultaneously scavenge energy in a variety of forms continues to develop. These systems are being considered to satisfy the energy needs of a range of electronic devices and adapt to a variety of working environments. This review demonstrates the latest progress in hybridized nanogenerators in accordance with their structure, operating principle, and applications. These studies demonstrate new approaches to developing hybrid techniques and novel assemblies for efficiently harvesting environmental energy from a number of sources.

The adaptation of standard integrated circuit (IC) technology as a transducer in cell-based biosensors in drug discovery pharmacology, neural interface systems and electrophysiology requires electrodes that are electrochemically stable, biocompatible and affordable. Unfortunately, the ubiquitous Complementary Metal Oxide Semiconductor (CMOS) IC technology does not meet the first of these requirements. For devices intended only for research, modification of CMOS by post-processing using cleanroom facilities has been achieved. However, to enable adoption of CMOS as a basis for commercial biosensors, the economies of scale of CMOS fabrication must be maintained by using only low-cost post-processing techniques. This review highlights the methodologies employed in cell-based biosensor design where CMOS-based integrated circuits (ICs) form an integral part of the transducer system. Particular emphasis will be placed on the application of multi-electrode arrays for in vitro neuroscience applications. Identifying suitable IC packaging methods presents further significant challenges when considering specific applications. The various challenges and difficulties are reviewed and some potential solutions are presented.