Harvesting energy from ubiquitous moisture is attracting growing interest for directly powering electronic devices. However, it is still challenging to fabricate high-performing moisture-electric ...generators (MEGs) with high and stable electric output. Herein, we report a simple strategy to modify the oxygen-based groups of graphene oxide using hydrochloric acid treatment, which boosts the electric output based on the device structure of graphene oxide/polyvinyl alcohol (GO/PVA) MEGs. The resulting MEG enables a stable voltage of 0.85 V and a current of 9.28 μA (92.8 μA∙cm-2), which are among the highest values reported so far. More excitingly, electric output gets further improved by simply assembling four MEG units in series or parallel. Moreover, the MEG shows great commercial potential for flexible and wearable applications. Driven by these advancements, the assembled MEGs can successfully power sensors and calculators. This work opens a new era of advance for a new energy conversion technology able to directly powering electronic devices.
Schematic illustration of graphene oxide-based MEG powering electronic devices Display omitted
•Acidification is a facile and effective way to tune the functional group density of GO materials.•MEGs achieve one of the highest continuous electrical outputs with a voltage of 0.85 V and current density of 92.8 μA∙cm-2.•The density of CO bonds significantly affects the output, providing a guideline to select the target materials.•A commercial pressure sensor and digital calculator can be directly powered by a single MEG and MEG array, respectively.
The working mechanisms, cathode design, recent progress and challenges of oxide-based cathodes for zinc ion batteries (ZIBs) are systematically reviewed.
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With the increasing demands ...for electrical energy storage technologies, rechargeable zinc ion batteries (ZIBs) have been rapidly developed in recent years owing to their high safety, low cost and high energy storage capability. The cathode is an essential part of ZIBs, which hosts zinc ions and determines the capacity, rate and cycling performance of the battery. The mainstream cathodes for ZIBs are oxide-based materials with tunnel, layer or 3D crystal structures. In this review, we mainly focus on the latest advanced oxide-based cathode materials in ZIBs, including manganese oxides, vanadium oxides, spinel compounds, and other metal oxide based cathodes. In addition, the mechanisms of zinc storage and recent development in cathode design have been discussed in detail. Finally, current challenges and perspectives for the future research directions of oxide-based cathodes in ZIBs are presented.
Power generation by converting energy from the ambient environment has been considered a promising strategy for developing decentralized electrification systems to complement the electricity supply ...for daily use. Wet gases, such as water evaporation or moisture in the atmosphere, can be utilized as a tremendous source of electricity by emerging power generation devices, that is, moisture‐enabled‐electric nanogenerators (MEENGs). As a promising technology, MEENGs provided a novel manner to generate electricity by harvesting energy from moisture, originating from the interactions between water molecules and hydrophilic functional groups. Though the remarkable progress of MEENGs has been achieved, a systematic review in this specific area is urgently needed to summarize previous works and provide sharp points to further develop low‐cost and high‐performing MEENGs through overcoming current limitations. Herein, the working mechanisms of MEENGs reported so far are comprehensively compared. Subsequently, a systematic summary of the materials selection and fabrication methods for currently reported MEENG construction is presented. Then, the improvement strategies and development directions of MEENG are provided. At last, the demonstrations of the applications assembled with MEENGs are extracted. This work aims to pave the way for the further MEENGs to break through the performance limitations and promote the popularization of future micron electronic self‐powered equipment.
This review focuses on the recent development of moisture‐enabled‐electric nanogenerators (MEENGs), which are distinguished from traditional hydropower production by directly generating electricity from ubiquitous moisture in the natural environment. In addition, MEENGs are also promising for next‐generation portable self‐powered or battery‐free systems, enabling the creation of a new range of intelligent device components to upgrade artificial intelligence and Internet of Things applications.
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The crystalline and electronic structures are two important factors for the design of electrocatalysts. In this work, Co-doped MnO electrocatalysts grown on nickel foam (NF) were ...prepared by a facile hydrothermal reaction, followed by H2 treatment process. The electrocatalytic performance of MnO was significantly improved after doping with Co and the Co0.1Mn0.9O-NF sample achieved excellent oxygen evolution reaction (OER) performance with low overpotential (370 mV at 10 mA cm−2) and reasonable Tafel slope (85.6 mV dec-1). Significantly, the low work function was obtained in the Co0.1Mn0.9O-NF sample (4.37 eV), which could accelerate the charge transfer process of the OER activity. The excellent OER performance of the Co0.1Mn0.9O-NF sample is also attributed to the rich active sites, which improved electrical conductivity and enlarged electrochemical surface areas.
Recently, there has been a surge of interest in nanogenerators within the scientific community because their immense potential for extracting energy from the surrounding environment. A promising ...approach involves utilizing ambient moisture as an energy source for portable devices. In this study, moisture-enabled nanogenerators (MENGs) are devised by integrating heterojunctions of graphene oxide (GO) and reduced graphene oxide (rGO). Benefiting from the unique structure, a larger ion concentration gradient is achieved as well as a lower resistance, which leads to enhanced electricity generation. The resulting MENG generates a desirable open-circuit voltage of 0.76 V and a short-circuit current density of 73 µA cm
with a maximum power density of 15.8 µW cm
. Notably, the designed device exhibits a high voltage retention of more than 90% after 3000 bending cycles, suggesting a high potential for flexible applications. Moreover, a large-scale integrated MENG array is developed by incorporating flexible printed circuit technology and connecting it to a power management system. This integrated system can provide ample energy to operate an electronic ink display and drive a heart rate sensor for health monitoring. The outcomes of this research present a novel framework for advancing next-generation self-powered flexible devices, thereby demonstrating significant promise for future wearable electronics.
In view of the drawbacks of high-cost and inherent brittleness of indium tin oxide (ITO) based transparent electrodes, silver nanowires (AgNW) networks have been considered as promising alternatives ...owing to their excellent optical transparency, mechanical flexibility, and compatibility with large scale printing process. AgNWs have been applied as transparent electrodes in many electronic devices, however, in many cases, they inevitably interact with the surrounding media (e.g., temperature, electric field, UV light irradiation, etc.) which will cause performance degradation. For instance, AgNWs show a typical Rayleigh instability phenomenon when the external temperature is higher than a critical point. Moreover, a specific range of UV light or/and intensive current density can accelerate the partial breakage of AgNW networks. To develop highly stable AgNW based transparent electrodes for flexible electronic devices, intensive research works have been conducted to mitigate the degeneration issues. In this review, the degradation mechanisms of AgNW based transparent electrodes have been systematically studied. Furthermore, the mainstream strategies for mitigating the deterioration of AgNW based transparent electrodes have been analyzed. Finally, the present challenges in current materials processing, and future research directions have been discussed.
Artificial perception technologies capable of sensing and feeling mechanical stimuli like human skins are critical enablers for electronic skins (E‐Skins) needed to achieve artificial intelligence. ...However, most of the reported electronic skin systems lack the capability to process and interpret the sensor data. Herein, a new design of artificial perceptual system integrating ZnO‐based synaptic devices with Pt/carbon nanofibers‐based strain sensors for stimuli detection and information processing is presented. Benefiting from the controllable ion migration after indium doping, the device can emulate various essential functions, such as short‐term/long‐term plasticity, paired‐pulse facilitation, excitatory post‐synaptic current, and synaptic plasticity depending on the number, frequency, amplitude, and width of the applied pulses. The Pt/carbon nanofibers‐based strain sensors can detect subtle human motion and convert mechanical stimuli into electrical signals, which are further processed by the ZnO devices. By attaching the integrated devices to finger joints, it is demonstrated that they can recognize handwriting and gestures with a high accuracy. This work offers new insights in designing artificial synapses and sensors to process and recognize information for neuromorphic computing and artificial intelligence applications.
A new bio‐inspired artificial perceptual system is fabricated by integrating In‐doped ZnO switching devices with Pt/carbon nanofiber strain sensors. The doped device successfully emulates typical synaptic functionalities. By attaching five strain sensors on the finger joints, the new device is demonstrated to recognize various hand gestures at a high recognition accuracy. Furthermore, the developed system can identify different alphabets for handwriting recognition.
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•A facile hydrothermal approach is reported to control the phase transition of MnO2.•The in-situ growth of MnO2 on NF has a hybrid nanowires-nanosheets morphology.•Rich Mn3+ and O ...vacancies, and well band-alignment tunability has been achieved.•The α-MnO2 with combined merits exhibits superior electrocatalytic performance.
The structural and electronic properties of MnO2 based electrocatalysts are key factors determining their electrochemical performance. To date, it is still challenging to synergistically tune the crystal structure, morphology, and electronic band (i.e., band gap and band alignments) of MnO2 through facile synthesis approaches. This study has reported a one-step hydrothermal method to synthesize a prototypical MnO2 electrocatalyst with optimized structural and electrochemical properties. By simply adjusting the hydrothermal time, the phase transition from polymorphic δ to α can be induced in MnO2. The obtained nanowires on nanosheets structure grown in-situ on nickel foam provides a large surface area, great accessible active sites, and good mass/charge transfer efficiency. Further investigation through first-principles calculations reveals that compared to δ-MnO2, the α-MnO2 polymorph with rich oxygen vacancies has better band-alignment tunability, which is also beneficial for improving the electrochemical performance. The α phase MnO2 exhibits superior catalytic performance for both OER and HER (OER overpotential of 0.45 V at 50 mA cm−2 and HER overpotential of 0.14 V at 50 mA cm−2). The developed synthesis method can be extended to catalyst designs that require precise control of phase and morphology evolution in a wide range of applications.
Artificial synapses are memristor-based devices mimicking biological synapses, and they are used in neuromorphic computing systems that process information in a parallel, energy efficient way and ...store information in an analog, non-volatile form. The next generation of computing systems are anticipated to use memristive circuits, as they can overcome the shortcomings of the von Neumann computer architecture in which the levels of memory and the CPU are separated, creating a bottleneck that causes energy-loss during information transfer. Memristors are utilized to build Resistive Random Access Memory (RRAM) that allows for multi-level data storage and construction of self-correcting, autonomous learning systems that can solve complex computational tasks that have historically required super-computing hardware. Artificial synapses have received attention since HP Labs fabricated the first practical memristor device. In this review we summarize the working principles, device architectures, fabrication and processing techniques, as well as the strategies for materials selection including binary metal oxide, perovskite, polymer, and organic materials. We also discuss the applications and challenges of using artificial synapses in artificial intelligence tasks such as image recognition, tactile sensing and speech recognition.
This review focuses on recent development in artificial synaptic devices, including working principles, device structures, processing techniques, energy consumption, the functional materials of artificial synapses and applications.
Moisture-electric generators (MEGs), harvesting ubiquitous moisture from the environment for electricity generation, have attracted great interest as power supply devices. However, there are great ...challenges associated with material availability, fabrication accessibility and operation environment, which are key factors to achieve high output with low cost for practical applications, and a deeper understanding of the underlying mechanism of interactions between MEGs and water is urgently required. Here, a whey protein available in supermarkets is used to fabricate low-cost MEGs with controllable performance through tuning surface charges and hydrophilicity, which provides new insights into the electricity generation mechanism and large-scale application. The MEGs exhibit the highest voltage output of 1.45 V at a room humidity level of 40% relative humidity. The whey protein films possess the merits of low cost (70 times cheaper than commonly used polymers), being flexible and semi-transparent, and having self-healing ability, presenting excellent comprehensive device performance. Besides, MEGs can operate well at extreme temperatures (−20 °C or 50 °C) and power a location tracker in a desert with 26% relative humidity. The modified functional layers with selective ion absorption and controllable outputs provided a deeper understanding of electricity generation in MEGs and demonstrated great potential in powering a wide range of electronic devices in various dynamic environments with high sustainability and reliability.
Illustration of protein-based MEG generating electricity by absorbing water from moisture.
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