Achieving active and stable oxygen evolution reaction (OER) in acid media based on single-atom catalysts is highly promising for cost-effective and sustainable energy supply in proton electrolyte membrane electrolyzers. Here, we report an atomically dispersed Ru1-N4 site anchored on nitrogen-carbon support (Ru-N-C) as an efficient and durable electrocatalyst for acidic OER. The single-atom Ru-N-C catalyst delivers an exceptionally intrinsic activity, reaching a mass activity as high as 3571 A gmetal−1 and turnover frequency of 3348 O2 h−1 with a low overpotential of 267 mV at a current density of 10 mA cm−2. The catalyst shows no evident deactivation or decomposition after 30-hour operation in acidic environment. Operando synchrotron radiation X-ray absorption spectroscopy and infrared spectroscopy identify the dynamic adsorption of single oxygen atom on Ru site under working potentials, and theoretical calculations demonstrate that the O-Ru1-N4 site is responsible for the high OER activity and stability.

The development of atomically precise dinuclear heterogeneous catalysts is promising to achieve efficient catalytic performance and is also helpful to the atomic-level understanding on the synergy mechanism under reaction conditions. Here, we report a Ni 2 (dppm) 2 Cl 3 dinuclear-cluster-derived strategy to a uniform atomically precise Ni 2 site, consisting of two Ni 1 −N 4 moieties shared with two nitrogen atoms, anchored on a N-doped carbon. By using operando synchrotron X-ray absorption spectroscopy, we identify the dynamically catalytic dinuclear Ni 2 structure under electrochemical CO 2 reduction reaction, revealing an oxygen-bridge adsorption on the Ni 2 −N 6 site to form an O−Ni 2 −N 6 structure with enhanced Ni−Ni interaction. Theoretical simulations demonstrate that the key O−Ni 2 −N 6 structure can significantly lower the energy barrier for CO 2 activation. As a result, the dinuclear Ni 2 catalyst exhibits >94% Faradaic efficiency for efficient carbon monoxide production. This work provides bottom-up target synthesis approaches and evidences the identity of dinuclear sites active toward catalytic reactions.

Recently, electronic skin and smart textiles have attracted considerable attention. Flexible sensors, as a kind of indispensable components of flexible electronics, have been extensively studied. However, wearable airflow sensors capable of monitoring the environment airflow in real time are rarely reported. Herein, by mimicking the spider's fluff, an ultrasensitive and flexible all‐textile airflow sensor based on fabric with in situ grown carbon nanotubes (CNTs) is developed. The fabric decorated with fluffy‐like CNTs possesses exceptionally large contact area, endowing the airflow sensor with superior properties including ultralow detection limit (≈0.05 m s−1), multiangle airflow differential response (0°–90°), and fast response time (≈1.3 s). Besides, the fluffy fabric airflow sensor can be combined with a pristine fabric airflow sensor to realize highly sensitive detection in a wide airflow range (0.05–7.0 m s−1). Its potential applications including transmitting information according to Morse code by blowing the sensors, monitoring increasing and decreasing airflow velocity, and alerting blind people walking outside about potential hazard induced by nearby fast‐moving objects are demonstrated. Furthermore, the airflow sensor can be directly integrated into clothing as stylish designs without sacrificing comfortness. It is believed that the ultrasensitive all‐textile airflow sensor holds great promise for applications in smart textiles and wearable electronics.

Skin, the largest organ in the human body, is sensitive to external stimuli.In recent years, an increasing number of skin-inspired electronics, including wearable electronics, implantable electronics, and electronic skin, have been developed because of their broad applications in healthcare and robotics.Physical sensors are one of the key building blocks of skin-inspired electronics. Typical physical sensors include mechanical sensors, temperature sensors, humidity sensors, electrophysiological sensors, and so on. In this review, we systematically review the latest advances of skin-inspired mechanical sensors, temperature sensors, and humidity sensors. The working mechanisms, key materials, device structures, and performance of various physical sensors are summarized and discussed in detail. Their applications in health monitoring, human disease diagnosis and treatment, and intelligent robots are reviewed. In addition, several novel properties of skin-inspired physical sensors such as versatility, self-healability, and implantability are introduced. Finally, the existing challenges and future perspectives of physical sensors for practical applications are discussed and proposed. K E Y W O R D Selectronics skin, flexible electronics, humidity sensors, mechanical sensors, temperature sensors, wearable sensors

especially irreplaceable role in the area of precision actuations, such as in lens driving in optical assemblies and optical communication, micro/nanopositioning in semiconductor and microelectromechanical system (MEMS) manufacturing, nanoscanning probes in scanning electron microscopy, etc. [1,2] Due to the huge market demand for piezoelectric actuators, the progress of piezoelectric materials and devices is new every year. New piezoelectric material compositions, novel fabrication processes and full assessments of materials are widely studied to improve the material properties or make devices more suitable for actuation applications. Pb(Zr,Ti)O 3 (PZT)-based ceramics are still dominant in the market because of their high piezoelectric properties, low cost, and stable thermal performance. Although single crystals' piezoelectric and electromechanical coupling coefficients show great advances compared with ceramics, actuation applications are limited to only some special cases due to high cost of single crystals. [3] Lead-free ceramics have also experienced fast development, and some compositions have been found to exhibit large strains, but they also result in large energy losses under high electric fields. This type of ceramic may have potential for use in nonresonant actuator applications. Additionally, various actuation configurations operating via different working modes or mechanisms have been developed.In this review, we first introduce materials used for the corresponding actuators and motors, and then, recent developments in the area of actuators including nonresonant multilayer ceramic actuators, step motors and inertial motors, and resonant ultrasonic motors, such as linear motors, rotary motors, multi-DOF motors, and MEMS actuators, are discussed. Actuation performance parameters such as the stroke length, resolution, loading force, velocity, lifetime, and power efficiency are the main concerns. We try to clarify and compare differences between devices. Finally, the challenges and outlook for the piezoelectric actuators are discussed. Piezoelectric Materials for ActuatorsPiezoelectricity in materials can be attributed to an asymmetric center of the crystalline structure or molecular chain, which Piezoelectric actuators are unique driving force-generation devices, which can transfer input electric energy into force, displacement, or movement outputs efficiently and precisely via piezoelectric effect-based electromechanical coupling instead of electromagnetic induction. In comparison with traditional electromagnetic actuators, the most important features of the piezoelectric actuators are their compact size, flexible design, and ability to provide nanometer or sub-micrometer positioning. Here, recent progress in nonresonance piezoelectric actuators including multilayer ceramic actuators, step motors, inertial motors, and resonance ultrasonic motors, such as linear motors, rotary motors, multidegree of freedom motors, and microelectromechanical system actuators, is comprehensively presented. The working p...

Recent flood events have demonstrated a demand for satellite-based inundation mapping in near real-time (NRT). Simulating and forecasting flood extent is essential for risk mitigation. While numerical models are designed to provide such information, they usually lack reference at fine spatiotemporal resolution. Remote sensing techniques are expected to fill this void. Unlike optical sensors, synthetic aperture radar (SAR) provides valid measurements through cloud cover with high resolution and increasing sampling frequency from multiple missions. This study reviews theories and algorithms of flood inundation mapping using SAR data, together with a discussion of their strengths and limitations, focusing on the level of automation, robustness, and accuracy. We find that the automation and robustness of non-obstructed inundation mapping have been achieved in this era of big earth observation (EO) data with acceptable accuracy. They are not yet satisfactory, however, for the detection of beneath-vegetation flood mapping using L-band or multi-polarized (dual or fully) SAR data or for urban flood detection using fine-resolution SAR and ancillary building and topographic data.

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Modulating the electronic structure of cocatalysts is critical for designing active sites toward efficient photocatalytic H 2 evolution. Here, we report an electronic modulation in atomically dispersed Pt as highly efficient H 2 -evolution sites on graphitic carbon nitride (g-C 3 N 4 ) nanosheets. Synchrotron radiation X-ray spectroscopic results confirm the singly dispersed Pt atoms anchored on g-C 3 N 4 via forming "Pt 1 −N 4 " moiety, where the strong interaction of Pt with supports leads to the redistribution of Pt valence electrons with the highly vacant 5d orbital. Mechanistic investigations reveal that the immobilization of Pt single atoms with electron-deficient 5d orbitals on g-C 3 N 4 nanosheets not only facilitate the separation of electron−holes pair but also optimize the water reduction kinetics on the surface. As a result, the Pt single atoms photocatalyst achieves a high intrinsic activity with turnover frequency of 250 h −1 , about 13 times higher than the 19.5 h −1 of its nanocrystal counterpart.