Timely monitoring abnormal gaits of teenagers is crucial for their physical health and development. Triboelectric nanogenerators (TENGs) are widely used in the wearable field. Choosing high-performance and safe triboelectric materials to monitor abnormal gaits remains challenging. Polyoxometalates (POMs) nanomaterials can effectively serve as triboelectric materials due to rich surface morphology and large specific surface area. Herein, six different sized POMs nanorods (Ag₄SiW₁₂O₄₀·nH₂O) synthesized through self-assembly of POMs (H₄SiW₁₂O₄₀·nH₂O) were used as triboelectric materials. The TENG composed of nanorod with a diameter of 100 nm and a length of 400-1000 nm has optimal performance with the voltage, current density and charge are 104.3 V, 1127.1 μA·m^-2, and 15.38 nC, respectively, which are more than two times of the TENG composed of POMs (H₄SiW₁₂O₄₀·nH₂O). The optimized TENG maintained a voltage of around 100 V throughout the 1000s stability test. The maximum power amounts to 25.2 μW at 500 MΩ external resistance. The reasons for the improved performance of nanorods TENG compared to POMs TENG are the increase in roughness and surface potential, which was confirmed through AFM and KPFM testing. Furthermore, optimized TENG was applied to the feet of different teenagers and the left and right feet of the same person to monitor abnormal gait. The changes in voltage can sensitively display the inconsistency and abnormal situations of gaits. This study confirms the potential and unique advantages of POMs nanomaterials as triboelectric materials and provides a design scheme for gait monitoring.

SnO₂ is widely used in perovskite photodetectors as an electron transport layer material. The matching of the energy levels of SnO₂ and perovskite is important in carrier transport. Polyoxovanadates (POVs), as semiconductor-like molecules, exhibit good redox and excellent optical properties, which can regulate the energy band structure of SnO₂. Here, K₅MnV₁₁O₃₂·10H₂O (MnV₁₁), K₇MnV₁₃O₃₈·18H₂O (MnV₁₃), (NH₄)₈[V₁₉O₄₁(OH)₉]·11H₂O (V₁₉), and K₁₀[V₃₄O₈₂]·20H₂O (V₃₄) were used to modify an SnO₂ colloidal solution. Energy level tests demonstrated that the conduction band potential (E_CB) of MnV₁₃-modified SnO₂ increased from −4.43 to −4.03 eV, which matched more with the energy level of perovskite. This facilitated the extraction and transmission of photogenerated carriers. X-ray diffraction showed that POV-modified SnO₂ exhibited better crystallinity. Scanning electron microscopy revealed that the grain size of perovskite increased to 580 nm after modification using MnV₁₃. The final results showed that the MnV₁₃-modified perovskite photodetector demonstrated the best efficiency. The photocurrent of the photodetector increased from 26 to 80 μA, and its stability was good. After 720 h, the normalized current values of unencapsulated devices on the MnV₁₃@SnO₂ substrate were maintained at more than 70% of the initial values. The study findings show that introducing POVs into photodetectors is a potential strategy for optimizing the performance of photovoltaic devices.

Atmospheric humidity is a sustainable low-value energy widely existing in natural environment, which is a promising candidate to solve the noncontinuous and low efficiency of low-value energy power generation. Here the mono-substituted Dawson-type polyoxometalates are constructed to be highly dispersed organic ammonium-polyoxoanion clusters and are assembled into thin films power generators with micropores, working in atmospheric humidity. The optimal polyoxometalates generator with the thickness of 7.2 μm and the area of 0.36 cm² produces a voltage of 0.68 V and a current density of 19.5 μA·cm⁻² under simulated natural environment, and works continuously and stably under almost all-natural environments (humidity 10%–90%). The highly dispersed polyoxometalate nanoclusters can form microporous in polyoxometalate films to effectively absorb atmospheric humidity and spontaneously form distribution gradient of water, which is the structural basis of power generation. The continuous power generation may be maintained by the effective adsorption and utilization of H₂O, the huge electrostatic field of organic ammonium-polyoxoanion clusters, and the reasonably designed polyoxometalates containing inorganic small ions with high mobility. It is the first humidity generator designed with polyoxometalates, which may provide a new research direction for polyoxometalates in sustainable utilization of low-value energy.

Polyoxometalates (POMs) can enable energy level tuning to match perovskite layers. They are considered electronic bridges to modify perovskite and improve the performance of photovoltaic devices. Therefore, in the present work, we dispersed the vacancy POMs K₈[α-SiW₁₁O₃₉]·H₂O ({SiW₁₁}) in the metal-organic frameworks (MOFs) to modify the perovskite layer. {SiW₁₁} could adjust the energy level between the layers of the perovskite photodetector. Moreover, the hydrogen bonds formed between SiW₁₁@ZIF-8 and perovskite effectively passivated the grain boundaries (GBs) of the perovskite layer. X-ray diffraction spectroscopy (XRD) showed that the crystallinity of perovskite was significantly improved. In addition, scanning electron microscopy (SEM) images demonstrated that the average size of perovskite grains increased from 254.50 to 719.27 nm, proving the effective passivation of the GBs. Furthermore, a series of tests such as infrared spectroscopy (IR), N₂ adsorption/desorption isotherms, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) also proved that {SiW₁₁} could be successfully loaded into the pores of ZIF-8 through electrostatic interactions. The photocurrent of the SiW₁₁@ZIF-8 doped device reached 41.95 μA, about three times as high as that of the blank device (14.41 μA). Also, under unencapsulated conditions, it could still maintain more than 90% stability for nearly 700 h. This work demonstrates the potential application of POM@MOF-type composites in the field of perovskite photodetectors.

Molybdenum carbide/molybdenum nitride hybrid N-doped graphene (abbreviated as Mo₂C/MoN/NG), as an efficient electrocatalyst for the hydrogen evolution reaction (HER), was synthesized via simple ion-exchange resin synthesis followed by a two-step annealing process, which increased the dispersion degree of the electrocatalyst's active sites on the support skeleton and simplified the synthetic conditions. Additionally, N-doped graphene (NG) enhanced the electron transfer and reduced the inner resistance. The material has a graphene-like morphology and highly dispersed Mo2C/MoN nanoparticles about 2 nm in diameter on the NG. X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy revealed that Mo₂C/MoN/NG consisted of Mo₂C and MoN composited together. Finally, Mo₂C/MoN/NG exhibited remarkable performance as an electrocatalyst for the HER with a small overpotential of 78.82 mV and a small Tafel slope of 39.3 mV·dec^-1 in a 0.5 mol·L^-1 H₂SO₄ solution. Its activity was approximately 30% lower than that of 20% Pt/C and 60% higher than that of NG. Also, it exhibited a low onset overpotential of 24.82 mV, which is similar to the theoretical HER potential. Our work provides a foundation for advanced HER applications of molybdenum compounds.