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Metal–oxide–semiconductor gas-sensing materials, due to their high operating temperatures and often using rigid materials as substrates, limit their application in the field of wearable electronic devices. In this work, a skin–core structure electrospun nanofiber core-spun yarn (ES-PY) with polypropylene yarn (PY) as the core yarn and polyvinylidene fluoride (PVDF) nanofibers as the wrapping layer was prepared by a coaxial electrospinning nanofiber yarn-forming technique. The yarn sensor (ZS-PY) was prepared by compounding it with ZnO/SnO2N–n-type metal–oxide–semiconductor heterojunction gas-sensing material prepared by a two-step hydrothermal method. The obtained yarn sensor utilized the synergistic effect of ZnO and SnO2, and the nanostructure effect of nanofibers and exhibited excellent gas-sensing performance for ammonia (NH3). The response to 100 ppm NH3 can reach 60.41%, with rapid response/recovery time even when exposed to an ammonia concentration as low as 10 ppm at room temperature. In addition, it has excellent gas selectivity and stability. Meanwhile, the yarn sensor retains the mechanical strength and flexibility of its core yarn, so it can be processed into specific electronic textiles using various textile molding techniques and is expected to be applied to the development of wearable smart textiles. [ABSTRACT FROM AUTHOR]

It is a great challenge to develop CoO-based electrocatalysts of excellent performance for oxygen evolution reaction, because of its poor electrical conductivity. In this paper, we have prepared pristine CoO (P-CoO) and CoO-C polyhedrons via two different calcination strategies. Then we have also displayed a simple and green reduction method to synthesize reduced CoO (R-CoO) polyhedron with abundant surface oxygen vacancies. Oxygen vacancies and the doping of carbon species can enhance conductivity of electrocatalysts, thus, improving their electrocatalytic activities obviously. R-CoO and CoO-C polyhedrons show lower overpotentials of 380 and 420 mV, respectively, compared to P-CoO polyhedron (520 mV) at the current density of 10 mA cm in 1 M KOH solution (pH 13.7). And they also have smaller Tafel slopes of 86 and 78 mV dec than that of P-CoO polyhedron (93 mV dec), respectively. The integrated strategy reported here provides the way to design high-performance electrocatalysts for water oxidation. [ABSTRACT FROM AUTHOR]