Developing efficient electrocatalysts for an oxygen evolution reaction (OER) is important for renewable energy storage. Here, we design high-density Ir single-atom catalysts supported by CoO x amorphous nanosheets (ANSs) for the OER. Experimental results show that Ir single atoms are anchored by abundant surface-absorbed O in CoO x ANSs. Ir single-atom catalysts possess ultrahigh mass activity that is 160-fold of commercial IrO 2 . The OER of IrCoO x ANSs reached a record low onset overpotential of less than 30 mV. In situ X-ray absorption spectroscopy reveals that Ir−O−Co pairs directly boosted the OER efficiency and enhanced the Ir stability.

Palladium diselenide (PdSe2) is an emerging 2D layered material with anisotropic optical/electrical properties, extra‐high carrier mobility, excellent air stability, etc. So far, ultrathin PdSe2 is mainly achieved via mechanical exfoliation from its bulk counterpart, and the direct synthesis is still challenging. Herein, the synthesis of ultrathin 2D PdSe2 on conductive Au foil substrates via a facile chemical vapor deposition route is reported. Intriguingly, an anisotropic growth behavior is detected from the evolution of ribboned flakes with large length/width ratios, which is well explained from the orthorhombic symmetry of PdSe2. A unique even‐layered growth mode from 2 to 20 layers is also confirmed by the perfect combination of onsite scanning tunneling microscopy characterizations, through deliberately scratching the flake edge to expose both even and odd layers. This even‐layered, ribboned 2D material is expected to serve as a perfect platform for exploring unique physical properties, and for developing high‐performance electronic and optoelectronic devices.

Hierarchical Cr-doped WO3 microspheres have been successfully synthesized for efficient sensing of H2S gas at low temperatures. The hierarchical structures provide an effective gas diffusion path via well-aligned micro-, meso-, and macroporous architectures, resulting in significant enhancement in sensing response to H2S. The temperature and gas concentration dependence on the sensing properties elucidate that Cr dopants remarkably improve the response and lower the sensor' operating temperature down to 80 °C. Under 0.1 vol % H2S, the response of Cr-doped WO3 sensor is 6 times larger than pristine WO3 sensor at 80 °C. We suggest the increasing number of oxygen vacancies created by Cr dopants to be the underlying reason for enhancement of charge carrier density and accelerated reactions with H2S.

Avermectin and its analogues are produced by the actinomycete Streptomyces avermitilis and are widely used in the field of animal health, agriculture, and human health. Here we have adopted a practical approach to successfully improve avermectin production in an industrial overproducer. Transcriptional levels of the wildtype strain and industrial overproducer in production cultures were monitored using microarray analysis. The avermectin biosynthetic genes, especially the pathway-specific regulatory gene, aveR, were up-regulated in the high-producing strain. The upstream promoter region of aveR was predicted and proved to be directly recognized by σ hrdB in vitro. A mutant library of hrdB gene was constructed by error-prone PCR and selected by high-throughput screening. As a result of evolved hrdB expressed in the modified avermectin high-producing strain, 6.38 g∕L of avermectin B1a was produced with over 50% yield improvement, in which the transcription level of aveR was significantly increased. The relevant residues were identified to center in the conserved regions. Engineering of the hrdB gene can not only elicit the overexpression of aveR but also allows for simultaneous transcription of many other genes. The results indicate that manipulating the key genes revealed by reverse engineering can effectively improve the yield of the target metabolites, providing a route to optimize production in these complex regulatory systems.precision engineering | RNA polymerase | overproduction

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