Exploring the oxygen electrocatalysts with both high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance is crucial to developing the rechargeable Zn−air batteries (ZABs). Herein, we prepared a bifunctional three-dimensional graphene-like iron-nitrogen doped oxygen electrocatalyst (3D Fe/N-G#4, polyacrylamide (PAM):-NaCl = 1:4, mass ratio) by a facile synthesis with PAM and iron as precursors and NaCl as template. The NaCl template melted during the pyrolysis process, which could fabricate a stable 3D network structure in the precursors to form more mesopores, higher specific surface area, and more exposed active sites and prevent the loss of precursors. The low-cost and water-soluble PAM as the N precursor provided abundant N and dissolved adequately with NaCl solution. The Fe precursor coordinated with the N to form Fe-N x active sites that were investigated by HR-TEM, XRD, XPS, and RDE techniques. The 3D Fe/N-G#4 exhibited excellent electrochemical activity with a high half-wave potential (0.852 V vs RHE) for ORR and a low overpotential (393 mV at 10 mA cm −2 ) for OER in the alkaline conditions. In addition, the homemade rechargeable ZAB based on the prepared 3D Fe/N-G#4 exhibits high power density (168.2 mW cm −2 ) and excellent discharge-charge cycling stability (over 60 h) at 20 mA cm −2 . This work provides a cost-efficient, simple, and eco-friendly method to synthesize excellent bifunctional nonnoble electrocatalysts for commercialization of ZABs.

Fungi of the genus Pestalotiopsis have drawn attention for their capability to produce an array of bioactive secondary metabolites that have potential for drug development. Here, we report the determination of a polyketide derivative compound, pestalotiollide B, in the culture of the saprophytic fungus Pestalotiopsis microspora NK17. Structural information acquired by analyses with a set of spectroscopic and chromatographic techniques suggests that pestalotiollide B has the same skeleton as the penicillide derivatives, dibenzodioxocinones, which are inhibitors of cholesterol ester transfer protein (CETP), and as purpactins A and C', inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). Strain NK17 can make a fairly high yield of pestalotiollide B (i.e., up to 7.22 mg/l) in a constitutive manner in liquid culture. Moreover, we found that a putative histone deacetylase gene, designated as hid1, played a role in the biosynthesis of pestalotiollide B. In the hid1 null mutant, the yield of pestalotiollide B increased approximately 2-fold to 15.90 mg/l. In contrast, deletion of gene hid1 led to a dramatic decrease of conidia production of the fungus. These results suggest that hid1 is a modulator, concerting secondary metabolism and development such as conidiation in P. microspora. Our work may help with the investigation into the biosynthesis of pestalotiollide B and the development for new CETP and ACAT inhibitors.

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