To obtain renewable and clean fuels, exploration of effective electrocatalysts is highly desirable due to the sluggish kinetics of water splitting. In this study, the oxygen plasma-activated hybrid structure of Ni−Fe Prussian blue analogue (PBA) interconnected by carbon nanotubes (O−CNT/NiFe) is reported as a highly effective electrocatalytic material for the oxygen evolution reaction (OER). The electrocatalytic performance is significantly influenced by different mass ratios of CNTs to Ni−Fe PBA. Benefiting from the conductive and oxygen plasma-activated CNTs as well as ordered and distributed metal sites in the framework, the optimized O−CNT/NiFe 1:18 exhibits a competitive overpotential of 279 mV at a current density of 10 mA cm −2 and a low Tafel slope of 42.8 mV dec −1 in 1.0 M KOH. Furthermore, the composite shows superior durability for at least 100 h. These results suggest that the O−CNT/NiFe 1:18 possesses promising potential as a highly active electrocatalyst.

Silver nanoparticles (AgNPs) synthesized on the surface of chitosan (CS) films using ultraviolet (UV) and natural light irradiation reduction methods were studied. Field-emission scanning electron microscopy revealed that the diameter of some AgNPs synthesized by the UV irradiation reduction method lay in the range of 5-15 nm. These AgNPs were isolated and dispersed on the surface of CS film. Meanwhile, some AgNPs aggregated to form larger cubic and irregular AgNPs with average size of 50-200 nm. Compared with those synthesized via the UV irradiation reduction method, AgNPs synthesized by the natural light irradiation reduction method were found to be much more individually isolated and uniformly dispersed on the CS film surface. The AgNPs synthesized using the natural light irradiation reduction method had spherical shape with average size of 10-30 nm. Thus, the size and morphology of AgNPs on the CS films (CS-AgNPs films) can be controlled by choosing an appropriate irradiation reduction method. The results of antibacterial testing illustrated that the CS-AgNPs films synthesized by both the ultraviolet and natural light irradiation reduction methods exhibited strong antibacterial activity against Escherichia coli.

Fabricating a robust and low-cost bifunctional electrocatalyst for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) becomes critical to realizing a high-performance rechargeable zinc−air battery (RZAB). Plasma treatment is a helpful way to preserve the uniformity of metal sites in the open framework of Prussian blue analogue (PBA) with highly active OER activity. Herein, we integrate the notable ORR performance of N-doped carbon nanotubes (N-CNT) with oxygen-plasmaactivated NiFe PBA (O-PBA), which serves as an active OER catalyst, to realize the bifunctionality of the oxygen conversion reaction. Integrating N-CNT with O-NiFe PBA frameworks provides the individual active sites for ORR and OER with a stable performance. OER performance of O-PBA/N-CNT exhibited an overpotential of 280 mV at a current density of 10 mA/cm 2 , outperforming the commercial RuO 2 due to the activated metal site of O-PBA anchored in conductive N-CNT. Even after the plasma treatment, the N-CNT still had its electrocatalytic ability to improve the ORR performance, and the structure of NiFe PBA was still maintained. The combined benefits of dual active electrocatalytic sites of O-PBA/N-CNT produced a low potential gap at the value of 0.83 V in the OER/ORR polarization curve, which also exhibited stable charge−discharge performance for 45 h with a negligible potential gap of 0.70 V in RZAB application. This study presents the exploration of producing a facile synthesis of a dualactive oxygen transformation electrocatalyst by utilizing the combination of surface engineering between surface doping and plasma activation.

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