Scalable 3‑D Carbon Nitride Sponge as an Efficient Metal-Free Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal–air batteries. Here, we developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO₂, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn–air batteries. The resulting primary Zn–air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm^–2, a specific capacity of 830 mA h g^–1, and better durability for 210 h after mechanical recharging. An extraordinary small charge–discharge voltage polarization (∼0.80 V at 25 mA cm^–2), superior reversibility, and stability exceeding prolonged charge–discharge cycles have been attained in rechargeable Zn–air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn–air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles

Scalable 3‑D Carbon Nitride Sponge as an Efficient Metal-Free Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal–air batteries. Here, we developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO₂, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn–air batteries. The resulting primary Zn–air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm^–2, a specific capacity of 830 mA h g^–1, and better durability for 210 h after mechanical recharging. An extraordinary small charge–discharge voltage polarization (∼0.80 V at 25 mA cm^–2), superior reversibility, and stability exceeding prolonged charge–discharge cycles have been attained in rechargeable Zn–air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn–air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles

Hierarchically Designed 3D Holey C₂N Aerogels as Bifunctional Oxygen Electrodes for Flexible and Rechargeable Zn-Air Batteries

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey C₂N aerogels (S-C₂NA) as bifunctional catalysts for Zn-air and Li-O₂ batteries. The S-C₂NA exhibited ultrahigh surface area (∼1943 m² g^–1) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO₂) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C–N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-C₂NA air cathodes exhibit superb energy densities (958 and 862 Wh kg^–1), low charge–discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO₂ catalysts, respectively. Notably, Li-O₂ batteries with S-C₂NA demonstrated an outstanding specific capacity of ∼648.7 mA h g^–1 and reversible charge–discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics

Toll-Like Receptor-Based Immuno-Analysis of Pathogenic Microorganisms

In this study, a novel mammalian cell receptor-based immuno-analytical method was developed for the detection of food-poisoning microorganisms by employing toll-like receptors (TLRs) as sensing elements. Upon infection with bacterium, the host cells respond by expressing TLRs, particularly TLR1, TLR2, and TLR4, on the outer membrane surfaces. To demonstrate the potential of using this method for detection of foodborne bacteria, we initially selected two model sensing systems, expression of TLR1 on a cell line, A549, for <i>Escherichia coli</i> and TLR2 on a cell line, RAW264.7, for <i>Shigella sonnei</i> (<i>S. sonnei</i>). Each TLR was detected using antibodies specific to the respective marker. We also found that the addition of immunoassay for the pathogen captured by the TLRs on the mammalian cells significantly enhanced the detection capability. A dual-analytical system for <i>S. sonnei</i> was constructed and successfully detected an extremely low number (about 3.2 CFU per well) of the pathogenic bacterium 5.1 h after infection. This detection time was 2.5 h earlier than the time required for detection using the conventional immunoassay. To endow the specificity of detection, the target bacterium was immuno-magnetically concentrated by a factor of 50 prior to infection. This further shortened the response to approximately 3.4 h, which was less than half of the time needed when the conventional method was used. Such enhanced performance could basically result from synergistic effects of bacterial dose increase and subsequent autocrine signaling on TLRs’ up-regulation upon infection with live bacterium. This TLR-based immuno-sensing approach may also be expanded to monitor infection of the body, provided scanning of the signal is feasible