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Aqueous zinc-air batteries possess inherent safety and are especially commendable facing high-temperature working conditions. However, their working feasibility at high temperatures has seldom been investigated. Herein, the working feasibility of high-temperature zinc-air batteries is systemically investigated. The effects of temperature on air cathode, zinc anode, and aqueous electrolyte are decoupled to identify the favorable and unfavorable factors. Specifically, parasitic hydrogen evolution reaction strengthens at high temperatures and leads to declined anode Faraday efficiency, which is identified as the main bottleneck. Moreover, zinc-air batteries demonstrate cycling feasibility at 80 °C. This work reveals the potential of zinc-air batteries to satisfy energy storage at high temperatures and guides further development of advanced batteries towards harsh working conditions.

Single-atom catalysts (SACs) with highly active sites atomically dispersed on substrates exhibit unique advantages regarding maximum atomic efficiency, abundant chemical structures, and extraordinary catalytic performances for multiple important reactions. In particular, M-N-C SACs (M=transition metal atom) demonstrate optimal electrocatalytic activity for the oxygen reduction reaction (ORR) and have attracted extensive attention recently. Despite substantial efforts in fabricating various M-N-C SACs, the principles for regulating the intrinsic electrocatalytic activity of their active sites have not been sufficiently studied. In this Review, we summarize the regulation strategies for promoting the intrinsic electrocatalytic ORR activity of M-N-C SACs by modulation of the center metal atoms, the coordinated atoms, the environmental atoms, and the guest groups. Theoretical calculations and experimental investigations are both included to afford a comprehensive understanding of the structure-performance relationship. Finally, future directions of developing advanced M-N-C SACs for electrocatalytic ORR and other analogous reactions are proposed.

Sustainable energy supply and sufficient chemical production are highly dependent on many essential catalytic processes for our sustainable society. On pursuing next‐generation catalysts, single‐atom catalysts (SACs) with high‐active sites atomically dispersed on substrates exhibit unique advantages regarding the maximum atomic efficiency, abundant chemical structures, and extraordinary catalytic performances for multiple vital reactions. In particular, M–N–C SACs (where M is a transition metal atom) demonstrate the optimal electrocatalytic activity for oxygen reduction reaction (ORR) and have attracted extensive attentions recently. Despite the substantial efforts on fabricating various M–N–C SACs, principles of regulating the intrinsic electrocatalytic activity of the M–N–C active sites are not yet sufficiently emphasized. In this review, regulation strategies of promoting the intrinsic electrocatalytic ORR activity of M–N–C SACs are summarized by modulating the center metal atoms, the coordinated atoms, the environmental atoms, and the guest groups, respectively. Theoretical calculations and experimental investigations are both included to afford comprehensive understandings on the structural‐performance relationship. Finally, future directions of developing advanced M–N–C SACs for electrocatalytic ORR and other analogous reactions are proposed.

Single-atom catalysts (SACs) have great potential in electrocatalysis. Their performance can be rationally optimized by tailoring the metal atoms, adjacent coordinative dopants, and metal loading. However, doing so is still a great challenge because of the limited synthesis approach and insufficient understanding of the structure-property relationships. Herein, we report a new kind of Mo SAC with a unique O,S coordination and a high metal loading over 10 wt %. The isolation and local environment was identified by high-angle annular dark-field scanning transmission electron microscopy and extended X-ray absorption fine structure. The SACs catalyze the oxygen reduction reaction (ORR) via a 2 e- pathway with a high H2 O2 selectivity of over 95 % in 0.10 m KOH. The critical role of the Mo single atoms and the coordination structure was revealed by both electrochemical tests and theoretical calculations.

The development of next‐generation high‐energy‐density batteries requires advanced electrode materials. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode with the merits of high specific capacity and long cycling stability for high‐performance lithium–sulfur (Li–S) batteries. Nevertheless, the practical performances of SPAN cathodes are severely limited by the unfavorable electron accessibility due to the relatively low intrinsic conductivity and large particle size. Herein, a redox mediation strategy is proposed to accelerate the electron transfer processes in working Li–S batteries with SPAN cathodes. Specifically, a quinone‐based redox mediator is introduced to provide an additional redox pathway with strengthened interfacial kinetics. The redox mediator assisted SPAN cathodes exhibit higher specific capacity, improved rate performance, reduced polarization, and longer cycling lifespan with both ether‐based and carbonate‐based electrolyte. This work demonstrates the feasibility of redox mediation to promote the electron accessibility for high‐performance Li–S batteries with SPAN cathodes.

Rechargeable zinc-air batteries afford great potential toward next-generation sustainable energy storage. Nevertheless, the oxygen redox reactions at the air cathode are highly sluggish in kinetics to induce poor energy efficiency and limited cycling lifespan. Air cathodes with asymmetric configurations significantly promote the electrocatalytic efficiency of the loaded electrocatalysts, whereas rational synthetic methodology to effectively fabricate asymmetric air cathodes remains insufficient. Herein, a strategy of asymmetric interface preconstruction is proposed to fabricate asymmetric air cathodes for high-performance rechargeable zinc-air batteries. Concretely, the asymmetric interface is preconstructed by introducing immiscible organic-water diphases within the air cathode, at which the electrocatalysts are in situ formed to achieve an asymmetric configuration. The as-fabricated asymmetric air cathodes realize high working rates of 50 mA cm

Lithium–sulfur (Li–S) batteries are highly considered for next‐generation energy storage due to their ultrahigh theoretical energy density of 2600 Wh kg−1. The conversion reactions between lithium polysulfides (LiPSs) constitute the core process in working Li–S batteries. Electrochemical impedance spectroscopy (EIS) analysis of LiPS symmetric cells is an effective tool to provide detailed information on the LiPS conversion reactions and direct further kinetic promotion. However, reasonable interpretation of the EIS responses is so far insufficiently addressed without a well‐defined equivalent circuit. Herein, a systematic analysis on the EIS responses of LiPS symmetric cells is conducted to provide a comprehensible equivalent circuit. Interfacial contact, surface reaction, and diffusion are decoupled according to their respective characteristic frequency using the distribution of relaxation time analysis method. A well‐defined equivalent circuit is proposed to accurately fit the experimental EIS responses, unambiguously interpret key parameters, and be feasible with a wide range of experimental conditions. This work presents the methodology of understanding the EIS responses of LiPS symmetric cells and inspires analogous analysis on vital electrochemical processes.

The apoptosis of myoblast in response to excessive cyclic stretch is crucial in adaptive construction of skeletal muscles in orthopedic functional therapy. Mitochondria signaling pathway is the central links in the execution of the intrinsic apoptotic cascade, but its molecular mechanism in stretch-induced apoptosis in myoblasts remains incompletely understood. The aim of this study was to investigate the mechanobiological roles of caspase-9 and Apoptosis Inducing Factor (AIF), two important components in mitochondrial pathway, in stretch-induced apoptosis of myoblast. Hoechst 33258 was used to observe apoptotic cells morphologically and flow cytometry to analyze apoptosis rate of myoblasts. Protein and mRNA of caspase-9 and AIF were detected by Western blotting and RT-PCR. Furthermore, caspase-9 specific inhibitor z-LEHD-fmk was applied to clear the mechanism of caspase-9 pathway in stretch-induced apoptosis. We found that apoptotic rate induced by cyclic stretch increased in a time-dependent manner, and the same tendency of mRNA and protein of caspase-9 and AIF. Caspase-9 inhibition reduced stretch-induced apoptosis, but had no effect on expression of AIF. We concluded that caspase-9 and AIF played an important role in stretch-induced apoptosis in myoblast, and AIF was involved in the process in a caspase-9 independent way. J. Cell. Biochem. 118: 829-838, 2017. © 2016 Wiley Periodicals, Inc.

Hydrogen peroxide (H2 O2 ) is a green oxidizer widely involved in a vast number of chemical reactions. Electrochemical reduction of oxygen to H2 O2 constitutes an environmentally friendly synthetic route. However, the oxygen reduction reaction (ORR) is kinetically sluggish and undesired water serves as the main product on most electrocatalysts. Therefore, electrocatalysts with high reactivity and selectivity are highly required for H2 O2 electrosynthesis. In this work, a synergistic strategy is proposed for the preparation of H2 O2 electrocatalysts with high ORR reactivity and high H2 O2 selectivity. A Co-Nx -C site and oxygen functional group comodified carbon-based electrocatalyst (named as Co-POC-O) is synthesized. The Co-POC-O electrocatalyst exhibits excellent catalytic performance for H2 O2 electrosynthesis in O2 -saturated 0.10 m KOH with a high selectivity over 80% as well as very high reactivity with an ORR potential at 1 mA cm-2 of 0.79 V versus the reversible hydrogen electrode (RHE). Further mechanism study identifies that the Co-Nx -C sites and oxygen functional groups contribute to the reactivity and selectivity for H2 O2 electrogeneration, respectively. This work affords not only an emerging strategy to design H2 O2 electrosynthesis catalysts with remarkable performance, but also the principles of rational combination of multiple active sites for green and sustainable synthesis of chemicals through electrochemical processes.

High-performance bifunctional oxygen electrocatalysis constitutes the key technique for the widespread application of clean and sustainable energy through electrochemical devices such as rechargeable Zn-air batteries. Single-atom electrocatalysts with maximum atom efficiency are highly considered as an alternative of the present noble-metal-based electrocatalysts. However, the fabrication of transition metal single-atoms is very challenging, requiring extensive attempts of precursors with novel design principles. Herein, an all-covalently constructed cobalt-coordinated framework porphyrin with graphene hybridization is innovatively designed and prepared as the pyrolysis precursor to fabricate single-atom Co-Nx -C electrocatalysts. Excellent electrochemical performances are realized for both bifunctional oxygen electrocatalysis and rechargeable Zn-air batteries with regard to reduced overpotentials, improved kinetics, and prolonged cycling stability comparable with noble-metal-based electrocatalysts. Design principles from multiple scales are proposed and rationalized with detailed mechanism investigation. This work not only provides a novel precursor for the fabrication of high-performance single-atom electrocatalysts, but also inspires further attempts to develop advanced materials and emerging applications.