Atomically dispersed Mn-N_(x) catalysts derived from Mn-hexamine coordination frameworks for oxygen reduction reaction

Metal-organic frameworks recently have been burgeoning and used as precursors to obtain various metal-nitrogen-carbon catalysts for oxygen reduction reaction(ORR).Although rarely studied,Mn-N-C is a promising catalyst for ORR due to its weak Fenton reaction activity and strong graphitization catalysis.Here,we developed a facile strategy for anchoring the atomically dispersed nitrogen-coordinated single Mn sites on carbon nanosheets(MnNCS)from an Mn-hexamine coordination framework.The atomically dispersed Mn-N_(4) sites were dispersed on ultrathin carbon nanosheets with a hierarchically porous structure.The optimized MnNCS displayed an excellent ORR performance in half-cells(0.89 V vs.reversible hydrogen electrode(RHE)in base and 0.76 V vs.RHE in acid in half-wave potential)and Zn-air batteries(233 mW cm^(−2)in peak power density),along with significantly enhanced stability.Density functional theory calculations further corroborated that the Mn-N_(4)-C(12)site has favorable adsorption of*OH as the rate-determining step.These findings demonstrate that the metal-hexamine coordination framework can be used as a model system for the rational design of highly active atomic metal catalysts for energy applications.

Cellulose nanofiber-derived carbon aerogel for advanced room-temperature sodium–sulfur batteries

Room-temperature sodium–sulfur(RT/Na–S)batteries are regarded as promising large-scale stationary energy storage systems owing to their high energy density and low cost as well as the earth-abundant reserves of sodium and sulfur.However,the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application.Herein,we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three-dimensional cellulose nanofiber-derived carbon aerogel on a glass fiber separator(denoted NSCA@GF).The hierarchical porous structures,favorable electronic conductivity,and three-dimensional interconnected network of N,S-codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion,which can act as the barrier layer and an expanded current collector to increase sulfur utilization.Moreover,the hetero-doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion,which is confirmed from experimental and theoretical results.As a result,the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity(788.8 mAh g^(−1) at 0.1 C after 100 cycles)and superior cycling stability(only 0.059%capacity decay per cycle over 1000 cycles at 1 C),thereby demonstrating the significant potential for application in high-performance RT/Na–S batteries.

Recent progress and future perspectives of flexible metal‐air batteries

With the rapid development of wearable and intelligent flexible electronic devices(FEDs),the demand for flexible energy storage/conversion devices(ESCDs)has also increased.Rechargeable flexible metal‐air batteries(MABs)are expected to be one of the most ideal ESCDs due to their high theoretical energy density,cost advantage,and strong deformation adaptability.With the improvement of the device design,material assemblies,and manufacturing technology,the research on the electrochemical performance of flexible MABs has made significant progress.However,achieving the high mechanical flexibility,high safety,and wearable comfortability required by FEDs while maintaining the high performance of flexible MABs are still a daunting challenge.In this review,flexible Zn‐air and Li‐air batteries are mainly exemplified to describe the most recent progress and challenges of flexible MABs.We start with an overview of the structure and configuration of the flexible MABs and discuss their impact on battery performance and function.Then it focuses on the research progress of flexible metal anodes,gel polymer electrolytes,and air cathodes.Finally,the main challenges and future research perspectives involving flexible MABs for FEDs are proposed.

Single-cell transcriptional profile of ACE2 in healthy and failing human hearts

Dear Editor,The coronavirus disease 2019(COVID-19)pandemic,which is caused by SARS-Co V-2,has gained serious attention from medical practitioners around the world in the past few months.Approximately 20%of critically ill COVID-19 patients were reported to have suffered myocardial injury.The specific mechanism of this pathology requires further investigation(Yang et al.,2020).

SARS-CoV-2 leads to myocardial injury in rhesus macaque

Dear Editor,Coronavirus disease 2019(COVID-19)is caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection,which induces multiple cardiovascular complications including acute myocardial injury resulting from acute coronary syndrome,myocarditis,stress-cardiomyopathy,arrhythmias,cardiogenic shock,and cardiac arrest.The incidence of myocardial injury in COVID-19 patients was up to 20%or higher in the subpopulation with existing cardiovascular diseases,accounting for 69.4%of mortality.1 Although the presence of angiotensin-converting enzyme 2(ACE2)in cardiomyocytes could result in viral myocarditis in COVID-19 patients,the cardiopathology involved in COVID-19 is still unclear.