Controllable synthesis of grain boundary-enriched Pt nanoworms decorated on graphitic carbon nanosheets for ultrahigh methanol oxidation catalytic activity

Although one-dimensional Pt nanocrystals have long been regarded as ideal electrode catalysts for fuel cells,the synthetic techniques commonly involve the use of various complicated templates or surfactants,which have largely hampered their large-scale industrial application.Herein,we present a convenient and cost-effective approach to the stereoassembly of quasi-one-dimensional grain boundary-enriched Pt nanoworms on nitrogen-doped low-defect graphitic carbon nanosheets(Pt NWs/NL-CNS).Benefiting from its numerous catalytically active grain boundaries as well as optimized electronic structure,the as-derived Pt NWs/NL-CNS catalyst possesses exceptionally good electrocatalytic properties for methanol oxidation,including an ultrahigh mass activity of 1949.5 mA mg^(-1), reliable long-term durability,and strong poison tolerance,affording one of the most active Pt-based electrocatalysts for methanol oxidation reaction.Density functional theory calculation further reveals that the formation of worm-shape Pt morphology is attributed to the modified electronic structure as well as controllable defect density of the carbon matrix,which could also weaken the adsorption ability of Pt towards CO molecule and meanwhile synergistically promotes the catalytic reaction kinetics.

Ultrafast synthetic strategies under extreme heating conditions toward single-atom catalysts

Dispersing atomic metals on substrates provides an ideal method to maximize metal utilization efficiency, which is important for the production of cost-effective catalysts and the atomic-level control of the electronic structure. However, due to the high surface energy, individual single atoms tend to migrate and aggregate into nanoparticles during preparation and catalytic operation. In the past few years, various synthetic strategies based on ultrafast thermal activation toward the effective preparation of single-atom catalysts(SACs) have emerged, which could effectively solve the aggregation issue. Here, we highlight and summarize the latest developments in various ultrafast synthetic strategy with rapid energy input by heating shockwave and instant quenching for the synthesis of SACs, including Joule heating, microwave heating, solid-phase laser irradiation, flame-assisted method, arc-discharge method and so on,with special emphasis on how to achieve the uniform dispersion of single metal atoms at high metal loadings as well as the suitability for scalable production. Finally, we point out the advantages and disadvantages of the ultrafast heating strategies as well as the trends and challenges of future developments.

已消退恐惧记忆重现的类型

很多焦虑失调的患者经过治疗后其恐惧记忆会再次出现,这给治疗带来了很大困难。了解恐惧重现的类型对进一步研究焦虑失调有重要意义。本文梳理了临床和实验研究中常见消退后恐惧记忆的重现类型,包括重现,再加强,再获得以及自发性恢复,并且还总结了目前一些治疗已消退恐惧记忆的方法。

Aligned porous carbon film with ultralow loadings of Pt single atoms and clusters for high-current-density hydrogen generation

The development of electrocatalysts toward the hydrogen evolution reaction(HER)with high-current-density capability is critical for the practical application of water splitting for hydrogen production.While Pt-based materials are regarded as the most efficient HER catalysts,they suffer from scarcity and high price.Thus,it is of vital importance to lower the loading of Pt while maintaining high activity.Here,we report the fabrication of a monolithic aligned porous carbon film electrode co-modified with Pt single atoms and Pt nanoclusters(Pt SA/NC-AF)containing ultralow Pt content(0.038 wt.%)via a facile electrochemical deposition process.Benefiting from the aligned porous structure of the carbon film and the high exposure of the Pt species,the optimized Pt SA/NCAF electrode exhibits outstanding HER performance in 0.5 M H_(2)SO_(4)with exceptional intrinsic activity(turnover frequency(TOF)=904.9 s^(−1)atη=100 mV)and ultrahigh mass activity(888.6 A·mg_(Pt)^(−1)atη=100 mV).Further,it can deliver an industrially relevant current density of 1,000 mA·cm−2 at an overpotential as low as 139 mV.This work provides a feasible avenue for the rational design of metal single-atom and nanocluster catalysts and additionally promotes the application of ultralow-loading noble metal-based catalysts in high-rate hydrogen production.

Recent progress in carbon-dots-based nanozymes for chemosensing and biomedical applications

Nanozymes are nanomaterials with enzyme-like activities that efficiently overcome the drawbacks of natural enzymes in biosensing,detection,and biomedical fields,and they are the most widely used artificial enzymes.Owing to their excellent catalytic characteristics,biocompatibility,and environmental favorability,carbondots-based(CDs) nanozymes have inspired a research upsurge.However,no review focusing on CDs nanozymes has been published,even though substantial advances have been achieved.Herein,the advances,catalytic activities,and applications of CDs nanozymes are highlighted and summarized.In addition,the critical issues and challenges of researching nanozymes are discussed.We hope that this review will broaden the horizons of nanozymes and CDs nanozymes,as well as promote their development.