Bimetallic AgNi nanoparticles anchored onto MOF-derived nitrogen-doped carbon nanostrips for efficient hydrogen evolution

Hydrogen energy has long been recognized as a clean alternative to conventional fossil fuels,which can be applied in a wide range of transportation and power generation applications.The rational design and engineering of high-performance and robust catalysts for hydrogen evolution reaction(HER)shows not a great significance but a challenge for efficient electrochemical water splitting.Herein,a new type of Nibased Ni-ABDC precursor has been obtained,which leads to the formation of N-doped porous carbon nanomaterials uniformly coated with wellproportioned bimetallic AgNi alloys via a stepwise strategy.To their credit,all samples of AgNi/NC-X are structurally calcined from the pristine AgNi-ABDC-X by tuning the different concentration of AgNO3,which means all of them maintain the vermicelli-like morphology compared with Ni-ABDC.The series of AgNi/NC-X materials can be regarded as effective electrocatalysts for HER both in acidic and alkaline media,but an acid-leaching phenomenon is observed.Among them,the as-prepared AgNi/NC-2 exhibits a low overpotential of 103 mV at the current density of 10 mA cm^(-2)and decent durability with a high retention rate of 90.9%after 10 h in 1.0 mol L^(-1)KOH electrolyte.The compelling HER properties of AgNi/NC-2 can be attributed to the synergistic effect between the hierarchical carbon materials,partial N-doping and abundant AgNi alloys.Meanwhile,this study provides a practicable method for the development of efficient HER electrocatalysts for energy applications,which can be conveniently prepared through the reasonable introduction of active components in the crystalline inorganic-organic precursors.©2021 Institute of Process Engineering,Chinese Academy of Sciences.Publishing services by Elsevier B.V.on behalf of KeAi Communications Co.,Ltd.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

含有丰富铁物种的配体诱导中空MOF衍生碳纳米材料用于高效氧还原反应

合理地设计和制备低成本、高效、稳定的非贵金属基碳纳米材料具有重要意义.本文中我们在不同温度条件下,通过有机配体交换将MOF-5转换为ZIF-8,其过程中可以捕捉到ZIF-8的中间态(ZIF-8-M)并得到最终态(ZIF-8-F).将掺杂Fe离子的MOF材料进行热解后,得到的Fe-ZIF-8-F-900材料具有大的比表面积、高的石墨化程度、丰富的碳纳米管以及高活性的铁物种等优点.这些特性有助于后续氧还原反应(ORR)更好的电子转移和质量传输.与Pt/C相比,Fe-ZIF-8-F-900具有优异的ORR性能,如较正的起始电位(0.982 V),大的极限电流密度(5.41 mA cm^(-2))和较小的Tafel斜率(40.6 mV dec^(-1)),且在10小时后电流保持率仍高达94.4%.此外,实验和理论结果均证实了Fe-ZIF-8-F-900组装的锌空气电池在实际应用中表现优异.本研究将为高效、低成本的非贵金属基电催化剂的开发和制备提供合理的设计策略,并为其在能源相关领域的实际应用指明方向.

Regulating f orbital of Tb electronic reservoir to activate stepwise and dual-directional sulfur conversion reaction

The sluggish kinetics in multistep sulfur redox reaction with different energy requirements for each step,is considered as the crucial handicap of lithium–sulfur(Li–S)batteries.Designing an electron reservoir,which can dynamically release electron to/accept electron from sulfur species during dis-charge/charge,is the ideal strategy for realizing stepwise and dual-directional polysulfide electrocatalysis.Herein,a single Tb^(3+/4+)oxide with moderate unfilled f orbital is synthetized as an electron reservoir to optimize polysulfide adsorption via Tb–S and N…Li bonds,reduce activation energy barrier,expe-dite electron/Li+transport,and selectively catalyze both long-chain and short-chain polysulfide conversions during charge and discharge.As a result,Tb electron reservoir enables stable operation of low-capacity decay(0.087%over 500 cycles at 1 C),high sulfur loading(5.2 mg cm^(2))and electrolyte-starved(7.5μL mg^(-1))Li–S batteries.This work could unlock the potential of f orbital engineering for high-energy battery systems.