NiSe_(2)/Ni(OH)_(2)/TM异质一体电极促进碱性析氧

低廉、高效稳定的催化电极对碱性电解水意义重大。利用水热法在钛网(TM)上原位构筑前驱体Ni(OH)_(2),通过固相硒化法在350℃对前驱体进行不同时长的硒化反应,制备出NiSe_(2)/Ni(OH)_(2)/TM异质一体电极。利用XRD、XPS对电极的物相和表面元素价态进行分析;通过SEM和TEM对电极的形貌和元素分布进行表征。并在1 mol/L KOH电解液中对电极进行电催化析氧性能测试。XRD和SEM分析证实了电极的物相和形貌依赖于硒化时间。电化学测试结果显示了电极的形貌对催化性能的影响较大。硒化2 h所得到的NiSe_(2)/Ni(OH)_(2)/TM电极具有最佳的异质形貌和最优的碱性析氧性能,驱动10 mA/cm^(2)电流密度仅需285 mV的过电位,Tafel斜率为50 mV/dec,100 h的恒电压测试中电流密度衰减率为16%。粗糙的表面显著地增多了有效活性位点,强化了异质界面上不同物种间的协调作用,中间产物的转换速率和电子的转移速率得以加快;该电极表现出优异的催化活性和耐久性。

Bimetallic selenide heterostructure with directional built-in electricfield confined in N-doped carbon nanofibers for superior sodium storage with ultralong lifespan

Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries(SIBs).However,realizing the orientated growth and uniform distribution of the heterostructure is still a great challenge.Herein,the regulated novel CoSe_(2)/NiSe_(2)heterostructure confined in N-doped carbon nanofibers(CoSe_(2)/NiSe_(2)@N-C)are prepared by using Co/Ni-ZIF template,in which,the CoSe_(2)/NiSe_(2)heterostructures realize uniform distribution on a micro level.Benefiting from the unique heterostructure and N-doped carbon nanofibers,the CoSe_(2)/NiSe_(2)@N-C deliveries superior rate capability and durable cycle lifespan with a reversible capacity of 400.5 mA h g^(-1)after 5000 cycles at 2 A g^(-1).The Na-ion full battery with CoSe_(2)/NiSe_(2)@N-C anode and layered oxide cathode displays a remarkable energy density of 563 W h kg^(-1)with 241.1 W kg^(-1)at 0.1 A g^(-1).The theoretical calculations disclose that the periodic and directional built-in electric-field along with the heterointerfaces of CoSe_(2)/NiSe_(2)@N-C can accelerate electrochemical reaction kinetics.The in(ex)situ experimental measurements reveal the reversible conversion reaction and stable structure of CoSe_(2)/NiSe_(2)@N-C during Na+insertion/extraction.The study highlights the potential ability of precisely controlled heterostructure to stimulate the electrochemical performances of advanced anode for SIBs.

异质结构NiSe_(2)/MoSe_(2)用于高效尿素辅助电解水制氢

电催化水分解是实现绿色制氢的理想方法之一.然而,阳极析氧反应(OER)固有的缓慢动力学和高理论电压(1.23V),使得电解水制氢的能效受到严重限制.采用理论电位更低和热力学更有利的小分子氧化反应替代OER过程,可以在降低电能耗的同时降解污染物或生成有附加值的产物,能够带来多重效益.尿素氧化反应(UOR)具有较低的理论电压(0.37V),是替代OER的潜在反应之一.然而,UOR中复杂的六电子转移严重阻碍了尿素电解的整体效率.因此,设计经济且高效的电催化剂来促进UOR固有的缓慢动力学过程非常必要.硒化镍具有电子构型多样和结构调控灵活等优点,被认为是有效的UOR催化剂.然而,UOR过程涉及催化剂表面多种反应中间体的吸附/解吸,单相催化剂要同时满足多种反应中间的吸附/解吸是一项艰巨的挑战.众所周知,非均相电催化涉及电子转移以及电催化剂表面反应物和产物的吸附和解吸.因此,催化剂的电催化性能在很大程度上取决于材料表面的电子特性.通过构建异质结构是一种有效策略,可以调节电催化剂的电子结构,优化反应中间体的化学吸附行为,实现不同组份高效协同电催化.研究表明,通过界面工程优化结构和电子特性可进一步促进UOR的动力学.MoSe_(2)具有良好的稳定性和导电性,与镍基催化剂组合构建异质结构能够改善电催化反应中的催化动力学.本文通过简单的水热和低温硒化方法构建了异质NiSe_(2)/MoSe_(2)微球作为UOR的电催化剂.差分电荷密度和Mulliken电荷分析结果表明,MoSe_(2)与NiSe_(2)的耦合引起界面处的电荷重新分布,促使电子从NiSe_(2)向MoSe_(2)转移,更容易形成高价态Ni(NiOOH)活性物种.另外,异质界面的构建优化了催化剂表面的电子结构并调节d带中心,改变反应途径,降低反应能垒,从而提高UOR的反应活性.异质结NiSe_(2)/MoSe_(2)微球由于其独特的结构特征、强的协同耦合作用、增加的活性中心和高含量的高价Ni3+物种的综合优势而具有高效的催化性能.当负载在玻碳电极上时,仅需1.33 V的电压就能驱动10 m Acm^(-2)的电流密度,该活性优于大多数已报道的非贵金属UOR催化剂.将NiSe_(2)/MoSe_(2)催化剂组装到UOR//HER电解槽中时,NiSe_(2)/MoSe_(2)|Pt/C具有较低的操作电压和长期稳定性,在1.47 V的电池电压下电流密度达到10 m Acm^(-2),比单纯的水电解降低了约220 m V.与OER相比,热力学上有利的UOR可以作为阳极OER替代反应.综上,本文为能源/环境相关的催化反应提供了一个有效的催化剂体系,对构建高效异质结催化系统具有借鉴意义.

Integrated host configuration of flexibly fibrous skeleton towards efficient polysulfide conversion and dendrite-free behavior in stable lithium-sulfur pouch cells

The commercialization of lithium-sulfur(Li-S) batteries is obstructed by the sluggish sulfur electrochemical reaction,severe polysulfide shuttling effect,and damaging dendritic lithium growth.Herein,a threedimensional(3D) conductive carbon nanofibers skeleton-based bifunctional electrode host material is fabricated,which consists of a two-dimensional(2D) ultra-thin NiSe_(2)-CoSe_(2)heterostructured nanosheet built on one-dimensional(1D) carbon nanofibers(NiSe_(2)-CoSe_(2)@CNF).When serving as cathodic host,the heterostructured NiSe_(2)-CoSe_(2)@CNF offers a synergistic function of polysulfide confinement and catalysis conversion.The S/NiSe_(2)-CoSe_(2)@CNF cathode shows outstanding cycling stability of 0.03% capacity decay rate per cycle over 500 cycles at 1 C.As anodic host,the NiSe_(2)-CoSe_(2)@CNF with high-flux Li+diffusion property and good lithiophilic capability realizes dendrite-free Li plating/stripping behavior.Benefiting from these synergistically merits,the Li-S full cell with S/NiSe_(2)-CoSe_(2)@CNFILi/NiSe_(2)-CoSe_(2)@CNF electrodes exhibits excellent electrochemical performance including a high specific capacity of1021 mA h g^(-1)over 100 cycles at 0.2 C and reversible areal capacity of 3.05 mA h cm^(-2)under a high sulfur loading of 4.33 mg cm^(-2)at 0.1 C.The pouch cell also delivers ultra-stable Li/S electrochemistry.This study demonstrates a rational and universal electrode construction strategy for developing practical and high-energy Li-S batteries.

Atomic Heterointerface Engineering of Nickel Selenide Confined Nickel Molybdenum Nitride for High-Performance Solar-Driven Water Splitting

A heterostructured electrocatalyst of small NiSe_(2) nanoparticles confined NiMoN nanorods(NiSe_(2)-NPs/NiMoN-NRs)is prepared to accelerate both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in a same alkaline medium.The synergistic effects caused by the combination of merits derived from NiSe_(2) and NiMoN phases trigger an optimum electronic structure with high density of state at near Fermi level and enhance adsorption free energy,thereby resulting in excellent catalytic activities and strengthened working stability.The catalyst requires a low overpotential of 58 mV for HER and 241 mV for OER to reach 10 mA cm^(−2) in 1.0 M KOH electrolyte.A twoelectrode electrolyzer based on the developed catalyst shows outstanding cell voltage of 1.51 and 1.46 V to reach 10 mA cm^(−2) in 1.0 M and 30 wt%KOH solution at 25℃ for overall water splitting,respectively.In addition,the solardriven water splitting process delivers a high solar-to-H_(2) conversion efficiency of∼18.4%,impressively unveiling that the developed bifunctional catalyst is highly potential for overall water splitting to produce green hydrogen fuel.