基于限域特性的电催化剂调控

开发高效催化剂是促进包括电能源、碳循环等洁净新能源技术发展的关键。这些新型物质能源转换过程往往涉及光子、电子、质子等量子尺度的粒子转换,而常规纳米尺度催化剂调控策略已略显困难。原子分子尺度的限域空间带来的强相互作用、强分子碰撞,一方面增加了反应几率,另一方面显著影响了内部分子/原子的电子结构。更为重要的是,限域空间赋予了内部物质不同于开放体系下的特性。这些限域特性在调控催化剂上展现出巨大优势。本文从限域角度出发,综述利用原子、分子尺度限域特性对电催化剂分子构型、配位结构、电荷转移填充、介观调控、催化剂表面能量场的调控机制与方法,以及在燃料电池、物质能源转换方面的应用和未来发展方向的展望。

Tailoring the interactions of heterostructured Ni_(4)N/Ni_(3)ZnC_(0.7)for efficient CO_(2)electroreduction

Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivity and large current density.Here,we report a Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructured electrocatalyst embedded in accordion-like N-doped carbon through a simple molten salt annealing strategy.The optimal Ni_(4)N/Ni_(3)ZnC_(0.7)electrocatalyst achieves a high CO Faraday efficiency of 92.3%and a large total current density of-15.8 m A cm^(-2)at-0.8 V versus reversible hydrogen electrode,together with a long-term stability about 30 h.Density functional theory results reveal that the energy barrier for*COOH intermediate formation largely decreased on Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructure compared with Ni_(4)N and Ni_(3)ZnC_(0.7),thus giving rise to enhanced activity and selectivity.A rechargeable Zn-CO_(2)battery is further assembled with Ni_(4)N/Ni_(3)ZnC_(0.7)catalyst as the cathode,which shows a maximum power density of 0.85 mW cm^(-2)and excellent stability.

Highly conductive S-doped FeSe_(2-x)S_(x)microsphere with high tap density for practical sodium storage

Metal selenides have been explored as promising sodium storage materials owing to their high theoretical capacity.However,sluggish Naþdiffusion and low electronic conductivity of selenides still hinder their practical applications.Herein,FeSe_(2-x)S_(x)microspheres have been prepared via a self-doping solvothermal method using NH4Fe(SO4)2 as both the Fe and S source,followed by gas phase selenization.The density functional theory calculation results reveal that S doping not only improves the Na adsorption,but also lower the diffusion energy barrier of Na atoms at the S doping sites,at the same time enhance the electronic conductivity of FeSe_(2-x)S_(x).The carbon-free nature of the FeSe_(2-x)S_(x)microspheres results in a low specific surface area and a high tap density,leading to an initial columbic efficiency of 85.6%.Compared with pure FeSe_(2),such FeSe_(2-x)S_(x)delivers a high reversible capacity of 373.6 mAh⋅g^(-1)at a high current density of 5 A⋅g^(-1)after 2000 cycles and an enhanced rate performance of 305.8 mAh⋅g^(-1)at even 50 A⋅g1.Finally,the FeSe_(2-x)S_(x)//NVP pouch cells have been assembled,achieving high energy and volumetric energy densities of 118 Wh⋅kg1 and 272 mWh⋅cm3,respectively,confirming the potential of applications for the FeSe_(2-x)S_(x)microspheres.

缺陷氮掺杂碳耦合Co-N5单原子位点用于高效锌-空气电池

锌-空气电池(ZAB)因其能量密度高、环境友好、成本低以及安全性高而备受关注.然而,空气电极上的氧还原反应(ORR)动力学缓慢,严重限制了ZAB的输出功率.尽管铂基催化剂展现出优异的ORR催化活性,但高昂的成本制约其大规模商业化应用.因此,迫切需要开发高效、低成本的ORR电催化剂.研究表明,具有原子分散Co-N4活性位点的Co-N-C单原子催化剂是理想的ORR非贵金属催化剂,但其仍然存在与反应关键中间体结合能较高的难题.目前的研究主要通过调控单原子配位环境与增大活性位点密度来提高Co-N-C催化剂的活性,但如何精确控制中心金属电子结构以及避免高温下金属原子的团聚仍面临巨大挑战.除了单原子活性位点外,催化剂载体的键合结构、电荷分布状态亦会影响载体本身和单原子位点的催化活性.然而,现有的研究主要聚焦于单原子位点或无金属催化剂单方面活性的提升,关于它们之间的相互作用对于催化性能影响的研究相对很少.为了进一步提高Co单原子催化剂的催化活性,本文通过简单的模板法与NH3二次处理策略制备了氮掺杂缺陷碳负载的Co-N_(5)位点单原子催化剂.电感耦合等离子体发射光谱结果表明,单原子Co的金属负载量高达2.57 wt%.此外,相比于未经过NH3二次处理的Co-Nx/HC样品,Co-N_(5)/DHC样品在电子顺磁共振谱中g=2.003处呈现出更明显的共振信号,在C 1s高分辨谱中具有更低的C-C(sp2杂化)/C-N(sp3杂化)比例以及明显增加的吡啶氮信号,证实了Co-N_(5)/DHC显著提升的氮掺杂碳缺陷浓度并具有丰富的边界/缺陷位点.同时,X射线吸收谱与球差矫正透射电子显微镜结果表明所制备的样品为原子分散的Co-N_(5)结构,从而证明成功制备了缺陷氮掺杂碳耦合Co-N_(5)位点单原子催化剂.电化学测试结果表明,缺陷氮掺杂碳耦合Co-N_(5)位点后表现较好的ORR性能,半波电位达到0.877 V,明显高于Co-Nx/HC对比样品和商业化Pt/C催化剂.Koutecky-Levich曲线和旋转盘环电极测试结果表明,Co-N_(5)/DHC催化剂的高效4e-反应路径.且在10000次的加速老化测试中,Co-N_(5)/DHC半波电位仅降低了7 m V,稳定性优于Pt/C.以Co-N_(5)/DHC为阴极催化剂组装的ZAB开路电压为1.45 V,峰值输出功率密度能够达到160.7 m W cm^(-2),并能提供766.2 m A h gZn-1的比容量,展现出较高的应用前景.密度泛函理论计算表明,Co-N_(5)位点与缺陷氮掺杂碳的相互作用诱导Co中心位点电子的重新分布,降低了ORR反应能垒.综上,本文为设计与合成高性能的Co单原子催化剂,用于先进的可再生能源转换系统提供了一种新思路.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.

NiS_(2)/FeS Heterostructured Nanoflowers for High-Performance Sodium Storage

Transition metal sulfides demonstrate attractive potential for sodium storage owing to their high theoretical specific capacity and high reserve.However,the low conductivity and volume expansion deteriorate their high-rate performance and cycling stability.In this work,we construct NiS_(2)/FeS heterostructure by growing Ni-based layered double hydroxide nanosheets on Fe-based Prussian Blue nanocrystals followed by gaseous sulfurization,giving rise to flower-like NiS_(2)/FeS nanoparticles.The as-prepared nanocomposite exhibits good rate performance of 156 mAh g^(−1) at 50 A g^(-1) and long cycle life of 606 mAh g^(−1) at 5 A g^(−1) after 1,000 cycles,which are superior to the heterostructure-free counterpart of NiS_(2) and FeS.Density functional theory calculation further verifies that the enhanced electrochemical performance of NiS_(2)/FeS is due to the existence of interface derived from the heterostructure.

HSP70L1-mediated intracellular priming of dendritic cell vaccination induces more potent CTL response against cancer

Heat-shock protein(HSP)-based immunotherapy is established on its adjuvant effects when applied via an extracellular approach to pulse and activate dendritic cells(DCs).Our previous studies indicate that DCs pulsed with recombinant fusion proteins of antigenic fragment and HSP70-like protein 1(HSP70L1)are potent in stimulating antigen-specific Th1 responses.We herein evaluated the cytotoxic T cell(CTL)response by an intracellular approach of priming DCs with transfection of recombinant adenovirus-expressing the fusion gene of the 576–699 fragment of carcinoembryonic antigen(CEA)and HSP70L1.As compared with DCs pulsed with extracellular fusion protein,the DCs transfected with recombinant adenovirus expressing the fusion gene displayed equivalent mature phenotypes but less inflammatory appearance.However,the transfected DCs were superior to the pulsed DCs in inducing CEA-specific CTLs.Consistently,immunization of HLA-A2.1/H-2Kb transgene mice with the transfected DCs could induce more quantities of HLA-A2.1-restricted CEA-specific CTLs,protecting nude mice more significantly from human CEA-expressing colon tumor challenge when adoptively transferred.Mechanistic investigation indicated that intracellular expression of the fusion protein empowered the transfected DCs by activation of STAT1 possibly via inducing IFN-βand ERK pathways.Therefore,the more potent ability to induce anti-CEA CTL responses enables the DCs,which transfected with recombinant adenovirus expressing the fusion gene of antigenic CEA fragment and Th1 adjuvant,as an alternative promising approach for the immunotherapy of CEA-positive tumors.

Stabilizing highly active atomically dispersed NiN_(4)Cl sites by Cl-doping for CO_(2)electroreduction

Nickel-nitrogen-carbon single-atom catalysts have attracted widespread interest for CO_(2)electroreduction but they suffer from poor stability.Herein,we report on the preparation of Cl-and N-doped porous carbon nanosheets with atomically dispersed NiN_(4)Cl active sites(NiN_(4)Cl-ClNC)through a molten-salt-assisted pyrolysis strategy.The optimized NiN_(4)Cl-ClNC catalyst delivers exceptional CO_(2)conversion activity with outstanding stability for over 220 h at−0.7 V versus RHE and a high CO Faradaic efficiency of 98.7%at a CO partial current density of 12.4 mA cm^(−2).Moreover,NiN_(4)Cl-ClNC displays a remarkable CO partial current density of approximately 349.4 mA cm^(−2)in flow-cell,meeting the requirements of industrial applications.Operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy and density functional theory calculations are used to understand the outstanding activity and stability.Results reveal that the introduced axial Ni-Cl bond on the Ni center and Cl─C bond on the carbon support synergetically induce electronic delocalization,which not only stabilizes Ni against leaching but also facilitates the formation of the COOH*intermediate that is found to be the rate-determining step.

In-situ construction of Li4Ti5O12/rutile TiO2 heterostructured nanorods for robust and high-power lithium storage

Li4Ti5O12 is considered as a safe and stable anode material for high-power lithium-ion batteries due to its“zero-strain”characteristic during the charge/discharge.However,the intrinsically low electronic conductivity leads to a deterioration in highrate performance,impeding its intensive application.Herein,the Li4Ti5O12/rutile TiO2(LTO/RT)heterostructured nanorods with tunable oxide phases have been in-situ fabricated by annealing the electrospun nanofiber precursor.By constructing such a heterostructured interface,the as-prepared sample delivers a high capacity of 160.3 mAh·g–1 at 1 C after 200 cycles,125.5 mAh·g–1 at 10 C after 500 cycles and a superior capacity retention of 90.3%after 1,000 cycles at 30 C,outperforming the heterostructure-free counterparts of pure LTO,RT and the commercial LTO product.Density Functional Theory calculation suggests a possible synergistic effect of the LTO/RT interface that would improve the electronic conductivity and Li-ion diffusion.

Correction: HSP70L1-mediated intracellular priming of dendritic cell vaccination induces more potent CTL response against cancer

In the published version of Fig.3D,the data of the CH and AdCtrl groups in the CFSE-Lovo/Medium panel were mistakenly presented with incorrected images.Figure 3D has now been corrected.The corrected version of Figure 3 is shown below.Although we regret our mistake during figure assembly and would like to apologize for any inconvenience it may have caused,we did not manipulate our data in any way.This unintentional error also has no bearing on the workʼs scientific conclusions.