金属Ni和Co氧化物与N掺杂的碳球协同作用用于电解水析氧反应

电解水制氢被认为是理想的清洁制氢技术,然而,阴阳两极过电位的存在,特别是阳极析氧反应涉及复杂的四电子转移过程,阳极过电位较高,严重制约了电解水制氢效率的提高.因此,研究发现高效且成本低的析氧反应电催化剂具有重要意义.因此,本课题组利用温和的浸渍-热解策略合成了具有高效析氧活性的Ni/Co3O4与N掺杂的碳复合电催化剂(Ni/Co3O4@NC).其中,第一步浸渍过程将无机Ni与Co源浸渍到聚合物纳米球结构中,可以有效地保证热解过程中产生均匀分散的极细Ni和Co3O4纳米颗粒;此外,高温热解过程形成的N掺杂的碳基质可以有效地阻止活性组分的团聚和交联,调控其电子结构.由于Ni, Co3O4和NC的协同作用,制备得到的Ni/Co3O4@NC电催化剂在碱性溶液中均展现了比由单一金属组成的Co3O4@NC和Ni@NC更优异的析氧活性和稳定性,当电流密度为10 m Acm-2时,所需要的过电位仅为350 m V, Tafel斜率低至52.27 m Vdec-1,电荷转移阻抗极小,双电层电容高达25.53 m Fcm-2.本文采用扫描电镜(SEM),高分辨透射电镜(HRTEM), X射线衍射(XRD)和X射线光电子能谱(XPS)等手段研究了Ni/Co3O4@NC电催化剂的微观结构、元素组成和价态,分析了复合Ni/Co3O4@NC电催化剂具有优异析氧性能的原因.SEM结果表明, Ni/Co3O4@NC电催化剂在经历浸渍-热解过程后,完整地继承了聚合物的纳米球状形貌,只是平均粒径由100 nm缩聚为90 nm左右, SEM mapping显示各元素均匀分散在每一个纳米球结构中.HRTEM结果显示,紧密耦合的Ni和Co3O4超细纳米颗粒均匀分散于纳米球结构中,且碳基质有效地限制了这些颗粒的过度生长及团聚.XRD和XPS结果再次印证Ni/Co3O4@NC是由Ni和Co3O4两种晶体结构构成,此外, XPS结果显示N原子成功掺杂到碳基质中,富电子的N原子掺杂到碳基质中可以有效地调控Ni/Co3O4@NC的电子结构,提高本征电催化活性.相应的催化反应结果表明, Ni/Co3O4@NC相较于单一的Co3O4@NC和Ni@NC析氧活性更高,这是由于Ni与Co3O4协同作用,使Co3O4的Co2+/3+氧化还原峰向阳极偏移,从而增加了Co3O4的本征活性;此外高导电性的Ni掺杂到Ni/Co3O4@NC复合物结构中,提高了催化剂的导电性,加快了电子传输能力;杂原子N的掺杂有效地调控了催化剂的电子结构,提高了催化剂的本征活性.总之, Ni、Co3O4和NC的协同作用使Ni/Co3O4@NC复合物在碱性溶液中具有高效催化析氧性能.该策略为制备杂原子掺杂的负载于高导电碳载体的氧化物基催化剂提供了有益参考.

Facile synthesis of V-doped CoP nanoparticles as bifunctional electrocatalyst for efficient water splitting

Adjusting the intrinsic activity and conductivity of electrocatalysts may be a crucial way for excellent performance for water splitting.Herein,the rational design of vanadium element doped cobalt phosphide(V-doped CoP)nanoparticles has been investigated through a facile gaseous phosphorization using cobalt vanadium oxide or hydroxide(Co-V hydr(oxy)oxide)as precursor.The physical characterization shows that the homogeneous dispersion of V element on V-doped CoP nanoparticles have obtained,which may imply the enhanced electrocatalytic activity for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).The electrochemical measurements of the prepared V-doped CoP in alkaline electrolyte demonstrate the superior electrocatalytic activity for both HER(overpotential of 235 mV@10 mA cm^-2)and OER(overpotential of 340 mV@10 mA cm^-2).Further,V-doped CoP nanoparticles used as anode and cathode simultaneously in a cell require only 370 mV to achieve a current density of 10 mA cm^-2.The outstanding electrocatalytic activity may be ascribed to the improved conductivity and intrinsic activity owing to phosphating and the doping of V element.In addition,the long-term stability of V-doped Co P has been obtained.Therefore,metal doping into transition metal-based phosphides may be a promising strategy for the remarkable bifunctional electrocatalyst for water splitting.

Fe-doped CoP core–shell structure with open cages as efficient electrocatalyst for oxygen evolution

Developing a facile approach based on transition metal-based Prussian blue(PB)and its analogues(PBAs)with core-shell nanostructure is a very promising choice for constructing cost-effective electrocatalysts for oxygen evolution reaction(OER).Herein,a bimetallic core-shell structure with open cages of Fe-doped CoP(Fe-CoP cage)has been synthesized using CoFe-PBA cage-4 as precursor through a facile hydrothermal method and following phosphating process.Interestingly,there is an open hole in each face center of Fe-CoP cage,which suggests the more exposure of active sites for OER.Electrochemical measurements show that Fe-CoP cage can afford a current density of 10 mA cm-2 at a low overpotential(300 mV),which is better than that of RuO2.The excellent performance can be attributed to Fe doping composition and unique open-cage core-shell structure.The synergistic effect derived from bimetallic active for OER has been discussed.And its great catalytic stability has been evaluated via 1000 cycles of CV and chronoamperometry measurement.This work provides a potential method to design multiple transitional metal-doping electrocatalysts with complex framework derived from PBAs for water splitting.

中空和基底支撑型普鲁士蓝及其类似物和衍生物用于绿色水分解

随着世界对能源需求的日益增长,为减少对化石燃料的严重依赖同时实现碳达峰和碳中和,迫切需要探索发现新型能源和能源载体.与其他燃料相比,氢气具有零碳排放、能量密度高、清洁可再生和来源广泛等特点,因此被认为是理想的能源载体.目前,工业制氢主要有三种策略,分别是甲烷水蒸气重整(SMR)、煤炭水蒸气(CG)和水电解(WE).其中SMR和CG制氢占95%,而WE制氢仅占4%.虽然前二者制氢成本较低,但会伴生大量的二氧化碳,相比之下,WE制氢纯度高,绿色无污染,更加符合目前的环保理念.目前WE制氢的核心问题之一就是设计和合成高效、廉价的电催化剂.具有类贵金属催化性能的过渡金属基电催化剂(例如钴基、镍基和铁基材料)已经引起了学术界的广泛关注.配位聚合物(CP)由于其具有固有的金属元素、内部结构化学可调、比表面积大和结构有序等优点,在吸附、催化和储能等领域得到了广泛的应用.作为18世纪发现的第一个人工配位聚合物,普鲁士蓝(PB)及其类似物(PBAs)和具有可调金属中心的衍生物作为一种新型的光催化剂或电催化剂受到了广泛的关注.本综述详细介绍了以普鲁士蓝及其类似物和衍生物构筑的中空结构和基底支撑型纳米材料在绿色水分解方面的基础研究及应用进展.本文首先简单介绍了普鲁士蓝及其类似物的基本结构组成,并对其优缺点进行了总结;随后,针对普鲁士蓝及其类似物的中空结构的合成策略和形成机理展开了详细地阐述,包括单层中空纳米盒、开孔式纳米笼以及复杂中空结构等;此外,针对基底支撑型普鲁士蓝及其类似物结构合成机理也进行了详细地解释,包括泡沫镍网、铁网、碳布、铜网等基底,并与中空结构进行了对比总结,该类负载型结构可以充分发挥活性位的利用效率,达到更好的催化性能.此外,结合最新的研究进展,介绍了普鲁士蓝及其类似物和衍生物(氢氧化物、磷化物、硫族化合物和碳化物)在水裂解中的应用,包括电解水和光催化制氢,并对电解水的机理进行了总结.最后,本文总结了该领域目前存在的局限性和面临的紧迫挑战.希望本综述能够激发更多研究者投身于复杂结构普鲁士蓝及其类似物和衍生物的高效绿色水裂解方面的研究工作.

原位构筑表面缺陷的碳掺杂型三元钴镍铁磷化物纳米立方体用于高效全水分解（英文）

本文以三元金属钴-镍-铁普鲁士蓝结构纳米立方体(Co0.9-Ni0.9Fe1.2NCs)为前驱体,通过简单气相磷化处理,得到优化比例的P-Co0.9Ni0.9Fe1.2纳米立方体磷化物,其具有高本征活性、导电性和高缺陷密度的特点. SEM和TEM结果表明,碳掺杂型P-Co0.9Ni0.9-Fe1.2保持了纳米立方体的结构,其粗糙的表面结构意味着丰富的缺陷位,暴露更多真实活性位.三元金属普鲁士蓝前驱体的磷化处理不仅提供了碳掺杂,而且原位构筑了立方体表面缺陷位.碳掺杂降低了电荷传输的阻抗,优化了电子传输速率.三元金属离子之间的协同作用以及丰富的缺陷活性位有效提高了电催化的性能.P-Co0.9Ni0.9Fe1.2拥有极其高的HER和OER催化活性,仅需要-200.7 mV(HER)和273.1 mV(OER)过电位就可以达到10 mA cm-2的电流密度.其全水分解仅需1.52 V就可以达到10 mA cm-2的电流密度.此外,本文还对催化剂的稳定性进行了测试.本工作为设计高效过渡金属基双功能电解水催化剂提供了一种简便方法.

High-pressure microwave-assisted synthesis of WS_(x)/Ni_(9)S_(8)/NF hetero-catalyst for efficient oxygen evolution reaction

Designing the specific crystal phase with better intrinsic activity and more active sites is a very promising strategy for earth-abundant electrocatalysts for oxygen evolution reaction(OER).Herein,a facile two-step method including the high-pressure microwave and the hydrothermal sulfurization is adopted to prepare the WS_(x)/Ni_(9)S_(8) hetero-catalyst on nickel foam(WS_(x)/Ni_(9)S_(8)/NF).Firstly,WO3 polyhedrons homogeneously cover the surface of NF through the high-pressure microwave hydrothermal process.Secondly,WS_(x)/Ni_(9)S_(8) nanoparticles on the surface of NF can be synthesized after a hydrothermal sulfurization,which has been confirmed by scanning electron microscopy(SEM) elemental mapping and high-resolution transmission electron microscopy(HRTEM).The amorphous WSx and Ni9 S8 phase may provide the dual active sites for OER.The electrochemical measurements show that WS_(x)/Ni_(9)S_(8)/NF has superior OER activity with a low overpotential of 320 mV at the current density of 100 mA·cm^(-2),better than those of other samples.The enhanced OER performance may be due to the synergistic catalysis from Ni9 S8 phase and high valence of W.Owing to the stable structure of Ni9 S8,the long-term stability of WS_(x)/Ni_(9)S_(8)/NF for at least 10 h can be obtained.This work may provide a new approach for the doped nickel sulfides crystal phase through high-pressure microwave hydrothermal assistance for OER.

Hollow Fe_(4)C/FeP Nanoboxes with Heterostructure and Carbon Armor for Efficient and Stable Hydrogen Evolution

The heterojunction interfacial modulation of FeP is an effective strategy to regulate the intrinsic activity and stability, which is a major challenge to promote the industrial application of FeP-based electrocatalysts. Herein, hollow Fe_(4)C/FeP box with heterojunction interface and carbon armor is successfully synthesized, which can expose numerous active sites and protect catalyst from corrosion. Electrochemical measurements show that Fe_(4)C/FeP exhibits excellent hydrogen evolution activity and stability. It only needs 180 mV to achieve the current density of 10 mA cm^(-2). The high-activity may be due to the synergistic effects of porous framework, graphitic carbon coating and heterojunction structure of FeC and FeP, which optimize the electronic structure and accelerates electron transfer. In addition, the target catalyst can withstand 5000 cycles of CV testing without significant change in properties. The excellent stability may be attributed to the graphitic carbon coating as the armor that can prevent the catalyst from corrosion of electrolyte. This work may provide a synthetic approach to produce a series of carbon-coated and heterojunction structure of transition metal phosphides for water splitting.