Cu-Pd Dual Catalyst System for Amide Styrylation Reaction from Potassium Styryltrifluoroborates and Amides

An interesting reaction procedure for the cross-coupling of potassium styryltrifluoroborates and amides has been developed by using PdCl2(dtbpf)-CuI dual catalyst system. By applying this method, good numbers of amide styrylation products are formed in 85% - 92% yields.

Dual metal atom catalysts:Advantages in electrocatalytic reactions

The dual-metal-atom catalysts(DACs)have aroused much attention as they possess the advantages of single-atom and metal alloy catalysts.And the DACs have exhibited enhanced performance in various electrocatalytic reactions,such as hydrogen/oxygen evolution and oxygen/carbon dioxide/nitrogen reduction.In this review,we mainly overview the latest understanding of the advantages of DACs for these reactions.This review will start with the familiar characterization methods for DACs,then the primary synthesis strategies for DACs will be discussed.Emphasis is given to the advantages of DACs in catalytic reactions,including the adsorption and activation,electronic structure regulation,breaking scaling relations,reducing energy barriers,cascading and coupling,synergy effect,and providing mechanism research platforms.Finally,personal perspectives and challenges for the further development of DACs are briefly discussed.

Dual atomic catalysts from COF-derived carbon for CO_(2)RR by suppressing HER through synergistic effects

The electrochemical carbon dioxide reduction reaction(CO_(2)RR)for highvalue-added products is a promising strategy to tackle excessive CO_(2) emissions.However,the activity of and selectivity for catalysts for CO_(2)RR still need to be improved because of the competing reaction(hydrogen evolution reaction).In this study,for the first time,we have demonstrated dual atomic catalytic sites for CO_(2)RR from a core-shell hybrid of the covalent-organic framework and the metal-organic framework.Due to abundant dual atomic sites(with CoN_(4)O and ZnN_(4) of 2.47 and 11.05 wt.%,respectively)on hollow carbon,the catalyst promoted catalysis of CO_(2)RR,with the highest Faradic efficiency for CO of 92.6%at-0.8 V and a turnover frequency value of 1370.24 h^(-1) at-1.0 V.More importantly,the activity and selectivity of the catalyst were well retained for 30 h.The theoretical calculation further revealed that CoN_(4)O was the main site for CO_(2)RR,and the activity of and selectivity for Zn sites were also improved because of the synergetic roles.

Precise construction of RuPt dual single-atomic sites to optimize oxygen electrocatalytic behaviors for high-performance Zn-air batteries

The development of redox bifunctional electrocatalysts with high performance,low cost,and long lifetimes is essential for achieving clean energy goals.This study proposed an atom capture strategy for anchoring dual single atoms(DSAs)in a zinc-zeolitic imidazolate framework(Zn-ZIF),followed by calcination under an N_(2) atmosphere to synthesize ruthenium-platinum DSAs supported on a nitrogendoped carbon substrate(RuPt DSAs-NC).Theoretical calculations showed that the degree of Ru 5dxz-~*O 2p_x orbital hybridization was high when^(*)O was adsorbed at the Ru site,indicating enhanced covalent hybridization of metal sites and oxygen ligands,which benefited the adsorption of intermediate species.The presence of the RuPtN_6 active center optimized the absorption-desorption behavior of intermediates,improving the electrocatalytic performance of the oxygen reduction reaction(ORR)and the oxygen evolution reaction(DER),RuPt DSAs-NC exhibited a 0.87 V high half-wave potential and a 268 mV low overpotential at 10 mA cm^(-2)in an alkaline environment.Furthermore,rechargeable zinc-air batteries(ZABs)achieved a peak power density of 171 MW cm^(-2).The RuPt DSAs-NC demonstrated long-term cycling for up to 500 h with superior round-trip efficiency.This study provided an effective structural design strategy to construct DSAs active sites for enhanced electrocata lytic performance.

Supported dual-atom catalysts: Preparation, characterization, and potential applications

Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocatalysts with excellent performance and low cost will facilitate the commercial use of these energy conversion technologies. Recently, dual-atom catalysts(DACs) have attracted considerable research interest since they exhibit higher metal atom loading and more flexible active sites compared to single-atom catalysts(SACs). In this paper, the latest preparation methods and characterization techniques of DACs are systematically reviewed. The advantages of homonuclear and heteronuclear DACs and the catalytic mechanism and identification technologies between the two DACs are highlighted. The current applications of DACs in the field of electrocatalysis are summarized. The development opportunities and challenges of DACs in the future are prospected. The ultimate goal is to provide new ideas for the preparation of new catalysts with excellent properties by customizing diatomic catalysts for electrochemical applications.

Improved visible-light photocatalytic H_2 generation over CdS nanosheets decorated by NiS_2 and metallic carbon black as dual earth-abundant cocatalysts

CdS nanosheets(NSs)photocatalysts modified with dual earth‐abundant co‐catalysts of metallic carbon black(CB)and NiS2were synthesized by a two‐step solvothermal/impregnation method.Allthe experiment results demonstrated that the co‐loading of CB and NiS2could significantly enhance the photocatalytic H2‐evolution activity of CdS NSs.The photocatalytic performance of the as‐prepared CdS/CB/NiS2samples was tested under visible light(λ≥420nm)by using an aqueous solution containing0.25mol L–1Na2S‐Na2SO3as the sacrifice agent.The CdS‐0.5%CB‐1.0%NiS2composite photocatalysts exhibited the highest H2‐evolution rate of166.7μmol h?1,which was approximately5.16and1.87times higher than those of pure CdS NSs and CdS‐1.0%NiS2,respectively.The possible mechanism for the enhanced H2‐evolution activity of CdS/CB/NiS2composite photocatalysts was proposed.The results showed that the enhanced photocatalytic H2‐evolution activities could be ascribed to the co‐loading of metallic CB and NiS2as co‐catalysts onto the surface of CdS NSs.The excellent synergetic effect between the CB and NiS2could obviously improve visible light absorption,promote separation of photogenerated electron‐hole pairs and boost the H2‐evolution kinetics,thus leading to an enhanced activity for H2evolution.More interestingly,the metallic CB could not only act as a cocatalyst for H2evolution,but also serve as a conductive electron bridge to promote the charge migration.This work not only demonstrates that loading CB as a co‐catalyst is a promising strategy to further boost the photocatalytic activity of CdS/NiS2composites,but also offers a new mechanistic insight into the construction of highly efficient and stable CdS NSs‐based hybrid photocatalysts with dual earth‐abundant co‐catalysts for photocatalytic applications.

Particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen:Construction and performance for oxidative coupling of methane

A novel particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen is constructed comprising of the upper-layer 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst and the under-layer 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst as well as a side tube in the interspaces of two layers for supplementing 02. The reaction performance of oxidative coupling of methane （OCM） in the dual-bed reactor system is evaluated. The effects of the reaction parameters such as feed CH4/O2 ratio, reaction temperature and side tube feed 02 flowrate on the catalytic performance are investigated. The results indicate that the suggested mode of dual-bed reactor exhibits an excellent performance for OCM. CH4 conversion of 33.2%, C2H4 selectivity of 46.5% and C2 yield of 22.5% could be obtained, which have been increased by 6.4%, 4.1% and 5.5%, respectively, as compared with 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst in a single-bed reactor and increased by 10.7%, 31.9% and 17.7%, respectively, as compared with 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst in a single-bed reactor. The effective promotion of OCM performance in the reactor would supply a valuable reference for the industrialization of OCM process.

Oxidative coupling of methane in a dual-bed reactor comprising of particle/cordierite monolithic catalysts

A dual-bed reactor was constructed comprising of a 5%Na2WO4-2%Mn/SiO2 particle catalyst and a 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst.The reaction performance of the oxidative coupling of methane （OCM） over the dual-bed reactor system was evaluated.The effects of the bed height and operation mode,as well as the reaction parameters such as reaction temperature,CH4/O2 ratio and flowrate of feed gas,on the catalytic performance were investigated.The results indicated that the suggested dual-bed reactor exhibited a good performance for the OCM reaction when the feed gases firstly passed through the particle catalyst bed and then to the monolithic catalyst bed.A CH4 conversion of 38.2% and a C2H4 selectivity of 43.3% could be obtained using the dual-bed reactor with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm.Both the CH4 conversion and C2H4 selectivity have increased by 2.5% and 12.8%,respectively,as compared with the 5%Na2WO4-2%Mn/SiO2 particle catalyst in a conventional single-bed reactor and by 12.9% and 23.0%,respectively,as compared with the 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst in a single-bed reactor.The catalytic performance of the OCM in the dual-bed reactor system has been improved remarkably.

Bimetallic ZIFs-derived electrospun carbon nanofiber membrane as bifunctional oxygen electrocatalyst for rechargeable zinc-air battery

The recharged zinc-air battery(ZAB) has drawn significant attention owing to increasing requirement for energy conversion and storage devices.Fabricating the efficient bifunctional oxygen catalyst using a convenient strategy is vitally important for the rechargeable ZAB.In this study,the bimetallic ZIFs-containing electrospun(ES) carbon nanofibers membrane with hierarchically porous structure was prepared by coaxial electrospinning and carbonization process,which was expected to be a bifunctional electrocatalyst for ZABs.Owing to the formed dual single-atomic sites of Co-N_(4) and Zn-N_(4),the obtained ES-Co/ZnCNZIFexhibited the preferable performance toward oxygen reduction reaction(ORR) with E1/2of 0.857 V and JLof 5.52 mA cm^(-2),which were more than Pt/C.Meanwhile,it exhibited a marked oxygen evolution reaction(OER) property with overpotential of 462 mV due to the agglomerated metallic Co nanoparticles.Furthermore,the ZAB based on the ES-Co/Zn-CNZIFcarbon nanofibers membranes delivered peak power density of 215 mW cm^(-2),specific capacity of 802.6 mA h g^(-1),and exceptional cycling stability,far larger than Pt/C+RuO_(2)-based ZABs.A solid-state ZAB based on ES-Co/Zn-CNZIFshowed better flexibility and stability with different bending angles.

多环芳烃双效耦合加氢催化剂制备及其加氢性能

多环芳烃加氢饱和既有利于环境保护,还能促进煤焦油的高效率利用。以煤焦油中(210~360)℃富含2-4环多环芳烃馏分为研究对象,采用加氢饱和催化剂与分子筛催化剂作为双效耦合催化剂,对不同反应条件下煤焦油催化加氢反应性能进行研究。结果表明,双效耦合催化剂具备分子筛催化剂与加氢饱和催化剂的催化特性,同时具备两者相互作用较小的稳态结构,且其在多环芳烃催化加氢反应中的活性介于分子筛催化剂和加氢饱和催化剂之间;活性金属组分Ni和Mo在催化剂表面分布稳定均匀。各操作条件对多环芳烃加氢性能存在不同程度的影响,双效耦合催化剂耦合比为4∶6时,多环芳烃催化加氢性能优于其他耦合比催化剂,在反应温度380℃、氢初压8.0 MPa、反应时间60 min和剂油比5∶100条件下,具有较好的加氢性能。馏分油多次选择性加氢后,饱和分量明显增加,胶质和芳香分量明显减少。

费托合成Co基催化剂的研究进展

Co基催化剂因具有高活性和强链增长能力等优势,成为费托合成(FTS)反应适宜的催化剂。总结了Co基催化剂FTS反应机理,并对活性相结构以及助剂与催化性能的构效关系进行了分析。同时,围绕催化剂载体的作用,总结金属-载体相互作用促进FTS反应性能的研究进展,重点分析了金属Co与分子筛耦合直接合成液体燃料的研究进展,归纳了采用双功能催化剂体系制备液体燃料的反应路线及催化剂特征。

CoSe_(2)-CuSe_(2)NF双功能电催化剂的制备及其电解水性能的研究

随着环境污染日益严重、不可再生资源日益枯竭,对清洁、可再生能源的开发非常重要。利用电解水析氢(HER)和析氧(OER)技术生产氢气和氧气,是一种高效、无污染的制备清洁能源的方法。但是,商业贵金属电催化剂价格昂贵、地球丰度低,因此,开发价格低廉、高活性、高稳定性的非贵金属电催化剂意义重大。本研究利用水热法成功制备出一系列具有纳米花结构的双功能电催化剂(CuSe_(2)-CoSe_(2)(1∶1)NF、CuSe_(2)-CoSe_(2)(3∶1)NF、CuSe_(2)-CoSe_(2)(1∶3)NF),通过一系列的表征对催化剂的结构、形貌、元素组成、元素价态进行分析。研究发现CuSe_(2)-CoSe_(2)NF双金属硒化物中CoSe_(2)和CuSe_(2)相互协同作用,促进电子转移,提高电解水性能。此外,CuSe_(2)-CoSe_(2)NF纳米花结构具有较大的比表面积(808 m^(2)/g),暴露更多的活性位点数,进一步提升了催化剂的电化学性能。结果表明,CuSe_(2)-CoSe_(2)(1∶1)NF催化剂在1 mol/L KOH电解液、电流密度为10 mA·cm^(-2)时,HER和OER的过电位为42和204 mV,可持续稳定工作100 h,与商业Pt/C和RuO_(2)性能接近。

Electronic structure and geometric construction modulation of carbon-based single/dual atom catalysts for electrocatalysis

Both carbon-based single atom catalysts(SACs)and dual atom catalysts(DACs)have garnered significant attention in the field of electrochemical reactions because of the impressive attributes,including exceptional catalytic activity,selectivity,and cost-effectiveness.The ability to modulate the electronic structure and geometric construction of active sites within SACs/DACs is paramount for unleashing their complete potential,which in turn can ultimately dictate catalytic behavior with unprecedented precision.In this review,the recent major developments of the regulation strategies for modulating electronic structure and geometric construction of carbon-based SACs/DACs are summarized.For the SACs,the recently reported modulation methods are categorized into four strategies,including adjusting the density of single atoms,defect engineering,confinement effect and strain engineering.And for the DACs,the five methods contain bonded dual-atom adjustment,non-bonded and bridged dual-atom adjustment,metal and nonmetal dual-atom adjustment,bilayer dual-atom adjustment and homogeneous dual-atom adjustment.The recently developed synthetic strategies are comprehensively summarized,especially their electronic structure and geometric configuration are discussed in detail,the different catalytic applications of electrochemical reactions,and their unique catalytic mechanism are highlighted.Finally,the challenges and prospects of SACs/DACs for tailoring their electronic structures and geometric arrangements are further discussed.

NiS和Pt双助催化剂增强BaTiO_(3)纳米纤维光催化制氢性能

采用静电纺丝、水热和光沉积的方法制备了一种以Pt和NiS为助催化剂的BaTiO_(3)/Pt/NiS双异质结光催化剂。优化后的BaTiO_(3)/Pt/NiS样品的制氢速率最高为489μmol·h^(-1)·g^(-1),是纯物质BaTiO_(3)的2.5倍。这主要归因于BaTiO_(3)与Pt之间形成的肖特基结促进了光生电子的快速转移,以及BaTiO_(3)与NiS之间构建的p-n结实现了对光生空穴的高效捕获。光电化学测试结果进一步证实了BaTiO_(3)/Pt/NiS异质结光催化剂中的光生电子和空穴被高效分离,从而具有更高的分解水制氢性能。

Recent progress of electrochemical reduction of CO_(2)by single atom catalysts

Powered by electricity from renewable energies,electrochemical reduction of CO_(2)could not only efficiently alleviate the excess emission of CO_(2),but also produce many kinds of valuable chemical feedstocks.Among various catalysts,single atom catalysts(SACs)have attracted much attention due to their high atom utilization efficiency and expressive catalytic performances.Additionally,SACs serve as an ideal platform for the investigation of complex reaction pathways and mechanisms thanks to their explicit active sites.In this review,the possible re-action pathways for the generation of various products(mainly C1 products for SACs)were firstly summarized.Then,recent progress of SACs for electrochemical reduction of CO_(2)was discussed in aspect of different central metal sites.As the most popular and efficient coordination modulation strategy,introducing heteroatom was then reviewed.Moreover,as an extension of SACs,the development of dual atom catalysts was also briefly discussed.At last,some issues and challenges regarding the SACs for CO_(2)reduction reaction(CO_(2)RR)were listed,followed by corresponding suggestions.

Pd/Zn Dual Catalysis for Site-,Enantio-,and Diastereo-Divergent 2-(Alkoxycarbonyl)allylation ofα-Hydroxyketones with Morita–Baylis–Hillman Adducts

A synergistic Pd/Zn dual chiral catalyst system has been developed for the stereodivergent transformation of Morita–Baylis–Hillman(MBH)carbonates and unprotectedα-hydroxyketones to afford the corresponding allylation products(>50 examples).These products bearing vicinal stereocenters were obtained in high yields with excellent regio-/diastereo-/enantioselectivities.On cyclization in an acidic medium,the allylation products could transform to the corresponding acyl-functionalizedβ,γ-disubstitutedα-methylene-γ-butyrolactones(AMGBLs).All four stereoisomers of AMGBL were readily accessed using the same starting materials with full control of the stereochemistry of the contiguous stereogenic centers,simply by switching the chiral ligand combination for the Pd/Zn system.A nucleophilic site-divergent reactivity was observed for the allylation of primary and secondaryα-hydroxyketones,suggesting that distinct enolate intermediates might have prevailed in these reactions.

用于氧还原反应的双原子钴-铁催化剂

金属-空气电池因其高效率和便携性受到广泛关注.然而,氧还原反应(ORR)的高能垒和缓慢的动力学导致其输出功率低.尽管贵金属铂基材料具有较高的ORR活性,但其在工业上的大规模应用受到高成本的制约.因此,迫切需要以储量丰富的非贵金属为原料,开发具有低成本、高性能和耐用性的催化剂.近年来,单原子过渡金属与氮共掺杂碳材料(M-N-C)成为替代贵金属催化剂的理想材料.理论模拟和实验结果均表明,单原子Fe/Co-N-C催化剂具有良好的ORR活性,其中FeN_(4)和CoN_(4)构型被认为是主要活性位点.此外,含有相邻金属位点的双金属单原子催化剂具有加速ORR动力学的巨大潜力.通过对ORR中间体的桥式-顺式吸附,双金属位点可以促进O-O键的裂解,从而提高催化活性.除固有活性外,双金属位点可减少ORR过程中含氧中间体对M-N键的攻击,提高M-N-C对ORR的耐久性和工业应用潜力.因此,近年来,研究者开始探索双金属单原子催化剂的合成和电催化性能,发现Fe-Co, Fe-Mn, Fe-Cu, Co-Zn和Co-Pt双位点可以有效催化ORR.为进一步提高ORR活性,需要合理调节双原子结构,并引入更多的双金属位点.本文在氮掺杂石墨烯纳米片上构建了一种含FeN_(3)-CoN_(3)位点的新型双原子催化剂(CoFe-NG),该催化剂具有较好的ORR催化活性,半波电位为0.917 V, Tafel斜率为46 mV dec^(-1),远远优于单原子Fe-NG、单原子Co-NG和Pt/C催化剂.Koutecky-Levich曲线和H_(2)O_(2)产率揭示了CoFe-NG具有高效的四电子ORR过程,不仅表现出高电流密度,而且对氧还原为OH-(而不是过氧化氢)更具选择性.计时安培测试结果表明, CoFe-NG对甲醇和一氧化碳中毒具有较高的耐受性.KSCN中毒实验结果表明, SCN^(-)离子与Fe和Co位点发生强配位作用并使活性位点中毒.以CoFe-NG为空气电极组装的锌-空气电池,开路电压为1.47 V,峰值功率密度高达230 mW cm^(-2),具有良好的充放电循环稳定性,可以为一个小灯泡供电,并且在5 mA cm^(-2)条件下持续充放电250 h,输出电压几乎不变.理论计算表明,掺氮石墨烯上的FeN_(3)-CoN_(3)位点比FeN_(4)和CoN_(4)位点具有更低的ORR能垒, FeN_(3)-CoN_(3)位点上的速控步是^(*)OH中间体向H_(2)O的转化,与单位点FeN_(4)和CoN_(4)不同.综上,本文为可控合成高性能双金属单原子催化剂及进一步深入分析其电催化氧还原反应机理提供参考.

用于纳米催化肿瘤治疗的异核双金属原子催化剂

癌症是威胁人类健康的重大疾病之一.目前,化疗、放疗和手术治疗是三大常规治疗癌症手段,虽然这些治疗技术成熟,但都存在不足,且治疗成本高昂,并使得患者在治疗过程中承受痛苦.因此,开发活性位点丰富、催化效率高、肿瘤组织识别准确的新型抗肿瘤催化材料,利用有限的治疗资源,以最低的毒性取得最佳的治疗效果,成为癌症治疗的研究新前沿.随着纳米材料的快速发展,异核双原子催化剂(HDACs)在保留单原子催化剂的最大原子利用率,活性位点分布均匀,孤立单原子的不饱和配位环境和有利于电荷转移的电子结构等优点的基础上,其两种不同金属原子不仅能提供更丰富的反应活性位点,两者之间还具有独特的协同作用,可以有效突破单原子催化剂的线性限制并优化活性中间物种的吸附能垒和构型,显著提高催化活性和选择性从而获得满意的治疗效果,在纳米催化肿瘤治疗领域展现出巨大的实际应用潜力.本文对HDACs的表征手段、制备方法及其近年来在纳米催化肿瘤治疗领域的应用进行了系统的综述.首先简要介绍了原子水平活性位点的各种表征方法,特别是原位技术,讨论了它们应用的侧重点,并比较了各自的优缺点.其次,由于反应原子的高表面自由能、难以调控的动力学行为以及与载体的弱结合使得HDACs在合成过程中极不稳定.一旦异质活性金属原子之间的距离变近,就不可避免地发生团聚,从而形成合金或大尺寸的纳米颗粒.因此,实现HDACs的精确和可控合成一直是该领域的研究重点.本文对HDACs的四大主要制备策略即传统的高温热解法、湿式化学双溶剂法、原子层沉积技术和软模板自组装技术进行了系统总结,并简要介绍了相关催化剂的应用潜力.再次,概括性地阐明了HDACs的抗肿瘤治疗机理,并依据其发挥疗效的机理,针对性地将近年来应用于抗癌领域的HDACs划分为芬顿/类芬顿反应或其他机制两大类,并对这两类HDACs进行了详细的介绍.最后,探讨了HDACs在抗肿瘤领域可能面临的问题和挑战并展望了未来研究方向和应用前景,以期为应用于该领域HDACs的研究提供富有价值的借鉴.

光催化产氢双助催化剂:类别、合成和设计策略

在低碳经济背景下,开发以氢能为代表的清洁可再生能源至关重要.利用太阳能驱动半导体进行光催化分解水,是未来可持续制取氢气的有效方法之一.然而,光催化制氢技术产业化受限于半导体表面光生载流子复合效率高和量子效率低.解决上述问题的办法是在半导体中引入双元助催化剂,这不仅可以促使三相界面的形成,促进界面电荷的有效转移,而且不同种类的双助催化剂可以为半导体提供各自的积极作用,协同提高光催化产氢效率和稳定性.因此,需要密切关注双助催化剂的开发,以建立一个集优异的光活性和光稳定性于一体的光催化产氢体系.本文系统地介绍了光催化产氢双助催化剂的类别、优势、合成方法和设计策略.首先,双助催化剂被分为双还原型(Red-Red)和还原-氧化型(Red-Ox)两类,详细概述了在光催化产氢领域中还原型和氧化型助催化剂相互匹配后形成的双助催化剂的实例及其协同效应.总结了在制氢体系中双助催化剂相对于单一助催化剂的五大优势:促进载流子快速迁移、实现电子-空穴空间分离、提高产氢吸附/脱附动力学、提高催化剂光稳定性和阻断可逆反应.随后,概括了双助催化剂-半导体光催化剂的合成策略,基于通常报道的水/溶剂热处理、煅烧、光沉积、自组装和化学沉积等助催化剂的合成方法,可以采用一步法和两步法将两种助催化剂加载到半导体上,获得三元复合材料.探讨了双助催化剂-半导体光催化体系的设计策略,详细总结了如何设计具有优化电子传递路径的Red-Red助催化剂体系和具有空间分离电荷的Red-Ox助催化剂体系.其中,为了优化电子传递路径,两种还原型助催化剂的位置关系可分为三类:核壳包裹结构、分散分布结构和相邻结构;为了实现氧化/还原位点空间分离,氧化-还原型双助催化剂在半导体表面可设计为三种结构:内外结构、晶面相关结构和端侧结构.最后,提出了双助催化剂在光催化制氢领域中的现状、挑战及未来发展方向.在未来,可以继续开发新型无贵金属助催化剂来降低催化剂体系总成本,真正达到经济实用目标;需要继续发展利于规模化生产的双助催化剂三元复合材料的合成策略;需要通过实验表征,结合同位素标记法、分子模拟和密度泛函理论计算,深入研究助催化剂的性质和作用机理.希望本文能够为构建高效实用的双助催化剂三元析氢光催化体系提供借鉴.

双助催化剂Ag/Ti_(3)C_(2)/TiO_(2)分层花状微球用于增强光催化产氢活性

在“碳达峰、碳中和”背景下,太阳能驱动的半导体光催化技术被认为是解决能源危机和环境问题的有效方法之一.开发高效的半导体光催化材料是半导体光催化技术发展的重中之重.在众多半导体光催化材料中,TiO_(2)因其无毒性、光化学稳定性良好和价格低廉等优点,在光催化领域备受关注.然而,单一TiO_(2)较低的光生载流子的分离和转移效率是制约其进一步应用的关键问题.通过负载助催化剂可以提供更多的活性位点、增强光吸收以及提高光生载流子的分离和转移效率,被认为是提高光催化活性的有效策略.本文利用静电自组装策略和光还原法成功地将双助催化剂Ti_(3)C_(2)纳米片和Ag纳米颗粒修饰在分层花状TiO_(2)微球表面,构筑了Ag/Ti_(3)C_(2)/TiO_(2)复合光催化材料,并考察其光催化产氢性能.Zeta电位测试结果表明,带有相反表面电荷的分层花状TiO_(2)微球和Ti_(3)C_(2)纳米片可以通过静电作用构筑稳定的Ti_(3)C_(2)/TiO_(2)复合光催化材料.同时,基于Ti_(3)C_(2)/TiO_(2)复合材料的光催化性能,在光照条件下Ag+可被还原为Ag而被固定在Ti_(3)C_(2)/TiO_(2)复合材料表面.通过X射线粉末衍射、拉曼光谱、扫描电子显微镜和透射电子显微镜等证明成功制备了Ag/Ti_(3)C_(2)/TiO_(2)复合光催化材料.此外,X射线光电子能谱也证明了复合材料中存在光生电子的分离和转移过程.接触角测试结果表明,构筑的Ag/Ti_(3)C_(2)/TiO_(2)复合材料具有较好的亲水性,可以更好地吸附水分子以保证还原反应的进行.紫外-可见漫反射光谱测试结果表明,Ti_(3)C_(2)和Ag助催化剂的引入提高了材料的光吸收能力.荧光光谱、时间分辨荧光光谱、光电流密度和电化学阻抗等测试结果表明,Ag/Ti_(3)C_(2)/TiO_(2)复合材料具有较好的光生载流子分离和转移效率以及更长的光生载流子寿命.另外,线性扫描伏安测试证明了Ag/Ti_(3)C_(2)/TiO_(2)复合材料具有低的过电势,更加有利于析氢反应.在模拟太阳光照射下,最佳Ti_(3)C_(2)(3 wt%)和Ag(2.5 wt%)含量的Ag/Ti_(3)C_(2)/TiO_(2)复合材料的光催化产氢速率为1024.72μmol g^(–1)h^(–1),分别约为单一TiO_(2),Ti_(3)C_(2)/TiO_(2)复合材料和Ag/TiO_(2)复合材料的40,2.3和1.8倍,且三次循环利用后仍保持较好的光催化产氢活性.光催化产氢活性的提高主要归因于Ti_(3)C_(2)和Ag双助催化剂的引入增强了光吸收能力和提高了光生载流子的分离和转移效率,从而增强了TiO_(2)的光催化活性.综上,本文揭示了构建双助催化剂的复合光催化材料更加有利于促进光催化材料的光生电子-空穴对的分离和转移,对高活性和高稳定性光催化剂的设计和性能调控有一定参考价值.