金属铁络合物光催化二氧化碳还原

二氧化碳(CO₂)光催化还原技术因兼具解决能源和全球变暖问题的潜力而受到关注。金属铁络合物作为分子型催化剂,具有价格低廉、量子效率高、结构可调控和选择性好等优势,表现出优异的CO₂光催化还原性能,成为CO₂光催化还原领域的研究热点。本文综述了近年来基于金属铁络合物光催化二氧化碳还原研究进展。介绍了铁金属络合物(如:铁卟啉、铁多吡啶、五齿铁配合物)CO₂均相光催化还原体系,总结了体系的构成以及作用机理等,着重关注了体系的催化效率和产物的选择性。此外,综述了以半导体纳米材料/量子点作为光敏剂,金属铁络合物作为催化剂的非均相催化体系的研究进展。最后,对该领域未来的研究方向和所面临的挑战做出展望。     

面式、经式异构体的钴-氨基硫脲配合物作为催化剂应用于可见光催化分解水产氢（英文）

近年来,作为替代贵金属铂催化剂的铁、钴和镍等非贵金属配合物分子催化剂,由于合成容易、结构调控方便以及具有良好的催化活性等特点,成为均相光催化分解水产氢领域的研究热点.其中,钴配合物具有结构简单、成本低廉、容易合成以及具有理想的氧化还原电位等优势,更是光催化分解水产氢领域的优先研究对象.由于稳定性及溶解度的问题,在已报道的研究工作中,大部分钴配合物测试环境均在有机溶剂或有机溶剂/水混合溶剂中.因此,寻找水溶性良好的钴配合物催化剂成为了目前的均相光催化分解水产氢领域的研究焦点之一.在此之前,氨基硫脲配合物已经广泛用于生物和制药等研究,例如:抗氧化、抗菌以及抗病毒等领域.而在人工光合产氢领域采用氨基硫脲配合物作为催化剂的例子则比较罕见.在该项研究中,我们报道了一对水溶性较好(40 mg mL~(–1),20°C)且具有几何异构特征的八面体钴-氨基硫脲配合物作为光、电催化质子还原产氢的分子催化剂.这对几何异构体分别为:面式异构体[Co(Htsc)_3]Cl_3·3H_2O(C1,Htsc=氨基硫脲配体)和经式异构体[Co(Htsc)_3]Cl_3·4H_2O(C2).我们将几何异构体C1和C2作为水还原分子催化剂,与有机光敏剂荧光素一起构筑了不含贵金属成分的光催化分解水产氢体系.在三乙胺作为牺牲剂及纯水环境中,体系展现出了良好的光催化制氢性能.可见光照15 h后,体系产氢相对于催化剂的TON接近900.对比实验结果表明,具有这对几何异构的C1和C2具有相似的光催化产氢性能,暗示其催化机理的相似性.汞中毒实验结果表明,光催化分解水产氢过程中并没有钴纳米胶体形成,可以确定这是一个均相光催化分解水产氢体系.在纯水环境下,我们将C1和C2与传统的钴配合物(钴肟配合物:[Co(dmgH)_2pyCl](dmg H=丁二酮肟,py=吡啶);联吡啶钴配合物:[Co(bpy)_3Cl_2](bpy=2,2'-联吡啶))的催化活性进行对比.结果表明,催化剂C1和C2展现出了较强的光催化产氢活性.此外,电催化实验表明,在乙腈中且乙酸作为质子源的条件下,C1和C2具有相同的电催化活性,过电位接近640毫伏,催化转化频率(TOF)为每秒210.同时,在pH=7的磷酸盐缓冲溶液中,C1和C2也同样表现出对水分子的电催化产氢性能,过电势为560毫伏.这是当前第一例具有几何异构体的分子催化剂对光、电催化产氢体系影响的工作.     

单原子催化剂在光催化二氧化碳还原中的研究进展

通过光催化技术将二氧化碳转化成增值的含碳化学品或燃料是解决能源危机和温室效应的一种可持续性方法. 开发高效、 廉价及高稳定性的光催化剂是提高光催化二氧化碳还原(CO₂RR)效率所面临的一大挑战. 单原子催化剂由于具有原子利用率高及电子环境可调等特性而在催化领域被广泛研究. 在光催化二氧化碳还原中, 金属单原子的加入不仅可调节光催化剂的能带结构及吸光性能等物理性质, 还可以有效提高其光生电荷转移效率, 并为研究光催化反应机理提供理想的平台. 近年来, 单原子光催化剂在二氧化碳还原领域的研究发展迅速. 本文综合评述了单原子催化剂在光还原二氧化碳反应中的研究进展, 介绍了不同载体的单原子催化剂的典型研究成果, 并展望了未来的研究趋势.     

钴联吡啶配合物在硅电极表面高效光电催化二氧化碳还原反应（英文）

光驱动二氧化碳还原实现可再生能源转化近年来引起普遍关注.利用小分子金属配合物电催化剂和吸光半导体材料构建的光电催化体系兼具电催化剂的高选择性和光电极的高光电转化效率等优点,在能源催化领域的应用日益广泛.已有将贵金属配合物催化剂用于光电催化二氧化碳还原的研究报道,但催化剂成本较高且制备方法不简便,在规模化实际应用中受到局限.基于早期的研究报道,我们发现非贵金属多联吡啶铁钴镍配合物在乙腈电解质中能高选择性电催化还原二氧化碳.结合半导体材料的特异性电荷分离性能从而将光能高效转化为电能驱动催化反应进行,我们选择廉价且易于制备的多联吡啶钴配合物催化剂,利用半导体硅晶片光电极,实现了均相体系二氧化碳的高效光电催化还原.我们采用电化学循环伏安法和恒电位电解法分别研究了催化剂在干燥和加水电解质环境中的催化还原行为,并且进一步研究了微量质子源的加入对半导体界面催化过程的影响,从而提出一种能改善半导体光电催化体系选择性的新方法.首先我们构建了电化学三电极体系,研究了在暗环境下三联吡啶钴和二联吡啶钴这两种配合物催化还原二氧化碳的电流密度和电解产物分布情况.由循环伏安曲线发现,这两种配合物都有两组催化还原峰,第二个基于吡啶配体还原的峰具有明显的催化特性.少量水的加入能进一步增加催化电流强度,而三联吡啶钴配合物的催化增强效果更加显著.在变扫速条件下将电流密度对扫速平方根进行归一化处理,发现无论在干燥环境还是少量加水环境下,两种催化剂的归一化电流密度均随扫速降低而明显增强,证明了催化剂具有电催化特性.推测水的催化增强作用可能与质子化电催化过程活性中间体有关.恒电位电解结果说明电催化产物以一氧化碳为主.基于上述研究,我们构建了光电化学三电极体系,以单晶硅片为工作电极,研究了在光照环境下这两种配合物催化还原二氧化碳的电流密度和电解产物分布情况.研究发现,催化剂对二氧化碳仍具有催化活性,光电压为400 m V.不同于硅线电极加水导致产氢,改用少量甲醇做质子源后,光电流强度进一步增强,竞争性产氢受到了抑制,从而使一氧化碳的法拉第效率得到显著提高,分别优化为94%和83%,并且光电流在14h内保持稳定.推测甲醇质子源的催化增强作用可能是与改变光电极液接界面传质动力学过程有关.     

H2TP(o-NO2)TBP及其锌和钴配合物的光谱电化学研究

采用循环伏安以及电化学和电子吸收光谱联用技术研究了邻硝基四苯基四苯并卟啉(H2TP(o-NO2)TBP)及其锌和钴配合物在DMF介质中的氧化和还原性质.结果表明 H2TP(o-NO2)TBP及其锌配合物的氧化和还原均发生于卟啉的大环π电子结构,伴随有紫外-可见光谱的明显变化,氧化和还原过程均为可逆.钴配合物的第一氧化和还原均发生于中心金属离子,第二氧化发生于卟啉的大环π电子结构.     

H2TP(o-NO2)TBP及其锌和钴配合物的光谱电化学研究

采用循环伏安以及电化学和电子吸收光谱联用技术研究了邻硝基四苯并卟啉（H2TP（o-NO2)TBP）及其锌和钴配合物在DMF介质的中氧化和还原性质。结果表明H2TP（o-NO2)TBP及其锌配合物的氧化和还原均发生于卟啉的大环π电子结构,伴随有紫外-可见光谱的明显变化,氧化和还原过程为可逆。钴配合物的第一氧化和还原均发生于中心金属离子,第二氧化发生于卟啉的大环π电子结构。     

钴基非均相催化剂在光催化水分解、二氧化碳还原和氮还原的研究进展与展望（英文）

利用大自然丰富的太阳能驱动水、二氧化碳或氮气转化为高附加值燃料(如H₂, CO, CH₄, CH₃OH或NH₃等),实现人工光合成,将储量丰富的太阳能转化为可利用的清洁化学能源,被认为是解决能源短缺和环境问题的关键技术之一,能够有效缓解能源危机和全球变暖,极具应用前景.因此,各种类型的光催化剂相继被开发出来,以满足光催化的需求.其中钴基多相催化剂是最有前途的光催化剂之一,它可以通过扩大光吸收范围、促进电荷分离、提供活性位点和降低反应能垒等途径有效提高光催化效率,为太阳能燃料转化利用开辟广阔的前景.本文首先介绍了光催化水分解、CO₂还原和N₂还原的基本原理.然后,总结了基于钴基催化剂的改性策略,包括形貌、晶面、结晶度、掺杂和表面修饰,重点讨论了钴基多相材料在水分解(产氢、产氧和全解水)、二氧化碳还原以及氮还原领域的光催化进展.最后,对钴基光催化剂当前面临的挑战和未来的发展作了展望和总结.提出了钴基光催化剂未来的一些研究方向.包括:(1)基于材料光催化体系的设...     

共价有机框架材料在光催化领域中的应用

共价有机框架(COFs)材料是有机构筑基元通过共价键连接而形成的晶态有机多孔材料. COFs具有孔道结构规整、 及比表面积高等特点, 被广泛地应用于气体储存与分离、 催化、 传感、 储能及光电转化等领域. 将具有可调吸光能力的有机构筑基元引入到COFs中, 可使其展现出强大的光催化潜力. 近年来, COFs在光催化领域中发展迅猛. 本文总结了COFs在光催化产氢、 光催化二氧化碳还原、 光催化有机反应以及光催化污染物降解等方面的研究进展, 并展望了其在光催化领域的应用前景.     

一个新的二茂铁-钴四核双螺旋配合物的合成，结构和电化学性质研究

利用1，1′-双羧酸二茂铁为配体设计合成了一个新的二茂铁-钴四核双螺旋配合物并研究了其电化学性能。该配合物具有一个垂直于其螺旋轴的C₂对称性，四个金属中心形成一个边长为5.4?菱形结构。二茂铁配体的两个羧基以顺式结构与两个金属中心配位。电化学研究表明作为桥联基团的金属钴配位中心能够有效传递二茂铁基团间的氧化还原性能。     

全固态Z-Scheme光催化材料应用于二氧化碳还原和光催化分解水研究进展

由两种不同的半导体催化剂和电子传输介质建立的Z-Scheme光催化体系,通过在可见光照射下分别在两种半导体催化剂上进行氧化反应和还原反应,实现两步法光催化分解水和二氧化碳还原.相较于离子型Z-Scheme光催化体系,全固态Z-Scheme光催化体系具有适用范围广、无副反应、光源利用率高等特性,具有更加广阔的应用前景.在此,我们简述了Z-Scheme光催化体系的反应机理,综述了全固态Z-Scheme光催化体系在光催化分解水和光催化还原CO₂领域的应用,并对未来全固态Z-Scheme光催化体系的发展进行了展望.     

基于CdS和CdSe纳米半导体材料的可见光催化二氧化碳还原研究进展

Carbon dioxide (CO₂) is one of the main greenhouse gases in the atmosphere. The conversion of CO₂ into solar fuels (CO, HCOOH, CH₄, CH₃OH, etc.) using artificial photosynthetic systems is an ideal way to utilize CO₂ as a resource and reduce CO₂ emissions. A typical artificial photosynthetic system is composed of three key components: a photosensitizer (PS) to harvest visible light, a catalyst (C) to catalyze CO₂ or protons into carbon-based fuels or H₂, respectively, and a sacrificial electron donor (SED) to consume the holes generated in the PS. In most cases, the PS and catalyst are two different components of a system. However, some components that possess both light harvesting and redox catalysis functionalities, e.g., nano-semiconductors, are referred to as photocatalysts. During photocatalysis, the PS is typically excited by photons to generate excited electrons. The excited electrons in the PS are transferred to the catalyst to generate a reduced catalyst. The reduced catalyst is used as an active intermediate to perform CO₂ binding and transformation. The PS can be recovered through a reaction with the SED. Nano-semiconductors have been used as photosensitizers and/or photocatalysts in photocatalytic CO₂ reduction systems owing to their excellent photophysical and photochemical properties and photostability. CdS and CdSe nano-semiconductors, such as quantum dots, nanorods, and nanosheets, have been widely used in the construction of photocatalytic CO₂ reduction systems. Systems based on CdS or CdSe nano-semiconductors can be classified into three categories. The first category is systems based on CdS or CdSe photocatalysts. In these systems, CdS or CdSe nano-semiconductors function as photocatalysts to catalyze CO₂ reduction without a co-catalyst under visible-light irradiation. The CO₂ reduction reaction occurs at the surface of the CdS or CdSe nano-semiconductors. The second category is systems based on CdS or CdSe composite photocatalysts. CdS or CdSe nano-semiconductors are combined with functional materials, such as reduced graphene oxide or TiO₂, to prepare composite photocatalysts. These composite photocatalysts are expected to improve the lifetime of the charge separation state and inhibit the photocorrosion of the nano-semiconductors during photocatalysis. The third category is hybrid systems containing a CdS nano-semiconductor and molecular catalysts, such as nickel and cobalt complexes and iron porphyrin. In these hybrid systems, CdS functions as a photosensitizer and the CO₂ reduction reaction occurs at the molecular catalyst. This review article introduces the construction of artificial photosynthetic systems and the photocatalytic mechanism of nano-semiconductors, and summarizes the representative works in the three aforementioned categories of systems. Finally, the challenges of nano-semiconductors for photocatalytic CO₂ reduction are discussed.     

基于单原子催化剂的二氧化碳选择性转化

Industrial revolution has led to increased combustion of fossil fuels. Consequently, large amounts of CO₂ are emitted to the atmosphere, throwing the carbon cycle out of balance. Currently, the most effective method to reduce the CO₂ concentration is direct CO₂ capture from the atmosphere and pumping of the captured CO₂ deep underground or into the mid-ocean. The transformation of CO₂ into high-value chemicals is an attractive yet challenging task. In recent years, there has been much interest in the development of CO₂ utilization technologies based on electrochemical CO₂ reduction, photochemical CO₂ reduction, and thermal CO₂ reduction, and CO₂ valorization has emerged as a hot research topic. In electrochemical CO₂ reduction, the cathodic reaction is the reduction of CO₂ to value-added chemicals. The anodic reaction should be the oxygen evolution reaction, and water is the only renewable and scalable source of electrons and protons in this reaction. There is a plethora of research on the use of various metals to catalyze this reaction. Among these, Cu-based materials have been demonstrated to show unique catalytic activity and stability for the electrochemical conversion of CO₂ to valuable fuels and chemicals. Moreover, the solar-driven conversion of CO₂ into value-added chemical fuels has attracted great attention, and much effort is being devoted to develop novel catalysts for the photoreduction of CO₂, especially by mimicking the natural photosynthetic process. The key step in the photocatalytic process is the efficient generation of electron-hole pairs and separation of these charge carriers. The efficient separation of photoinduced charge carriers plays a crucial role in the final catalytic activity. Compared with CO₂ reduction via electrocatalysis and photocatalysis, thermal reduction is more attractive because of its potential large-scale application in the industry. Heterogeneous nanomaterials show excellent activity in the electrocatalytic, photocatalytic, and thermal catalytic conversion of CO₂. However, nanostructured materials have drawbacks on the investigation of the intrinsic activity of the active sites. In recent years, single-site catalysts have become popular because they allow for maximum utilization of the metal centers, show specific catalytic performance, and facilitate easy elucidation of the catalytic mechanism at the molecular level. Accordingly, numerous single-site catalysts were developed for CO₂ reduction to produce value-added chemicals such as CO, CH₄, CH₃OH, formate, and C₂₊ products. Value-added chemicals have also been synthesized with the aid of amines and epoxides. This review summarizes recent state-of-the-art single-site catalysts and their application as heterogeneous catalysts for the electroreduction, photoreduction, and thermal reduction of CO₂. In the discussion, we will highlight the structure-activity relationships for the catalytic conversion of CO₂ with single-site catalysts.     

可见光驱动丰产金属卟啉类配合物催化的二氧化碳选择性还原反应

随着能源短缺和环境问题日益突出, 寻找清洁和可再生能源来替代化石燃料是本世纪科学家面临的最紧迫的任务之一. 为了实现我国“双碳”战略目标, 利用太阳能将二氧化碳(CO₂)转化为清洁燃料和化学品是实现社会可持续发展的途径之一. 催化剂是CO₂光还原技术的核心组成部分, 其可以吸附气态CO₂分子, 在可见光照射下将CO₂还原为一氧化碳(CO)、 甲酸(HCOOH)、 甲醇(CH₃OH)或甲烷(CH₄)等能源小分子. 目前, 新型CO₂还原光催化体系的开发取得了很好的进展. 本文综合评述了近年来均相及非均相丰产金属卟啉类催化剂在光催化CO₂还原中的研究进展, 并对在金属卟啉均相催化剂作用下, CO₂光还原为CO或CH₄的反应机理分别进行了介绍, 还讨论了金属卟啉基多孔有机聚合物与卟啉有机金属框架在光催化CO₂方面的重要应用. 最后, 对可见光驱动卟啉类金属配合物催化的CO₂还原的发展前景进行了展望.     

Visible‐Light‐Driven CO2 Reduction by Mesoporous Carbon Nitride Modified with Polymeric Cobalt Phthalocyanine

The integration of molecular catalysts with low‐cost, solid light absorbers presents a promising strategy to construct catalysts for the generation of solar fuels. Here, we report a photocatalyst for CO₂ reduction that consists of a polymeric cobalt phthalocyanine catalyst (CoPPc) coupled with mesoporous carbon nitride (mpg‐CN_x) as the photosensitizer. This precious‐metal‐free hybrid catalyst selectively converts CO₂ to CO in organic solvents under UV/Vis light (AM 1.5G, 100 mW cm^?2, λ>300 nm) with a cobalt‐based turnover number of 90 for CO after 60 h. Notably, the photocatalyst retains 60 % CO evolution activity under visible light irradiation (λ>400 nm) and displays moderate water tolerance. The in situ polymerization of the phthalocyanine allows control of catalyst loading and is key for achieving photocatalytic CO₂ conversion.     

Thermodynamics and kinetics of CO2, CO, and H+ binding to the metal centre of CO2 reduction catalysts

In our developing world, carbon dioxide has become one of the most abundant greenhouse gases in the atmosphere. It is a stable, inert, small molecule that continues to present significant challenges toward its chemical activation as a useful carbon end product. This tutorial review describes one approach to the reduction of carbon dioxide to carbon fuels, using cobalt and nickel molecular catalysts, with particular focus on studying the thermodynamics and kinetics of CO(2) binding to metal catalytic sites.     

Construction of Z-Scheme In2S3-TiO2 for CO2 Reduction under Concentrated Natural Sunlight

Producing chemical fuels from sunlight enables a sustainable way for energy consumption.Among various solar fuel generation approaches,photocatalytic CO₂ reduction has the advantages of simple structure,mild reaction condition,directly reducing carbon emissions,etc.However,most of the current photocatalytic systems can only absorb the UV-visible spectrum of solar light.Therefore,finding a way to utilize infrared light in the photocatalytic system has attracted more and more attention.Here,a Z-scheme In₂S₃-TiO₂ was constructed for CO₂ reduction under concentrated natural sunlight.The infrared light was used to create a high-temperature environment for photocatalytic reactions.The evolution rates of H2,CO,and C2H5OH reached 262.2,73.9,and 27.56μmol?h^-1?g^-1,respectively,with an overall solar to fuels efficiency of 0.002%.This work provides a composite photocatalyst towards the utilization of full solar light spectrum,and could promote the research on photocatalytic CO₂ reduction.     

Homogeneous Molecular Iron Catalysts for Direct Photocatalytic Conversion of Formic Acid to Syngas (CO+H2)

The catalytic decomposition of formic acid to generate syngas (a mixture of H₂ and CO) is a highly valuable strategy for energy conversion. Syngas can be used directly in internal combustion engines or can be converted to liquid fuels, meeting future energy challenges in a sustainable manner. Herein, we report the use of homogeneous molecular iron catalysts combined with a CdS nanorods (NRs) semiconductor to construct a highly efficient photocatalytic system for direct conversion of formic acid to syngas at room temperature and atmospheric pressure. Under optimal conditions, the photocatalytic system presents an activity of 150 mmol g_catalyst^?1 h^?1 towards H₂, and an apparent quantum yield (AQY) of 16.8 %, making it among the most active noble‐metal‐free photocatalytic systems for H₂ evolution from formic acid under visible light. Meanwhile, these iron‐based molecular catalysts also demonstrate remarkable enhancement in CO evolution with robust stability. The mechanistic role of the molecular catalyst is further investigated by using cyclic voltammetry, which suggests the formation of Fe^I species as the key step in the catalytic conversion of formic acid to syngas.     

Recent advances in Cu-based nanocomposite photocatalysts for CO_2 conversion to solar fuels

CO_2 conversion via photocatalysis is a potential solution to address global warming and energy shortage.Photocatalysis can directly utilize the inexhaustible sunlight as an energy source to catalyze the reduction of CO_2 to useful solar fuels such as CO, CH_4, CH_3OH, and C_2H_5OH. Among studied formulations, Cubased photocatalysts are the most attractive for CO_2 conversion because the Cu-based photocatalysts are low-cost and abundance comparing noble metal-based catalysts. In this literature review, a comprehensive summary of recent progress on Cu-based photocatalysts for CO_2 conversion, which includes metallic copper, copper alloy nanoparticles(NPs), copper oxides, and copper sulfides photocatalysts, can be found. This review also included a detailed discussion on the correlations of morphology, structure, and performance for each type of Cu-based catalysts. The reaction mechanisms and possible pathways for productions of various solar fuels were analyzed, which provide insight into the nature of potential active sites for the catalysts. Finally, the current challenges and perspective future research directions were outlined, holding promise to advance Cu-based photocatalysts for CO_2 conversion with much-enhanced energy conversion efficiency and production rates.     

Electroreduction of CO2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes

Electrocatalytic CO₂ reduction to value‐added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine‐thiolate complexes as electrocatalysts for CO₂ reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2‐pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s^?1. Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands.     

Electroreduction of CO2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes

Electrocatalytic CO₂ reduction to value-added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine-thiolate complexes as electrocatalysts for CO₂ reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2-pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s⁻¹. Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands.