氮化铌电催化还原CO2

通过电化学的方法将CO₂转化为CO是解决资源和环境问题的经济友好的策略。在本次工作中,利用湿化学方法制备了铌/碳的前驱体,在NH₃和Ar氛围下煅烧后分别转化为Nb₄N₅/C和Nb₂O₅/C。当氮化温度达到700℃时,制备的Nb₄N₅/C表现出优异的催化活性,在CO₂饱和的0.5 mol·L^-1的NaCl溶液中,电解电位为-0.83V（RHE）时,CO的法拉第效率最高,达到57%。实验结果表明,Nb₄N₅/C的催化活性与Nb₄N₅中的N掺杂有关。     

CaO对Cu-ZnO-ZrO_2催化CO_2加H_2合成甲醇性能影响

用CaO作为改性助剂,采用并流共沉淀法制备了CuO∶ZnO∶ZrO_2为5∶4∶1(物质的量比),CaO添加量为0、1%、2%、4%、8%、16%(摩尔分数)的六组催化剂。用X射线衍射(XRD)、微商热重(TG-DTG)、傅里叶红外(FT-IR)、N2吸附脱附(BET)、X射线光电子能谱(XPS)、氢气程序升温还原(H_2-TPR)、CO_2程序升温脱附(CO_2-TPD)、NH_3程序升温脱附(NH_3-TPD)对催化剂进行了表征。用自制固定床评价了催化剂活性。结果表明,添加CaO后,催化剂路易斯酸性和表面碱性增强;催化剂母体中高温碳酸盐含量增加,热稳定性增强,CuO颗粒粒径变小,Cu-Zn协同作用增强,Cu比表面积增大,分散性变好。催化剂活性受到表面酸碱性、铜比表面积、Cu-Zn协同作用和铜分散性共同影响。当CaO为2%时,铜比表面积为79.3 m2/g、铜分散度为34.8%、CO_2转化率为24.55%、甲醇选择性为19.01%、甲醇收率为0.044 g/(gcat·h),催化剂活性最好。过量CaO占据催化剂孔道和覆盖表面活性位,使催化剂路易斯酸性和表面碱性过强,CuO与H_2有效接触减少,CO_2难以脱附,催化活性下降。因此,适量CaO(2%)添加可促进CO_2加氢反应合成甲醇。     

Dy和Y掺杂改性对CuO/CeZrO_2催化剂在富氢气氛中CO优先氧化催化性能的影响

采用水热-浸渍法制备了系列Dy和Y掺杂改性的CuO/CeZrO_2催化剂,使用X射线粉末衍射(XRD)、N_2吸附脱附和程序升温还原(H_2-TPR)等手段对催化剂进行了表征,研究了Dy和Y掺杂改性对CuO/CeZrO_2在富氢气氛中CO优先氧化催化性能的影响。结果表明,所制备的CuO-CeZrO_2催化剂均为萤石结构;添加适当比例的Dy_2O_3和Y_2O_3能增强活性组分与载体间的相互作用,有利于CuO活性组分的分散和低温还原能力的提高,从而改善了CuO/CeZrO_2用于CO优先氧化的催化活性。同时,掺杂Dy和Y能够提高CuO/CeZrO_2催化剂的抗CO_2抑制作用的能力,改善其催化稳定性。     

以类水滑石为前驱体的Cu/ZnO/Al2O3催化剂用于COx加氢合成甲醇：CO在反应混合物中的作用

近年来,催化CO₂加氢合成甲醇被视为有望解决温室效应和燃料枯竭的有效途径。目前,铜基催化剂因具有较高的反应活性被广泛应用于工业生产。然而,竞争逆水煤气变换反应产生的CO导致甲醇选择性较低,同时副产物水引起Cu发生不可逆烧结,进而降低甲醇产率。众所周知,CO能够调整分子的表面竞争吸附和活性位的氧化还原行为,本工作拟向原料气中掺入具有还原性的CO以抑制逆水煤气变换反应和防止表面氧化中毒。另一方面,通常认为铜基催化的CO₂加氢制甲醇是结构敏感性反应,不同的前驱体能够显著影响催化剂结构和形貌,进而影响催化活性。因此,我们首先通过共沉淀法和蒸氨法制备了含有类水滑石前驱体(CHT-CZA)和复合物前驱体(CNP-CZA)结构的Cu/ZnO/Al₂O₃催化剂。随后,为探究CO掺杂后反应机理,在250 ℃,5 MPa的反应条件下,含有不同比例CO的原料气中(CO₂:CO:H₂:N₂ = x:(24.5 - x):72.5:3)评价两种催化剂对甲醇合成的性能。评价结果显示两种催化剂反应性能趋势相同,随着CO含量增加,CO₂转化率和STY_H2O不断降低,STY_MeOH逐渐增加。X射线光谱(XPS)显示随CO含量增加,催化剂表面还原性Cu比例增加。评价和表征结果说明CO引入抑制了逆水煤气变换反应的发生,通过还原被H₂O氧化的活性Cu表面,促使更多的活性Cu位点暴露参与甲醇合成。另一方面,透射电镜(TEM)显示掺杂的CO会过度还原而引起颗粒团聚,导致催化剂逐渐失活。相比之下,含有水滑石前驱体的催化剂在任何气氛下均表现出更加优越的反应性能和长周期稳定性。这可归因于类水滑石前驱体独特的片层结构通过结构限域作用有效避免了因CO过度还原而导致的金属颗粒团聚,从而减少活性位点损失。     

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.     

基于金属氧化物材料的二氧化碳电催化还原

The CO₂ level in the atmosphere has been increasing since the industrial revolution owing to anthropogenic activities. The increased CO₂ level has led to global warming and also has detrimental effects on human beings. Reducing the CO₂ level in the atmosphere is urgent for balancing the carbon cycle. In this regard, reduction in CO₂ emission and CO₂ storage and usage are the main strategies. Among these, CO₂ usage has been extensively explored, because it can reduce the CO₂ level and simultaneously provide opportunities for the development in catalysts and industries to convert CO₂ as a carbon source for preparing valuable products. However, transformation of CO₂ to other chemicals is challenging owing to its thermodynamic and kinetic stabilities. Among the CO₂ utilization techniques, electrochemical CO₂ reduction (ECR) is a promising alternative because it is generally conducted under ambient conditions, and water is used as the economical hydrogen source. Moreover, ECR offers a potential route to store electrical energy from renewable sources in the form of chemical energy, through generation of CO₂ reduction products. To improve the energy efficiency and viability of ECR, it is important to decrease the operational overpotential and maintain large current densities and high product selectivities; the development of efficient electrocatalysts is a critical aspect in this regard. To date, many kinds of materials have been designed and studied for application in ECR. Among these materials, metal oxide-based materials exhibit excellent performance as electrocatalysts for ECR and are attracting increasing attention in recent years. Investigation of the mechanism of reactions that involve metallic electrocatalysts has revealed the function of trace amount of oxidized metal species—it has been suggested that the presence of metal oxides and metal-oxygen bonds facilitates the activation of CO₂ and the subsequent formation and stabilization of the reaction intermediates, thereby resulting in high efficiency and selectivity of the ECR. Although the stability of metal oxides is a concern as they are prone to reduction under a cathodic potential, the catalytic performance of metal oxide-based catalysts can be maintained through careful designing of the morphology and structure of the materials. In addition, introducing other metal species to metal oxides and fabricating composites of metal oxides and other materials are effective strategies to achieve enhanced performance in ECR. In this review, we summarize the recent progress in the use of metal oxide-based materials as electrocatalysts and their application in ECR. The critical role, stability, and structure-performance relationship of the metal oxide-based materials for ECR are highlighted in the discussion. In the final part, we propose the future prospects for the development of metal oxide-based electrocatalysts for ECR.     

膜电极构型CO2还原电解单池的稳定性研究

电化学还原CO₂可实现CO₂的资源化转化,是缓解因其过度排放所导致诸多环境问题的关键技术. 本文提出了一种膜电极（membrane electrode assembly,MEA）构型CO₂还原电解单池的结构设计,可同步实现气体扩散阴极两侧CO₂的供给与电解质液层的更新. 基于该MEA构型电解池,实验考察了电解质液层中KHCO₃浓度和更新与否对氮掺杂石墨烯锚定的Ni电极表面CO₂电还原制备CO的反应活性、产物分布与稳定性的影响. 结果表明,若电流密度低于5 mA·cm^-2,KHCO₃浓度显著影响电解电势而非产物分布. CO₂还原电解单池在稳定运行中存在着“可逆”与“不可逆”两种衰减模式. 其中,阴极/电解质界面处催化剂的流失是 “不可逆”衰减形成的原因;而电解质液层中KHCO₃溶液的流失导致了MEA构型CO₂还原单池的“可逆”衰减,周期性更新KHCO₃电解质是降低其“可逆”衰减的有效方法.     

金属-有机框架基材料在二氧化碳光催化转化中的应用

将大气中的二氧化碳(CO₂)转化为燃料或高附加值化学品是降低大气中CO₂含量、 减缓温室效应的有效途径之一. 光催化CO₂化学转化条件温和, 能耗低, 在CO₂转化中占有重要地位. 金属-有机框架(MOF)基材料由于具有比表面积大、 光电性质优良和可调节性强等特点, 是CO₂光催化转化的常用催化剂之一. 本文综合评述了近两年MOF基材料在光催化CO₂还原反应、 CO₂环加成反应和CO₂羧基化反应中的应用, 阐释了MOF基材料在CO₂光催化转化中的优势和局限性, 并展望了其未来发展.     

Ni-W Catalysts Supported on Mesoporous SBA-15: Trace W Steering CO2 Methanation

Aseries of Ni-W catalysts supported on mesoporous SBA-15 with different Ni:W ratios(Ni_xW/SBA-15, Ni-5%, x=1,10,50) was prepared and fully characterized by powder X-ray diffraction(PXRD), Brunner-Emmet-Teller(BET), transmission electronic microscopy(TEM), H₂-temperature programmed reduction(H₂-TPR), and X-ray photoelectron spectroscopy(XPS). High-resolution TEM images, XPS measurements, H₂-TPR experiments coupled with PXRD results determined the evolution of Ni and W species. It is found that a trace amount of W from H₂WO₄ can significantly improve Ni dispersion on SBA-15 (Ni₅₀W/SBA-15) with Ni⁰ andnon-stoichiometric WO_x species as small as ca. 3.6 nm. The prepared Ni_xW/SBA-15 was utilized for CO₂ hydrogenation, which showed that a higher W content restrained the CO₂ hydrogenation while a lower W ratio promoted both conversion rate and selectivity for methane compared with Ni/SBA-15. The Ni₅₀W/SBA-15 catalyst showed the best performance with a 93.3% CO₂ conversion rate and 99.7% selectivity for methane at 400 ^oC under 0.1 MPa and maintained ca. 97% initial performance for 24 h. Tracking product evolution experiments by in-situ Fourier transform infrared spectrascopy(FTIR) indicated that a small amount of W can modify the surface of Ni particles by geometric coverage and electronic modification, which facilitates the adsorption of the CO intermedia and results in the formation of CH₄. This work provides a new clue to fabricating efficient CO₂ conversion bimetallic materials.     

理论计算研究二维/二维BP/g-C3N4异质结的光催化CO2还原性能

Photocatalytic reduction of CO₂ to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO₂ reduction performance. In addition, metal-free materials such as g-C₃N₄ and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C₃N₄ composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO₂ reduction reaction processes of 2D/2D BP/g-C₃N₄ composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C₃N₄. Based on the calculated work function, it is inferred that electrons transfer from g-C₃N₄ to BP owing to the higher Fermi level of g-C₃N₄ compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its single-component counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C₃N₄ hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C₃N₄, leaving photogenerated electrons and holes in the conduction band of g-C₃N₄ and the valence band of BP, respectively. Compared with pristine g-C₃N₄, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO₂ reduction on g-C₃N₄ and BP/g-C₃N₄ is discussed by computing the free energy of each step. It was found that CO₂ reduction on the composite occurs most readily on the g-C₃N₄ side. The reaction path on the composite is different from that on g-C₃N₄. The heterojunction reduces the maximum energy barrier for CO₂ reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C₃N₄ heterojunction is theoretically proven to be an excellent CO₂ reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C₃N₄. It also provides a theoretical basis for the design of other high-performance CO₂ reduction photocatalysts.      

Ni2P纳米片用于光催化二氧化碳还原

Artificial photosynthesis is an ideal method for solar-to-chemical energy conversion, wherein solar energy is stored in the form of chemical bonds of solar fuels. In particular, the photocatalytic reduction of CO₂ has attracted considerable attention due to its dual benefits of fossil fuel production and CO₂ pollution reduction. However, CO₂ is a comparatively stable molecule and its photoreduction is thermodynamically and kinetically challenging. Thus, the photocatalytic efficiency of CO₂ reduction is far below the level of industrial applications. Therefore, development of low-cost cocatalysts is crucial for significantly decreasing the activation energy of CO₂ to achieving efficient photocatalytic CO₂ reduction. Herein, we have reported the use of a Ni₂P material that can serve as a robust cocatalyst by cooperating with a photosensitizer for the photoconversion of CO₂. An effective strategy for engineering Ni₂P in an ultrathin layered structure has been proposed to improve the CO₂ adsorption capability and decrease the CO₂ activation energy, resulting in efficient CO₂ reduction. A series of physicochemical characterizations including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM) were used to demonstrate the successful preparation of ultrathin Ni₂P nanosheets. The XRD and XPS results confirm the successful synthesis of Ni₂P from Ni(OH)₂ by a low temperature phosphidation process. According to the TEM images, the prepared Ni₂P nanosheets exhibit a 2D and near-transparent sheet-like structure, suggesting their ultrathin thickness. The AFM images further demonstrated this result and also showed that the height of the Ni₂P nanosheets is ca 1.5 nm. The photoluminescence (PL) spectroscopy results revealed that the Ni₂P material could efficiently promote the separation of the photogenerated electrons and holes in [Ru(bpy)₃]Cl₂·6H₂O. More importantly, the Ni₂P nanosheets could more efficiently promote the charge transfer and charge separation rate of [Ru(bpy)₃]Cl₂·6H₂O compared with the Ni₂P particles. In addition, the electrochemical experiments revealed that the Ni₂P nanosheets, with their high active surface area and charge conductivity, can provide more active centers for CO₂ conversion and accelerate the interfacial reaction dynamics. These results strongly suggest that the Ni₂P nanosheets are a promising material for photocatalytic CO₂ reduction, and can achieve a CO generation rate of 64.8 μmol·h^-1, which is 4.4 times higher than that of the Ni₂P particles. In addition, the XRD and XPS measurements of the used Ni₂P nanosheets after the six cycles of the photocatalytic CO₂ reduction reaction demonstrated their high stability. Overall, this study offers a new function for the 2D transition-metal phosphide catalysts in photocatalytic CO₂ reduction.     

铜基串联催化剂电催化CO2还原的研究进展

化石燃料的燃烧和其他人类活动排放了大量的CO₂气体,引发了诸多环境问题。电催化CO₂还原反应(CO₂RR)可以储存间歇可再生能源,实现人为闭合碳循环,被认为是获得高附加值化学品和燃料的有效途径。电催化CO₂RR涉及多个电子-质子转移步骤,其中^*CO通常被认为是关键中间体。铜由于对^*CO具有合适的吸附能,已被广泛证明是唯一能够有效地将CO₂还原为碳氢化合物和含氧化合物的金属催化剂。然而,纯Cu稳定性差、产品选择性低、过电位高,阻碍了工业级多碳产品的生产。构筑Cu基串联催化剂是提高CO₂RR性能的一种有前途的策略。本文首先介绍电催化CO₂RR的反应路线和串联机理。然后,系统地总结铜基串联催化剂对电催化CO₂RR的最新研究进展。最后,提出合理设计和可控合成新型电催化CO₂RR串联催化剂面临的挑战和机遇。     

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.     

铜基串联催化剂电催化CO2还原的研究进展

Through the combustion of fossil fuels and other human activities, large amounts of CO₂ gas have been emitted into the atmosphere, causing many environmental problems, such as the greenhouse effect and global warming. Thus, developing and utilizing renewable clean energy is crucial to reduce CO₂ emission and achieve carbon neutrality. The electrochemical CO₂ reduction reaction (CO₂RR) has been considered as an effective approach to obtain high value-added chemicals and fuels, which can store intermittent renewable energy and achieve the artificial carbon cycle. In addition, due to its multiple advantages, such as mild reaction conditions, tunable products, and simple implementation, electrochemical CO₂RR has attracted extensive attention. Electrochemical CO₂RR involves multiple electron–proton transfer steps to obtain multitudinous products, such as C₁ products (CO, HCOOH, CH₄, etc.) and C₂ products (C₂H₄, C₂H₅OH, etc.). The intermediates, among which ^*CO is usually identified as the key intermediate, and reaction pathways of different products intersect, resulting in an extremely complex reaction mechanism. Currently, copper has been widely proven to be the only metal catalyst that can efficiently reduce CO₂ to hydrocarbons and oxygenates due to its suitable adsorption energy for ^*CO. However, the low product selectivity, poor stability, and high overpotential of pure Cu hinder its use for the production of industrial-grade multi-carbon products. Tandem catalysts with multiple types of active sites can sequentially reduce CO₂ molecules into desired products. When loaded onto a co-catalyst that can efficiently convert CO₂ to ^*CO (such as Au and Ag), Cu acts as an electron donor owing to its high electrochemical potential. ^*CO species generated from the substrate can spillover onto the surface of electron-poor Cu due to the stronger adsorption and be further reduced to C₂₊ products. The use of Cu-based tandem catalysts for electrochemical CO₂RR is a promising strategy for improving the performance of CO₂RR and thus, has become a research hotspot in recent years. In this review, we first introduce the reaction routes and tandem mechanisms of electrochemical CO₂RR. Then, we systematically summarize the recent research progress of Cu-based tandem catalysts for electrochemical CO₂RR, including Cu-based metallic materials (alloys, heterojunction, and core-shell structures) as well as Cu-based framework materials, carbon materials, and polymer-modified materials. Importantly, the preparation methods of various Cu-based tandem catalysts and their structure–activity relationship in CO₂RR are discussed and analyzed in detail. Finally, the challenges and opportunities of the rational design and controllable synthesis of advanced tandem catalysts for electrochemical CO₂RR are proposed.     

Mg-Ni/BaTiO_3催化剂上CH_4/CO_2重整反应研究

采用等体积浸渍法制备了MgO改性的一系列Mg-Ni/BaTiO3催化剂,并在固定床反应装置上考察了这些催化剂对CO2重整CH4反应的催化活性。结果表明,MgO质量负载为5%的Mg-Ni/BaTiO3催化剂活性最好。考察了不同浸渍顺序对催化剂性能的影响,结果表明,先浸镁盐后浸镍盐制得的催化剂催化性能更为理想。XRD、TPR和TPD表征发现,与催化剂Ni/BaTiO3相比,MgO的添加有利于提高催化剂的催化活性和抗积炭性能,对催化剂起到了良好的改性作用。     

纳米SiC基光催化剂研究进展

Industrialization undoubtedly boosts economic development and improves the standard of living; however, it also leads to some serious problems, including the energy crisis, environmental pollution, and global warming. These problems are associated with or caused by the high carbon dioxide (CO₂) and sulfur dioxide (SO₂) emissions from the burning of fossil fuels such as coal, oil, and gas. Photocatalysis is considered one of the most promising technologies for eliminating these problems because of the possibility of converting CO₂ into hydrocarbon fuels and other valuable chemicals using solar energy, hydrogen (H₂) production from water (H₂O) electrolysis, and degradation of pollutants. Among the various photocatalysts, silicon carbide (SiC) has great potential in the fields of photocatalysis, photoelectrocatalysis, and electrocatalysis because of its good electrical properties and photoelectrochemistry. This review is divided into six sections: introduction, fundamentals of nanostructured SiC, synthesis methods for obtaining nanostructured SiC photocatalysts, strategies for improving the activity of nanostructured SiC photocatalysts, applications of nanostructured SiC photocatalysts, and conclusions and prospects. The fundamentals of nanostructured SiC include its physicochemical characteristics. It possesses a range of unique physical properties, such as extreme hardness, high mechanical stability at high temperatures, a low thermal expansion coefficient, wide bandgap, and superior thermal conductivity. It also possesses exceptional chemical characteristics, such as high oxidation and corrosion resistance. The synthesis methods for obtaining nanostructured SiC have been systematically summarized as follows: Template growth, sol-gel, organic precursor pyrolysis, solvothermal synthesis, arc discharge, carbon thermal reduction, and electrospinning. These synthesis methods require high temperatures, and the reaction mechanism involves SiC formation via the reaction between carbon and silicon oxide. In the section of the review involving the strategies for improving the activity of nanostructured SiC photocatalysts, seven strategies are discussed, viz., element doping, construction of Z-scheme (or S-scheme) systems, supported co-catalysts, visible photosensitization, construction of semiconductor heterojunctions, supported carbon materials, and construction of nanostructures. All of these strategies, except element doping and visible photosensitization, concentrate on enhancing the separation of holes and electrons, while suppressing their recombination, thus improving the photocatalytic performance of the nanostructured SiC photocatalysts. Regarding the element doping and visible photosensitization strategies, element doping can narrow the bandgap of SiC, which generates more holes and electrons to improve photocatalytic activity. On the other hand, the principle of visible photosensitization is that photo-induced electrons move from photosensitizers to the conduction band of SiC to participate in the reaction, thus enhancing the photocatalytic performance. In the section on the applications of nanostructured SiC, photocatalytic H₂ production, pollutant degradation, CO₂ reduction, photoelectrocatalytic, and electrocatalytic applications will be discussed. The mechanism of a photocatalytic reaction requires the SiC photocatalyst to produce photo-induced electrons and holes during irradiation, which participate in the photocatalytic reaction. For example, photo-induced electrons can transform protons into H₂, as well as CO₂ into methane, methanol, or formic acid. Furthermore, photo-induced holes can convert organic waste into H₂O and CO₂. For photoelectrocatalytic and electrocatalytic applications, SiC is used as a catalyst under high temperatures and highly acidic or basic environments because of its remarkable physicochemical characteristics, including low thermal expansion, superior thermal conductivity, and high oxidation and corrosion resistance. The last section of the review will reveal the major obstacles impeding the industrial application of nanostructured SiC photocatalysts, such as insufficient visible absorption, slow reaction kinetics, and hard fabrication, as well as provide some ideas on how to overcome these obstacles.      

La2O3助剂对Rh/SiO2催化CO加氢反应性能的影响

采用溶胶凝胶法制备了SiO_2和La_2O_3-SiO_2载体,再通过浸渍法分别引入Rh-La和Rh组分,研究考察了La引入方式对Rh/SiO_2催化CO加氢反应性能的影响。结果表明,La的添加有利于提高Rh的分散度,促进Rh+中心数的增加,有效地抑制产物中CO2的生成,提高含氧化合物选择性。此外,La的引入方式会影响La与Rh间的相互作用强弱,Rh和La共浸渍制得的2Rh-5La_2O_3/SiO_2催化剂中Rh-La相互作用较强,削弱的Rh-CO键有利于反应过程中CO的插入反应,使得产物以C_(2+)含氧化合物为主。而La以助剂形式掺入SiO_2制得的2Rh/5La_2O_3-SiO_2催化剂具有较弱的La-Rh相互作用,其产物则以甲醇、乙醇等低碳醇为主。     

通过脱碳控制全球平均温度

Establishing a reliable method to predict the global mean temperature (T_e) is of great importance because CO₂ reduction activities require political and global cooperation and significant financial resources. The current climate models all seem to predict that the earth's temperature will continue to increase, mainly based on the assumption that CO₂ emissions cannot be lowered significantly in the foreseeable future. Given the earth's multifactor climate system, attributing atmospheric CO₂ as the only cause for the observed temperature anomaly is most likely an oversimplification; the presence of water (H₂O) in the atmosphere should at least be considered. As such, T_e is determined by atmospheric water content controlled by solar activity, along with anthropogenic CO₂ activities. It is possible that the anthropogenic CO₂ activities can be reduced in the future. Based on temperature measurements and thermodynamic data, a new model for predicting T_e has been developed. Using this model, past, current, and future CO₂ and H₂O data can be analyzed and the associated T_e calculated. This new, esoteric approach is more accurate than various other models, but has not been reported in the open literature. According to this model, by 2050, T_e may increase to 15.5 ℃ under "business-as-usual" emissions. By applying a reasonable green technology activity scenario, T_e may be reduced to approximately 14.2 ℃. To achieve CO₂ reductions, the scenario described herein predicts a CO₂ reduction potential of 513 gigatons in 30 years. This proposed scenario includes various CO₂ reduction activities, carbon capturing technology, mineralization, and bio-char production; the most important CO₂ reductions by 2050 are expected to be achieved mainly in the electricity, agriculture, and transportation sectors. Other more aggressive and plausible drawdown scenarios have been analyzed as well, yielding CO₂ reduction potentials of 1051 and 1747 gigatons, respectively, in 30 years, but they may reduce global food production. It is emphasized that the causes and predictions of the global warming trend should be regarded as open scientific questions because several details concerning the physical processes associated with global warming remain uncertain. For example, the role of solar activities coupled with Milankovitch cycles are not yet fully understood. In addition, other factors, such as ocean CO₂ uptake and volcanic activity, may not be negligible.     

纳米SiC基光催化剂研究进展

工业化无疑促进了经济的发展,提高了生活水平,但也导致了一些问题,包括能源危机、环境污染、全球变暖等, 其中这些所产生问题主要是由燃烧煤炭、石油和天然气等化石燃料引起的。光催化技术具有利用太阳能将二氧化碳转化为碳氢化合物燃料、从水中制氢、降解污染物等优点,从而在解决能源危机的同时避免环境污染,因此被认为是解决这些问题的最有潜力的技术之一。在各种光催化剂中,碳化硅(SiC)由于其优良的电学性能和光电化学性质,在光催化、光电催化、电催化等领域具有广阔的应用前景。本文首先系统地阐述了各种SiC的合成方法,具体包括模板生长法、溶胶凝胶法、有机前驱物热解法、溶剂热合成法、电弧放电法,碳热还原法和静电纺丝等方法。然后详细地总结了提升SiC光催化活性的各种改性策略,如元素掺杂、构建Z型(S型)体系、负载助催化剂、可见光敏化、构建半导体异质结、负载炭材料、构建纳米结构等。最后重点论述了半导体的光催化机理以及SiC复合物在光催化产氢、污染物降解和CO₂还原等领域的应用研究进展,并提出了前景展望。     

Basic Catalytic Performance of Amino and Acylamide Functionalized Metal-organic Framework in the Synthesis of Chloropropene Carbonate from CO2 Under Atmospheric Pressure

In this work, a metal-organic framework with free standing basic groups(e. g., amino and acylamide groups) decorated in the pore wall was utilized to catalyze the CO₂ cycloaddition reaction and its basic properties were tested in Knoevenagel condensation reactions. The results reveal that the metal-organic framework(MOF) material has excellent catalytic activity and high repeatability for the synthesis of chloropropene carbonate from CO₂ and epichlorohydrin with no co-catalyst under mild reaction conditions, suggesting that it is a promising heteroge-neous catalyst for CO₂ cycloaddition reaction.