具有丰富晶界的铜催化剂在气-液平衡扩散电极上高效电还原CO2制C2H4(英文)

电催化二氧化碳还原反应(CO₂RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO₂RR转化为多碳产物(C₂₊)的活性.然而,电催化CO₂还原成C₂₊产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C₂₊产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO₂RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO₂RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO₂RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C₂H₄).以一种碱式碳酸铜(Cu₂     

电催化CO2还原过程中非均相界面的动态行为(英文)

自工业革命以来, CO₂的过量排放导致了环境污染和气候变化,对人类可持续发展造成了极大的威胁.由可再生电力驱动的电催化CO₂还原反应(CO₂RR)技术可在较温和的条件下将CO₂转化为高附加价值的燃料和化学品,因而是一种有效的CO₂转换和利用的方法.尽管电催化CO₂RR已经取得了较大的研究进展,但其工业化应用依旧面临着许多挑战:CO₂RR的反应路径涉及多步电子-质子转移,其产物组分较复杂(包括C₁到C₃的产物),并且反应过程伴随着析氢反应(HER)副反应发生.此外,不同电催化剂的使用以及实验操作条件均对CO₂RR影响较大,导致目前CO₂RR催化剂性能尚不够理想,因而难以获得实际应用.为进一步开发性能良好的电催化CO₂RR体系,以及认识实际反应过程中催化体系真正的活性位点,理解电催化剂表面结构演变机制至关重要.本文综述了CO     

电催化二氧化碳还原的铜基催化剂设计与反应机理研究进展

利用电催化技术和阴极区的还原反应将CO₂转化为高能化学品是解决温室效应和实现人工碳循环的有效途径。与其它金属催化剂相比,Cu基催化剂因其能生成多碳产物而备受关注,但其缺点是对产物的选择性差。因此,近年来,研究者致力于探究Cu基催化剂在反应过程中的C-C偶联机制及影响因素,并对Cu基催化剂进行针对性的结构设计和实验合成。本文总结了Cu基电极上电催化CO₂还原反应(CO₂RR)的基本原理,分析了影响电催化CO₂RR的关键因素(电催化反应器、pH值、压力和温度、CO₂的流速与浓度),综述了针对Cu基催化剂改性的相关策略(合金化、纳米结构改性、杂原子掺杂、亲/疏水性、单原子催化剂)的研究进展,最后,展望了电催化CO₂RR的Cu基催化剂领域的机遇与挑战,以期为今后开展相关研究提供有益参考。     

通过实验和理论验证Pt0/SrTiO3-δ复合催化剂双反应路径促进CO2还原(英文)

在以H₂O为质子源的光催化二氧化碳还原反应(CO₂RR)过程中,光解H₂O产氢气(H₂)被认为是一个竞争反应.因此,光催化CO₂RR过程需要抑制H₂的产生,以提高碳氢产物的选择性和产率.以CO₂和H₂为反应物的逆水气变换反应(RWGS)是常见的CO₂加氢反应,在较高的温度和催化剂作用下生成CO和H₂O.目前,光催化CO₂RR研究主要聚焦于产物的选择性,而有关光解H₂O产生的还原性气体H₂在光热效应的促进下成为CO₂RR中新的质子源研究较少.光热催化是一种新的高效催化反应方式,在反应过程中需要光照和加热.光照能够促进半导体光生载流子的激发,热效应则能降低反应物分子的活化势垒,并能够促进中间产物的表面迁移以及生成物的脱附.利用光热催化热力学和动力学上的有利条件,为以H₂     

Cu改性的FeMg@SiO2纳米级核壳催化剂实现合成气一步法制备液化石油气(英文)

本实验系统研究了纳米级核壳催化剂由合成气经费托合成路线一步法直接制备液化石油气。通过采用共沉淀法、改性溶胶-凝胶法和浸渍法相结合的方法将Cu纳米颗粒浸渍在介孔二氧化硅壳包覆的FeMg催化剂上,所制备的Cu/FeMg@SiO₂纳米核壳催化剂的物理化学性质通过一系列的表征技术进行分析,如XRD、TEM、N₂吸附-脱附、H₂-TPR,XPS和CO₂-TPD等。Cu/FeMg@SiO₂纳米核壳催化剂在液化石油气合成反应中表现出较高的CO转化率(96.6%)和较低CO₂选择性(21.9%),其中,液化石油气的选择性到达37.9%。反应结果表明,SiO₂壳层抑制了CH₄的形成,有助于增加长链产物。同时,高的CO转化率归因于Cu/FeMg@SiO₂上活性金属Cu元素在SiO₂壳上的高分散,进一步促进了烯烃加氢和C₅₊烃类产物的裂解。本实验中所提出的催化剂制备方法...     

B原子掺杂调控CuIn纳米合金电子结构以实现电化学CO2还原宽电位活性(英文)

杂原子掺杂可以调节电子结构以调整中间体吸附并优化反应路径,是设计高效CO₂还原反应(CO₂RR)催化剂的有应用前景的方法.B原子是常用的掺杂剂,引入B原子可以有效打破*COOH和OCHO*中间体的吉布斯自由能线性关系,并且可以通过与CO₂中O原子结合来增强CO₂吸附能力.B掺杂碳材料、单金属和金属氧化物的研究结果表明, B原子掺杂催化剂的CO₂RR活性和/或选择性有明显提高,然而多数报道的单个活性位点的B掺杂催化剂仅表现出在相对狭窄的电位范围内的CO₂RR高性能,设计制备CO₂RR的宽电位高选择性催化剂仍是巨大挑战.研究表明,合金化是提供多种类的活性位点相互协调和增强催化剂固有活性,进而改善CO₂RR性能并调节产物分布的可行策略.引入B原子到合金中以调节电子结构,最终优化关键中间体吸附的活性位点,对于寻找具有宽电位窗口的先进催化剂具有重要意义.本文提出了一种通过B掺杂调节CuIn合金电子结构以实现宽电位高选择性的...     

CO2/C2H4耦合制备丙烯酸及其衍生物的研究进展

二氧化碳(CO₂)不仅仅是一种温室气体,更是一种重要的、有效的碳一资源,其来源丰富、无毒、无污染、不易燃烧,可用于生产有机化学品、材料、糖类等.由于CO₂分子中的碳处于最高氧化态,且其分子具有热力学和动力学惰性,因此人们不断探索新型反应途径,以及新型的催化体系来有效资源化利用CO₂.近年来,利用各种不饱和烃类,在过渡金属催化剂协助下催化CO₂与烯烃生成不饱和羧酸及其衍生物引起了极大关注.其中,催化CO₂/C₂H₄耦合反应制备丙烯酸及其衍生物因其原子经济性而备受瞩目.以镍系催化体系为主的过渡金属催化CO₂/C₂H₄偶联反应是CO₂化学转化与高值利用非常重要的研究热点之一.综述了近年来CO₂/C₂H₄偶联反应的最新进展,对相应的催化反应机理进行了评述.从多个角度对各位学者的研究进行分析比...     

一维g-C3N4/二维Ti3C2Tx界面调制促进光催化CO2还原活性与选择性(英文)

碳中和是实现绿色可持续发展重要途径之一,以半导体光催化CO₂还原.反应(CO₂RR)为核心的人工光合成技术极具发展前景.石墨相氮化碳(g-C₃N₄)作为一种二维层状光催化剂,化学性质稳定,且满足CO₂RR的热力学要求,但传统的g-C₃N₄光催化活性和选择性较低,这主要归因于高的电荷复合几率和低的光电子利用效率.采用二维碳化钛(Ti₃C₂T_x)等碳基助催化剂作为电子受体,促进光生载流子的快速分离与转移,成为提高g-C₃N₄光催化CO₂RR效率的有效手段.然而,g-C₃N₄光催化剂与Ti₃C₂T_x助催化剂多数以2D/2D构型界面耦合,受限于二者界面弱的范德华相互作用、高的界面静电势垒和缓慢的界面电荷转...     

构建Cu台阶位促进电催化CO2还原制醇类化学品的研究(英文)

电催化CO₂制备高附加值的化学品是解决当前碳排放问题的可行技术路线之一.其中,合成醇类化合物因具有广泛用途和高价值而备受关注.在电催化CO₂还原合成多碳醇反应中,关键中间体*CH₂CHO容易发生热力学有利的脱氧反应而生成C2H4,降低了醇类产物的选择性.由于电催化CO₂还原是一个表面结构敏感的反应,因此可以通过设计Cu基催化剂的特定表面结构,实现对反应路径的有效调节,从而提升醇类产物的选择性.本课题组前期通过密度泛函理论(DFT)计算和主成分分析法等对Cu基催化剂的构效关系进行解析,说明配位不饱和的台阶位点有望高效地促进醇类产物的生成.本文进一步从实验角度,证明了配位不饱和的台阶位点是生成醇类产物的活性位点.本文采用CO分子作为还原剂制备了CuO衍生的金属Cu催化剂(COD-Cu),利用CO分子对Cu表面的重构作用,获得了具有丰富台阶位点的Cu催化剂.而通过H₂还原制备的金属Cu催化剂(HOD-Cu)对照样表面则多为平面位点.X射线衍射和原位拉曼光谱结果表明, CuO前驱体经过...     

Fe2O3晶型对Fe基催化剂的CO2加氢性能影响

以共沉淀法制备FeAl母体,采用浸渍法添加Zn、K和Cu助剂制成催化剂,利用低温N2物理吸附、XRD、H2-TPR等手段对FeAl母体和催化剂进行表征,并用固定床反应器考察它们的CO₂加氢反应性能。XRD结果表明,加入Al助剂、并采用无水乙醇洗涤沉淀能促进酌-Fe₂O₃晶相生成,其中,Al₂O₃/Fe₂O₃质量比为10%的母体具有最强的酌-Fe₂O₃衍射峰;加入Al使得母体中的a-Fe₂O₃晶粒粒径变小,引起比表面积明显增大;浸渍助剂过程没有改变上述两种效应。母体比表面积增大提高了助剂Cu的分散度,促进了催化剂还原,但酌-Fe₂O₃晶相的生成才是催化剂的CO₂加氢反应活性被提高的主要原因。     

Surface Adsorbed Hydroxyl: A Double-Edged Sword in Electrochemical CO2 Reduction over Oxide-Derived Copper

Oxide-derived Cu (OD−Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO₂ reduction (ECO₂RR). With surface adsorbed hydroxyls (OH_ad) identified during ECO₂RR, it is realized that OH_ad, sterically confined and adsorbed at OD−Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C₂) product selectivity. In situ spectral investigations and theoretical calculations reveal that OH_ad favors the adsorption of low-frequency *CO with weak C≡O bonds and strengthens the *CO binding at OD−Cu surface, promoting *CO dimerization and then selective C₂ production. However, excessive OH_ad would inhibit selective C₂ production by occupying active sites and facilitating competitive H₂ evolution. In a flow cell, stable C₂ production with high selectivity of ∼60 % at −200 mA cm⁻² could be achieved over OD−Cu, with adsorption of OH_ad well steered in the fast flowing electrolyte.     

CuPd催化剂调节中间反应能垒提高电催化CO2生成二碳产物的选择性

过度的碳排放已造成了严重的全球环境问题,电催化CO2还原是一种利用间歇性过剩电能将CO2转化为有价值的化学物质的有效策略.在多种CO2还原产物中,二碳(C2)产物(如乙烯、乙醇)因其比一碳产物(如甲酸、甲烷、甲醇)具有更高的能量密度而备受关注.Cu是唯一能用电化学方法将CO2转化为多碳产物的单金属催化剂.如何提高Cu基催化剂上CO2还原为C2产物的效率已引起了极大关注.电催化还原CO2生成C2产物有两个重要步骤:一是参与碳碳偶联反应的CO*中间体的量(*代表中间体吸附在基底表面),二是碳碳偶联步骤的能垒.对于Cu单金属催化剂,虽然其表面碳碳偶联步骤的能垒相对较低,但是Cu对CO2的吸附能力和CO2*加氢能力并不高,导致在Cu表面不能生成足量的CO*中间体参与碳碳偶联反应,因而对C2产物的选择性和活性并不理想.与Cu单金属催化剂相反,在Pd单金属催化剂表面,CO*中间体的形成具有超快的反应动力学,但是CO*易在Pd表面中毒且后续碳碳偶联步骤的能垒极高,使其表面不能生成C2产物.为了充分发挥Cu(碳碳偶联步骤能垒较低)和Pd(CO*形成具有超快反应动力学)的双重优势,本文构建了一种紧密的CuPd(100)界面,以调节中间反应能垒,从而提高C2产率.密度泛函理论(DFT)计算表明,CuPd(100)界面增强了CO2的吸附,且降低了CO2*加氢步骤的能垒,从而能够催化生成更多的CO*中间体参与碳碳偶联反应.且CuPd(100)界面上CO2还原为C2产物的电位决定步骤能垒为0.61 eV,低于Cu(100)表面的(0.72 eV).本文采用了一种简便的湿化学法制备了CuPd(100)界面催化剂.X射线衍射和X射线光电子能谱测试以及扩展X射线吸收精细结构光谱结果表明,合成的是相分离的CuPd双金属催化剂,而非CuPd合金催化剂.同时高分辨透射电镜可以观察到清晰的CuPd(100)界面.由此可见,本文成功合成了CuPd(100)界面催化剂.程序升温脱附实验结果表明,CuPd(100)界面对CO2和CO*的吸附比Cu强,结果与理论预测一致.气体传感实验结果表明,CuPd(100)界面CO2*加氢能力比Cu强.为评估CuPd(100)界面催化剂的催化活性,进行了CO2电化学还原实验.结果表明,在0.1 mol/L的KHCO3电解液中,CuPd(100)界面催化剂在–1.4 VRHE下,C2产物的法拉第效率为50.3％ ±1.2％,是同电位下Cu催化剂的(23.6％ ±1.5％)的2.1倍,C2产物的选择性是Cu催化剂的2.4倍,且具有更高的电流密度和更大的电化学活性面积.本文通过调控中间反应能垒以合理设计铜基CO2还原电催化剂提供了参考.     

Designs of Tandem Catalysts and Cascade Catalytic Systems for CO2 Upgrading

Upgrading CO₂ into multi-carbon (C2+) compounds through the CO₂ reduction reaction (CO₂RR) offers a practical approach to mitigate atmospheric CO₂ while simultaneously producing high value chemicals. The reaction pathways for C2+ production involve multi-step proton-coupled electron transfer (PCET) and C−C coupling processes. By increasing the surface coverage of adsorbed protons (*H_ad) and *CO intermediates, the reaction kinetics of PCET and C−C coupling can be accelerated, thereby promoting C2+ production. However, *H_ad and *CO are competitively adsorbed intermediates on monocomponent catalysts, making it difficult to break the linear scaling relationship between the adsorption energies of the *H_ad/*CO intermediate. Recently, tandem catalysts consisting of multicomponents have been developed to improve the surface coverage of *H_ad or *CO by enhancing water dissociation or CO₂-to-CO production on auxiliary sites. In this context, we provide a comprehensive overview of the design principles of tandem catalysts based on reaction pathways for C2+ products. Moreover, the development of cascade CO₂RR catalytic systems that integrate CO₂RR with downstream catalysis has expanded the range of potential CO₂ upgrading products. Therefore, we also discuss recent advancements in cascade CO₂RR catalytic systems, highlighting the challenges and perspectives in these systems.     

Breaking K+ Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2 Reduction to Multi-Carbon Products

Electrocatalytic CO₂ reduction reaction (CO₂RR) to multi-carbon products (C₂₊) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C₂₊ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K⁺) concentration at the cathode's surface can inhibit proton-diffusion and accelerate the desirable carbon-carbon (C−C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K⁺ concentration at the reaction sites and thus the overall acidic CO₂RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K⁺ concentrations (4.22 M) – thus breaking the K⁺ solubility limit (3.5 M) – which enables a highly efficient CO₂RR in 3 M KCl at pH=1. As a result, a Faradaic efficiency of 90.69±2.15 % for C₂₊ (FE_C2+) can be achieved at 1400 mA.cm⁻², simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82 % at a CO₂ flow rate of 7 sccm.     

Promoting CO2 Electroreduction to Multi-Carbon Products by Hydrophobicity-Induced Electro-Kinetic Retardation

Advancing the performance of the Cu-catalyzed electrochemical CO₂ reduction reaction (CO₂RR) is crucial for its practical applications. Still, the wettable pristine Cu surface often suffers from low exposure to CO₂, reducing the Faradaic efficiencies (FEs) and current densities for multi-carbon (C₂₊) products. Recent studies have proposed that increasing surface availability for CO₂ by cation-exchange ionomers can enhance the C₂₊ product formation rates. However, due to the rapid formation and consumption of *CO, such promotion in reaction kinetics can shorten the residence of *CO whose adsorption determines C₂₊ selectivity, and thus the resulting C₂₊ FEs remain low. Herein, we discover that the electro-kinetic retardation caused by the strong hydrophobicity of quaternary ammonium group-functionalized polynorbornene ionomers can greatly prolong the *CO residence on Cu. This unconventional electro-kinetic effect is demonstrated by the increased Tafel slopes and the decreased sensitivity of *CO coverage change to potentials. As a result, the strongly hydrophobic Cu electrodes exhibit C₂₊ Faradaic efficiencies of ≈90 % at a partial current density of 223 mA cm⁻², more than twice of bare or hydrophilic Cu surfaces.     

镍掺杂对Fe催化剂上CO_2加氢制烃影响的理论计算研究

为研究镍掺杂对铁基催化剂上二氧化碳加氢生成C_1和C_2烃类产物的影响,应用密度泛函理论进行了相关计算.在Fe(110)和Ni-Fe(110)表面上, CH~*物种是最有利的生成CH_4和C_2H_4的C_1物种(CH_x~*),其最可能的生成路径为CO_2→HCOO~*→HCO~*→CH~*.尽管CO_2直接解离为CO~*在动力学上相较于加氢生成HCOO~*和COOH~*是较为有利的,但CO~*进一步加氢生成HCO~*在能量上是不利的,其倾向于逆向解离回到CO~*. CH~*物种可以通过三步加氢反应生成CH_4或者经C—C耦合及两步加氢生成C_2H_4.在Fe(110)表面上,对甲烷和乙烯产物选择性起决定作用的基元反应能垒之间差异仅为0.10 eV,因此两者选择性相近.在将Ni原子引入Fe(110)表面后,生成甲烷与乙烯的选择性差异变大,导致乙烯的选择性提高.计算结果表明,添加少量金属Ni能够促进CO_2转化为CH~*,及两个CH~*物种发生C—C耦合和进一步加氢转化为乙烯.     

Proton Shuttling by Polyaniline of High Brønsted Basicity for Improved Electrocatalytic Ethylene Production from CO2

Hybrid organic/inorganic composites with the organic phase tailored to modulate local chemical environment at the Cu surface arise as an enchanting category of catalysts for electrocatalytic CO₂ reduction reaction (CO₂RR). A fundamental understanding on how the organics of different functionality, polarity, and hydrophobicity affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polypyrrole (PPy) and polyaniline (PANI) manifesting different Brønsted basicity are compared for their regulatory roles on the CO₂RR pathways regarding *CO coverage, proton source and interfacial polarity. Concerted efforts from in situ IR, Raman and operando modelling unveil that at the PPy/Cu interface with limited *CO coverage, hydridic *H produced by the Volmer step favors the carbon hydrogenation of *CO to form *CHO through a Tafel process; Whereas at the PANI/Cu interface with concentrated CO₂ and high *CO coverage, protonic H⁺ shuttled through the benzenoid -NH- protonates the oxygen of *CO, yielding *COH for asymmetric coupling with nearby *CO to form *OCCOH under favored energetics. As a result of the tailored chemical environment, the restructured PANI/Cu composite demonstrates a high partial current density of 0.41 A cm⁻² at a maximal Faraday efficiency of 67.5 % for ethylene production, ranking among states of the art.     

Insight into the Formation and Transfer Process of the First Intermediate of CO2 Reduction over Ag-Decorated Dendritic Cu

It is still poorly understood how the first intermediates of CO₂ reduction are formed and converted to multi-carbon products over Cu-based electrodes. Herein, Ag is used to decorate dendritic Cu and a high Faradaic efficiency (FE) for C₂H₄ (25 %) is obtained on a CuAg electrode, which is about five times higher than dendritic Cu. The intermediates including *CO₂⁻, OH groups, Cu-CO, C-O rotation, and CH_x species are investigated by in situ Raman spectroscopy. This work provides spectroscopic evidence that the first intermediate of CO₂ reduction on Ag-decorated Cu is carboxylate anion *CO₂⁻ bonded with the catalyst surface through the C and O atom. The formation and evolution process of the *CO₂⁻ intermediate over the applied potential are investigated in depth as well. This research contributes to a better understanding of the mechanism of CO₂ reduction and multi-carbon product formation pathways over Ag-decorated Cu.     

Decrypting the Controlled Product Selectivity over Ag−Cu Bimetallic Surface Alloys for Electrochemical CO2 Reduction

Electrochemical CO₂ reduction reaction (ECO₂RR) with controlled product selectivity is realized on Ag−Cu bimetallic surface alloys, with high selectivity towards C2 hydrocarbons/alcohols (≈60 % faradaic efficiency, FE), C1 hydrocarbons/alcohols (≈41 % FE) and CO (≈74 % FE) achieved by tuning surface compositions and applied potentials. In situ spectral investigations and theoretical calculations reveal that surface-composition-dependent d-band center could tune *CO binding strengths, regulating the *CO subsequent reaction pathways and then the product selectivity. Further adjusting the applied potentials will alter the energy of participated electrons, which leads to controlled ECO₂RR selectivity towards desired products. A predominant region map, with an indicator proposed to evaluate the thermodynamic predominance of the *CO subsequent reactions, is then provided as a reliable theoretical guidance for the controllable ECO₂RR product selectivity over bimetallic alloys.     

光催化剂活性位点调控及其光还原CO2制C2 产物研究进展

工业发展与人类活动导致大气中CO₂浓度逐年升高, 引发一系列生态环境问题. 将CO₂光催化转化为高附加值化学物质不仅有利于缓解环境压力,也可以带来额外经济价值. 然而, 由于多电子利用效率低和C―C偶联动力学缓慢, 光还原CO₂制多碳产品面临产率低和选择性差等挑战. 光催化剂活性位点调控能够有效解决上述问题. 我们综述了近几年用于光还原CO₂催化剂表面活性位点设计的研究进展, 主要包括缺陷位点、 金属位点以及掺杂位点等, 从活性位点的角度为光还原CO₂催化剂设计提供新视角, 并对开发高效光催化剂具有启发意义.