Ru修饰Pd二十四面体纳米晶的合成及其甲醇电催化氧化性能

表面结构控制和表面异种金属修饰是调控催化剂反应性的重要方法。因此,我们结合高指数晶面结构的高反应性与表面修饰异种金属,合成具有{730}高指数晶面的钯二十四面体纳米晶,并通过循环伏安扫描电沉积法得到Ru修饰的钯二十四面体纳米晶。电化学测试结果表明,低的Ru覆盖度(θ_(Ru)=0.08)可显著提高对碱性介质中甲醇电氧化的催化性能。电化学原位红外光谱结果表明,少量Ru的修饰没有减少CO的生成,而是促进了低电位下甲醇氧化成甲酸根。     

TiO2负载的高分散Cd团簇催化剂高效催化CO2加氢制甲醇

近年来,利用可再生能源分解水制氢进而开展二氧化碳资源化利用的研究引起了学术界和工业界的极大兴趣.科学层面上它暗合了自然光合作用的理念;应用层面上它把二氧化碳变废为宝,既可以得到人类必需的含碳化学品,又可以实现碳中和.甲醇被认为是二氧化碳资源化的最佳选择,可在动力、交通、化工等领域替代煤炭等传统化石能源,也是良好的载氢分...     

过渡金属催化CO2/H2参与的羰基化研究进展

Ever-increasing energy demands due to rapid industrialization and urban population growth have drastically reduced petroleum reserves and increased greenhouse-gas production, and the latter has consequently contributed to climate change and environmental damage. Therefore, it is highly desirable to produce fuels and chemicals from non-petroleum feedstocks and to reduce the atmospheric concentrations of greenhouse gases. One solution has involved using carbon dioxide (CO₂), a main greenhouse gas, as a C1 feedstock for producing industrial fuels and chemicals. However, this requires high energy input from reductants or reactants with relatively high free energy (e.g., H₂ gas) because CO₂ is a highly oxidized, thermodynamically stable form of carbon. H₂ can be generated through water photolysis, making it an ideal reductant for hydrogenating CO₂ to CO. In situ generation of CO such as this has been developed for various carbonylation reactions that produce high value-added chemicals and avoid deriving CO from fossil fuels. This is beneficial because CO is toxic, and when extracted from fossil fuels it requires tedious separation and transportation. This combination of CO₂ and H₂ allows for functional molecules to be synthesized as entries into the chemical industry value chain and would generate a carbon footprint much lower than that of conventional petrochemical pathways. Based on this, CO₂/H₂ carbonylations using homogeneous transition metal-based catalysts have attracted increasing attention. Through this process, alkenes have been converted to alcohols, carboxylic acids, amines, and aldehydes. Heterogeneous catalysis has also provided an innovative approach for the carbonylation of alkenes with CO₂/H₂. Based on these alkene carbonylations, the scope of CO₂/H₂ carbonylations has been expanded to include aryl halides, methanol, and methanol derivatives, which give the corresponding aryl aldehyde, acetic acid, and ethanol products. These carbonylations revealed indirect CO₂-HCOOH-CO pathways and direct CO₂ insertion pathways. The use of this process is ever-increasing and has expanded the scope of CO₂ utilization to produce novel, high value-added or bulk chemicals, and has promoted sustainable chemistry. This review summarizes the recent advances in transition-metal-catalyzed carbonylations with CO₂/H₂ and discusses the perspectives and challenges of further research.     

多相催化剂催化二氧化碳加氢合成甲醇的研究进展

近年来, 随着空气中二氧化碳含量的不断升高, 二氧化碳的催化转化在科研界和工业界受到了广泛关注. 非均相催化的二氧化碳加氢合成甲醇是实现二氧化碳资源化利用的重要手段之一, 具有良好的应用前景. 本文系统概述了非均相催化二氧化碳加氢合成甲醇反应的近期研究进展, 重点介绍了金属催化剂和金属氧化物催化剂, 对反应机理进行了阐述, 并对该领域仍待解决的问题和发展前景进行了展望.     

Effect of Zr Addition on Catalytic Performance of Cu-Zn-Al Oxides for CO2 Hydrogenation to Methanol

A series of 50%CuO-25%ZnO-25%Al(Zr) oxide catalysts was synthesized by a reverse co-precipitation method and characterized by XRD, N₂ adsorption-desorption, H₂-TPR, H₂-TPD and CO₂-TPD, and used as catalyst for CO₂ hydrogenation to methanol under mild conditions(200-260℃ and 1-3 MPa). Consequently, H₂-TPR exhibited that the dispersed CuO species increased with the zirconium content, while the H₂-TPD showed that small amount of zirconia can increase the H₂ desorption amount. As a result, Cat-2 and Cat-3 exhibited an enhanced H₂-spillover effect, the most H₂ desorption amount, which showed an optimum activity of about 7% methanol yield.     

二氧化碳加氢制甲醇多相催化剂研究进展

化石燃料的利用为人类社会带来了前所未有的繁荣和发展. 然而, 化石燃料燃烧引起的过量的二氧化碳(CO₂)排放导致全球气候变化和海洋酸化; 而且作为一种有限的资源, 化石燃料的消耗将迫使人们寻找其它碳源以维持可持续的发展. 利用可再生能源获取电能分解水制得的绿色氢气(H₂)与捕集后的CO₂反应制成甲醇, 不仅能有效利用工业废气中多余的CO₂, 还能获取清洁、 可再生的甲醇化学品, 该过程的技术核心是开发高效稳定的CO₂加氢制甲醇催化剂. 本文综合评述了现有研究关注较多的多相催化CO₂加氢制甲醇催化剂的反应机理和构效关系, 总结了目前多相催化CO₂加氢制甲醇催化剂(Cu基催化剂、 贵金属与双金属催化剂、 氧化物催化剂以及其它新型催化剂)的设计与合成方面的研究进展, 最后对该领域所面临的机遇和挑战进行了展望.     

反应气中活化后的镍酸镧用于二氧化碳加氢生成甲烷

采用柠檬酸法制备了钙钛矿镍酸镧,并将其作为催化剂的前躯体用于二氧化碳甲烷化反应中。催化剂在400℃~700℃温度下反应气中进行活化处理。活化过程中生成了金属镍颗粒和碳酸氧化镧。金属镍呈高度分散状并被碳酸氧化镧包裹,这种现象有助于反应在400℃和500℃的高温下仍保持高活性和稳定性。XRD、XPS、TEM和H₂-TPD等表征测试表明,在活化过程中生成的碳酸氧化镧对反应起到了至关重要的作用。     

Cu@UiO-66衍生的Cu+-ZrO2界面位点用于高效催化CO2加氢制甲醇

Cu/ZrO₂ catalysts have demonstrated effective in hydrogenation of CO₂ to methanol, during which the Cu-ZrO₂ interface plays a key role. Thus, maximizing the number of Cu-ZrO₂ interface active sites is an effective strategy to develop ideal catalysts. This can be achieved by controlling the active metal size and employing porous supports. Metal-organic frameworks (MOFs) are valid candidates because of their rich, open-framework structures and tunable compositions. UiO-66 is a rigid metal-organic skeleton material with excellent hydrothermal and chemical stability that comprises Zr as the metal center and terephthalic acid (H₂BDC) as the organic ligand. Herein, porous UiO-66 was chosen as the ZrO₂ precursor, which can confine Cu nanoparticles within its pores/defects. As a result, we constructed a Cu-ZrO₂ nanocomposite catalyst with high activity for CO₂ hydrogenation to methanol. Many active interfaces could form when the catalysts were calcined at a moderate temperature, and the active interface was optimized by adjusting the calcination temperature and active metal size. Furthermore, the Cu-ZrO₂ interface remained after CO₂ hydrogenation to methanol, as confirmed by transmission electron microscopy (TEM), demonstrating the stability of the active interface. The catalyst structure and hydrogenation activity were influenced by the content of the active component and the calcination temperature; therefore, these parameters were explored to obtain an optimized catalyst. At 280 ℃ and 4.5 MPa, the optimized CZ-0.5-400 catalyst gave the highest methanol turnover frequency (TOF) of 13.4 h^-1 with a methanol space-time yield (STY) of 587.8 g·kg^-1·h^-1 (calculated per kilogram of catalyst, the same below), a CO₂ conversion of 12.6%, and a methanol selectivity of 62.4%. In situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO adsorption over the optimized catalyst revealed a predominant, unreducible Cu⁺ species that was also identified by X-ray photoelectron spectroscopy (XPS). The favorable activity observed was due to this abundant Cu⁺ species coming from the Cu⁺-ZrO₂ interface that served as the methanol synthesis active center and acted as a bridge for transporting hydrogen from the active Cu species to ZrO₂. In addition, the oxygen vacancies of ZrO₂ promoted the adsorption and activation of CO₂. These vacancies and Cu⁺ trapped in the ZrO₂ lattice are the active sites for methanol synthesis from CO₂ hydrogenation. The X-ray diffraction (XRD) patterns of the catalyst before and after reaction revealed the stability of its structure, which was further verified by time-on-stream (TOS) tests. Furthermore, in situ DRIFTS and temperature-programmed surface reaction-mass spectroscopy (TPSR-MS) revealed the reaction mechanism of CO₂ hydrogenation to methanol, which followed an HCOO-intermediated pathway.     

Poly(N,N-dimethylaminoethyl methacrylate)–poly(ethylene oxide) copolymer membranes for selective separation of CO2

A series of copolymers containing ether oxygen groups and amino groups were prepared based on N,N-dimethylaminoethyl methacrylate (DMEMA) and polyethylene glycol methyl ether methyl acrylate (PEGMEMA). The effect of PEGMEMA content in the copolymer on density, free volume, mechanical performance, and H₂, CO₂, N₂ and CH₄ gas transport properties of the copolymer was determined. Free volume was characterized using the polymer density and group contribution theory. The permeability of the copolymer to CO₂ is high, and both the CO₂/N₂ and CO₂/H₂ selectivities are high. For example, the permeability coefficient of PDMAEMA–PEGMEMA-90 (“90” represents the weight percent of PEGMEMA) to CO₂ is 112 Barrer and the CO₂/N₂ and CO₂/H₂ selectivity coefficients are 31 and 7, respectively. The effect of the temperature on gas transport properties was also determined. Finally, the potential application of the copolymer membranes for CO₂/light gases separation was explored.     

富氮多级孔炭材料的制备及其吸附分离CO2的性能

使用新型含氮聚合物席夫碱为炭源, SBA-15为模板,通过纳米铸型法原位合成微孔-中孔-大孔串联的多级孔富氮炭材料.材料的比表面积为752 m²·g^-1,孔容0.79 cm³·g^-1; X光电子能谱分析表明炭材料中的氮含量高达7.85%(w).将所制备的多孔炭材料应用于CO₂的吸附分离,发现炭材料的微孔发挥主导作用,表面氮掺杂发挥辅助作用.在两者的协同作用下, CO₂吸附量在常压、273 K下可达97 cm³·g^-1, CO₂/N₂和CO₂/CH₄的分离比(摩尔比)分别为7.0和3.2,低压亨利吸附选择性分别为23.3和4.2.采用Toth模型对单组分平衡吸附进行拟合,并根据理想溶液吸附理论(IAST)预测双组分CO₂/N₂和CO₂/CH₄混合气体的分离选择性分别为40和18.     

面向CO2电化学转化的铜基催化剂研究进展

Burning of fossil fuels increases CO₂ concentration in the atmosphere, resulting in a series of climate- and environment-related concerns such as global warming, sea-level rise, and melting of glaciers. Therefore, utilization of renewable energy to reduce the CO₂ concentration, in order to realize a sustainable development, is urgent. Capturing and utilizing CO₂, a greenhouse gas, can not only address these concerns but also alleviate the current scenario of energy shortage. Thermal catalytic CO₂ hydrogenation offers various pathways with high conversion efficiencies to produce fuels and industrial chemicals including CO, HCOOH, CH₃OH, and CH₄. However, CO₂ is chemically inert due to the highly stable C＝O bond. Thus, harsh reaction conditions such as high temperature and pressure are required for CO₂ hydrogenation.     

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.     

利用ZnO@ZIF-8核壳结构构建高选择性、高稳定性的Pd/ZnO催化剂用于CO2加氢制甲醇

Catalytic CO₂ hydrogenation to methanol is a promising route to mitigate the negative effects of anthropogenic CO₂. To develop an efficient Pd/ZnO catalyst, increasing the contact between Pd and ZnO is of the utmost importance, because "naked" Pd favors CO production via the reverse water-gas shift path. Here, we have utilized a ZnO@ZIF-8 core-shell structure to synthesize Pd/ZnO catalysts via Pd immobilization and calcination. The merit of this method is that the porous outer layer can offer abundant "guest rooms" for Pd, ensuring intimate contact between Pd and the post-generated ZnO. The synthesized Pd/ZnO catalysts (PZZ8-T, T denotes the temperature of calcination in degree Celsius) is compared with a ZnO nanorod-immobilized Pd catalyst (PZ). When the catalytic reaction was performed at lower reaction temperatures (250, 270, and 290 ℃), the highest methanol space time yield (STY) and highest STY per Pd achieved by PZ at 290 ℃ were 0.465 g g_cat^-1 h^-1 and 13.0 g g_Pd^-1 h^-1, respectively. However, all the PZZ8-T catalysts exhibited methanol selectivity values greater than 67.0% at 290 ℃, in sharp contrast to a methanol selectivity value of 32.8% for PZ at the same temperature. Thus, we performed additional investigations of the PZZ8-T catalysts at 310 and 360 ℃, which are unusually high temperatures for CO₂ hydrogenation to methanol because the required endothermic reaction is expected to be severely inhibited at such high temperatures. Interestingly, the PZZ8-T catalysts were observed to achieve a methanol selectivity value of approximately 60% at 310 ℃, and PZZ8-400 was observed to maintain a methanol selectivity value of 51.9% even at a temperature of 360 ℃. Thus, PZZ8-400 attains the highest methanol STY of 0.571 g g_cat^-1 h^-1at 310 ℃. For a better understanding of the structure-performance relationship, we characterized the catalysts using different techniques, focusing especially on the surface properties. X-ray photoelectron spectroscopy (XPS) results indicated a linear relationship between the methanol selectivity and the surface PdZn : Pd ratio, proving that the surface PdZn phase is the active site for CO₂ hydrogenation to methanol. Furthermore, analysis of the XPS O 1s spectrum together with the electronic paramagnetic resonance results revealed that both, the oxygen vacancy as well as the ZnO polar surface, played important roles in CO₂ activation. Chemisorption techniques provided further quantitative and qualitative information regarding the Pd-ZnO interface that is closely related to the CO₂ conversion rate. We believe that our results can provide insight into the catalytic reaction of CO₂ hydrogenation from the perspective of surface science. In addition, this work is an illustrative example of the use of novel chemical structures in the fabrication of superior catalysts using a traditional formula.     

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.     

Supported carbon molecular sieve membranes based on a phenolic resin

The preparation of a composite carbon membrane for separation of gas mixtures is described. The membrane is formed by a thin microporous carbon layer (thickness, 2 μm) obtained by pyrolysis of a phenolic resin film supported over a macroporous carbon substrate (pore size, 1 μm; porosity, 30%). The microporous carbon layer exhibits molecular sieving properties and it allows the separation of gases depending on their molecular size. The micropore size was estimated to be around 4.2 Å. Single and mixed gas permeation experiments were performed at different temperatures between 25°C and 150°C, and pressures between 1 and 3.5 bar. The carbon membrane shows high selectivities for the separation of permanent gases like O₂/N₂ system (selectivity≈10 at 25°C). Gas mixtures like CO₂/N₂ and CO₂/CH₄ are successfully separated by means of prepared membranes. For example, the membrane prepared by carbonization at 700°C shows at 25°C the following separation factors: CO₂/N₂≈45 and CO₂/CH₄≈160.     

Recent Progress on Bismuth-based Nanomaterials for Electrocatalytic Carbon Dioxide Reduction

Due to the burning of fossil fuels, the level of carbon dioxide(CO₂) in the atmosphere gradually rises, leading to serious greenhouse effect and environmental problems. Electrocatalytic reduction of CO₂ is currently an efficient way to convert CO₂ to value-added products. Bismuth(Bi)-based nanomaterials have raised great interests due to their excellent activity and high selectivity to electrocatalytic CO₂ reduction. In this review, the fundamental principles of electrochemical CO₂ reduction reaction(CO₂RR) are introduced at first. Moreover, the recent development of Bi-based electrocatalytic materials including Bi with various nanostructures(nanoparticle, nanosheet, etc.), Bi-based compounds(Bi oxide, bimetal chalcogenide, etc.), and Bi/C nanocomposites are summarized. In the end, the future prospects and challenges of electrocatalysts for CO₂ reduction are discussed.     

Microporous Zinc Formate for Efficient Separation of Acetylene over Carbon Dioxide

Separation of acetylene(C₂H₂) from carbon dioxide(CO₂) by adsorbents is very challenging owing to their high similarity on molecular shape and dimension. Exploring inexpensive and easily available porous materials is of importance to facilitate the practical implementation of the challenging but energy-efficient separation. Herein, we utilize an easily available porous material[Zn₃(HCOO)₆] for the selective separation of C₂H₂ over CO₂. Because of the pore confinement in[Zn₃(HCOO)₆](pore size of 0.47 nm) and accessible oxygen sites for preferential binding of C₂H₂, this material exhibits high low-pressure uptake for C₂H₂(63 cm³/cm³ at 10 kPa and 298 K) and high C₂H₂/CO₂ selectivity(7.4 under ambient conditions) that is comparable to those of out-performing porous materials. The efficient separation of[Zn₃(HCOO)₆] for C₂H₂/CO₂ mixture has also been confirmed by the breakthrough experiments.     

还原氧化石墨烯@泡沫镍载CoO纳米花电极制备及催化CO2性能

本文以氧化石墨烯包覆泡沫镍电极(GO@NF)作为基底,采用水热法在GO@NF基底上原位生长CoO纳米花,同时GO在水热过程中被同步热还原为还原氧化石墨烯(RGO),从而一步制得还原氧化石墨烯包覆泡沫镍负载CoO纳米花电极(CoO/RGO@NF)。使用XRD和SEM对CoO/RGO@NF电极进行表征,发现CoO纳米花均匀生长在泡沫镍三维网络结构上,CoO纳米花为大量针状纳米棒围绕一个中心而成的花状结构,纳米棒的长度约为10 ~ 15 μm,直径约为100 ~ 200 nm。使用循环伏安和线性扫描法测试了CoO/RGO@NF电极电催化CO₂的还原性能,在-0.76 V（vs. SHE）电位下,CoO/RGO@NF电极电催化CO₂还原的电流效率达到70.9%,产甲酸法拉第效率达到65.2%,甲酸产率为59.8 μmol·h^-1·cm^-2,且电极可持续稳定电催化还原CO₂ 4 h,表明CoO/RGO@NF电极对CO₂电还原有着优良的催化活性、选择性和稳定性。     

反应条件对铜催化CO2电还原的影响

工业规模的化石能源消耗导致大气中二氧化碳含量不断增加,CO₂转化利用成为人们日益关注的热点问题. 金属铜因其成本低廉、储量丰富,并且具有独特的CO₂亲和力能够生成多碳化合物,是目前CO₂电还原中研究最为广泛深入的电极材料. 由于阴、阳离子的特征吸附对Cu电极性能有显著影响,并且不同反应体系中对Cu电极上CO₂吸附、活化影响也有所不同,因此导致金属Cu电极上报道的电催化活性、产物种类与选择性等都非常宽泛. 基于此,有必要系统地研究各种反应条件对金属Cu电极电催化CO₂还原性能的影响. 作者选择了平均粒径为600 nm的商品化金属Cu颗粒作为电还原CO₂的催化剂,研究了不同反应条件包括各种常用电解质溶液、KHCO₃的浓度以及H型电解池和流动池. 实验结果表明,浓度为0.5 mol·L ^-1的KHCO₃作为电解质溶液具有较好催化活性和较高的产物分电流密度,流动池可以进一步提高主要产物甲酸盐和CO的分电流密度. 本研究工作从反应条件的角度对CO₂还原的电催化转化进行了系统研究,有助于理解电解液和反应器等因素对CO₂电还原反应过程的影响规律.     

用于二氧化碳电催化还原的电解器研究进展

The electrocatalytic CO₂ reduction reaction (CO₂RR) driven by renewable energy is an efficient approach to achieve the conversion and utilization of CO₂. In this context, CO₂RR has become an emerging research focus in the field of electrocatalysis over the past decade. While a large number of nanostructured catalysts have been developed to accelerate CO₂RR, the tradeoff between activity and selectivity usually renders the overall electrocatalytic performance very poor. Beyond catalyst design, rationally designing electrolyzers is also of substantial importance for improving the CO₂RR performance and achieving its scale-up for practical applications. To a large extent, the electrolyzer configuration determines the local reaction environment near an electrode by affecting the process conditions, thereby resulting in remarkably different electrocatalytic performances. To be techno-economically viable, the performance of CO₂ electrolyzers is expected to be at least comparable to that of the current state-of-the-art proton exchange membrane (PEM) water electrolyzers, with regard to their activity, selectivity, and stability. Researchers have made great progress in the development of CO₂ electrolyzers over the past few years, but they are also facing many issues and challenges. This review aims to provide an in-depth analysis of the research progress and status of current CO₂ electrolyzers including H-cell, flow-cell, and membrane electrode assembly cell (MEA-cell) electrolyzers. Herein, operation at industrial current densities (> 200 mA∙cm⁻²) is set as a basis when these electrolyzers are discussed and compared in terms of the four main figures of merit (current density, Faradic efficiency, energy efficiency and stability) that describe the CO₂RR performance of an electrolyzer. The advantages and drawbacks of each electrolyzer are discussed and highlighted with emphasis on the key achievements reported to date. Compared to conventional H-cell electrolyzers that work well in mechanistic studies, the newly developed electrolyzers using gas diffusion electrodes, both flow-cell and MEA-cell electrolyzers, are able to break the limitation of CO₂ solubility in water and acquire industrial current densities. Although flow-cell electrolyzers have achieved current densities exceeding 1 A∙cm⁻², they suffer from low energy efficiencies because of the significant iR drop and poor stability owing to the use of alkaline electrolytes. These issues can be overcome in the case of zero-gap MEA-cell electrolyzers with ion exchange membranes being as solid electrolytes. The anion exchange membrane (AEM)-based CO₂ electrolyzers are at the center of the current research, as they demonstrate promising activity and selectivity toward specific CO₂RR products and exhibit excellent stability for over thousands of hours in few cases. Meanwhile, the crossover of CO₂ and liquid products from the cathode to the anode through the membrane tends to lower the utilization efficiency of the CO₂ supplied to the AEM electrolyzers. MEA-cell electrolyzers using cation exchange membranes and bipolar membranes have also been explored; however, neither of them have shown satisfactory CO₂RR performance. The development of new polymer electrolyte membranes and ionomers would help address these problems. While issues and challenges still exist, MEA-cell electrolyzers hold the greatest promise for practical applications. As concluding remarks, research strategies and opportunities for the future have been proposed to accelerate the development of CO₂RR technology for practical applications and to deepen the mechanistic understanding behind improved performance. This review provides new insights into rational electrolyzer design and guidelines for researchers in this field.