水热合成二硫化钨/石墨烯复合材料及其氧还原性能

以六氯化钨、硫代乙酰胺、氧化石墨烯为原料,采用一步水热法合成了二维的二硫化钨/石墨烯(WS₂/RGO)复合材料。水热合成的WS₂/RGO具有薄层的二维结构,且由于石墨烯的存在,WS₂以较少的层数形成薄片状生长在石墨烯的表面。尝试将这种非Pt类材料用于电催化氧化原反应,测试结果表明,WS₂在碱性条件下氧还原活性非常低,但是复合RGO形成WS₂/RGO复合材料后,电催化氧化原性能有了极大的提高,其起始电位为-0.17 V(vs SCE),转移电子数为3.7,极限电流密度为2.5 mA·cm^-2,同时其具有较好的抗甲醇性能和循环稳定性。这是因为WS₂/RGO复合材料的二维结构具有更高的电子传输速率,同时硫化钨和石墨烯可以发挥协同催化作用。这种新型的二硫化钨/石墨烯(WS₂/RGO)复合材料作为非贵金属催化剂表现出良好的氧还原性能,在燃料电池上具有较好的应用前景。     

室温快速合成Ag基金属有机骨架材料用于电催化还原CO2

选择具有强给电子能力的1,2,4-三唑为配体,成功合成了银基金属有机骨架材料(Ag-MOF)并用于电催化还原CO₂反应(CO₂RR)。借助粉末X射线衍射、透射电子显微镜、扫描电子显微镜、计时电流法等表征手段对材料的晶体结构、形貌和电催化CO₂RR性能进行了系统的研究。与商品化的纳米Ag颗粒对比,Ag-MOF展现出更优异的电催化CO₂RR产物选择性、催化活性和稳定性,在-0.9 V (vs RHE)时,CO的法拉第效率高达96.1%。当电压为-1.1 V (vs RHE)时,电流密度可达17 mA·cm^-2,且电极可以稳定运行300 min。这说明通过选择合适的配体结构,可以改变催化位点周围的化学环境,从而高效将CO₂转化为目标产物。     

室温快速合成Ag基金属有机骨架材料用于电催化还原CO2

选择具有强给电子能力的1,2,4-三唑为配体,成功合成了银基金属有机骨架材料(Ag-MOF)并用于电催化还原CO₂反应(CO₂RR)。借助粉末X射线衍射、透射电子显微镜、扫描电子显微镜、计时电流法等表征手段对材料的晶体结构、形貌和电催化CO₂RR性能进行了系统的研究。与商品化的纳米Ag颗粒对比,Ag-MOF展现出更优异的电催化CO₂RR产物选择性、催化活性和稳定性,在-0.9 V (vs RHE)时,CO的法拉第效率高达96.1%。当电压为-1.1 V (vs RHE)时,电流密度可达17 mA·cm^-2,且电极可以稳定运行300 min。这说明通过选择合适的配体结构,可以改变催化位点周围的化学环境,从而高效将CO₂转化为目标产物。     

室温快速合成Ag基金属有机骨架材料用于电催化还原CO2

选择具有强给电子能力的1,2,4-三唑为配体,成功合成了银基金属有机骨架材料(Ag-MOF)并用于电催化还原CO₂反应(CO₂RR)。借助粉末X射线衍射、透射电子显微镜、扫描电子显微镜、计时电流法等表征手段对材料的晶体结构、形貌和电催化CO₂RR性能进行了系统的研究。与商品化的纳米Ag颗粒对比,Ag-MOF展现出更优异的电催化CO₂RR产物选择性、催化活性和稳定性,在-0.9 V (vs RHE)时,CO的法拉第效率高达96.1%。当电压为-1.1 V (vs RHE)时,电流密度可达17 mA·cm^-2,且电极可以稳定运行300 min。这说明通过选择合适的配体结构,可以改变催化位点周围的化学环境,从而高效将CO₂转化为目标产物。     

Ce助剂对V/SiO2催化CO2氧化乙苯脱氢性能的影响

通过N₂吸附、X射线衍射(XRD)、X射线光电子能谱(XPS)、H₂程序升温还原(H₂-TPR)、CO₂程序升温脱附(CO₂-TPD)和热重分析(TGA)等多种表征手段和催化反应性能评价,研究了铈助剂的添加对V/SiO₂催化CO₂氧化乙苯脱氢性能的影响. 结果表明,Ce助剂不仅提高了催化剂活性组分分散性和氧化还原性能,抑制了钒物种的深度还原,而且增强了催化剂碱性和CO₂吸附能力,减缓了积炭生成,从而显著提高了V-Ce/SiO₂对CO₂氧化乙苯脱氢反应的催化活性和稳定性. 在本实验中,V(0.8)-Ce(0.25)/SiO₂催化剂表现出最佳的催化性能,苯乙烯(ST)收率可达55.6%,选择性为98.5%,反应12 h 后,催化剂活性基本不变,与惰性N₂气氛比较,CO₂明显促进了乙苯脱氢反应,归因于CO₂能保持催化剂表面钒物种的高价态.     

K2CO3含量对Ni-Cu-Mn-K/Al2O3水煤气变换催化剂结构和性能的影响

以γ-Al₂O₃为载体，采用等体积浸渍法，制备了不同K₂CO₃含量的Ni-Cu-Mn-K/Al₂O₃水煤气变换催化剂，采用低温N₂吸附、XRD、TPD和TPR，考察了K₂CO₃含量对催化剂结构和性能的影响。结果表明:K₂CO₃的加入使催化剂的还原温度有所提高，适量的K₂CO₃能增加活性组分的电子密度，从而增强其给电子活化CO的能力，提高催化剂的活性。但过量的K₂CO₃使得催化剂比表面积和孔容降低，且导致催化剂对CO吸附过强，催化活性降低。当Ni-Cu-Mn-K/γ-Al₂O₃催化剂中K₂CO₃的添加量为7.5%时，且催化剂经530 ℃耐热15 h后，在350 ℃时水煤气变换反应中CO转化率达62.29%。     

生物质焦油组分甲苯在镍/凹凸棒石上的二氧化碳催化重整

 以大比表面积的天然纳米矿物材料凹凸棒石 (PG) 为载体, 采用等体积浸渍法制备了 Ni/PG 催化剂. 运用 X 射线衍射、透射电镜和 CO₂ 程序升温脱附对 Ni/PG 催化剂进行了表征, 并用于以甲苯为生物质焦油模型化合物的 CO₂ 催化重整反应. 考察了反应温度、CO₂ 浓度以及催化剂中 Ni 负载量对甲苯与 CO₂ 重整性能的影响. 结果表明, 吸附在催化剂表面的 CO₂ 存在三个脱附峰, 其中高温脱附 CO₂ 与反应密切相关; 随着 CO₂ 浓度、Ni 负载量和反应温度的增加, 甲苯转化率和 H₂ 产率升高. 在 800 ^oC, CO₂/PhCH₃ 摩尔比为 0.2~0.26 时, 甲苯转化率达最高; 而在 CO₂/PhCH₃ 摩尔比为 0.2 时, H₂ 产率最高. 催化剂上积炭量随 CO₂ 浓度的增加和反应温度的升高而显著降低.     

碳黑预处理对Pt/C催化剂对甲醇氧化电催化活性的影响

直接甲醇燃料电池(DMFC)由于具有较多的优点而受到广泛的关注. 但是碳载Pt (Pt/C)阳极催化剂电催化活性低是限制其应用的一个主要问题. 为了提高Pt/C催化剂对甲醇氧化的电催化性能, 分别用CO₂, 空气, H₂O₂或HNO₃对常用作为载体的Vulcan XC-72碳黑进行预处理. 结果表明, 在用CO₂, 空气, HNO₃, H₂O₂处理的及未处理的碳黑作载体制得的Pt/C催化剂电极上, 甲醇氧化峰的峰电流密度顺序为39, 33, 32, 20和18 mA•cm^－2, 表明用CO₂处理的碳载体制备的Pt/C催化剂对甲醇氧化有最好的电催化活性和稳定性. 其主要原因是用CO₂处理能减少碳黑表面的含氧基团和增加石墨化程度, 而使碳黑的电阻降低及Pt粒子在碳黑上的分散性变好.     

FeMn、FeMnNa和FeMnK催化剂上合成气制低碳烯烃的比较

研究了钠、钾助剂对FeMn 合成低碳烯烃催化剂结构及性能的影响. 低温N₂吸附、X射线光电子能谱（XPS）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、CO/CO₂程序升温脱附（CO/CO₂-TPD）、Mössbauer 谱和CO+H₂反应的研究结果表明,增加Mn助剂含量促进了活性相的分散和低碳烯烃的生成,而过多锰助剂在催化剂表面的富集则降低了费托合成反应的CO转化率;钾助剂和钠助剂的加入均抑制了催化剂的还原并且促进了CO₂和CO的吸附. 比较还原后（H₂/CO摩尔比为20）和反应后（H₂/CO摩尔比为3.5）催化剂的体相结构可以发现,在FeMn、FeMnNa和FeMnK催化剂中,由于钾助剂的碱性和CO吸附能力较强,因此体相中FeC_x的含量相对较高;而活性测试结果表明,FeMnNa催化剂拥有最好的CO转化率（96.2%）和低碳烯烃选择性（30.5%,摩尔分数）.     

MgFe0.1Al1.9O4 的合成及其催化乙苯与 CO2 的氧化脱氢反应

 以柠檬酸为络合剂, 采用溶胶-凝胶法制备了具有尖晶石结构的 MgFe_0.1Al_1.9O₄ 催化剂, 并将其用于催化乙苯与 CO₂ 氧化脱氢反应. 运用 X 射线衍射、X 射线能量色散光谱分析、红外光谱、热重-差热、N₂ 吸附-脱附和 H₂ 程序升温还原等技术对催化剂进行了表征. 结果表明, 在 650 ºC 以上焙烧即可制得结构确定、组成均一的 Mg-Fe-Al-O 复合氧化物催化剂, 其中 Fe 物种主要以同晶取代的形式存在于尖晶石骨架中. 随着焙烧温度的升高, 尖晶石结晶度提高, Fe 物种还原能力下降, 催化剂晶粒度增大, 比表面积降低. 700 ºC 焙烧制备的 MgFe_0.1Al_1.9O₄ 具有较好的催化乙苯与 CO₂ 氧化脱氢反应活性和稳定性.     

Organic molecules involved in Cu-based electrocatalysts for selective CO2 reduction to C2+ products

Electrocatalytic carbon dioxide (CO₂) reduction reaction (CO₂RR) is a promising process to mitigate the environmental issues caused by CO₂, as well as to produce valuable multicarbon (C₂₊) products. Significant progresses have been made to explore highly efficient Cu-based electrocatalysts for CO₂RR in recent years. Adding organic molecules into electrocatalytic systems can tune the CO₂ interaction with the electrocatalysts for CO₂RR, therefore, the final C₂₊ products, which are not solely achieved by inorganic modification. In this review, we will summarize the recent progress of the organic molecules participation in CO₂ electroreduction to C₂₊ products on Cu-based electrocatalysts. The applied organic molecules are reviewed based on the heteroatoms (N and S), with the emphasis on their roles in activity and selectivity toward C₂₊ products. A perspective on the application of organic molecules for efficient and selective CO₂RR has been provided.     

Electrochemical Reduction of Carbon Dioxide to Ethanol: An Approach to Transforming Greenhouse Gas to Fuel Source

Converting carbon dioxide (CO₂) into high-value fuels or chemicals is considered as a promising way to utilize CO₂ and alleviate the excessive greenhouse gas emission. Among multiple catalysis approaches, electrochemical reduction of CO₂ to ethanol has an important prospect due to the high energy density and widely applications of ethanol. In recent years, many electrocatalysts for CO₂ reduce reaction (CO₂RR) have shown promising catalytic activity for ethanol production. In this review, we will introduce the recent progress in this field. The basic principles and electrochemical performances of CO₂RR are reviewed at first. Then, several categories of active electrocatalysts for CO₂RR to ethanol are summarized, including the discussion of reaction mechanism and catalytic sites. Finally, several possible strategies are proposed, providing guidance for future design and preparation of high-performance catalysts.     

Crystal facet-dependent electrocatalytic performance of metallic Cu in CO2 reduction reactions

Developing high-performance electrocatalysts for CO₂ reduction reaction(CO₂ RR) is crucial since it is beneficial for environmental protection and the resulting value-add chemical products can act as an alternative to fossil feedstocks. Nonetheless, the direct reduction of CO₂ into long-chain hydrocarbons and oxygenated hydrocarbons with high selectivity remains challenging. Copper(Cu) shows a distinctive advantage that it is the only pure metal catalyst for redu...     

Investigation of Structural Evolution of SnO2 Nanosheets towards Electrocatalytic CO2 Reduction

In‐depth understanding of the catalytic active sites is of paramount importance for the design of efficient electrocatalysts for CO₂ conversion. Here we highlight the structural evolution of SnO₂ nanosheets for electrocatalytic CO₂ reduction. The transformation of SnO₂ into metallic Sn would occur on the surface of catalyst during the catalytic process, followed by enhanced selectivity and activity for the conversion of CO₂ to HCOOH. Electrocatalytic characterization and structural analysis demonstrate that the metallic Sn derived from structural evolution plays a dominant role in the CO₂ reduction to HCOOH. This work deepens the understanding of the catalytic mechanism and provides a new pathway for the rational design of advanced electrocatalysts for CO₂ reduction.     

Electrocatalyst Fabrication Using Metal Nanoparticles Prepared in Ionic Liquids

Metal nanoparticle-based electrocatalysts are widely used in electronic devices, which serve for electrochemical reactions like oxygen reduction reaction, alcohol oxidation and CO₂ reduction reaction. These catalyst-dependent reactions are the key of the emerging clean energy systems. Catalyst design and synthesis therefore have received keen attention in past decades. We are motivated to study synthesis approaches of metal nanoparticle-based electrocatalysts using ionic liquids (ILs), which are promising solvents for the nanoparticle preparation because of their unique physicochemical properties. In this personal account, we review our previous and present works on nanoparticle preparation in IL and utilization of the obtained nanoparticles as electrocatalysts.     

Recent advances in carbon-based materials for electrochemical CO2 reduction reaction

The increase of atmospheric CO₂ concentration has caused many environmental issues. Electrochemical CO₂ reduction reaction（CO₂RR） has been considered as a promising strategy to mitigate these challenges. The electrocatalysts with a low overpotential, high Faradaic efficiency, and excellent selectivity are of great significance for the CO₂RR. Carbon-based materials including metal-free carbon catalysts and metal-based carbon catalysts have shown great p...     

Metal-Organic Frameworks for Efficient Electrochemical Reduction of Carbon Dioxide

The large concentration of carbon dioxide (CO₂) in the atmosphere can be utilized in industrial production using effective electrocatalysts such as metal-organic frameworks (MOFs). Due to good properties such as high surface area, designable functionality, and uniform constitution, MOFs are regarded as promising electrocatalysts for the carbon dioxide electrochemical reduction reaction (eCO₂RR). This review covers the importance, challenges, and mechanism of eCO₂RR, and simply discusses the progress in the synthesis methods and characterization of MOFs. The review also thoroughly discusses the advances of single metal-based MOFs, mixed metal-based MOFs, and MOF derivatives as electrocatalysts for efficient eCO₂RR.     

Electrochemical Reduction of Carbon Dioxide to Value‐Added Products: The Electrocatalyst and Microbial Electrosynthesis

The electrochemical reduction of carbon dioxide (CO₂) to value‐added products obtains great attention and investigation worldwide in recent years. The commercialization of this green process relies on the progress of relating high‐performance electrocatalysts and their feasibility with proper reactor design. The microbial electrosynthesis (MES) is an alternative route to reduce CO₂ with electroactive bio‐film electrode as catalyst. This review presents the research status and development of cathode catalysts, particularly focusing on the active sites and development tendency, for highly efficient electrochemical reduction CO₂ from personal viewpoint. Some of our results are also presented to exhibit contributions. MES shows a similar process to the typical electrochemical reduction of CO₂. Their combination is an important trend, and the future research in this field is full of challenges and opportunities.     

Sulfur Changes the Electrochemical CO2 Reduction Pathway over Cu Electrocatalysts

Electrochemical CO₂ reduction to value-added chemicals or fuels offers a promising approach to reduce carbon emissions and alleviate energy shortage. Cu-based electrocatalysts have been widely reported as capable of reducing CO₂ to produce a variety of multicarbon products (e.g., ethylene and ethanol). In this work, we develop sulfur-doped Cu₂O electrocatalysts, which instead can electrochemically reduce CO₂ to almost exclusively formate. We show that a dynamic equilibrium of S exists at the Cu₂O-electrolyte interface, and S-doped Cu₂O undergoes in situ surface reconstruction to generate active S-adsorbed metallic Cu sites during the CO₂ reduction reaction (CO₂RR). Density functional theory (DFT) calculations together with in situ infrared absorption spectroscopy measurements show that the S-adsorbed metallic Cu surface can not only promote the formation of the *OCHO intermediate but also greatly suppress *H and *COOH adsorption, thus facilitating CO₂-to-formate conversion during the electrochemical CO₂RR.     

Nanostructures for Electrocatalytic CO2 Reduction

One of the most effective ways to cope with the problems of global warming and the energy shortage crisis is to develop renewable and clean energy sources. To achieve a carbon-neutral energy cycle, advanced carbon sequestration technologies are urgently needed, but because CO₂ is a thermodynamically stable molecule with the highest carbon valence state of +4, this process faces many challenges. In recent years, electrochemical CO₂ reduction has become a promising approach to fix and convert CO₂ into high-value-added fuels and chemical feedstock. However, the large-scale commercial use of electrochemical CO₂ reduction systems is hindered by poor electrocatalyst activity, large overpotential, low energy conversion efficiency, and product selectivity in reducing CO₂. Therefore, there is an urgent need to rationally design highly efficient, stable, and scalable electrocatalysts to alleviate these problems. This minireview also aims to classify heterogeneous nanostructured electrocatalysts for the CO₂ reduction reaction (CDRR).