Cadmium-based metal-organic frameworks for high-performance electrochemical CO2 reduction to CO over wide potential range

Electrochemical CO₂ reduction (ECR) powered by renewable energy sources provides a sustainable avenue to producing carbon–neutral fuels and chemicals. The design and development of high performance, cost-effective, and stable catalysts for ECR remain a focus of intense research. Here, we report a novel electrocatalyst, two-dimensional cadmium-based 1,4-benzenedicarboxylate metal–organic frameworks (Cd-BDC MOFs) which can effectively convert CO₂ to CO with a faradaic efficiency (FE) of more than 80.0% over the voltage range between -0.9 and -1.1 V (versus reversible hydrogen electrode, vs. RHE) in 0.1 mol·L^-1 CO₂-saturated KHCO₃ solution with an H-type cell, reaching up to 88.9% at -1.0 V (vs. RHE). The performance outperforms commercial CdO and many other MOF-based materials demonstrated in prior literature. The catalytic property can be readily tuned by manipulating synthesis conditions as well as electrolyte type. Especially, high CO FEs exceeding 90.0% can be attained on the Cd-BDC electrode at potentials ranging from -0.16 to -1.06 V (vs. RHE) in 0.5 mol·L^-1 KHCO₃ solution by using a gas diffusion electrode cell system. The maximum CO FE approaches ~97.6% at -0.26 V (vs. RHE) and the CO partial geometric current density is as high as about 108.1 mA cm^-2 at -1.1 V (vs. RHE). This work offers an efficient, low cost, and alternative electrocatalyst for CO₂ transformation.     

金属有机骨架材料储存CO2的研究进展

随着温室效应日益严重,研发高效捕获CO_2的新型材料对于缓解环境压力具有重要意义。金属有机骨架材料具有高比表面积、结构多样性和孔道可调控性等优点,尤其在储存CO_2方面展现出惊人潜质。简要介绍金属有机骨架材料及其延伸化合物——沸石咪唑酯骨架材料和共价有机骨架材料作为新型储存CO_2材料,在结构、储存CO_2性能和机理等方面的研究进展,并阐述了该类材料在研究过程中存在的不足与发展前景。     

Promotional effect for SCR of NO with CO over MnOx-doped Fe3O4 nanoparticles derived from metal-organic frameworks

MnO_x-Fe₃O₄ nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H₂-TPR and O₂-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O^2- species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway.     

NH4Cl辅助热解制备镍-氮-碳纳米管催化剂及其电还原CO2性能

二氧化碳（CO₂）的资源化利用是实现“碳达峰,碳中和”的重要手段。在众多CO₂转化技术当中,电催化CO₂还原反应因反应条件温和、工艺过程简单等优点,被认为是极具应用前景的减碳技术之一,其关键在于高效、高稳定性电催化剂的开发。过渡金属-氮-碳（M-N-C）材料是电还原CO₂生成CO的有效催化剂,针对其高温热解制备过程中活性金属原子容易聚集且氮原子流失严重,进而使得活性位密度降低,催化性能下降等问题,本文提出以双氰胺（DCDA）为碳源和氮源,以乙酰丙酮镍（Ni（acac）₂）为金属源,以氯化铵（NH₄Cl）为第二氮源和造孔剂,采用简单的NH₄Cl辅助热解-酸刻蚀的方法制备得到镍-氮-碳纳米管（Ni-N-CNTs）电还原CO₂催化剂,并详细考察NH₄Cl添加量对催化剂结构和催化性能的影响。表征结果表明：NH₄Cl的加入有利于催化剂纳米管状形貌和多级孔结构的生成,同时有利于催化剂中Ni-Nx （1.6%,摩尔分数）和pyridinic-N （1.75%,摩尔分数）物种含量的增加。一系列性能测试结果表明：催化剂的活性中心为Ni-Nx,同时pyridinic-N的存在也有利于催化性能的提高,当前体中NH₄Cl加入量与氮源和金属源总质量比为1∶1时,所得Ni-N-CNTs-1催化剂催化性能最好,在电压为-0.65 V （vs RHE）时,CO法拉第效率最高达92%,此时CO部分电流密度为8 mA·cm^-2。此外,该催化剂还表现出良好的催化稳定性,连续恒电位电解12 h,催化性能基本不变。该催化剂制备工艺简单,制备条件可控,研究结果可为高效M-N-C电还原CO₂催化剂的设计和制备提供一种切实有效的研究思路和方法。     

NH4Cl辅助热解制备镍-氮-碳纳米管催化剂及其电还原CO2性能

二氧化碳（CO₂）的资源化利用是实现“碳达峰,碳中和”的重要手段。在众多CO₂转化技术当中,电催化CO₂还原反应因反应条件温和、工艺过程简单等优点,被认为是极具应用前景的减碳技术之一,其关键在于高效、高稳定性电催化剂的开发。过渡金属-氮-碳（M-N-C）材料是电还原CO₂生成CO的有效催化剂,针对其高温热解制备过程中活性金属原子容易聚集且氮原子流失严重,进而使得活性位密度降低,催化性能下降等问题,本文提出以双氰胺（DCDA）为碳源和氮源,以乙酰丙酮镍（Ni（acac）₂）为金属源,以氯化铵（NH₄Cl）为第二氮源和造孔剂,采用简单的NH₄Cl辅助热解-酸刻蚀的方法制备得到镍-氮-碳纳米管（Ni-N-CNTs）电还原CO₂催化剂,并详细考察NH₄Cl添加量对催化剂结构和催化性能的影响。表征结果表明：NH₄Cl的加入有利于催化剂纳米管状形貌和多级孔结构的生成,同时有利于催化剂中Ni-Nx （1.6%,摩尔分数）和pyridinic-N （1.75%,摩尔分数）物种含量的增加。一系列性能测试结果表明：催化剂的活性中心为Ni-Nx,同时pyridinic-N的存在也有利于催化性能的提高,当前体中NH₄Cl加入量与氮源和金属源总质量比为1∶1时,所得Ni-N-CNTs-1催化剂催化性能最好,在电压为-0.65 V （vs RHE）时,CO法拉第效率最高达92%,此时CO部分电流密度为8 mA·cm^-2。此外,该催化剂还表现出良好的催化稳定性,连续恒电位电解12 h,催化性能基本不变。该催化剂制备工艺简单,制备条件可控,研究结果可为高效M-N-C电还原CO₂催化剂的设计和制备提供一种切实有效的研究思路和方法。     

BiVO4/rGO复合物的制备及其 光催化还原CO2研究

采用水热法制备了颗粒状单斜相钒酸铋（BiVO4）/还原氧化石墨烯（rGO）复合催化剂。采用傅里叶红外光谱、拉曼光谱、X射线衍射和紫外-可见漫反射光谱对合成的复合材料做了表征。采用透射电镜、扫描电镜和氮吸附脱附实验对复合材料的表面形貌和表面积做了分析测试。实验结果表明,BiVO4复合物能选择性将CO2还原成甲醇,石墨烯的引入能很好地改善BiVO4光催化还原CO2的性能。当石墨烯的加入量为3%（质量分数）时,在氙灯功率为600 W的条件下,光照6 h后,BiVO4/rGO复合材料光催化还原CO2生成的甲醇产量达到513.1 μmol/L,比相同形貌的纯BiVO4的甲醇产量高73.6%。     

高效可见光响应微生物/光电化学耦合人工光合作用系统

人工光合作用系统可以利用太阳能将二氧化碳转化为高附加值的化学产品,能够有效地解决人类面临的能源与环境问题,极具发展前景。然而,人工光合作用系统面临产物选择性差、过电位高、太阳能利用率低等重大挑战。本文提出了一种新型微生物/光电化学耦合人工光合作用系统,该系统由固碳产甲烷微生物阴极和复合光阳极组成,其中复合光阳极由TiO₂电极与硅太阳能电池串联组成。该耦合系统在仅输入太阳能且不施加外部偏压的条件下,可实现化学燃料甲烷的产生。甲烷产量高达（10.7±0.2） L·d^-1·m^-2,相比已有研究高出13倍,同时该耦合系统固碳产甲烷的法拉第效率高达98.5%±2.1%,远高于传统的人工光合作用系统。该新型人工光合作用系统的提出,为制取具有高附加值的化学产品和发展可再生能源提供了新的思路。     

Direct reduction of diluted CO2 gas to C2 products by copper hydroxyphosphate microrods

Electrochemical reduction of CO₂ is widely researched in recent years. However, direct electro-reduction of diluted CO₂ to C₂ products is seldomly studied. In this work, electrocatalytic reduction of CO₂ with different concentrations were conducted on Cu₂(PO₄)(OH) catalysts. The catalytic performance in diluted CO₂ is comparable with that in pure CO₂ by using Cu₂(PO₄)(OH) as catalyst. Besides, the selectivity of C₂ product is still as high as 64.6% in 50%CO₂ concentration. The normalized C₂ current density of Cu₂(PO₄)(OH) was over 6.8 times higher than that of commonly used Cu₂O–Cu catalyst with similar size. In situ Raman spectroscopy proved that Cu⁺ is the main active site at higher potentials. More importantly, a higher local pH is realized under diluted CO₂ test conditions which is favorable for promoting C–C coupling. Finally, in situ ATR-FTIR spectroscopy was performed to further monitor and identify the adsorbed intermediates and help reveal the mechanism for the catalysts.     

Tuning of ferrimagnetic nature and hyperfine interaction of Ni2+ doped cobalt ferrite nanoparticles for power transformer applications

Ferrites may contain single domain particles which gets converted into super-paramagnetic state near critical size. To explore the existence of these characteristic feature of ferrites, we have performed magnetization(M-H loop) and Mössbauer spectroscopic studies of Ni²⁺ substitution effect in Co_1-xNi_xFe₂O₄ (where x?=?0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated by solution combustion route using mixture of carbamide and glucose as fuels for the first time. As prepared samples exhibit spinel cubic structure with lattice parameters which decreases linearly with increase in Ni²⁺ concentration. The M-H loops reveals that saturation magnetization(M_s), coercive field(H_c) remanence magnetization(M_r) and magnetron number(η_B) decreases significantly with increasing Ni²⁺ substitution. The variation of saturation magnetization has been explained on the basis of Neel's molecular field theory. The coercive field(H_c) is found strongly dependent on the concentration of Ni²⁺ and decrease of coercivity suggests that the particles have single domain and exhibits superparamagnetic behavior. The Mössbauer spectroscopy shows two ferrimagnetically relaxed Zeeman sextets distribution at room temperature. The dependence of Mössbauer parameters such as isomer shift, quadru pole splitting, line width and hyperfine magnetic field on Ni²⁺ concentration have been discussed. Hence our results suggest that synthesized materials are potential candidate for power transformer application.     

Covalent organic frameworks-incorporated thin film composite membranes prepared by interfacial polymerization for efficient CO2 separation

Thin film composite (TFC) membranes with nanofillers additives for CO₂ separation show promising applications in energy and environment-related fields. However, the poor compatibility between nanofillers and polymers in TFC membranes is the main problem. In this work, covalent organic frameworks (COFs, TpPa-1) with rich —NH— groups were incorporated into polyamide (PA) segment via in situ interfacial polymerization to prepare defect-free TFC membranes for CO₂/N₂ separation. The formed covalent bonds between TpPa-1 and PA strengthen the interaction between nanofillers and polymers, thereby enhancing compatibility. Besides, the incorporated COFs disturb the rigid structure of the PA layer, and provide fast CO₂ transfer channels. The incorporated COFs also increase the content of effective carriers, which enhances the CO₂ facilitated transport. Consequently, in CO₂/N₂ mixed gas separation test, the optimal TFC (TpPa_0.025-PIP-TMC/mPSf) membrane exhibits high CO₂ permeance of 854 GPU and high CO₂/N₂ selectivity of 148 at 0.15 MPa, CO₂ permeance of 456 GPU (gas permeation unit) and CO₂/N₂ selectivity of 92 at 0.5 MPa. In addition, the TpPa_0.025-PIP-TMC/mPSf membrane also achieves high permselectivty in CO₂/CH₄ mixed gas separation test. Finally, the optimal TFC membrane showes good stability in the simulated flue gas test, revealing the application potential for CO₂ capture from flue gas.     

焦炉煤气综合利用及CO_2减排潜力分析"

焦炉煤气是我国特有的能源和化工原料气,我国每年副产大量的焦炉气,其综合利用对于焦化企业的节能减排具有重要意义。本文综述了目前我国焦炉煤气的各种综合利用方式,包括焦炉气制甲醇、发电、制天然气等。结合焦化企业现场调研采样分析了焦炉气的典型组成、缺省碳含量及燃烧利用碳氧化因子。结果表明我国焦炉气的缺省碳含量明显低于政府间气候变化专业委员会(IPCC)的缺省值,焦炉气燃烧利用的碳氧化因子为1。同时分析了焦炉气综合利用对CO_2减排的贡献及潜力,指出我国富余焦炉煤气的综合利用,尤其是制化学品等对于节能减排潜力巨大。     

BiVO4催化剂的制备及其光催化还原CO2的研究

采用化学沉淀法制备BiVO4光催化剂并应用于光催化还原CO2/H2O体系中。通过TG-DTA、FTIR、XRD对光催化剂进行表征,研究了pH和焙烧温度等对光催化性能的影响。结果表明,pH=7并于600℃煅烧制得的单斜相BiVO4活性最高。在催化剂用量为0.6 g/L,反应时间为7 h,CO2流量为200 mL/min,反应温度为80℃,反应液中NaOH和Na2SO3的浓度均为0.10 mol/L条件下,甲醇产率高达249.18μmol/g。并对BiVO4催化剂光催化还原CO2的机理进行了探究。     

基于碳素流分析炼焦生产CO_2排放及减排措施

为了降低钢铁企业炼焦生产CO2排放量,应用物质流分析法,建立炼焦生产CO2排放计算模型,以某钢铁联合企业的实际炼焦生产为基础,进行含碳材料取样和检测,定量分析炼焦生产中各碳源和碳汇对CO2排放的影响。研究表明,该钢铁企业65孔和36孔焦炉,吨焦炭生产所需炼焦煤分别涉及986.76和984.87 kg碳元素的转化,其中,80.40%和80.65%的碳元素转移至焦炭,即碳元素有效利用率为80.40%和80.65%,剩余19.60%和19.35%的碳元素转移到其他产物中。炼焦生产潜在存在大量CO2排放;增大炭化室容量可减少炼焦生产CO2排放,采用焦炉煤气回收、粗苯和煤焦油回收、干熄焦和煤调湿技术可降低炼焦生产CO2排放量。     

氮掺杂碳限域的花状SnS催化CO2电还原制甲酸

合理设计高效的电催化剂是二氧化碳电化学还原（CO₂ER）为高附加值化学品和燃料的关键。本文利用水热-煅烧法制备了氮掺杂碳限域的花状SnS催化剂（SnS@NC）并研究了其电催化CO₂的特性。基于超薄氮掺杂碳层的限域效应,SnS的层厚由原始的30nm缩减至20nm,电化学活性面积明显增强,同时氮掺杂碳层增强了对CO₂的吸附和活化。SnS@NC催化CO₂转化为甲酸的能力明显增强,在-1.3V（vs. RHE）的H型电解池中法拉第效率为81.2%,电流密度为29.5mA/cm²,本文为金属硫化物复合催化剂功能化提供了新策略。     

Cu基纳米材料电催化还原CO2的结构-性能关系

通过电催化方法,在常温、常压下将CO₂还原为高附加值化学品,是解决目前能源短缺和环境污染问题的理想选择之一。铜基材料是目前被证实的还原CO₂生成烃类、醇类等高附加值产物的最有效非均相电催化剂,因此受到国内外研究者的广泛关注。综述了纳米Cu材料在电催化还原CO₂领域的研究进展,重点阐述催化剂结构（晶界、表面结构与晶面、孔结构等）与性能关系,并讨论了测试条件如传质、局部pH对催化性能的影响,最后论述了该领域目前存在的问题和未来发展趋势。     

Cu/LaFeO3 as an efficient and stable catalyst for CO2 reduction: Exploring synergistic effect between Cu and LaFeO3

Cu-based catalysts, which are regarded as the most promising catalysts for CO₂ conversion, suffer dramatic deactivation at high temperatures. In this work, LaFeO₃, a typical perovskite-type oxide, is employed to disperse and stabilize Cu particles for the reverse water gas shift reaction. Compared to traditional Cu-based catalysts, Cu/LaFeO₃ exhibits a higher conversion with 100% CO selectivity and better stability at 873 K. Structural and spectroscopic characterization including N₂O chemisorption, high-resolution transmission electron microscopy, in situ x-ray diffraction, and x-ray absorption fine structure show that metallic Cu is well dispersed on LaFeO₃, forming more Cu-LaFeO₃ interface. CO₂ temperature-programmed surface reaction (CO₂-TPSR), two-step transient surface reaction (two-step TSR), and transient in situ diffuse reflectance infrared Fourier transformed spectroscopy experiments demonstrate that the superior activity is attributed to the synergistic effect between the highly dispersed Cu particles for H₂ dissociation and the abundant oxygen vacancies in LaFeO₃ support for CO₂ activation. The synergistic effect between metal and perovskite-type oxide increases metal-support interfaces and enhances CO₂ activation, leading to a potential application in a variety of chemical reactions.     

CuO-SiO2气凝胶@TiO2纳米纤维无牺牲剂光催化还原CO2

采用溶胶-凝胶法制备CuO-SiO2复合气凝胶,通过在气凝胶孔道内填充TiCl4,然后将其气相水解,得到了在CuO-SiO2气凝胶表面生长了高结晶度的TiO2纳米纤维(CuO-SiO2@TiO2),纤维直径～16 nm.通过XPS、UPS、UV-Vis DRS、荧光光谱(PL)等表征了材料的结构及光电性能.结果表明,制备的CuO-SiO2@TiO2对可见光有明显吸收,且荧光强度较商用TiO2(P25)大幅降低,光生电子-空穴对更加稳定.再在纳米纤维上负载CuO,所得CuO-SiO2@TiO2/CuO在可见光区的荧光强度进一步增强.以300 W氙灯为光源,分别以CuO-SiO2@TiO2及CuO-SiO2@TiO2/CuO为催化剂,无牺牲剂条件下光催化还原CO2,4 h后甲醇产率分别为1304.0及1589.0μmol/g-cat,转换频率(TOF)分别为0.038及0.046 h–1.循环实验表明,纳米纤维具有较好的光催化稳定性,经过4次光催化循环实验后,CuO-SiO2@TiO2/CuO的保留率～94％,甲醇产率可达1472.0μmol/g-cat,TOF为0.042 h–1.     

An efficient methodology for utilization of K-feldspar and phosphogypsum with reduced energy consumption and CO2 emissions

The issues of reducing CO2 emissions, sustainably utilizing natural mineral resources, and dealing with industrial waste offer challenges for sustainable development in energy and the environment. We propose an efficient methodology via the co-reaction of K-feldspar and phosphogypsum for the extraction of soluble potassium salts and recovery of SO2 with reduced CO2 emission and energy consumption. The results of characterization and reactivity evaluation indicated that the partial melting of K-feldspar and phosphogypsum in the high-temperature co-reaction significantly facilitated the reduction of phosphogypsum to SO2 and the exchange of K+(K-feldspar) with Ca2+(CaSO4 in phosphogypsum). The reaction parameters were systematical y investigat-ed with the highest sulfur recovery ratio of~60%and K extraction ratio of~87.7%. This novel methodology possesses an energy consumption reduction of~28%and CO2 emission reduction of~55%comparing with the present typical commercial technologies for utilization of K-feldspar and the treatment of phosphogypsum.     

Preparation of high entropy nitride ceramic nanofibers from liquid precursor for CO2 photocatalytic reduction

Subjected to the manufacturing methods (sputtering or mechanochemical synthesis), the reported high entropy nitrides (HENs) were limited to the forms of coating and powder. Here, we report a novel strategy in preparing HEN ceramic nanofibers (HENCNFs) from liquid precursor via electrospinning followed by high-temperature NH₃ atmosphere nitridation. The as-prepared HENCNFs include five uniform dispersed metal elements, Ti, Hf, Nb, Ta, and Mo, and have a single face-centered cubic structure. Interestingly, the obtained HENCNFs show photocatalyst activity in CO₂ reduction. The product selectivity of photocatalytic CO₂ reduction reaction is 96.4%, and no performance degradation was detected during five cycles photocatalysis test.     

Optimization-based identification of CO2 capture and utilization processing paths for life cycle greenhouse gas reduction and economic benefits

This paper introduces a mathematical formulation to identify promising CO₂ capture and utilization (CCU) processing paths and assess their production rates by solving an optimization problem. The problem is cast as a multi-objective one by simultaneously maximizing a net profit and life cycle greenhouse gas (GHG) reduction. Three case studies are illustrated using an exemplary CCU processing network. The results indicate the optimal solution is greatly influenced by the scale of CO₂ emission source, market demand, and hydrogen availability. Moreover, with the current system of measuring the GHG reduction regarding a business-as-usual level, if the aim is to achieve a GHG reduction within a national boundary, the question of whether CCU plants producing a product of same functionality through conventional means, which the CO₂-based product can replace, exists in the country can come into consideration. This systematic identification will assist decision-making regarding future R&D investment and construction of large-scale CCU plants.