A computational study of CO2, N2, and CH4 adsorption in zeolites

The adsorption properties of CO₂, N₂ and CH₄ in all-silica zeolites were studied using molecular simulations. Adsorption isotherms for single components in MFI were both measured and computed showing good agreement. In addition simulations in other all silica structures were performed for a wide range of pressures and temperatures and for single components as well as binary and ternary mixtures with varying bulk compositions. The adsorption selectivity was analyzed for mixtures with bulk composition of 50:50 CO₂/CH₄, 50:50 CO₂/N₂, 10:90 CO₂/N₂ and 5:90:5 CO₂/N₂/CH₄ in MFI, MOR, ISV, ITE, CHA and DDR showing high selectivity of adsorption of CO₂ over N₂ and CH₄ that varies with the type of crystal and with the mixture bulk composition.     

A Nanocomposite of Bismuth Clusters and Bi2O2CO3 Sheets for Highly Efficient Electrocatalytic Reduction of CO2 to Formate

The renewable-electricity-driven CO₂ reduction to formic acid would contribute to establishing a carbon-neutral society. The current catalyst suffers from limited activity and stability under high selectivity and the ambiguous nature of active sites. Herein, we report a powerful Bi₂S₃-derived catalyst that demonstrates a current density of 2.0 A cm⁻² with a formate Faradaic efficiency of 93 % at −0.95 V versus the reversible hydrogen electrode. The energy conversion efficiency and single-pass yield of formate reach 80 % and 67 %, respectively, and the durability reaches 100 h at an industrial-relevant current density. Pure formic acid with a concentration of 3.5 mol L⁻¹ has been produced continuously. Our operando spectroscopic and theoretical studies reveal the dynamic evolution of the catalyst into a nanocomposite composed of Bi⁰ clusters and Bi₂O₂CO₃ nanosheets and the pivotal role of Bi⁰−Bi₂O₂CO₃ interface in CO₂ activation and conversion.     

NO、CO和O_2在铜离子分子筛上吸附的理论研究

以Ｃｕ－ＺＳＭ－５离子交换分子筛为例,利用Ｈａｒｔｒｅｅ－Ｆｏｃｋ和ＤＦＴ理论,对小分子（ＮＯ,ＣＯ和Ｏ２）在Ｃｕ＋上吸附的空间立体模型进行了优化计算 结果表明,ＣＵ＋与小分子之间形成直线形吸附最为稳定,也存在其他成一定角度的吸附,但是不稳定．计算了吸附过程的势能曲线和温度对吸附的影响,在５００－８００ Ｋ的反应温度下,温度越低吸附越稳定．ＮＯ在 Ｃｕ表面能够形成 Ｃｕ＋（ＮＯ）（ＯＮ）双分子吸附．最后,比较了价态的变化对金属吸附性质的影响．     

Supercritical CO2-Induced Amorphization in 2D Materials: Mechanism and Applications

Supercritical carbon dioxide (SC CO₂)-assisted chemical and material processing has shown great success in the fabrication of 2D amorphous materials, while the amorphization mechanism in SC CO₂ is quite complicated to be understand. In this review, we introduce different kinds of 2D amorphous materials prepared with SC CO₂ and discuss the possible amorphization mechanism and how they affect the structures and properties of 2D materials. Their applications are further presented and discussed. In addition, the prospective of future development of SC CO₂-assisted fabrication of 2D amorphous materials is also involved. The investigation of SC CO₂ induced amorphization not only provides theoretic understanding of amorphization process, but also directs to the preparation and application of 2D amorphous materials with specific structure and property, suggesting the promising future of SC CO₂-assisted process in material design and engineering.     

Adsorption Mechanism of Composite Whisker on Copper Ions and Lead Ions

A new kind of inorganic composite adsorbent based on chitin whiskers(CHW) and potassium tetratitanate whiskers(PTW) was synthesized via the thermal deposition to remove Cu²⁺ and Pb²⁺ from wastewater. CHW could be successfully coated on the surface of PTW when thermal treated 8 times. The adsorption process was better fitted with the Langmuir and Freundlich models. The adsorption process was more conformed to the Pseudo-second-order model. The results from XPS(X-ray photoelectron spectrum) further show that the adsorption mechanism between CHW-PTW and Cu²⁺, Pb²⁺ are both ion exchange and chemical adsorption. Thermodynamic parameters suggest that the adsorption processes are nonspontaneous. The adsorption of Cu²⁺ and Pb²⁺ is endothermic and exothermic, respectively.     

Isolated Tin(IV) Active Sites for Highly Efficient Electroreduction of CO2 to CH4 in Neutral Aqueous Solution

The development of efficient electrocatalysts with non-copper metal sites for electrochemical CO₂ reduction reactions (eCO₂RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal–organic framework (DMA)₄[Sn₂(THO)₂] (Sn-THO, THO⁶⁻ = triphenylene-2,3,6,7,10,11-hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO₆²⁻ active sites is reported as an electrocatalyst for eCO₂RR, showing an exceptional performance for eCO₂RR to the CH₄ product rather than the common products formate and CO for reported Sn-based catalysts. The partial current density of CH₄ reaches a high value of 34.5 mA cm⁻², surpassing most reported copper-based and all non-Cu metal-based catalysts. Our experimental and theoretical results revealed that the isolated SnO₆²⁻ active site favors the formation of key *OCOH species to produce CH₄ and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively.     

Photoelectrochemical Reduction of Highly Concentrated CO2 Using a p-InP Electrode

Carbon dioxide was photoelectrochemically reduced at a p-type InP photocathode in highly concentrated CO₂ solution in methanol at elevated pressure (40 atm). Relatively high current densities were achieved (200 mA/cm²) with high current efficiencies for CO production (~90%). These current densities are approximately an order of magnitude higher than those reported previously in the literature for photoelectrochemical reduction due to the very high CO₂ concentration (~8 mol/L). Other products were hydrogen and methyl formate (produced via reaction between formic acid and the methanol solvent), Hydrocarbons were produced in only trace amounts.     

一种二价季铵盐在粘土矿物上的吸附

研究了一种不显著降低界面张力的二价季铵盐化合物(MD膜驱剂)在粘土矿物上的吸附. 选取蒙脱土(Su-M)和膨润土(B)两种粘土矿物作为研究对象，其阳离子交换容量(CEC)分别为0.44和0.88 mmol•g^-1. 研究结果表明，MD膜驱剂在低的加入浓度下，MD膜驱剂分子在两种粘土矿物上能全部被吸附，此外，其在Su-M上的饱和吸附量达到100% CECSu-M，而在B上仅为77%CECB. MD膜驱剂只能吸附在粘土矿物的负电荷点上，而不能吸附在单元层外表面的Si-OH中性点上. XRD数据显示，随MD膜驱剂添加浓度的增大，两种粘土矿物的干态层间距略有减小，并根据分子的理论空间尺寸，认为MD膜驱剂在粘土层间只能以单层平卧方式排列.     

Effect of pH Value on the Adsorption Behavior and Inhibition Mechanism of Dodecylamine on Carbon Steel

The effect of pH value on the adsorption behavior and inhibition mechanism of dodecylamine for carbon dioxide corrosion of carbon steel was investigated by electrochemical methods and scanning electron microscopy (SEM). The results indicated that the pH value of the solution played the crucial role to the adsorption behavior and inhibition mechanism of dodecylamine. The inhibition performance of dodecylamine on carbon steel was dependent on the pH value and the inhibition efficiency increased with the increase of pH value. At pH 4.9, dodecylamine mainly inhibited the cathode process of the corrosion. The adsorption energy of dodecylamine on the metal surface was lower. The adsorption of dodecylamine on the metal surface was not stable and an anode desorption phenomenon could be observed. Hence, dodecylamine did not provide effective inhibition to the corrosion. While at pH 6.9, it had much higher adsorption energy. Dodecylamine adsorbed on the metal surface tightly and formed the effective diffusion barrier which inhibited both the cathode and anode processes effectively.     

pH值对十二胺在碳钢表面的吸附行为及缓蚀机理的影响

采用电化学方法和扫描电镜技术, 研究了pH值对十二胺在碳钢表面的吸附以及对碳钢CO2腐蚀缓蚀机理的影响. 研究结果表明, 溶液的pH值对十二胺的吸附和缓蚀机理起决定性作用. 十二胺对碳钢的缓蚀作用随溶液pH值的增加而增强. pH值为4.9时, 十二胺主要抑制腐蚀的阴极过程. 缓蚀剂分子在金属表面上的吸附能比较低, 缓蚀剂容易发生脱附, 因此不能有效抑制腐蚀反应的进行. pH值为6.9时, 缓蚀剂的吸附能较高, 能够牢固地吸附在金属表面, 形成有效的扩散阻挡层, 同时抑制腐蚀的阴、阳极过程, 从而有效地抑制腐蚀反应的进行.     

Comproportionation of CO2 and Cellulose to Formate Using a Floating Semiconductor-Enzyme Photoreforming Catalyst

Formate production via both CO₂ reduction and cellulose oxidation in a solar-driven process is achieved by a semi-artificial biohybrid photocatalyst consisting of immobilized formate dehydrogenase on titanium dioxide (TiO₂| FDH ) producing up to 1.16±0.04 mmol_formate g ⁻¹ in 24 hours at 30 °C and 101 kPa under anaerobic conditions. Isotopic labeling experiments with ¹³C-labeled substrates support the mechanism of stoichiometric formate formation through both redox half-reactions. TiO₂| FDH was further immobilized on hollow glass microspheres to perform more practical floating photoreforming allowing vertical solar light illumination with optimal light exposure of the photocatalyst to real sunlight. Enzymatic cellulose depolymerization coupled to the floating photoreforming catalyst generates 0.36±0.04 mmol_formate per m² irradiation area after 24 hours. This work demonstrates the synergistic solar-driven valorization of solid and gaseous waste streams using a biohybrid photoreforming catalyst in aqueous solution and will thus provide inspiration for the development of future semi-artificial waste-to-chemical conversion strategies.     

NO、CO和O2在铜离子分子筛上吸附的理论研究

以Cu-ZSM-5离子交换分子筛为例,利用Hartree-Fock和DFT理论,对小分子（NO,CO和O2）在CU+上吸附的空间立体模型进行了优化计算,结果表明,Cu+与小分子之间形成直线形吸附最为稳定,也存在其他成一定角度的吸附,但是不稳定,计算了吸附过程的势能曲线和温度对吸附的影响,在500-800K的反应温度下,温度越低吸附越稳定,NO在Cu表面能够形成Cu+(NO)(ON)双分子吸附,最后,比较了价态的变化对金属吸附性能的影响。     

Theoretical Study About Effects of H2O and Na+ on Adsorption of CO2 on Kaolinite Surfaces

The density functional theory(DFT) was used to investigate the adsorptions of carbon dioxide(CO₂) on kaolinite surfaces and the influences of Na⁺ and H₂O on the adsorption. Both cluster and periodic models of kaolinite were considered. The calculated results indicate that stable complexes can be formed between adsorbed CO₂ and the surfaces of kaolinite in the presence or absence of sodium cation and water molecule. The Al-O octahedral surface has a larger adsorption affinity for CO₂ than the Si-O tetrahedral surface of kaolinite because the hydroxyl groups of kaolinite Al-O surface present more activity than the basal O atoms of the Si-O tetrahedral surface in the inter-molecular interactions. The existence of exchangeable sodium cations exerts the significant effect on the adsorption of CO₂ with the dramatic increase of the adsorption energy, while the presence of water molecule decreases the adsorption strength insignificantly. The calculated Gibbs free energies of the adsorption reveal that the adsorptions of CO₂ on all the investigated kaolinite surfaces are feasible thermodynamically in the gas phase. Surface free energy was calculated to provide the predictions of the surface stability as a function of temperature.     

CO在某些过渡金属表面吸附活化的DFT研究

采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C－O键长都变长了,均不同程度地削弱了C－O键,继而活化了CO分子；从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因.     

A Biomass-Ligand-Based Ru(III) Complex as a Catalyst for Cycloaddition of CO2 and Epoxides to Cyclic Carbonates and a Study of the Mechanism

Aiming highly efficient conversion of greenhouse gas CO₂ to cyclic carbonates, a biomass Ru(III) Schiff base complex catalyst ( SalRu ) was constructed by employing a derivative of Lignin degradation (5-aldehyde vanillin). The SalRu catalyst had a remarkable conversion for epoxides into corresponding cyclic carbonates even at atmospheric pressure of CO₂ without the presence of co-catalyst. As the condition at 120 °C and 2 MPa CO₂ the conversion reached to 94 % with selectivity at 99 % after 8 h. 32 % cyclic carbonate production was obtained even under 0.2 MPa CO₂ pressure. The epoxide activation and ring opening, CO₂ insertion and cyclic carbonate formation were illuminated explicitly through the of characteristic absorption peaks changing, which further providing direct and visual evidence for the mechanism proposing. This study has important theoretical significance for the comprehensive utilization of environmental pollutants and energy.     

聚乙烯链在碳纳米管侧壁吸附的动力学模拟研究

利用经典的分子动力学模拟方法对聚乙烯(PE)分子在两种不同类型的碳纳米管(CNT)中的吸附进行了研究. 计算了两者之间的扩散系数和相互作用能; 利用PE链自身的扭转角分布和取向参数对PE链构象进行了分析. 结果表明, PE链可以在CNT上很好的吸附, 且PE的构象和吸附位置主要与温度和CNT的半径有关, 与管的类型关系不大.     

Super-fast Charging Biohybrid Batteries through a Power-to-formate-to-bioelectricity Process by Combining Microbial Electrochemistry and CO2 Electrolysis

Extensive study on renewable energy storage has been sparked by the growing worries regarding global warming. In this study, incorporating the latest advancements in microbial electrochemistry and electrochemical CO₂ reduction, a super-fast charging biohybrid battery was introduced by using pure formic acid as an energy carrier. CO₂ electrolyser with a slim-catholyte layer and a solid electrolyte layer was built, which made it possible to use affordable anion exchange membranes and electrocatalysts that are readily accessible. The biohybrid battery only required a 3-minute charging to accomplish an astounding 25-hour discharging phase. In the power-to-formate-to-bioelectricity process, bioconversion played a vital role in restricting both the overall Faradaic efficiency and Energy efficiency. The CO₂ electrolyser was able to operate continuously for an impressive total duration of 164 hours under Gas Stand-By model, by storing N₂ gas in the extraction chamber during stand-by periods. Additionally, the electric signal generated during the discharging phase was utilized for monitoring water biotoxicity. Functional genes related to formate metabolism were identified in the bioanode and electrochemically active bacteria were discovered. On the other hand, Paracoccus was predominantly found in the used air cathode. These results advance our current knowledge of exploiting biohybrid technology.     

Kinetically Limited CO Adsorption: Spill-Over as a Highly Effective Adsorption Pathway on Bimetallic Surfaces

We demonstrate that the (local) adsorbed carbon monoxide, CO_ad, coverage on the Pt-free areas of bimetallic Pt/Ru(0001) surfaces (a Ru(0001) substrate partly covered by Pt monolayer islands) can be increased to ∼0.80 monolayers (ML), well above the established saturation CO_ad coverage of 0.68 ML, even under ultrahigh vacuum conditions by using spill-over of CO adsorbed on the Pt islands to the Ru areas as an highly effective adsorption channel. The apparent CO_ad saturation coverage of 0.68 ML on pure Ru(0001) is identified as due to kinetic limitations, hindering further uptake from the gas phase, rather than being caused by thermodynamic reasons. This spill-over mechanism is proposed to be a general phenomenon for adsorption on bimetallic surfaces.     

一氧化碳分子在Pt/t-ZrO2(101)表面的吸附性质

运用广义梯度密度泛函理论(GGA-PW91)结合周期平板模型方法,研究了CO分子在完整与Pt负载的四方ZrO2(101)表面的吸附行为.结果表明:表面第二层第二氧位和表面第二桥位分别为CO分子和Pt原子在完整ZrO2(101)表面的稳定吸附位,且覆盖度为0.25ML(monolayer)时均为稳定吸附构型,吸附能分别为56.2和352.7kJ·mol-1.CO分子在负载表面的稳定吸附模式为C-end吸附,吸附能为323.8kJ·mol-1.考察了CO分子在负载表面吸附前后的振动频率、态密度和轨道电荷布居分析,并与CO分子和Pt原子在ZrO2表面的结果进行比较.结果表明,C端吸附CO分子键长为0.1161nm,与自由的和吸附在ZrO2表面后的CO相应值(0.1141和0.1136nm)相比伸长.吸附后C―O键伸缩振动频率为2018cm-1,与自由CO分子相比发生红移;吸附后CO带部分正电荷,电子转移以Pt5dCO2π的π反馈机理占主导地位.     

Carboxylation of Acetylene without Salt Waste: Green Synthesis of C4 Chemicals Enabled by a CO2-Pressure Induced Acidity Switch

The inherent formation of salt waste in C−H carboxylations is a key obstacle precluding the utilization of CO₂ as C₁ building block in the industrial synthesis of base chemicals. This challenge is addressed in a circular process for the production of the C₄ base chemical dimethyl succinate from CO₂ and acetylene. At moderate CO₂ pressures, acetylene is doubly carboxylated in the presence of cesium carbonate. Hydrogenation of the C−C triple bond stabilizes the product against decarboxylation. By increasing the CO₂ pressure to 70 bar, the medium is reversibly acidified, allowing an esterification of the succinate salt with methanol. The cesium base and the hydrogenation catalyst are regenerated and can be reused. This provides the proof of concept for a salt-free route to C₄ chemicals from biogas (CH₄/CO₂). The origin of this reversible acidity switch and the critical roles of the cesium base and the NMP/MeOH solvents were elucidated by thermodynamic modeling.