High C2 Research Articles

#5012 THE EFFECT OF GLOMERULAR C3 DEPOSITION ON RENAL OUTCOME IN PATIENTS WITH MEMBRANOUS NEPHROPATHY: DATA OF THE TSN-GOLD STUDY

Abstract Background and Aims We aimed to evaluate the effect of glomerular C3 deposits on clinical and laboratory findings and outcome in patients with idiopathic membranous nephropathy (MN) included in the Primary Glomerular Diseases Study of Turkish Society of Nephrology Glomerular Diseases Study Group (TSN-GOLD). Method The data of 1595 patients with MN in the database has been evaluated. 114 patients were excluded due to lack of data about C3 staining, 54 patients due to secondary MN and 523 due to lack of data about the follow-up. Patients with glomerular C3 deposits were compared with those with no C3 staining. Results Glomerular C3 deposits were detected in kidney biopsy specimens of 601 patients of the 888 patients analysed. The demographic data, clinical and laboratory findings at the time of diagnosis of C3 (+) and C3 (-) groups are presented in Table 1. They were similar except serum albumin level that was lower in C3 (+) group. Subepithelial deposits and interstitial fibrosis was more prominent, IgG, Kappa and Lambda staining more intense, positivity for C1q and IgA was more frequent in C3 (+) group (Table 2). The study groups were similar regarding remission rates after the first imuunosuppressive treatment (p = 0.582). 155 patients (25.8%) had partial, 152 (25.3%) had complete remission while no remission was detected in 92 patients (15.3%) in C3 (+) group. 69 patients (24.0%) had partial and 81 patients (28.2%) had complete remission; 40 patients (13.9%) had no remission in C3 (-) group. The relapse rates were 17.6% and 19.9% in C3 (+) and C3 (-) groups (p = 0.360). The percentage of patients who died or needed renal replacement therapy (RRT) were higher C3 (+) group (p = 0.013) (Figure 1). Conclusion Need for RRT and mortality is higher in patients with C3 deposition showing the importance of C3 deposition in the prognosis of MN. More prominent interstitial fibrosis may be related with the worse outcome.

Pressure dependence and mechanism of Mn promotion of silica-supported Co catalyst in the Fischer-Tropsch reaction

The mechanism of Mn promotion of a silica-supported Co catalyst in the Fischer-Tropsch reaction has been studied at varying pressures up to 20 bar. IR spectroscopy in combination with DFT calculations suggest adsorbed CO is activated by reaction with an oxygen vacancy in the MnO, which covers the Co surface. This leads to a higher activity, higher CHx coverage and thus higher C5+ and lower CH4 selectivity. Increasing the pressure magnifies the selectivity differences. However, above around 4 bar, the effect of Mn on the selectivities is reversed and the C5+ selectivity is decreased by Mn addition. This is tentatively attributed to Mn promoting the C-O bond dissociation but not the chain growth. Formed monomers have to migrate to stepped sites for chain growth on the Co surface. Whilst this is migration is not impeded by co-adsorbates at low pressure, migration could be hindered by especially the high CO coverage at high pressure.

CO2 electroreduction to multicarbon products from carbonate capture liquid

CO2 electroreduction to multicarbon products from carbonate capture liquid

Fischer-Tropsch synthesis: Osmium promoted Co@HCS catalysts

Little attention has been given to the use of osmium as a promoter for Fischer-Tropsch Synthesis (FTS). In previous studies, Os has proven to be a poor FT catalyst, but its use as a catalyst promoter has not been studied. In this study, the synthesis and use of Os nanoparticles supported on/in Co@HCS (HCS = hollow carbon sphere) FT catalysts are reported. The hollow morphology of the HCSs was exploited to study the influence of Os promoter nanoparticle location relative to the Co3O4 nanoparticles (dCo = 3.5–12.5 nm) and on the effect of Os on the reduction behaviour and activity of the Co FT catalyst. Os (0.1, 0.5 and 1 wt%) nanoparticles were loaded both inside and outside the HCSs, while the Co3O4 particles (Co 10 wt%) were loaded inside of the HCSs to give CoOs@HCS and Os/(Co@HCS). Electron microscopy, in situ PXRD, PDF, TGA, BET, and TPR studies revealed that both catalysts were successfully synthesized. The use of ex-situ PXRD, PDF and TPR studies provided information on the Co phases and reduction pathways of the Co3O4 metal catalyst and the spillover effect from Os to Co. Co3O4 and CoO phases were observed for the CoOs@HCS and Os/(Co@HCS) catalysts. More interesting was the observation of the Co fcc phase in the OsCo@HCS catalysts, indicating the importance of the Os-Co interaction. The catalyst with Co and Os close together (primary spillover process) gave a higher Fischer-Tropsch activity (38.5–46.4 × 10−6 molCO/gCo.s) and higher C5+ production than both the unpromoted catalyst (27.8 × 10−6 molCO/gCo.s), and the catalysts where Os and Co were separated (25.1–36.4 × 10−6 molCO/gCo.s) by the mesoporous carbon shell (secondary spillover effect). The studies on both CoOs@HCS and Co/(Os@HCS) catalysts have indicated for the first time the effect of Os on Co catalysts, with particular reference to FTS.

Facet-Controlled Cu-doped and K-promoted Fe2O3 nanosheets for efficient CO2 hydrogenation to liquid hydrocarbons

Hydrogenation of CO2 into liquid hydrocarbons is an attractive route for chemical utilization of CO2, but suffers from limited product selectivity. By controlling the exposed surface atoms of metal catalyst, purposefully enhancing the reaction rate of bottleneck steps for CO2 activation and C-C coupling is expected to solve this problem. Here, we tuned the exposed surface atoms of catalysts separately and simultaneously by facet control, doping and promoter modification; a nanosheet-shaped Fe2O3 rich in oxygen vacancies was first constructed to enhance the adsorption and activation of CO2. Cu doping and K promoter were further used to promote the formation of active χ-Fe5C2 phase and facilitate the coupling of C-C bond to form long chain fuels. The optimized K-promoted and Cu-doped Fe2O3 nanosheets (3 K/6Cu-Fe-S) exhibited high CO2 conversion (46.5%) and C5+ hydrocarbons selectivity (53.6%), accompanied with low CO (5.3%) and CH4 selectivity (12.2%) at 300 °C, outperforming other reported Fe-based catalysts significantly. Meanwhile, a 205 h on stream test indicated the excellent stability of 3 K/6Cu-Fe-S. The effects of each tuning method on catalytic activity and product selectivity were further studied by combining the change of the phase and surface electronic structure of the catalyst before and after the reaction. Cu doping and K promoter were verified to have a synergistic enhancement effect on the hydrogenation performance of CO2, rather than just the sum of the two. These findings would be beneficial for the rational design of CO2 hydrogenation catalysts.

Effect of Charge on Carbon Support on the Catalytic Activity of Cu2O toward CO2 Reduction to C2 Products

Electrochemical carbon dioxide (CO2) reduction for C2 products has been studied on a series of supported Cu-based catalysts; however, the charge-promotion effects from the substrates for the selectivity of CO2 reduction are still unclear. Here we localize nanosized Cu2O on three carbon-based substrates that provide different charge-promotion effects: positively charged boron-doped graphene (BG), negatively charged nitrogen-doped graphene (NG), and weak negatively charged reduced graphene oxide (rGO). We demonstrate that the charge-promotion effects lead to an increase in faradaic efficiency (FE) for C2 products with an order of rGO/Cu < BG/Cu < pure Cu < NG/Cu and an FEC2/FEC1 ratio from 0.2 to 7.1. By performing in situ characterization, electrokinetic investigations, and density functional theory (DFT) calculations, we reveal that the negatively charged NG is favorable for stabilizing Cu+ species under CO2 reduction, which strengthens CO* adsorption to further boost C-C coupling for C2 products. As a result, we achieve a high C2+ FE of ∼68% at high current densities of 100-250 mA cm-2.

Co0−Coδ+ Interface Double‐Site‐Mediated C−C Coupling for the Photothermal Conversion of CO2 into Light Olefins

AbstractSolar‐driven CO2 hydrogenation into multi‐carbon products is a highly desirable, but challenging reaction. The bottleneck of this reaction lies in the C−C coupling of C1 intermediates. Herein, we construct the C−C coupling centre for C1 intermediates via the in situ formation of Co0−Coδ+ interface double sites on MgAl2O4 (Co−CoOx/MAO). Our experimental and theoretical prediction results confirmed the effective adsorption and activation of CO2 by the Co0 site to produce C1 intermediates, while the introduction of the electron‐deficient state of Coδ+ can effectively reduce the energy barrier of the key CHCH* intermediates. Consequently, Co−CoOx/MAO exhibited a high C2–4 hydrocarbons production rate of 1303 μmol g−1 h−1; the total organic carbon selectivity of C2–4 hydrocarbons is 62.5 % under light irradiation with a high ratio (≈11) of olefin to paraffin. This study provides a new approach toward the design of photocatalysts used for CO2 conversion into C2+ products.

Effect of different valence metals doping on methane activation over La2O3(001) surface

La2O3 as a catalyst is used for oxidative coupling of methane (OCM) reactions due to its excellent stability and high C2 selectivity, but poor activity on methane dissociation limits its wide application. Different valence metals are doped on the La2O3(001) surface to improve the methane conversion activity, and the activation of methane on metal-doped La2O3(001) surfaces has been investigated via the density functional theory (DFT) calculations. The relationship between the valence states of doped metals and the methane conversion activities shows that doping low valence metals (Li, Na, K, Mg, Ca, Sr and Ba) and equivalent metals (Al, Ga, In) can significantly improve the conversion activity of methane. Among them, the activation energy of methane on the Li-La2O3(001) surface is the lowest, which is only 13.0 kJ/mol. However, doping of high valence metals (Zr, Nb, Re and W) cannot improve the CH4 dissociation activity. Furthermore, the relationships between surface oxygen vacancy formation energies, acid-base properties and the activation energies of CH4 have also been investigated. The results show that with the increase of metal valence state, the oxygen vacancy formation energy increases, while the dissociation activity of CH4 decreases. The introduction of alkali and alkaline earth metals increases the alkalinity of La2O3(001) surface, and the alkalinity of La2O3(001) doped with the alkali metal is stronger than that with the alkaline earth metal, exhibiting higher dissociation activity of CH4. Our research may provide a guide for improving methane conversion activity on La2O3 catalysts.

Interface-Induced Phase Evolution and Spatial Distribution of Fe-Based Catalysts for Fischer–Tropsch Synthesis

Fe-based catalysts undergo complex reduction, carburization, and phase interconversion as well as oxidation during Fischer–Tropsch synthesis (FTS). Unraveling the evolution of carbides and establishing the dominant factors are essential for rational design and modulation of Fe-based catalysts. In this work, Fe–oxide interfaces were constructed to investigate the effect on phase transformation and FTS performance. By correlating performance to the composition of iron species, the crucial role of Fe2.2C in high CO conversion and C5+ productivity has been confirmed. More importantly, a heterogeneous spatial distribution of iron carbides and oxides induced by Fe–oxide interfaces was observed. Fe3O4 preferentially forms at interfaces with the coexistence of carbon-rich Fe2.2C at subadjacent interfaces, while Fe5C2 locates at the region away from oxides or in the bare Fe catalyst. Further ex/in situ characterizations, including XPS, TPO, in situ XRD, and in situ IR, were conducted for revealing the mechanism. This study provides insights for iron carbides formation and stability by modulating interfaces, which guides the further development of Fe-based FTS catalysts.

Overcoming the Trade-Off between C2 H2 Sorption and Separation Performance by Regulating Metal-Alkyne Chemical Interaction in Metal-Organic Frameworks.

Designing porous materials for C2 H2 purification and safe storage is essential research for industrial utilization. We emphatically regulate the metal-alkyne interaction of PdII and PtII on C2 H2 sorption and C2 H2 /CO2 separation in two isostructural NbO metal-organic frameworks (MOFs), Pd/Cu-PDA and Pt/Cu-PDA. The experimental investigations and systematic theoretical calculations reveal that PdII in Pd/Cu-PDA undergoes spontaneous chemical reaction with C2 H2 , leading to irreversible structural collapse and loss of C2 H2 /CO2 sorption and separation. Contrarily, PtII in Pt/Cu-PDA shows strong di-σ bond interaction with C2 H2 to form specific π-complexation, contributing to high C2 H2 capture (28.7 cm3 g-1 at 0.01 bar and 153 cm3 g-1 at 1 bar). The reusable Pt/Cu-PDA efficiently separates C2 H2 from C2 H2 /CO2 mixtures with satisfying selectivity and C2 H2 capacity (37 min g-1 ). This research provides valuable insight into designing high-performance MOFs for gas sorption and separation.

Hydroxypillar[5]arene‐Confined Silver Nanocatalyst for Selective Electrochemical Reduction of CO2 to Ethanol

AbstractCO is usually the dominant product on silver‐based catalysts in electrochemical CO2 reduction reaction (CO2RR) possibly due to weak *CO adsorption. In this report, a hydroxypillar[5]arene‐extended porous polymer‐confined silver catalyst (PAF‐PA5‐Ag‐0.8) for electrochemical CO2RR which can selectively produce ethanol with a maximum Faradaic efficiency of 55% at 11 mA cm−1 is described. The study reveals that the hydroxypillar[5]arene‐confined Ag clusters are the active sites for ethanol formation. Moreover, temperature‐programmed desorption measurements demonstrate an enhanced adsorption strength of CO* on PAF‐PA5‐Ag‐0.8 compared with that on commercial Ag nanoparticles, which is favored by the C‐C coupling to form ethanol. The density functional theory study indicates that the confined Ag clusters in PAF‐PA5‐Ag‐0.8 contribute to high C2 selectivity in CO2RR through facilitating *COOH formation, stabilizing *CO intermediates, and inhibiting hydrogen evolution. This work provides a new design strategy by modulating *CO adsorption strength on non‐copper electrocatalysts in converting CO2 into “green” C2 products.

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2 H6 /C2 H4 Separation.

Developing adsorptive separation processes based on C2 H6 -selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C2 H4 purification from C2 H4 /C2 H6 mixtures, which however remains challenging. During our studies on two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2), we found that Ni-MOF 2 exhibited significantly higher performance for C2 H6 /C2 H4 separation than Ni-MOF-1, as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C-H⋅⋅⋅π with C2 H6 over C2 H4 while the suitable pore spaces enforce its high C2 H6 uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg-1 of polymer-grade C2 H4 product from equimolar C2 H6 /C2 H4 mixtures at ambient conditions.

Reconstructed Cu/Cu2O(I) catalyst for selective electroreduction of CO2 to C2+ products

It is particularly desirable for the development of carbon utilization technologies to synthesize multicarbon products (C2+) from the electrochemical CO2 reduction reaction (CO2RR). In this work, Cu/Cu2O(X) catalysts (where X = I, Br, Cl) for selective electroreduction of CO2 to C2+ were reconstructed via cyclic voltammetry on carbon paper. The Faradaic efficiency (FE) for C2+ (C2H4, C2H5OH, C3H8OH) production over Cu/Cu2O(Cl), Cu/Cu2O(Br) and Cu/Cu2O(I) reached 31%, 34% and 58%, respectively, at a potential of −0.76 V vs. the reversible hydrogen electrode (RHE). The Cu+ and Cu0 species obtained from the reconstruction of Cu/CuX are primarily responsible for the high C2+ producing activity.

Inverse CO2/C2H2 Separation with MFU-4 and Selectivity Reversal via Postsynthetic Ligand Exchange.

Although many porous materials, including metal-organic frameworks (MOFs), have been reported to selectively adsorb C2H2 in C2H2/CO2 separation processes, CO2-selective sorbents are much less common. Here, we report the remarkable performance of MFU-4 (Zn5Cl4(bbta)3, bbta = benzo-1,2,4,5-bistriazolate) toward inverse CO2/C2H2 separation. The MOF facilitates kinetic separation of CO2 from C2H2, enabling the generation of high purity C2H2 (>98%) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C2H2 is excluded from MFU-4 by narrow pore windows formed by Zn-Cl groups. Postsynthetic F-/Cl- ligand exchange was used to synthesize an analogue (MFU-4-F) with expanded pore apertures, resulting in equilibrium C2H2/CO2 separation with reversed selectivity compared to MFU-4. MFU-4-F also exhibits a remarkably high C2H2 adsorption capacity (6.7 mmol/g), allowing fuel grade C2H2 (98% purity) to be captured from C2H2/CO2 mixtures and harvested by room temperature desorption.

Enriching the Local Concentration of CO Intermediates on Cu Cavities for the Electrocatalytic Reduction of CO2 to C2+ Products

The electrochemical carbon-dioxide reduction reaction (CO2RR) to high-value multi-carbon (C2+) chemicals provides a hopeful approach to store renewable energy and close the carbon cycle. Although copper-based catalysts with a porous architecture are considered potential electrocatalysts for CO2 reduction to C2+ chemicals, challenges remain in achieving high selectivity and partial current density simultaneously for practical application. Here, the porous Cu catalysts with a cavity structure by in situ electrochemical-reducing Cu2O cavities are developed for high-performance conversion of CO2 to C2+ fuels. The as-described catalysts exhibit a high C2+ Faradaic efficiency and partial current density of 75.6 ± 1.8% and 605 ± 14 mA cm-2, respectively, at a low applied potential (-0.59 V vs RHE) in a microfluidic flow cell. Furthermore, in situ Raman tests and finite element simulation indicated that the cavity structure can enrich the local concentration of CO intermediates, thus promoting the C-C coupling process. More importantly, the C-C coupling should be major through the *CO-*CHO pathway as demonstrated by the electrochemical Raman spectra and density functional theory calculations. This work can provide ideas and insights into designing high-performance electrocatalysts for producing C2+ compounds and highlight the important effect of in situ characterization for uncovering the reaction mechanism.

Highly efficient ZnCeZrOx/SAPO-34 catalyst for the direct conversion of CO2 into light olefins under mild reaction conditions

Currently, restricting the formation of CO and paraffin by-products at mild reaction conditions, and avoiding the waste of carbon resources remain challenging for CO2 hydrogenation into light olefins. Herein, we constructed a bifunctional catalyst consisting of Zn0.3Ce0.2Zr1.8O4 solid solution and SAPO-34 zeolite. The catalyst shows excellent performance with a high C2= – C4= selectivity of 90.1% and an O/P ratio of 60.1 at a CO2 conversion of 6.0% at 280 ºC and 0.5 MPa, while the selectivity of CO is only 7.9%. Various characterization and designed experiment results demonstrate that incorporating appropriate amounts of Ce in Zn0.3ZrOx generates more oxygen vacancies that improve CO2 activation to form formate and methoxy intermediates at low temperature and pressure. This promotes the evolution of these intermediates into light olefins over the SAPO-34 zeolite, enhancing the overall capacity of the bifunctional Zn0.3Ce0.2Zr1.8O4/SAPO-34 composited catalyst in CO2 hydrogenation under mild conditions.

Palladium-Catalyzed C2-Selective Oxidative Olefination of Benzo[b]thiophene 1,1-Dioxides with Styrenes and Acrylates.

Here, we disclose a novel Pd(II)-catalyzed oxidative Heck reaction of benzo[b]thiophene 1,1-dioxides with styrenes and acrylates. This transformation features broad functional group tolerance and high C2 selectivity. Furthermore, the photoluminescence properties of C-2 alkenylated products have been characterized, which illustrates the potential usefulness of our protocol in constructing π-conjugated fluorescent molecules.

Tuning flow-through cu-based hollow fiber gas-diffusion electrode for high-efficiency carbon monoxide (CO) electroreduction to C2+products

Electrochemical carbon monoxide reduction (CORR) to C2+ products has advantages over electrochemical CO2 conversion (CO2RR) as issues such as carbonation, and CO2 loss during CO2RR are omitted in CORR due to the stability of CO in alkaline solutions. Facing common challenges as CO2RR, CORR suffers more from mass transport resistance and intrinsically lower aqueous CO solubility. Therefore gas-diffusion electrodes (GDEs) are desired to boost the formation of triple phases and active sites to obtain higher reaction rates. Herein, for the first time Cu-based hollow fiber GDEs (HFGDEs) are tuned for CORR to C2+ products. By growing a layer of Cu nanocubes as the catalyst layer on HFGDEs, non-selective pristine copper HFGDE became highly selective for C2+ products (FE>90%), with ethylene as the main product (FE>65%), owing to the dominant Cu (100) facet in Cu nanocubes with high C2+ selectivity. In addition, ultra-high ethylene partial current density of > 470 mA cm−2 at − 0.8 V vs. RHE in 5.0 M KOH was obtained, owing to the abundant porosity and surface area available for triple-phase formation on microtubular GDEs and their enhanced mass transport. The electrodes exhibited one of the highest partial current densities achieved for ethylene production, indicating the promises of flow-through hollow fiber configuration for other desired products or gas-phase electrochemical reactions with low aqueous solubility.

Cu+-Mediated CO Coordination for Promoting C–C Coupling for CO2 and CO Electroreduction

Selective electrochemical upgrading of CO2 to multicarbon (C2+) products requires a C-C coupling process, yet the underlying promoting mechanism of widely involved Cu oxidation states remains largely unclear, hindering the subtle design of efficient catalysts. Herein, we unveil the critical role of Cu+ in promoting C-C coupling via coordination with a CO intermediate during electrochemical CO2 reduction. We find that, relative to other halogen anions, iodide (I-) in HCO3- electrolytes accelerates the generation of strongly oxidative hydroxyl radicals that accounts for the formation of Cu+, which can be dynamically stabilized by I- via the formation of CuI. The in situ generated CO intermediate strongly binds to CuI sites, forming nonclassical Cu(CO)n+ complexes, leading to an approximately 3.0-fold increase of C2+ Faradaic efficiency at -0.9 VRHE relative to that of I--free Cu surfaces. Accordingly, a deliberate introduction of CuI into I--containing HCO3- electrolytes for direct CO electroreduction brings about a 4.3-fold higher C2+ selectivity. This work provides insights into the role of Cu+ in C-C coupling and the enhanced C2+ selectivity for CO2 and CO electrochemical reduction.

Synergy of Ag and AgBr in a Pressurized Flow Reactor for Selective Photocatalytic Oxidative Coupling of Methane.

Oxidation of methane into valuable chemicals, such as C2+ molecules, has been long sought after but the dilemma between high yield and high selectivity of desired products remains. Herein, methane is upgraded through the photocatalytic oxidative coupling of methane (OCM) over a ternary Ag-AgBr/TiO2 catalyst in a pressurized flow reactor. The ethane yield of 35.4 μmol/h with a high C2+ selectivity of 79% has been obtained under 6 bar pressure. These are much better than most of the previous benchmark performance in photocatalytic OCM processes. These results are attributed to the synergy between Ag and AgBr, where Ag serves as an electron acceptor and promotes the charge transfer and AgBr forms a heterostructure with TiO2 not only to facilitate charge separation but also to avoid the overoxidation process. This work thus demonstrates an efficient strategy for photocatalytic methane conversion by both the rational design of the catalyst for the high selectivity and reactor engineering for the high conversion.