Piotr M. KrzywdaAinoa Paradelo RodriguezNieck E. Benes
9页
查看更多>>摘要：We demonstrate by Raman Spectroscopy that simultaneous reduction of NO_3~- and CO2 on Cu surfaces leads to formation of Cu-C≡N-like species, showing Raman bands at 2080 and 2150 cm~(-1) when associated with reduced or oxidized Cu surfaces, respectively. Furthermore Cu-C≡N-like species are soluble, explaining vast restructuring of the Cu surface observed after co-electrolysis of CO2 and nitrate. Oxidation of deposited Cu-C≡N-like species results in the formation of NO. Cu-C≡N-like species do not form in electrolytes containing i) NH_4~+ and CO2, or ii) NO_3~- and HCOO~-, suggesting these likely originate from Cu-CO, the commonly accepted intermediate in electrochemical reduction of CO2, and Cu-NH_x species, previously identified in the literature as intermediate towards C-N bond formation. The implications of the previously unresolved formation of Cu-C≡N-like species for the development of electrodes and processes for electrochemical formation of carbon-nitrogen bonds, including urea, amines or amides, are briefly discussed.
查看更多>>摘要：A composite catalyst comprised of ceria-manganese oxide and Cu-SSZ-13 components represents a potential solution for improving selective catalytic reduction (SCR) of NOx by ammonia. Here, clarity is provided to the pathway of promotion on these catalysts at low temperatures (< 200 °C), and it is shown that improved performance comes solely from interaction of the oxide phase with Bronsted acid bound NH3. We demonstrate that at low temperatures, the catalytic components interact via oxide-derived nitrites/nitrite-precursors (e.g., HONO, N2O3) reacting with Bronsted acid bound NH3 from the zeolite. Then, only at elevated temperatures is the influence of the oxide phase on Cu redox in the Cu-SSZ-13 observed. Furthermore, we show how the oxide component has the great potential to circumvent NH4NO3 inhibition on Cu-SSZ-13 in the composite catalysts at low temperatures by bypassing the formation of nitrates from NO2 disproportionation, thus providing a practical solution to improving low temperature SCR reactivity.
查看更多>>摘要：Photocatalytic biorefinery is receiving increasing attention as a promising approach for biomass utilization. In this field, I-III-VI quantum dots have emerged as efficient photocatalysts with unique physical and chemical properties that stem from their quantum and size effects. To fully exploit the advantages of quantum dots, a three-dimensional flexible self-supporting material (CIS@FSM) is fabricated with the assistance of defect-rich graphene oxide (GO), which is employed as a supporter to trap the quantum dots and promote charge separation/migration. Under visible-light irradiation, a xylonic acid yield of 65.05 % is obtained and no obvious decline of die photocatalytic performance is observed after nine runs. Moreover, the photocatalytic performance of CIS@FSM can be tuned by modulating the crystallinity and defect density. The investigation of the mechanism of the xylonic acid production reveals the presence of all oxidation active species, with h~+ playing the primary role. This work provides insights for semiconductor-based photocatalytic biorefinery.
查看更多>>摘要：This study investigates the effects of cobalt (Co) doped TiO2 @SiO2 photocatalyst in the polysulfone (PSf) membrane that performed a combined membrane filtration and photocatalytic process under UV light irradiation for petroleum refinery wastewater (PRW) treatment. The photocatalyst composites were synthesized using the sol-gel method, and the membranes were prepared using the phase inversion technique. Characterization results showed that the Co doping in TiO2 successfully improved the photo-sensitivity and photocatalytic activity of the composite, suggesting the reduction of the bandgap energy from 3.10 eV to 3.00 eV, which promoted the photocatalytic activity improvement. The addition of Co-TiO2 @SiO2 photocatalyst improved die membrane's porosity, hydrophilicity, water uptake ability, affinity towards water molecules, and mechanical strength. Furthermore, the PSf/Co-TiO2 @SiO2 membrane also exhibited enhanced performance on permeate flux, pollutant rejection, stability, recyclability, and durability. The fabricated photocatalytic membranes also exhibited superior antifouling performance and flux recovery ability when they performed under UV light irradiation.
查看更多>>摘要：The character of coke is typically regarded as a 'deactivator' in zeolite catalysis. We report the interdependence of coke nature and location with its true character in die mechanisms of ethylene oligomerization: a model zeolite catalyzed transformation involved in many sustainable processes. We prepared, characterized, and tested ZSM-5 zeolites of different diffusion paths and acidities, using polymeric-, organic-template, or template-free strategies and various Si/Al ratios. The results indicate that coke can improve the selectivity/yield of higher olefins and jet-fuel aliphatics, and this positive effect is better than modifying the number of acid sites. The molecular-level nature of these coke species is elucidated using high-resolution mass spectrometry. The 'enhancer' character of the coke can be better exploited in polymeric templated (hierarchical) ZSM-5 zeolite because mesopores retain coke without critically affecting accessibility or causing deactivation. Furthermore, this catalyst is stable for at least 74 h on stream and in multiple reaction-regeneration cycles.
查看更多>>摘要：S-scheme photocatalysts are more efficient than the conventional type-II configuration, but the CO2 reduction performances are still unsatisfactory. Herein, we firstly report the layered double hydroxide (LDH) based S-scheme heterostructure photocatalyst (Niln LDH/In2S3) with n-type NiIn LDH and p-type In2S3. The built-in internal electric field directs the photogenerated electrons flow from the conductive band of In2S3 to the valance band of Niln LDH, which is confirmed by operando and theoretical experiments. The CO2 photoreduction intermediates are monitored by in-situ Raman spectra, and the density functional calculations disclose the reduced energy barrier for CO desorption on the heterojunction. Therefore, without cocatalysts or sacrificial agents, the Niln LDH/In2S3 heterojunction delivers a high CO yield rate of 29.43 μmol g~(-1) h~(-1) under visible light irradiation, ecu 3.5 and 4.3 times higher than the single counterpart Niln LDH and In2S3. Notably, this value is the highest among S-scheme CO2 photocatalysts and surpasses most top-ranking benchmarks.
查看更多>>摘要：This study presents the first instance of the application of hydrogenated nanodiamonds (H-NDs) for persulfate activation and the associated organic degradation. Surface hydrogenation at 600 °C, confirmed by the increased surface density of the C-H moiety in XPS and FT-IR spectra, produced H-NDs that outperformed graphitized NDs (prepared via annealing at 1000 °C) in terms of organic degradation and persulfate utilization efficiency. Hydrogenation improved the electrical conductivity of NDs; however, it was not accompanied by an increase in the sp~2 carbon content - in contrast to energy-intensive ND graphitization - resulting from sp~3-to-sp~2 carbon transformation. In addition to the enhanced electron-transfer mediating activity, evidenced by the negative shift of the open circuit potential and current generation, isothermal titration calorimetry measurements indicated a significantly higher binding affinity of H-ND toward persulfate compared with that of graphitized ND. Multiple empirical results confirmed the progress of electron-transfer mediation as a major activation pathway.
查看更多>>摘要：Dual-metal single-atom catalysts (DACs) with an intrinsic synergy and multiple coordination structures are flourishing for oxygen reduction reaction (ORR), on the basis of optimization and regulation of the electron configuration for active centers. Herein, a two-step strategy consisting of cavity confinement and post-adsorption is developed to prepare a nitrogen-doped carbon catalyst co-supported by high-density ZnN4 and CoN4 sites (denoted as ZnCo-NC-II) through metal-organic framework (MOF) engineering. Structural characterization incorporated with density functional theory (DFT) calculation demonstrates that electrons are transferred from Zn (donors) to nearby Co (acceptors) through the conjugated graphene π-bond. The optimized Co d-band center achieves a moderate adsorption strength between O2 and CoN4 active sites. So, the rate-determining step (RDS) for the ~*OOH formation is accelerated. Therefore, ZnCo-NC-II exhibits a distinguished ORR activity with a half-wave potential (E_(1/2)) of 0.86 and 0.79 V (vs RHE) in alkaline and acid media, respectively. The zinc-air battery built with the ZnCo-NC-II catalyst shows excellent electrochemical performance for an immediate practical application. Our work is conducive to an atomic-level clarification on both the composition and design and thereof the synergistic catalytic mechanism with dual-metal sites.
查看更多>>摘要：In Fenton-like reaction, peroxymonosulfate (PMS) could be activated by either transition metals or graphitized carbon. These two activation paths had their own advantages and disadvantages. To simultaneously increase the PMS activation efficiency and degradation performance, lower the metal leaching, and improve the environmental adaption; herein, a yolk@shell nanoreactor was designed, where Kirkendall effect induced abundant hollow CoO nanoparticles were encapsulated inside a Co, N atoms co-doped graphitized carbon (Co-N-GC) shell. Because of the full exploitation of active sites on yolk@shell nanoreactor, nearly 100% of PMS activation efficiency was realized and 80.0% of tetracycline (TC) (50 mg/L) was degraded within 40 min. Under the protection of Co-N-GC shell, TC were effectively degraded over the full pH range or in the presence of various inorganic anions, and the leached Co~(2+) was only 0.462 mg/L even after 5 cycles. This study provided a new vision to improve the Fenton-like reaction using yolk@shell nanoreactor.
查看更多>>摘要：Metal-free carbocatalysts have sparked intensive interest in oxidative dehydrogenation. However, efficient metal-free carbocatalysts for non-oxidative dehydrogenation with H2 liberation under mild conditions has rarely been reported. Herein, we successfully fabricated B,F co-doped nitrogen-assembly carbons (BF-NCs), which display outstanding catalytic performance and reaction generality in acceptorless dehydrogenation of N-heterocycles at mild and even at room temperatures, observably outperforming that of undoped NCs or single-doped B-NCs (B-NCs). Specifically, dual-active-sites were achieved in BF-NCs, i.e., the closely-placed graphitic nitrogen (CGN) and the pyridinic N banded -BF_x. The results of kinetic analysis and DFT directly reveal that the dual-active-sites on carbocatalysts lower the energy barriers for tetrahydroquinolme (THQ) dehydrogenation, thereby accelerating H2 liberation even at room temperature. BF-NC shows promising recyclability and an ability to achieve 98.2% product yield without sacrificing efficacy in a 50-fold scale-up experiment, making the cost-effective and robust carbocatalysts a great contender for H2 liberation in practical industrial application.
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