查看更多>>摘要：Herein, we demonstrate that the rare-earth La single catalyst with multi-shell characteristic is an excellent choice for this purpose. By merit of its unsaturated orbitals of La, the single La atom strongly bonds with the two-coordinated lattice oxygen on the oxygen-deficient MoO3-x to form O-2c-La-O-2c coordination. This robust metal-support interaction frees single atoms from detachment or aggregation, and prevents catalyst from deactivation. Meanwhile, the occupied 5d orbitals of La back-donate electrons to the 2 pi* molecular orbitals of adsorbed N-2 that substantially activate the inert N equivalent to N bond towards successive hydrogenation. And single La atom could optimize the electron property of the MoO3-x support to promote photocatalytic nitrogen fixation. Without any sacrificial agents, this single atom La catalyst with a well-designed coordination structure delivers an impressive NH3 production rate of 209.0 mu mol h(-1) g(-1) under visible light, outperforming most reported single atom photocatalysts.
查看更多>>摘要：Lignin is a renewable aromatics resource that can be converted into high-value chemicals through the beta-O-4 linkage cleavage. Self-hydrogen transfer hydrogenolysis (STH) is a promising way to produce monomers from lignin through the beta-O-4 linkage cleavage with no additional hydrogen sources, but usually with low yield toward native lignin. Here, a Pd-PdO/TiO2 catalyst was prepared for the STH of native lignin. Compared with Pd/TiO2 and PdO/TiO2, Pd-PdO/TiO2 showed the highest activity in the STH of C-beta-O bond in beta-O-4 models. In the STH process, the C alpha H-OH in beta-O-4 linkage is dehydrogenated to form beta-O-4 ketone intermediates, and hydrogens are adsorbed on Pd sites to form a "hydrogen pool" which participates in the following hydrogenolysis of C-beta-O bond. DFT calculation shows that PdO more effectively activates the beta-O-4 ketone intermediate and shows lower activation energy toward C-beta-O bond cleavage compared with Pd. Pd acts as the dehydrogenation site and PdO activates the C-beta-O bond. The co-existence of Pd and PdO facilitates the C-beta-O bond cleavage of beta-O-4 linkage and about 40 wt % yields of lignin monomers can be obtained from poplar lignin at 180 degrees C.
查看更多>>摘要：Via redox chemistry, chemical looing water splitting driven by the reduction of coke oven gas (COG) over an oxygen carrier was proposed to co-produce pure H-2 and H-2-rich syngas without a separation step. We designed an efficient LaFeO3-based perovskite oxygen carriers by doping a small amount of Ni for preferentially oxidizing methane to syngas in the presence of CO and H-2 at relatively low temperatures (700-800.), which further improves the H-2 yield via water splitting. Compared with pure LaFeO3, the methane conversion and syngas yield for LaNi0.07Fe0.93O3-lambda increase from 49.4% and 8.55 mol.kg(-1) to 98.6% and 12.58 mol.kg(-1) in the COG conversion step at 800 degrees C, respectively, and the H-2 yield rises from 1.91 mol.kg(-1) to 3.30 mol.kg(-1) in the water splitting step. Results from combined experimental characterizations and density functional theory (DFT) calculation reveal that the incorporation of Ni cations into LaFeO3 lattice can greatly weaken the Fe-O bond and increase the lattice oxygen mobility, and the exsolved surface Ni species during the early stage of the reduction promote the activation of methane for further conversion. This contributes to the enhanced activity and lowered reaction temperature for syngas and H-2 generation. The LaNi0.07Fe0.93O3-lambda oxygen carriers also shows high stability in either reaction performance or material structure aspect during the successive redox cycles. This work demonstrates that it is feasible to design a high-performance oxygen carrier to preferentially convert methane in COG into syngas and further produce pure hydrogen via water splitting by using a chemical looping concept.
查看更多>>摘要：Non-thermal plasma (NTP) coupled with catalysis provides a way to enable the dry reforming of methane (DRM) reaction to occur at low temperatures. While assistance of NTP brings the negative issue of coke deposition due to the faster rate of CH4 dissociation induced by NTP. Herein, beta-Mo2C was employed as an effective component to activate CO2 and collaborated with Ni/gamma-Al2O3 for the plasma-assisted DRM reaction. Addition of beta-Mo2C facilitated the charge deposition, and Ni nanoparticles were found to re-disperse over the beta-Mo2C surface due to the strong interaction between Ni and beta-Mo2C. Benefiting from the new active interface of Ni-Mo2C, the mechanically mixed Mo2C-Ni/Al2O3 catalyst exhibited much better activity and stability as compared with the undoped Ni/Al2O3 catalyst. The present study reveals the crucial roles of beta-Mo2C additives, providing practical solutions to depress carbon deposition, and thereby enhance the catalytic stability in plasma-assisted DRM reaction.
Pan, Uday NarayanPaudel, Dasu RamDas, Amit KumarSingh, Thangjam Ibomcha...
14页
查看更多>>摘要：Metallic (1T) transition metal dichalcogenides (TMDCs) shows great potential for electrocatalytical water-splitting (ECWS). Among different 1T-TMDCs, vanadium (V)-based 1T-TMDCs has highest thermodynamic stability. Now, among different V-based 1T-TMDCs, 1T-VTe2 holds the best potential for ECWS due to strongest interlayer coupling between V and Te. In the present study, we have developed nickel nanoclusters (NiNCs) hybridized and manganese (Mn) intercalated and doped 1T-VTe2 nanosheets (NiNCs-1T-Mn-VTe2 NS) for ultra-low potential ECWS. Mn doping and intercalation in 1T-VTe2 (1T-Mn-VTe2) significantly improve ECWS efficacy following improving oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances. Hybridization of NiNCs with1T-Mn- VTe2 develop a true ECWS-catalyst NiNCs-1T-Mn-VTe2 NS for ultra-low potential water-splitting. NiNCs-1T-Mn-VTe2 NS showed excellent performance requiring only HER-overpotential of 61 mV to reach 10 mA cm-2 and OER overpotential of 258 mV to reach 40 mA cm-2. NiNCs-1T-Mn-VTe2NS (+ -) device required a cell potential of 1.51 V to reach 10 mA cm-2.
查看更多>>摘要：At present, formic acid with the high energy value is the promising product generated by the large-scale renewable electricity-driven CO2 conversion, yet challenges remain in the high-throughput and low-energy production accompanied by the considerable selectivity. Herein, in view of the contribution of electronic modulation to electrocatalytic CO2 reduction reaction (CO2RR) activity of catalysts, the thin BiCu-bimetallic film was designed and built on Cu foam (BiCu/CF) by coupling a facile hydrothermal reaction and an immediate electrochemical transformation. The theoretical evidences demonstrate that Bip-orbital delocalization triggered by the close-contact metal Cu optimizes reaction pathway of CO2RR, and also favours the orbital hybridization between Bi atom and *OCHO intermediate to form more anti-bonding orbitals, resulting in stabilizing *OCHO intermediate and lowering the thermodynamic barrier of CO2RR. Meanwhile, the electron transferred from catalyst-sites to reaction species also accelerates during CO2RR. Integrating the improved intrinsic activity of Bi catalytic-sites and the superiority of Cu foam in exposing more active sites and the mechanical strength, the BiCu/CF electrode with optimal thickness can acquire satisfactory indicators for industrial application, yielding a record formate current density of 856 mA cm(-2), higher than 85% Faradic efficiency, along with a remarkable stability, which outperforms state-of-the-art Bi-based catalysts. This study offers potential avenues of engineering orbital delocalization to rationally construct advanced CO2RR electrodes for the carbon-neutral cycle and utilization.
查看更多>>摘要：The atomically dispersed dual metal atom catalysts exhibit significant promise for the electrochemical energy conversion technologies. Herein, the hetero-nuclear precious-non-precious (Au-Co) dual atoms have been synthesized and subsequently applied for the acidic oxygen reduction reaction (ORR). The (Au-Co) dual atoms exhibit an outstanding activity with half-wave potential (E-1/2) of 0.82 V in 0.1 M HClO4. Additionally, the proton exchange membrane fuel cell (PEMFC) analysis reveals a peak power density of 360 mW cm(-2) under H-2/air condition. Co-N2C2 with axial Au atom moieties act as the active sites of the (Au-Co) dual atoms towards ORR. Further, *OH adsorbed on the Co atom induces a coordinated change in the adjacent Au atom symmetry, which leads the anti-bond spin orbitals to a low energy level, thus, further improving ORR performance. The development of (Au-Co) dual atoms via the regulation of D-orbitals symmetry provides an encouraging way to design highly efficient (electro)catalysts.
查看更多>>摘要：A N/O-codoped carbon-based catalyst (N/O-C-8) designed with dual reaction sites (pyridinic N and carbonyl group) was fabricated in this work, for persulfate based advanced oxidation reaction. The pyridinic N served as the adsorption site for target molecule, via series of high resolution XPS analysis and DFT calculation. Meanwhile, the carbonyl group functioned as the persulfate activation site, to generate oxidative O-1(2). Engineering and isolating the two reaction sites on catalyst surface can greatly shorten the migration distance from O-1(2) to target organic molecule, resulting in good catalytic removal efficiency. As demonstrated, during a 4-hour continuous flow experiment, our catalyst showed stable and efficient removal of tetracycline, with a flow rate of 4 mL/min. The study provides keen insights into the design of effective non-metal based catalysts for practical water remediation.
查看更多>>摘要：The influence of SO2 on the amounts of NO2, NH3 and NO adsorbed on CeWOx and the reaction pathway of fast and standard SCR were investigated using transient reaction experiments and in situ DRIFTS. The negative effect of SO2 was less severe during fast SCR. The SO2 adsorption inhibited NO adsorption and the "nitrite path", which is detrimental for standard SCR at low temperatures. For fast SCR, although "nitrite path" and "NH4NO3 path" were inhibited, the greater amount of nitrates from NO2 adsorption, acceleration of NH4HSO4 decomposition, and promoted reaction between the NO gas, surface nitrates and adsorbed NH3 made the inhibitory effect of SO2 less severe. Bronsted acid sites are more active and make the main contribution to SCR with SO2. NH4HSO4 may not be the main cause of deactivation. When H2O and SO2 were present, "nitrite path" was seriously inhibited and "NH4NO3 path" was absent, causing decreased activity.
查看更多>>摘要：Carbon fibers with intrinsic carbon defects (D-CFs) were fabricated through heteroatoms doping and de-doping using seaweed polysaccharide as the precursor. When evaluated as oxygen reduction reaction (ORR) electro-catalyst, D-CFs display an initial potential of 0.92 V (vs. RHE) and a limiting diffusion current density of 5.38 mA.cm(-2) in KOH electrolyte (0.1 M). The high peak power density of zinc-air batteries (ZABs) assembled by D-CFs is 238 mW.cm(-2), that is much better than commercial Pt/C (154 mW.cm(-2)). In the light of density functional theory (DFT) results, enriched electrons in defects make the hybridization energy levels of active defective sites and adsorbed oxygen atoms rise to Fermi level, indicating that O-2 molecules are inclined to be adsorbed onto defective carbon atoms. Therefore, abundant renewable seaweed sources, together with the excellent ORR catalytic activity, make D-CFs as the substitute of Pt/C catalyst for large-scale application of ZABs.
NSTL
Elsevier