查看更多>>摘要：Antimony (Sb) as a tow-toxic and cost-effective metal is a promising material to catalyse CO2 electroreduction to formate with practical viability. However, monometallic Sb suffers from intrinsically low catalytic activity and the competing hydrogen evolution. Here, we report nanoporous Sb-Bi alloys for substantially improving the catalytic activity of Sb and suppressing hydrogen evolution. The optimal Sb-Bi alloy exhibits a maximum Faradaic efficiency of 95.8 % toward formate production, surpassing the 11.6% of monometallic Sb counterpart. Operating the catalyst in the flow cell demonstrates a formate partial current density of 734 mA cm~(-2) and cathodic energy efficiency of 59 % at a moderate overpotential of 800 mV, representing a record formate-production performance so far. Experimental and theoretical studies indicate that the Sb-Bi interactions activate Sb sites to selectively stabilize ~*OCHO intermediates, facilitating CO2-to-formate conversion. This work offers insights in manipulating bimetallic interactions to transform inert materials into active catalysts for efficient electrocatalysis.
查看更多>>摘要：Copper-ceria (Cu-Ce) catalysts with unique catalytic properties have high prospects as alternatives for noble metals in low-temperature catalytic oxidations. However, the quantitative description of the active sites in the redox processes still remains a challenge. Herein, a series of Cu-Ce catalysts were prepared by regulating the synthesis method, AR_(Cu/Ce) (atomic ratios of Cu to Ce), and pH of precipitation, so as to investigate CO and VOCs oxidations. Cu~+-O_v-Ce~(3+) configuration, as an asymmetric oxygen vacancy (ASO_v), was formed in the copper-ceria interface. Its concentration was accurately regulated under varying pH, and was quantificationally identified by ex-situ techniques in static conditions. The maximum ASO_v concentration was recorded for the CuCe3-11 catalyst, accounting for the best catalytic activity and stability. Moreover, the dynamic exchange behaviors (Cu~+-O_v-Ce~(3+)<-> Cu~(2+)-O_((ad))~(2-)-Ce~(4+)) of the ASO_v were quantificationally studied by in-situ techniques under the same reaction conditions. In the oxygen-containing reaction, 13% ASO_v was first converted to Cu~(2+)-O_((ad))~(2-)-Ce~(4+) species, and then wholly recovered in the presence of CO. In the CO oxidation processes, the dynamic exchange of ASO_v maintained equilibrium under T_(50) and T_(100). This work offers future prospects for the quantification tracking of the active sites in catalysts, while also providing a universal strategy for the rational fabrication of high-performance environmental catalysts.
查看更多>>摘要：Cu is widely used to prepare high-value products in photocatalytic CO2 reduction reaction (CO2PR). The valence state of transition metals usually has a great impact on the catalytic process. However, the research on Cu valence in CO2PR is lack for its complex valence change. In current work, Cu_x/P25 with stable Cu valence composition in CO2PR is prepared. The results show that Cu is composed of Cu~0 and Cu2O, and their proportions change regularly as Cu loading changing, which are linearly related to the selectivity of the corresponding products of CO2PR. Combined with thermodynamic and kinetic analysis, the CO adsorption and activation on the surface of Cu~0 and Cu2O are considered to be the key to determine the product of CO2PR, which is further confirmed by DFT calculation. Cu~0 and Cu2O are proved to be active site of producing CH4 and CO, respectively. In this case, a reference for the study of highly selectivity Cu based photocatalysts is provided.
查看更多>>摘要：Modulation of photoelectrochemical properties and facilitation of O2 adsorption through defective sites is of great significance for photocatalytic O2-involved organic transformations. Herein, we report an oxygen-vacancy (OV)-rich semiconductor Nb2O5 nanorod via N atoms doping strategy for visible-light driven oxidative dehydrogenation (ODH) of saturated N-heterocycles at room temperature. A spectrum of pharmaceutically important unsaturated N-heteroarene including C-nucleoside analogues was synthesized in good to excellent yields with good tolerance of functional groups. Remarkably, the catalyst is reusable up to 10 times with high stability and is also applicable for gram-scale synthesis under visible light or even sunlight illumination, highlighting the potential for practical application. Comprehensive characterizations and theoretical calculations reveal that the OVs play an essential role on effectively enhancing visible light response and accelerating separation efficiency for photogenerated hole-electron pairs, and also greatly facilitating adsorption and activation of molecular O2 and reactant, thereby substantially boosting the photocatalytic activity.
查看更多>>摘要：Bimetallic Pd/Pt catalysts have recently attracted considerable attention in controlling emission control of methane. Here, we show the impact of Pd/Pt ratio (1:0, 9:1, 3:1, 1:1, 1:3, 1:9, 0:1) on the catalytic methane oxidation under simulated exhaust environments from the CH4-rich to -lean feed. Under dry feed conditions, the CH4 oxidation activity was linear to the Pd:Pt ratio, where the Pd-only (1:0) exhibited the best performance. However, under wet feed conditions containing 5% of water vapor, bimetallic Pd/Pt catalysts having a small fraction of Pt showed superior overall activities in a wide range of reaction environments. The interaction of Pd-Pt, forming active PdO-Pt pair sites, was confirmed by a series of analysis such as STEM-EDS, XPS and H2-TPR. The evidence by DFT calculations relates the distinct properties of bimetallic Pd/Pt sites to (i) stable CH4 adsorption, (ii) facile C-H bond cleavage and (iii) weaker adsorption of water on Pt site.
查看更多>>摘要：Although novel donor-acceptor conjugated microporous polymers (D-A CMPs) that absorb visible light broadly and allow the efficient isolation of photoinduced electrons and holes are being sought for water splitting photocatalysis, their elusive energy band structures have made it a challenge to produce both H2 and O2 simultaneously. In this paper, for the first time, we develop a series of semiconducting D-A CMPs with various sulfur and nitrogen contents and degrees of conjugation for effective photocatalytic H2 and O2 generation from water. Here, we used a carbazole (Cz) moiety as the donor, and pyrene (Py), triphenyltriazine (TPT), benzothiadiazole (BT), and thiazolylthiazole (TzTz) as the acceptors. The resulting D-A CMPs had large surface areas (up to 1530 m~2 g~(-1)) and high thermal stabilities (Xno- up to 623 °C; char yield: up to 83 wt%). Moreover, the Cz-TzTz CMP provided an excellent hydrogen evolution rate CHER), reaching 15.3 mmol g~(-1) h~(-1) in the presence of ascorbic acid as the sacrificial electron donor, but without the need for an additional Pt co-catalyst. Interestingly, the Cz-TPT CMP provided an excellent oxygen evolution rate (OER) of 3.38 mmol g~(-1) h~(-1) when using AgNO3 as a sacrificial electron acceptor; this value is competitive with those of most previously reported organic photocatalysts. These highly active CMP-based photocatalysts appear to be useful materials for solar energy harvesting and conversion.
查看更多>>摘要：One-pot catalytic conversion of raw woody biomass into valuable chemicals and fuels is a promising strategy for relieving energy depletion. Here, we proposed an efficient catalyst combining highly dispersed and ultrafine platinum nanoparticles on ceria doped with Cr, enabling nearly complete conversion, and obtaining value-added chemicals and bio-fuel with high energy density. The key part of our approach lies on the flexible utilization of a synergetic catalysis system consisting of a redox potential CeCrO_(2-x), balanced acid-base properties and strong metal-support interaction. Abundant oxygen vacancies and enhanced wettability have been achieved by properly doping of Cr. Under nitrogen atmosphere, the catalyst still shows excellent conversion performance, not only can hydrogen transfer be achieved by using the 'borrowed' hydrogen, but also the Guerbet reaction can suppress the formation of intractable chars. Moreover, alcoholophilicity facilitates the dispersion of the catalyst particles in ethanol, leading to higher mass transfer efficiency. The catalyst can be separated facilely and reused three times without obvious deactivation.
查看更多>>摘要：Efficiency of the electrocatalysts for hydrogen evolution reaction (HER) strongly depends on their extrinsic physical properties and intrinsic electronic structures. Among various modulation strategies, nanoalloying is an efficient route to regulate the intrinsic activities of HER intermediates. Herein, we develop a facile and universal one-step pyrolyzed method to fabricate bimetallic Ru-based nanoalloy catalysts encapsulated by B/N co-doped graphitic nanotubes (RuM@BCN, M=Ir, Pt, Ag, Co, and Fe) for high-performance alkaline HER. BCN nano-tube substrates provide sufficient open channels, porous structures and strong anchoring effect to achieve fast kinetics and high stability. The bimetallic nanoalloying strategy greatly promotes the water dissociation and hydrogen adsorption ability of the electrocatalysts via modulation on their intrinsic electronic structures. Therefore, the as-made RuM@BCN demonstrates varied HER behaviors by alloying metals, in which RuIr@BCN exhibits the highest alkaline HER activity with an overpotential of 23.6 mV at the current density of 10 rnA cm~(-2), outperforming commercial Pt/C.
查看更多>>摘要：Reversible proton-conducting solid oxide cells (R-PSOCs) have been proposed to address energy storage and conversion challenges. However, under harsh operating conditions (550 °C ～700 °C containing CO2 and H2O), the application of single-atom catalysts (SACs) in R-PSOCs is challenging due to the migration/agglomeration of isolated atoms and the lack of universal processing techniques for catalyst loading. Here, we firstly report a single-atom customizing strategy to create four-coordinated Pt-O-Ni (4) that selective anchors Pt atoms to the B-site in Pr4Ni3O_(10+δ). The resultant SAC is thermally stable, controllable, and highly active for oxygen reduction and oxygen evolution reactions, withstanding treatment at 700 °C for 800 h in air, and its electrochemical performance was improved by almost 100%. This work bridges the application gap between SACs and R-PSOCs, are amenable to the large-scale manufacture of stable, efficient, high-loading SACs for industrial applications, which can also be extended to Pd, Ir, Ru, and Fe SACs.
查看更多>>摘要：Direct syngas conversion to gasoline-range hydrocarbons particularly environmental-friendly, high octane number multi-branched isoparaffins attracts wide attention from both academia and industry but remains challenging. We report herein that ZnCrO_x-HMCM-22 upon phosphorus modification enables selective syngas conversion to gasoline (C5-C_(11)) with a selectivity of 77%. Following a simple hydrogenation in the same reactor, the fraction of isoparaffins among gasoline reaches 67%, particularly multi-branched isoparaffins as high as 27.5%, which is three times higher than that obtained by FTS-zeolites and four times higher than that in commercial 92# gasoline. This is attributed to the inhibited hydrogenation of olefins over the acid sites of phosphorus modified MCM-22 with weakened strength. Thus, methylation of olefins is significantly facilitated leading to formation of multi-branched isohydrocarbons. The fundamental understanding gained here will allow further optimization and development of catalysts for direct syngas conversion to high-quality gasoline.
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