The challenge in the artificial photosynthesis of fossil resources from CO by utilizing solar energy is to achieve stable photocatalysts with effective CO adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO to CO, yielding a CO evolution rate of 27.2 µmol g h without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C N alone (10.3 µmol g h ). The enhanced photocatalytic activity of the Z-scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin-like hematite and preferable basic sites which promotes the CO adsorption, and (ii) the unique Z-scheme feature efficiently promotes the separation of the electron-hole pairs and enhances the reducibility of electrons in the conduction band of the g-C N . The origin of such an obvious advantage of the hierarchical Z-scheme is not only explained based on the experimental data but also investigated by modeling CO adsorption and CO adsorption on the three different atomic-scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal-oxide-based Z-scheme system for solar fuel generation.
By simply changing the oxide support, the selectivity of a metal-oxide catalysts can be tuned. For the CO2 hydrogenation over PtCo bimetallic catalysts supported on different reducible oxides (CeO2 , ZrO2 , and TiO2 ), replacing a TiO2 support by CeO2 or ZrO2 selectively strengthens the binding of C,O-bound and O-bound species at the PtCo-oxide interface, leading to a different product selectivity. These results reveal mechanistic insights into how the catalytic performance of metal-oxide catalysts can be fine-tuned.
The CO 2 electroreduction reaction (CO 2 RR) to chemicals and fuels is of both fundamental and practical significance, since it would lead to a more efficient storage of renewable energy while closing the carbon cycle. Here we report enhanced activity and selectivity for the CO 2 RR to multicarbon hydrocarbons and alcohols (∼69% Faradaic efficiency and −45.5 mA cm −2 partial current density for C 2+ at −1.0 V vs RHE) over O 2 -plasma-activated Cu catalysts via electrolyte design. Increasing the size of the alkali-metal cations in the electrolyte, in combination with the presence of subsurface oxygen species which favor their adsorption, significantly improved C−C coupling on CuO x electrodes. The coexistence of Cs + and I − induced drastic restructuring of the CuO x surface, the formation of shaped particles containing stable CuI species, and a more favorable stabilization of the reaction intermediates and concomitant high C 2+ selectivity. This work, combining both experiment and density functional theory, provides insights into the active sites and reaction mechanism of oxide-derived Cu catalysts for the CO 2 RR.
The selective hydrodeoxygenation (HDO) reaction is desirable to convert glycerol into various value-added products by breaking different numbers of C–O bonds while maintaining C–C bonds. Here we combine experimental and density functional theory (DFT) results to reveal that the Cu modifier can significantly reduce the oxophilicity of the molybdenum carbide (Mo2C) surface and change the product distribution. The Mo2C surface is active for breaking all C–O bonds to produce propylene. As the Cu coverage increases to 0.5 monolayer (ML), the Cu/Mo2C surface shows activity towards breaking two C–O bonds and forming ally-alcohol and propanal. As the Cu coverage further increases, the Cu/Mo2C surface cleaves one C–O bond to form acetol. DFT calculations reveal that the Mo2C surface, Cu-Mo interface, and Cu surface are distinct sites for the production of propylene, ally-alcohol, and acetol, respectively. This study explores the feasibility of tuning the glycerol HDO selectivity by modifying the surface oxophilicity.
Here we present a new visible light active composite based on porous graphitic carbon nitride decorated hierarchical yolk–shell TiO2 spheres for water pollution treatment and H2 evolution.
Hydrodeoxygenation (HDO) is an important reaction for converting biomass-derived furfural to value-added 2-methylfuran, which is a promising fuel additive. In this work, the HDO of furfural to produce 2-methylfuran occurred on the NiCu bimetallic surfaces prepared on either Ni(111) or Cu(111). The reaction pathways of furfural were investigated on Cu(111) and Ni/Cu(111) surfaces using density functional theory (DFT) calculations, temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) experiments. These studies provided mechanistic insights into the effects of bimetallic formation on enhancing the HDO activity. Specifically, furfural weakly adsorbed on Cu(111), while it strongly adsorbed on Ni/Cu(111) through an η 2 (C,O) configuration which led to the HDO of furfural on Ni/Cu(111). The ability to dissociate H 2 on Ni/Cu(111) is also an important factor for enhancing the HDO activity over Cu(111).
The formation of carbides can significantly modify the physical and chemical properties of the parent metals. In the current review, we summarize the general trends in the reactions of water and C1 molecules over transition metal carbide (TMC) and metal-modified TMC surfaces and thin films. Although the primary focus of the current review is on the theoretical and experimental studies of reactions of C1 molecules (CO, CO, CHOH, etc.), the reactions of water will also be reviewed because water plays an important role in many of the C1 transformation reactions. This review is organized by discussing separately thermal reactions and electrochemical reactions, which provides insights into the application of TMCs in heterogeneous catalysis and electrocatalysis, respectively. In thermal reactions, we discuss the thermal decomposition of water and methanol, as well as the reactions of CO and CO over TMC surfaces. In electrochemical reactions, we summarize recent studies in the hydrogen evolution reaction, electrooxidation of methanol and CO, and electroreduction of CO. Finally, future research opportunities and challenges associated with using TMCs as catalysts and electrocatalysts are also discussed.
Selectively cleaving the CO
bond of the aldehyde group in furfural is critical for converting
this biomass-derived platform chemical to an important biofuel molecule,
2-methylfuran. This work combined density functional theory (DFT)
calculations and temperature-programmed desorption (TPD) and high-resolution
electron energy loss spectroscopy (HREELS) measurements to investigate
the hydrodeoxygenation (HDO) activity of furfural on bimetallic surfaces
prepared by modifying Pt(111) with 3d transition metals (Cu, Ni, Fe,
and Co). The stronger binding energy of furfural and higher tilted
degree of the furan ring on the Co-terminated bimetallic surface resulted
in a higher activity for furfural HDO to produce 2-methylfuran in
comparison to that on either Pt(111) or Pt-terminated PtCoPt(111).
The 3d-terminated bimetallic surfaces with strongly oxophilic 3d metals
(Co and Fe) showed higher 2-methylfuran yield in comparison to those
surfaces modified with weakly oxophilic 3d metals (Cu and Ni). The
effect of oxygen on the HDO selectivity was also investigated on oxygen-modified
bimetallic surfaces, revealing that the presence of surface oxygen
resulted in a decrease in 2-methylfuran yield. The combined theoretical
and experimental results presented here should provide useful guidance
for designing Pt-based bimetallic HDO catalysts.
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