Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAn In Situ Surface-Enhanced Infrared Absorption Spectroscopy Study of Electrochemical CO2 Reduction: Selectivity Dependence on Surface C-Bound and O-Bound Reaction Intermediates
200
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The CO_{2} electro-reduction reaction (CORR) is a promising avenue to convert greenhouse gases into high-value fuels and chemicals, in addition to being an attractive method for storing intermittent renewable energy. Although polycrystalline Cu surfaces have long known to be unique in their capabilities of catalyzing the conversion of CO_{2} to higher-order C1 and C2 fuels, such as hydrocarbons (CH_{4}, C_{2}H_{4} etc.) and alcohols (CH_{3}OH, C_{2}H_{5}OH), product selectivity remains a challenge. In this study, we select three metal catalysts (Pt, Au, Cu) and apply in situ surface enhanced infrared absorption spectroscopy (SEIRAS) and ambient-pressure X-ray photoelectron spectroscopy (APXPS), coupled to density-functional theory (DFT) calculations, to get insight into the reaction pathway for the CORR. We present a comprehensive reaction mechanism for the CORR, and show that the preferential reaction pathway can be rationalized in terms of metal-carbon (M-C) and metal-oxygen (M-O) affinity. We show that the final products are determined by the configuration of the initial intermediates, C-bound and O-bound, which can be obtained from CO_{2} and (H)CO_{3}, respectively. C1 hydrocarbons are produced via OCH_{3, ad} intermediates obtained from O-bound CO_{3, ad} and require a catalyst with relatively high affinity for O-bound intermediates. Additionally, C2 hydrocarbon formation is suggested to result from the C-C coupling between C-bound CO_{ad} and (H)CO_{ad}, which requires an optimal affinity for the C-bound species, so that (H)CO_{ad} can be further reduced without poisoning the catalyst surface. Our findings pave the way towards a design strategy for CORR catalysts with improved selectivity, based on this experimental/theoretical reaction mechanisms that have been identified.
rate research
Read More
Biomass compounds adsorbed on surfaces are challenging to study due to the large number of possible species and adsorption geometries. In this work, possible intermediates of erythrose, glyceraldehyde, glycerol and propionic acid are studied on the Rh(111) surface. The intermediates and elementary reactions are generated from first 2 recursions of a recursive bond-breaking algorithm. These structures are used as the input of an unsupervised Mol2Vec algorithm to generate vector descriptors. A data-driven scheme to classify the reactions is developed and adsorption energies are predicted. The lowest mean absolute error (MAE) of our prediction on adsorption energies is 0.39 eV, and the relative ordering of different surface adsorption geometries is relatively accurate. We show that combining geometries from density functional tight-binding (DFTB) calculations with energies from machine-learning predictions provides a novel workflow for rapidly assessing the stability of various molecular geometries on the Rh(111) surface.
We report on a many-electron wavefunction theory study for the reaction energetics of hydrogen dissociation on the Si(100) surface. We demonstrate that quantum chemical wavefunction based methods using periodic boundary conditions can predict chemically accurate results for the activation barrier and the chemisorption energy in agreement with experimental findings. These highly accurate results for the reaction energetics enable a deeper understanding of the underlying physical mechanism and make it possible to benchmark widely used density functional theory methods.
Electrochemical CO2 reduction is a promising strategy for utilization of CO2 and intermittent excess electricity. Cu is the only single-metal catalyst that can electrochemically convert CO2 to multi-carbon products. However, Cu has an undesirable selectivity and activity for C2 products, due to its insufficient amount of CO* for C-C coupling. Considering the strong CO2 adsorption and ultra-fast reaction kinetics of CO* formation on Pd, an intimate CuPd(100) interface was designed to lower the intermediate reaction barriers and then improve the efficiency of C2 products. Density functional theory (DFT) calculations showed that the CuPd(100) interface has enhanced CO2 adsorption and decreased CO2* hydrogenation energy barrier, which are beneficial for C-C coupling. The potential-determining step (PDS) barrier of CO2 to C2 products on CuPd(100) interface is 0.61 eV, which is lower than that on Cu(100) (0.72 eV). Motivated by the DFT calculation, the CuPd(100) interface catalyst was prepared by a facile chemical solution method and demonstrated by transmission electron microscope (TEM). The CO2 temperature programmed desorption (CO2-TPD) and gas sensor experiments proved the enhancements of CO2 adsorption and CO2* hydrogenation abilities on CuPd(100) interface catalyst. As a result, the obtained CuPd(100) interface catalyst exhibits a C2 Faradaic efficiency of 50.3 (+/-) 1.2% at -1.4 VRHE in 0.1 M KHCO3, which is 2.1 times higher than 23.6(+/-) 1.5% of Cu catalyst. This work provides a rational design of Cu-based electrocatalyst for multi-carbon products by fine-tuning the intermediate reaction barriers.
Electrochemical reduction of CO2 to CO is a promising strategy. However, achieving high Faradaic efficiency with high current density using ILs electrolyte remains a challenge. In this study, the IL N octyltrimethyl 1,2,4 triazole ammonium shows outstanding performance for electrochemical reduction of CO2 to CO on the commercial Ag electrode, and the current density can be up to 50.8 mA cm-2 with a Faradaic efficiency of 90.6%. The current density of CO is much higher than those reported in the ILs electrolyte. In addition, the density functional theory calculation further proved that IL interacts with CO2 to form IL CO2 complex which played a key role in reducing the activation energy of CO2. According to the molecular orbital theory, the electrons obtained from ILs was filled in the anti bonding orbit of the CO2, resulting in reducing the C=O bond energy. This work provides a new strategy to design novel ILs for high efficiency electrochemical reduction of CO2 to CO.
Waveguide-integrated plasmonics is a growing field with many innovative concepts and demonstrated devices in the visible and near-infrared. Here, we extend this body of work to the mid-infrared for the application of surface-enhanced infrared absorption (SEIRA), a spectroscopic method to probe molecular vibrations in small volumes and thin films. Built atop a silicon-on-insulator (SOI) waveguide platform, two key plasmonic structures useful for SEIRA are examined using computational modeling: gold nanorods and coaxial nanoapertures. We find resonance dips of 80% in near diffraction-limited areas due to arrays of our structures and up to 40% from a single resonator. Each of the structures are evaluated using the simulated SEIRA signal from poly(methyl methacrylate) and an octadecanethiol self-assembled monolayer. The platforms we present allow for a compact, on-chip SEIRA sensing system with highly efficient waveguide coupling in the mid-IR.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
