Oxygen reduction reaction, which proceeds at the cathode of a fuel cell, is primarily important as its rate determines the overall performance of the device. However, designing a single-phase material...
drawing attention as a promising technology to mitigate excess anthropogenic CO 2 emissions because it can convert carbon dioxide into high-value-added chemicals and fuels in an eco-friendly and economical way. [2] Among suitable metals, Cu (and its compounds) is the only one capable of producing high value-added C 2+ products, such as C 2 H 4 and C 2 H 5 OH, with high selectivity through CO dimerization. [3] However, the C 2+ selectivity of Cu-based electrocatalysts can be further improved by tailoring the active sites of Cu through doping, [4] tuning the catalyst particle shapes and sizes, [5] and increasing the number of low coordination sites, for example, the grain boundary density. [6] In particular, the use of mixed oxidation states (i.e., Cu + and Cu 0 ) has been suggested as an effective means to achieve high C 2+ product selectivity by lowering the energy barrier for CO dimerization. [7] However, Cu + is not stable and is easily converted to metallic Cu (Cu 0 ) at the negative applied potentials used for the CO 2 RR. As a result, many strategies have been developed to sustain the mixed oxidation state of Cu during the CO 2 RR. [8] For instance, doping Cu with B atoms can induce the formation of Cu + under CO 2 RR conditions, and increase its stability. [4a,9] Nevertheless, it is still challenging to achieve controllable Cu + coverage at the catalytically active Cu top-surface.Ceria (CeO 2 ) is a reducible metal oxide and an excellent support for metal catalysts in many catalytic processes, such as the water-gas shift reaction, [10] CO oxidation, [11] and CO 2 hydrogenation reaction. [12] As a catalyst support, CeO 2 can disperse metals at various scales uniformly, from the nanometre in scale to single atoms. [13] In addition, CeO 2 forms strong metal-support interactions (SMSIs) with the active metals, which allows the formation of a partially charged metal at the metal-CeO 2 interface. [14] These unique characteristics of CeO 2 can also promote the electrocatalytic CO 2 RR activity of metals such as Au and Cu supported on CeO 2 . In particular, Cu on ceria (Cu-CeO 2 ) shows wide tunability in CO 2 RR product selectivity, and this is dependent on the sizes and compositions of Cu-CeO 2 . For example, CeO 2 can stabilize a single-atom (SA) Cu in the Cu 2+ valence state and generate CH 4 with a faradaic efficiency (FE) of Ceria (CeO 2 ) is one of the most extensively used rare earth oxides. Recently, it has been used as a support material for metal catalysts for electrochemical energy conversion. However, to date, the nature of metal/CeO 2 interfaces and their impact on electrochemical processes remains unclear. Here, a Cu-CeO 2 nanorod electrochemical CO 2 reduction catalyst is presented. Using operando analysis and computational techniques, it is found that, on the application of a reductive electrochemical potential, Cu undergoes an abrupt change in solubility in the ceria matrix converting from less stable randomly dissolved single atomic Cu 2+ ions to (Cu 0 ,Cu 1+ ) nanoclusters. Unlike single ...
We report on atom probe tomography analyses of Pd and Pd@Au nanoparticles embedded in a Ni matrix and the effects of local evaporation field variations on the atom probe data. In order to assess the integrity of the reconstructed atom maps, we performed numerical simulations of the field evaporation processes and compared the simulated datasets with experimentally acquired data. The distortions seen in the atom maps for both Pd and Pd@Au nanoparticles could be mostly ascribed to local variations in chemical composition and elemental evaporation fields. The evaporation field values for Pd and Ni, taken from the image hump model and assumed in the simulations, yielded a good agreement between experimental and simulation results. In contrast, the evaporation field for Au, as predicted from the image hump model, appeared to be substantially overestimated and resulted in a large discrepancy between experiments and simulations.
Capping ligands are crucial to synthesizing colloidal nanoparticles with functional properties. However, the synergistic effect between different ligands and their distribution on crystallographic surfaces of nanoparticles during colloidal synthesis is still unclear despite powerful spectroscopic techniques, due to a lack of direct imaging techniques. In this study, atom probe tomography is adopted to investigate the three-dimensional atomic-scale distribution of two of the most common types of these ligands, cetrimonium (C19H42N) and halide (Br and Cl) ions, on Pd nanoparticles. The results, validated using density functional theory, demonstrate that the Br anions adsorbed on the nanoparticle surfaces promote the adsorption of the cetrimonium cations through electrostatic interactions, stabilizing the Pd {111} facets. In contrast, the Cl anions are not strongly adsorbed onto the Pd surfaces. The high density of adsorbed cetrimonium cations for Br anion additions results in the formation of multiple-twinned nanoparticles with superior oxidation resistance.
The development of Cu-based catalysts for electrochemical CO2 reduction reaction (CO2RR) with stronger CO-binding elements had been unsuccessful in improving multicarbon production from the CO2RR due to CO-poisoning. Here, we discover that trace doping levels of Co atoms in Cu, termed CoCu single-atom alloy (SAA), achieve up to twice the formation rate of CO as compared to bare Cu and further demonstrate a high j C2H4 of 282 mA cm–2 at −1.01 VRHE in a neutral electrolyte. From DFT calculations, Cu sites neighboring CO-poisoned Co atomic sites accelerate CO2-to-CO conversion and enhance the coverage of *CO intermediates required for the formation of multicarbon products. Furthermore, CoCu SAA also exhibits active sites that favor the deoxygenation of *HOCCH, which increases the selectivity toward ethylene over ethanol. Ultimately, CoCu SAA can simultaneously boost the formation of *CO intermediates and modulate the selectivity toward ethylene, resulting in one of the highest ethylene yields of 15.6%.
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