Highly Dense Cu Nanowires for Low-Overpotential CO₂ Reduction

Electrochemical reduction of CO₂, an artificial way of carbon recycling, represents one promising solution for energy and environmental sustainability. However, it is challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of highly dense Cu nanowires as advanced electrocatalysts for CO₂ reduction. CuO nanowires were first grown by oxidation of Cu mesh in air and then reduced by either annealing in the presence of hydrogen or applying a cathodic electrochemical potential to produce Cu nanowires. The two reduction methods generated Cu nanowires with similar dimensions but distinct surface structures, which have provided an ideal platform for comparative studies of the effect of surface structure on the electrocatalytic properties. In particular, the Cu nanowires generated by electrochemical reduction were highly active and selective for CO₂ reduction, requiring an overpotential of only 0.3 V to reach 1 mA/cm² electrode current density and achieving Faradaic efficiency toward CO as high as ∼60%. Our work has advanced the understanding of the structure–property relationship of Cu-based nanocatalysts, which could be valuable for the further development of advanced electrocatalytic materials for CO₂ reduction

Macromolecular Brushes as Stabilizers of Hydrophobic Solute Nanoparticles

Macromolecular brushes bearing poly­(ethylene glycol) and poly­(d,l-lactide) side chains were used to stabilize hydrophobic solute nanoparticles formed by a rapid change in solvent quality. Unlike linear diblock copolymers with the same hydrophilic and hydrophobic block chemistries, the brush copolymer enabled the formation of ellipsoidal β-carotene nanoparticles, which in cosolvent mixtures developed into rod-like structures, resulting from a combination of Ostwald ripening and particle aggregation. The stabilizing ability of the copolymer was highly dependent on the mobility of the hydrophobic component, influenced by its molecular weight. As shown here, asymmetric amphiphilic macromolecular brushes of this type may be used as hydrophobic drug stabilizers and potentially assist the shape control of nonspherical aggregate morphologies

Three-Dimensional Hierarchical Copper-Based Nanostructures as Advanced Electrocatalysts for CO₂ Reduction

Cu-based nanomaterials have received increasing interest for electrocatalytic applications in the CO₂ reduction reaction. However, it is challenging to design nanostructured Cu electrodes to improve both the chemical kinetics and molecular transport under the reaction conditions. Here we report on a new type of three-dimensional Cu-based nanostructures as advanced electrocatalysts for CO₂ reduction. Driven by thermal oxidation, CuO nanowires and/or porous nanostructures are grown on commercial Cu foams with three-dimensional (3D) frameworks. An electrochemical method is used to reduce CuO to Cu with the structural features largely preserved. The derived Cu-based hierarchical nanostructures demonstrate high catalytic activity and selectivity for CO₂ reduction, achieving >80% Faradaic efficiency and ∼3 times enhancement in terms of CO₂ conversion rate as compared to the Cu nanowires grown on planar electrodes. Our work highlights the great potential of 3D Cu nanostructures for improving the energy efficiency and power performance of CO₂ electrolysis

Improved Prediction of Nanoalloy Structures by the Explicit Inclusion of Adsorbates in Cluster Expansions

Density functional theory (DFT) is widely used to predict the properties of materials, but its direct application to nanomaterials of experimentally relevant size can be prohibitively expensive. It has previously been demonstrated that this problem can be addressed through the generation of cluster expansion models trained on DFT calculations. Here, we evaluate the use of the cluster expansion method to calculate the structures of bimetallic Pt–Cu nanoparticles of varying sizes and compositions and in different chemical environments. The predicted surface composition, shape, and lattice parameters of the alloy nanoparticles are found to be in good agreement with experimental characterization. We demonstrate that, to account for adsorbate-induced surface segregation, the best agreement for surface composition can be achieved by constructing a novel cluster expansion for alloy nanoparticles of varying shapes and sizes that explicitly includes adsorbed oxygen

Mechanistic Insights for Low-Overpotential Electroreduction of CO₂ to CO on Copper Nanowires

Recent developments of copper (Cu)-based nanomaterials have enabled the electroreduction of CO₂ at low overpotentials. The mechanism of low-overpotential CO₂ reduction on these nanocatalysts, however, largely remains elusive. We report here a systematic investigation of CO₂ reduction on highly dense Cu nanowires, with the focus placed on understanding the surface structure effects on the formation of *CO (* denotes an adsorption site on the catalyst surface) and the evolution of gas-phase CO product (CO­(g)) at low overpotentials (more positive than −0.5 V). Cu nanowires of distinct nanocrystalline and surface structures are studied comparatively to build up the structure–property relationships, which are further interpreted by performing density functional theory (DFT) calculations of the reaction pathway on the various facets of Cu. A kinetic model reveals competition between CO­(g) evolution and *CO poisoning depending on the electrode potential and surface structures. Open and metastable facets such as (110) and reconstructed (110) are found to be likely the active sites for the electroreduction of CO₂ to CO at the low overpotentials

Synthesis of Platinum Nanotubes and Nanorings via Simultaneous Metal Alloying and Etching

Metallic nanotubes represent a class of hollow nanostructures with unique catalytic properties. However, the wet-chemical synthesis of metallic nanotubes remains a substantial challenge, especially for those with dimensions below 50 nm. This communication describes a simultaneous alloying-etching strategy for the synthesis of Pt nanotubes with open ends by selective etching Au core from coaxial Au/Pt nanorods. This approach can be extended for the preparation of Pt nanorings when Saturn-like Au core/Pt shell nanoparticles are used. The diameter and wall thickness of both nanotubes and nanorings can be readily controlled in the range of 14–37 nm and 2–32 nm, respectively. We further demonstrated that the nanotubes with ultrathin side walls showed superior catalytic performance in oxygen reduction reaction

Low-Overpotential Electroreduction of Carbon Monoxide Using Copper Nanowires

We report on Cu nanowires as highly active and selective catalysts for electroreduction of CO at low overpotentials. The Cu nanowires were synthesized by reducing pregrown CuO nanowires, with the surface structures tailored by tuning the reduction conditions for improved catalytic performance. The optimized Cu nanowires achieved 65% faradaic efficiency (FE) for CO reduction and 50% FE toward production of ethanol at potentials more positive than −0.5 V (versus reversible hydrogen electrode, RHE). Structural analyses and computational simulations suggest that the CO reduction activity may be associated with the coordinately unsaturated (110) surface sites on the Cu nanowires