An official website of the United States government
Bimetallic heterostructures, including core–shell and Janus configurations, often offer unique electrocatalytic properties compared to monometallic nanoparticles. However, achieving precise control over both elemental composition and spatial arrangement within these structures remains a challenge. Here, an electrosynthesis method is introduced that enables the fabrication of heterostructured bimetallic nanoparticles with precise, independent control of their elemental distribution. By leveraging dual‐channel scanning electrochemical cell microscopy (SECCM), the local ionic environment is dynamically modulated in situ, adjusting the deposition bias between channels to achieve selective electrodeposition. This approach allows temporal control over the solution conditions within the SECCM droplet, facilitating the synthesis of multi‐layer core–shell nanoparticles with tunable thickness, number, and sequence of layers. This technique is demonstrated with Pt–Cu and Pt–Ni systems, synthesizing arrays of Cu@Pt and Pt@Cu core–shell structures, which are then screened for catalytic activity in hydrogen evolution (HER) and oxygen reduction (ORR) reactions. The high spatial resolution and on‐demand control over the composition and structure make this method well‐suitable for creating arrays of complex, multi‐metallic heterostructures, which is expected to accelerate the discovery of advanced electrocatalytic materials, offering a platform for efficient and scalable electrocatalyst screening.
more »
« less
Precision Synthesis of Bimetallic Nanoparticles via Nanofluidics in Nanopipets
Bimetallic nanoparticles often show properties superior to their single-component counterparts. However, the large parameter space, including size, structure, composition, and spatial arrangement, impedes the discovery of the best nanoparticles for a given application. High-throughput methods that can control the composition and spatial arrangement of the nanoparticles are desirable for accelerated materials discovery. Herein, we report a methodology for synthesizing bimetallic alloy nanoparticle arrays with precise control over their composition and spatial arrangement. A dual-channel nanopipet is used, and nanofluidic control in the nanopipet further enables precise tuning of the electrodeposition rate of each element, which determines the final composition of the nanoparticle. The composition control is validated by finite element simulation as well as electrochemical and elemental analyses. The scope of the particles demonstrated includes Cu–Ag, Cu–Pt, Au–Pt, Cu–Pb, and Co–Ni. We further demonstrate surface patterning using Cu–Ag alloys with precise control of the location and composition of each pixel. Additionally, combining the nanoparticle alloy synthesis method with scanning electrochemical cell microscopy (SECCM) allows for fast screening of electrocatalysts. The method is generally applicable for synthesizing metal nanoparticles that can be electrodeposited, which is important toward developing automated synthesis and screening systems for accelerated material discovery in electrocatalysis.
more »
« less
- Award ID(s):
- 2240113
- PAR ID:
- 10499326
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- ACS Nano
- Volume:
- 17
- Issue:
- 22
- ISSN:
- 1936-0851
- Page Range / eLocation ID:
- 22499 to 22507
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The nucleation and growth of nanoparticles are critical processes determining the size, shape, and properties of resulting nanoparticles. However, understanding the complex mechanisms guiding the formation and growth of colloidal multielement alloy nanoparticles remains incomplete due to the involvement of multiple elements with different properties. This study investigates in situ colloidal synthesis of multielement alloys using transmission electron microscopy (TEM) in a liquid cell. Two different pathways for nanoparticle formation in a solution containing Au, Pt, Ir, Cu, and Ni elements, resulting in two distinct sets of particles are observed. One set exhibits high Au and Cu content, ranging from 10 to 30 nm, while the other set is multi‐elemental, with Pt, Cu, Ir, and Ni, all less than 4 nm. The findings suggest that, besides element miscibility, metal ion characteristics, particularly reduction rates, and valence numbers, significantly impact particle composition during early formation stages. Density functional theory (DFT) simulations confirm differences in nanoparticle composition and surface properties collectively influence the unique growth behaviors in each nanoparticle set. This study illuminates mechanisms underlying the formation and growth of multielement nanoparticles by emphasizing factors responsible for chemical separation and effects of interplay between composition, surface energies, and element miscibility on final nanoparticles size and structure.more » « less
-
Bimetallic nanomaterials have shown great potential across various fields of application. However, the synthesis of many bimetallic particles can be challenging due to the immiscibility of their constituent metals. In this study, we present a synthetic strategy to produce compositionally tunable silver–copper (Ag-Cu) bimetallic nanoparticles using plasma-driven liquid surface chemistry. By using a low-pressure nonthermal radiofrequency (RF) plasma that interacts with an Ag-Cu precursor solution at varying electrode distances, we identified that the reduction of Ag and Cu salts is governed by two “orthogonal” parameters. The reduction of Cu2+ is primarily influenced by plasma electrons, whereas UV photons play a key role in the reduction of Ag+. Consequently, by adjusting the electrode distance and the precursor ratios in the plasma–liquid system, we could control the composition of Ag-Cu bimetallic nanoparticles over a wide range.more » « less
-
AgCu bimetallic materials have attracted significant interest as catalysts for selective oxidation reactions. Near‐surface alloys of Ag on Cu have been shown to activate O2 efficiently at exposed reverse‐segregated isolated Cu atoms within the surface Ag layers. This study focuses on the synthesis of nanoparticle analogs of these alloys and measurement of their performance for ethylene and propylene epoxidation. Supported Cu/SiO2 catalysts were prepared by strong electrostatic adsorption and partial galvanic replacement of Cu atoms with Ag cations in aqueous media, which led to bimetallic nanoparticles of 3–10 nm average size and 0.25–1.6 Ag:Cu atomic ratios. Galvanic exchange stoichiometry, elemental maps and UV–vis spectroscopy reveal coexistence of Ag and Cu in the nanoparticles. Diffuse reflectance infrared spectra of bound CO indicate the formation of nanoparticles with a Cu core and Ag shell when catalysts with high Ag:Cu ratios are reduced to metallic form. The bimetallic catalysts show improvement over monometallic Ag and Cu and their physical mixtures, exhibiting higher rates, higher initial selectivity than Ag, and resistance to secondary reactions that decrease the selectivity of Cu catalysts at higher alkene conversion. These results demonstrate a simple synthesis method of more selective bimetallic AgCu nanoparticles with core‐shell like structures, which may be of use in a variety of selective oxidation reactions.more » « less
-
In situ identification of surface sites in Cu–Pt bimetallic catalysts: Gas-induced metal segregationThe effect of gases on the surface composition of Cu–Pt bimetallic catalysts has been tested by in situ infrared (IR) and x-ray absorption spectroscopies. Diffusion of Pt atoms within the Cu–Pt nanoparticles was observed both in vacuum and under gaseous atmospheres. Vacuum IR spectra of CO adsorbed on CuPt x /SBA-15 catalysts (x = 0–∞) at 125 K showed no bonding on Pt regardless of Pt content, but reversible Pt segregation to the surface was seen with the high-Pt-content (x ≥ 0.2) samples upon heating to 225 K. In situ IR spectra in CO atmospheres also highlighted the reversible segregation of Pt to the surface and its diffusion back into the bulk when cycling the temperature from 295 to 495 K and back, most evidently for diluted single-atom alloy catalysts (x ≤ 0.01). Similar behavior was possibly observed under H 2 using small amounts of CO as a probe molecule. In situ x-ray absorption near-edge structure data obtained for CuPt 0.2 /SBA-15 under both CO and He pointed to the metallic nature of the Pt atoms irrespective of gas or temperature, but analysis of the extended x-ray absorption fine structure identified a change in coordination environment around the Pt atoms, from a (Pt–Cu):(Pt–Pt) coordination number ratio of ∼6:6 at or below 445 K to 8:4 at 495 K. The main conclusion is that Cu–Pt bimetallic catalysts are dynamic, with the composition of their surfaces being dependent on temperature in gaseous environments.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acsnano.3c06011
