Zone-Specific Crystallization and a Porosity-Directed Scaling Marker for the Catalytic Efficacy of Au–Ag Alloy Nanoparticles

Abstract

Bimetallic Au–Ag hollow nanoprisms (HNPrs) with variable effective surface areas, dynamic atomic compositions (Au:Ag), and distinct stepped surfaces between the central porous region and crystalline periphery are synthesized through a modified seed-mediated growth followed by a sacrificial galvanic replacement method. Porous central-cavity-induced distortion from prism to disk shape generates an increased number of numerous low-coordinated crystal defects on the crystalline nanodisk surface along with extended d-orbital spacing of the respective crystal disorders in the central-cavity region of HNPrs to control their adsorption efficiency for different redox reactions. Among the different HNPrs, HNPr250 possesses the highest density of the grain boundary with a preferable Au0:Ag0 ratio to form an extensive porous ligamentous central cavity, acts as a superior electrocatalyst to accelerate the kinetics of the uric acid (UA) oxidation (8.4 times compared to the blank electrode), and allows us to detect UA even in the nanomolar range. Experimental observations have been supported by density functional theory calculation to approximate the effective Au–Au displacement with a suitable percentage of Ag in different HNPrs to explain their measured catalytic activity.

Au-Seeded Ag-Nanorod Networks for Electrocatalytic Sensing

“…66 In contrast, gold−silver nanoalloys with a {220} orientation show enormous oxidizing capability for uric acid. 50 Thus, the chemical composition (pure vs alloy) of the nanocatalyst determines the adsorption efficiency and facet selectivity of the substrate and subsequent bond-breaking and bond-forming process during a reaction. However, to construct a universal catalyst, one has to think of every aspect of catalytic properties, i.e., (a) it should be stable in a broad pH range, (b) the catalytic activity should be of equal order in both the organic and aqueous solvents, and (c) it should show longterm stability under ambient conditions.…”

“…For the calculation of strain (ε) in the Hy-Au@AgNRs, we used the following relation: Here, d * is the average Ag–Ag bond length of the system under consideration and d 0 is the Ag–Ag bond length (2.89 Å) in their pure face-centered cubic bulk structure. The above relation signifies the effect on the mechanical strain when a system (bulk) goes through structural reconstruction/evolution.…”

“…The catalytic activity of monometallic plasmonic nanomaterials depends on various factors like their size and shape, , effective charge density on the edges or tips, differential chemical states of metals within a single nanostructure, − presence of low coordination sites, , and density as well as the area of crystal defects . Compared to monometallic plasmonic nanostructures, bimetallic − or multimetallic (as both seeded and unseeded) nanostructures may involve several additional factors that have the potential to influence their catalytic activity. Possible additional factors include differential crystal boundaries between metals due to their difference in crystal parameters, inclusion of highly energetic twin boundaries (TBs) to terminate the nanostructure growth, and the direct influence on the d-band shifting with respect to the Fermi energy surface .…”

Void-Enriched and Highly Strained Porous Au–Ag Nanoalloy as a Bifunctional Electro-Catalyst in Alkaline Direct Alcohol Fuel Cell

“…6 Moreover, our previous studies also point out that the presence of sharp edges and corners during their evolution to anisotropic geometry as well as mesoporous structure positively influences their catalytic activity. 7,8 Thus, the fabrication of tailored shaped AuNPs with porous ligamentous crystalline zones and coordinatively ultraunsaturated surfaces that contain high-density steps and kinks as active sites is a promising field of research in designing catalysts suitable in alcohol fuel cells for effective substitution of the costly Pt/C or Pt-and Pd-based nanoalloys. 9 In a combined theoretical and experimental study, Xiong et al show that MOR in an alkaline medium is promisingly accelerated by using porous Au−Ag nanoframes and the corresponding chronoamperometric and CO striping studies show their enhanced stability compared to the commercial Pt/ C catalyst.…”

“…The dimension of GBs in NP core−shell is much bigger than the GBs present in NP Au−Ag (white dotted line in Figure 1B). The atoms specifically situated on the GB are coordinatively unsaturated and highly energetic 8 and hence found to be catalytically more active than other atoms in the same crystal. However, to achieve the best catalytic efficiency, we have performed further modification to the NP core−shell where the galvanic replacement of Ag in NP core−shell is carried out by introducing Au 3+ into the NP core−shell system.…”