Grain‐Boundary‐Rich Noble Metal Nanoparticle Assemblies: Synthesis, Characterization, and Reactivity

Abstract

Here, a comprehensive study on the synthesis, characterization, and reactivity of grain‐boundary (GB)‐rich noble metal nanoparticle (NP) assemblies is presented. A facile and scalable synthesis of Pt, Pd, Au, Ag, and Rh NP assemblies is developed, in which NPs are predominantly connected via Σ3 (111) twin GBs, forming a network. Driven by water electrolysis, the random collisions and oriented attachment of colloidal NPs in solution lead to the formation of Σ3 (111) twin boundaries and some highly mismatched GBs. This synthetic method also provides convenient control over the GB density without altering the crystallite size or GB type by varying the NP collision frequency. The structural characterization reveals the presence of localized tensile strain at the GB sites. The ultrahigh activity of GB‐rich Pt NP assembly toward catalytic hydrogen oxidation in air is demonstrated, enabling room‐temperature catalytic hydrogen sensing for the first time. Finally, density functional theory calculations reveal that the strained Σ3(111) twin boundary facilitates oxygen dissociation, drastically enhancing the hydrogen oxidation rate via the dissociative pathway. This reported large‐scale synthesis of the Σ3 (111) twin GB‐rich structures enables the development of a broad range of high‐performance GB‐rich catalysts.

Ultrathin Rh Nanosheets with Rich Grain Boundaries for Efficient Hydrogen Oxidation Electrocatalysis

“…These advantageous features endow ultrathin 2D NSs with immense potential as highly efficient electrocatalysts. However, unlike traditional layered materials, such as graphene, 2D transition-metal dichalcogenides, and MXenes, Pt-group metals tend to spontaneously grow into three-dimensional structures due to their nonlayered nature. − Furthermore, the surface energy of Pt-group metals increases significantly with decreasing thickness, promoting the formation of metal nanoparticles (NPs) . Consequently, developing effective synthesis routes for atomically thin 2D Pt-group metal NSs remains a formidable challenge compared to traditional layered materials.…”

“…22−25 Furthermore, the surface energy of Pt-group metals increases significantly with decreasing thickness, promoting the formation of metal nanoparticles (NPs). 26 Pt-group metal NSs remains a formidable challenge compared to traditional layered materials. Accordingly, multiple strategies have been exploited to controllably construct 2D Pt-group ultrathin NSs, consisting of a surfactant-assisted synthesis method, a polyol reduction method, and solvothermal methods.…”

Paper-Based Hydrogen Sensors Using Ultrathin Palladium Nanowires

“…This is analogous to the catalytic dissociation of H 2 over Pd surfaces, where it is known as the H 2 spillover effect, and which has been achieved previously with the use of Pt or with Pd . Moreover, defects and lattice misalignment at crystallite boundaries may further enhance the diffusion of H 2 into polycrystalline PdNWs . H 2 dissociation and H atom diffusion are much more likely to be rate-limiting steps determining the speed of sensor response compared to electron transport, and thus, these factors favoring faster response of the polycrystalline PdNWs have a greater influence than reduced electron scattering in quasi-single-crystalline PdNWs.…”

“…33 Moreover, defects and lattice misalignment at crystallite boundaries may further enhance the diffusion of H 2 into polycrystalline PdNWs. 34 H 2 dissociation and H atom diffusion are much more likely to be rate-limiting steps determining the speed of sensor response compared to electron transport, and thus, these factors favoring faster response of the polycrystalline PdNWs have a greater influence than reduced electron scattering in quasi-singlecrystalline PdNWs. Similarly, when the H 2 pulse is stopped and air is purged through the system, due to the decrease in partial pressure of H 2 , the H atoms diffuse out of the Pd FCC lattice, recombine, and leave the system.…”

Hydrogen on Colloidal Gold Nanoparticles

“…50 H 2 has been used to prepare grain-boundary-rich AuNP assemblies. 51 A number of studies have examined hydrogen on supported AuNPs, for instance on Al 2 O 3 . 24,38,52−56 These and other papers have provided strong but indirect evidence for surface H, but very few have suggested substantial and stable surface hydrogen.…”