Single Nanoparticle Activities in Ensemble: A Study on Pd Cluster Nanoportals for Electrochemical Oxygen Evolution Reaction

Abstract

Comprehensive understanding of the electrochemical activity of single nanoparticles (NPs) is in critical need for opening new avenues in the broad field of electrochemistry. Published reports on single-NP electrocatalysts typically include complicated and difficult methods of synthesis and characterization; moreover, these methods usually fail to provide a reliable way to measure the activities of individual NPs within larger ensembles of particles, i.e., in real-life nanocatalyst systems. In the present work, we synthesized from the gas phase Pd NPs that act as nanoportals for electron transfer within surfaceoxidized Mg thin films. The physical synthesis method provided excellent control over the deposition density and, hence, enabled the design of a system where each individual open nanoportal forms an independent active single-NP electrode (SNPE). Being uncoupled from one another, these SNPEs contribute separately toward the total electrocatalytic activity while simultaneously providing a measure of their average, individual activities. We were thus able to fabricate a stable, steady-state electrode for the electrochemical oxygen evolution reaction (OER) and to study the activity and stability of the SNPEs over a period of 20 days; the former depended on the size of the NPs, while the latter depended on the SNPEs' resistance to aerial oxidation. The remarkable stability of the ensemble catalysts under OER conditions proves that this concept can be used for further studies on the activities of different single NPs in numerous real-life systems.

NanoMaterialsCAD: Flexible Software for the Design of Nanostructures

“…The methodology is described in detail in the Supporting Information and in refs. [ 26 and 27 ] . Figure 5b shows a charge density transfer plot of the system, that is, a projection on the x – z plane of the total charge density difference between the overall structure (i.e., the relaxed Pt NP resting on the CuO NW) and its corresponding isolated constituents (i.e., the relaxed Pt NP and the bare CuO NW surface).…”

“…Pronounced electron charge transfer is observed at the interfacial area, mainly caused by the highly electronegative O atoms bonding with the Pt atoms of the NP. [ 27 ] Polarization and charge separation also occurred in the volume of the NP and the CuO; this is more visible in the CuO where the polarity of the polar covalent bonds between Cu and O changes. The increased strong electric dipoles located on Pt atoms close to the interfacial area evidently increase the positive charges of Pt atoms.…”

“…Surface charge and charge transfer between metallic NPs and metal-oxide supports are of great importance for various applications in catalysis, surface plasmonics, electrochemistry, etc. [26,27,48] Especially in the field of chemical (bio-) sensing, the nature of the NP-oxide support interface and the resulting interactions can determine the sensitivity and selectivity of the sensor device. [49][50][51] Ab initio theoretical studies based on reallife experimental data are often necessary to characterize these interfaces accurately.…”

“…Of particular significance has been the demand to reproduce surfaces and interfaces obtained from microscopy characterization of experimental samples, because of their importance in the determination of, e.g., electronic structures and chemical, magnetic, or plasmonic properties, etc. [ 21,22,26–28 ] With this work, we are introducing our newly developed software, NanoMaterialsCAD, [ 29 ] which caters for such needs. It is a free tool for modeling and manipulation of nanoobjects at the atomic level that provides an easy and automated way to create various kinds of crystalline structures such as nanoparticles, nanodots, nanowires, nanotubes, nanoscrolls, spatial vacuums, etc., all packed into a single integrated application.…”

Atomic-scale structure and chemical sensing application of ultrasmall size-selected Pt nanoparticles supported on SnO2

“…Magnetron sputtering inert-gas condensation, a versatile technique for the growth of single-and multicomponent nanoparticles with controlled size and morphology, [21][22][23] was employed for the deposition of pre-formed, size-selected Pt nanoparticles. A wide range of nanoparticle functionalities has been achieved with this method, e.g., percolating nanoparticle films for chemoresistive sensing, [24][25][26][27][28][29][30] nanoparticle-decorated metal oxide nanowire devices for chemoresistive sensing, [31][32][33] supported nanoparticles for catalysis and electrochemistry, [34][35][36][37] magnetic nanoparticles, 30,[38][39][40] nanoparticles embedded in multi-layered anodes for lithium ion batteries 41 and nanoportals for hydrogen storage applications. 42 Here, we demonstrate a new approach for the surface functionalization of micro-machined chemical sensor devices realized in complementary metal-oxide-semiconductor (CMOS) technology, in particular by depositing ultrasmall Pt nanocatalysts by magnetron sputtering inert-gas condensation onto nanocrystalline SnO 2 thin films integrated on a suspended microhotplate platform.…”