Correlating Surface Structures and Electrochemical Activity Using Shape-Controlled Single-Pt Nanoparticles

Abstract

We report a method for synthesizing and studying shape-controlled, single Pt nanoparticles (NPs) supported on carbon nanoelectrodes. The key advance is that the synthetic method makes it possible to produce single, electrochemically active NPs with a vast range of crystal structures and sizes. Equally important, the NPs can be fully characterized, and, therefore, the electrochemical properties of the NPs can be directly correlated to the size and structure of a single shape. This makes it possible to directly correlate experimental results to first-principles theory. Because just one well-characterized NP is analyzed at a time, the difficulty of applying a theoretical analysis to an ensemble of NPs having different sizes and structures is avoided. In this article, we report on two specific Pt NP shapes having sizes on the order of 200 nm: concave hexoctahedral (HOH) and concave trapezohedral (TPH). The former has {15 6 1} facets and the latter {10 1 1} facets. The electrochemical properties of these single NPs for the formic acid oxidation (FAO) reaction are compared to those of a single, spherical polycrystalline Pt NP of the same size. Finally, density functional theory, performed prior to the electrochemical studies, were used to interpret the experimental results of the FAO experiments.

Unraveling the Structural Sensitivity of CO2 Electroreduction at Facet-Defined Nanocrystals via Correlative Single-Entity and Macroelectrode Measurements

“…To realize the knowledge-guided design of next-generation CO 2 RR electrocatalysts with superior activity, selectivity, and durability, the measurement of intrinsic electrocatalytic parameters at the single-nanocrystal level and comparison with macroelectrode data to establish reliable structure–activity correlations are critical. With such correlations, the impact of extrinsic factors such as electrode morphology, local pH variation, and mass transfer hindrance can be further elucidated. − Scanning electrochemical cell microscopy (SECCM) is especially adept at achieving single-entity electrochemical measurements. − SECCM has been used to resolve the spatial heterogeneity of MoS 2 , and Fe 4.5 Ni 4.5 S 8 catalysts for HER and polycrystalline Au catalysts for CO 2 RR. , SECCM has also been used recently to extract kinetic information for oxygen reduction at Pt electrodes and probing oxygen evolution at superparticles and ZIF-derived composites …”

Heterogeneity between and within Single Hematite Nanorods as Electrocatalysts for Oxygen Evolution Reaction

“…4,20,21 One approach is to simplify the complex electrochemical interface using a single-entity approach: one electrocatalyst is measured at a time. 22,23 To this end, single nanoparticle (NP) collision experiments have been designed where individual NPs stochastically collide with a substrate electrode, resulting in a current signal that measures the activity of the NP. 24−26 Other experiments include evaluating the activity of immobilized single NP.…”

Pt Nanoelectrodes Sealed in Quartz Capillaries Modified with Underpotential‐Deposited Bismuth for Formic Acid Electrooxidation

“…As shown in Figure 6 (black lines), at both bare micro‐ and nano‐electrodes, two anodic peaks (1 and 2) in the direct scan, and the broad bell‐shaped peak (3), in the reverse scan are recorded at the Bi(0) unloaded electrodes. This voltammetric behaviour is typical for the electrooxidation of HCOOH at polycrystalline platinum electrodes [8d–h,9] . Accordingly, Peak (1) is due to the direct oxidation of HCOOH, occurring at Pt surface sites poison‐free, leading to CO 2 .…”

“…Peak (2) is related to the oxidation of adsorbed CO, which results from dehydration of formic acid at lower potentials. This electrode process leads to the release of the surface locations of the catalyst, and on the negative‐going scan the markedly larger peak 3 is observed, reflecting the HCOOH oxidation on the catalyst surface free from CO, as well as from Pt oxides [8d–h,9] . At both Bi‐loaded Pt electrodes, the CVs are drastically modified and in both cases the onset of the anodic wave is shifted towards less positive values (by about 0.15 V), the current intensity of the forward wave is larger compared with that of peak 1 obtained with the Bi‐UPD‐free Pt electrodes, and the hysteresis between positive‐ and negative‐going sweeps becomes smaller.…”

“…It is known that the reaction mechanism on Pt electrodes proceeds through two parallel paths: the direct oxidation to CO 2 and that mediated by a poison species. The latter involves the dehydration of HCOOH to yield CO, which adsorbs onto the electrode surface and blocks the Pt catalytic sites [8d–h] . The behaviour of the Pt nano‐ and micro‐electrodes, unloaded and loaded with Bi‐UPD, was investigated in a Bi 3+ ‐free 0.5 M H 2 SO 4 solution containing 0.1 M HCOOH.…”