Probing Size and Substrate Effects on the Hydrogen Evolution Reaction by Single Isolated Pt Atoms, Atomic Clusters, and Nanoparticles

Abstract

We report the catalytic activity of a single, isolated Pt deposit on Bi and Pb supports to probe the size and substrate effects on the electrochemical hydrogen evolution reaction (HER). Deposits were made electrolytically by an atom-by-atom method in a controlled plating; we prepared an individual Pt deposit on Bi and Pb ultramicroelectrodes (UMEs) such as a single isolated atom, clusters containing one to five Pt atoms, and nanoparticles to about 10 nm radius. A steady-state voltammogram on the single Pt deposits is observed by electrocatalytic amplification of the HER, with a negligible contribution by the HER at the substrate UME. A single Pt atom can act as an electrode for the HER, showing a diffusion-limiting current plateau in the voltammogram that can be used to estimate the radius of a single deposit. We simulated the voltammograms of the individual deposits, assuming the Volmer step of the HER is appropriate for a Pt cluster deposit, to obtain kinetic parameters for each deposit. The HER kinetics increases as the particle radius increases from ∼0.2 to ∼4 nm for Bi and Pb substrates and then reaches a limiting plateau. The limiting kinetics on the Bi substrate approaches that of bulk Pt while that on the Pb substrate is much smaller.

Electrooxidation, Size Stability, and Electrocatalytic Activity of 0.9 nm Diameter Gold Nanoclusters Coated with a Weak Stabilizer

“…There are several examples in the literature of a NC/NP losing its catalytic activity below a certain size. For example, Bard and coworkers recently showed that the catalytic activity of Pt NPs for the HER increased with increasing Pt NP size from 0.25 nm to 0.75 nm, indicating that there is an optimum size of NPs for their specific catalytic applications . Our results indicate that the HER and CO 2 RR is favored with THPC Au 1.6nm NCs, but not favored for TPPS Au 0.9nm NCs or Cit Au 4.1nm NPs.…”

“…For example, Bard and coworkers recently showed that the catalytic activity of Pt NPs for the HER increased with increasing Pt NP size from 0.25 nm to 0.75 nm, indicating that there is an optimum size of NPs for their specific catalytic applications. [60] Our results indicate that the HER and CO 2 RR is favored with THPC Au 1.6nm NCs, but not favored for TPPS Au 0.9nm NCs or Cit Au 4.1nm NPs. The lower reactivity of TPPS Au 0.9nm NCs and Cit Au 4.1nm NPs could be due to the lack of specific surface atom coordination such as edge atoms, [20] the main active site for catalytic HER with Au, [15] or due to instability or change in electronic structure in the case of the smaller TPPS Au 0.9nm NCs.…”

“…Our results indicate that the HER and CO 2 RR is favored with THPC Au 1.6nm NCs, but not favored for TPPS Au 0.9nm NCs or Cit Au 4.1nm NPs. The lower reactivity of TPPS Au 0.9nm NCs and Cit Au 4.1nm NPs could be due to the lack of specific surface atom coordination such as edge atoms, the main active site for catalytic HER with Au, or due to instability or change in electronic structure in the case of the smaller TPPS Au 0.9nm NCs . We do not believe the lower catalytic activity is due to the TPPS stabilizer inhibiting the Au surface more than THPC based on the lower oxidation potential and low stability of the 0.9 nm TPPS Au NCs.…”

Intrinsic Effect of Carbon Supports on the Activity and Stability of Precious Metal Based Catalysts for Electrocatalytic Alcohol Oxidation in Fuel Cells: A Review

“…The inherent problems are the wide range of size distributions of metal catalysts on carbon supports, from single atoms to NPs or clusters. Zhou et al . recently reported the measurement of kinetic parameters of single Pt atoms, clusters, and NPs for HER on ultramicro electrodes.…”

Stability and reactivity analysis of single metal and bimetallic nanostructures by anodic stripping voltammetry.

“…If the Au NPs remained on the surface, then we should observe the Au peak in the ASV after ozone cleaning. We studied the TPPS Au0.9nm NPs as a catalyst for the hydrogen evolution 217 and also could be due to the instability 9 of NPs during applications.…”