Electrocatalytic Hydrogen Evolution at Full Atomic Utilization over ITO-Supported Sub-nano-Ptn Clusters: High, Size-Dependent Activity Controlled by Fluxional Pt Hydride Species

Simran Kumari; Tsugunosuke Masubuchi; Henry S White; Anastassia Alexandrova; Scott L Anderson; Philippe Sautet

doi:10.1021/jacs.2c13063

Electrocatalytic Hydrogen Evolution at Full Atomic Utilization over ITO-Supported Sub-nano-Pt_n Clusters: High, Size-Dependent Activity Controlled by Fluxional Pt Hydride Species

J Am Chem Soc. 2023 Mar 15;145(10):5834-5845. doi: 10.1021/jacs.2c13063. Epub 2023 Mar 3.

Authors

Simran Kumari¹, Tsugunosuke Masubuchi², Henry S White², Anastassia Alexandrova^{3

4}, Scott L Anderson², Philippe Sautet^{1

3

4}

Affiliations

¹ Chemical and Biomolecular Engineering Department, University of California, Los Angeles, California 90095, United States.
² Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States.
³ Chemistry and Biochemistry Department, University of California, Los Angeles, California 90095, United States.
⁴ California NanoSystems Institute, University of California, Los Angeles, California 90094, United States.

PMID: 36867416
DOI: 10.1021/jacs.2c13063

Abstract

A combination of density functional theory (DFT) and experiments with atomically size-selected Pt_n clusters deposited on indium-tin oxide (ITO) electrodes was used to examine the effects of applied potential and Pt_n size on the electrocatalytic activity of Pt_n (n = 1, 4, 7, and 8) for the hydrogen evolution reaction (HER). Activity is found to be negligible for isolated Pt atoms on ITO, increasing rapidly with Pt_n size such that Pt₇/ITO and Pt₈/ITO have roughly double the activity per Pt atom compared to atoms in the surface layer of polycrystalline Pt. Both the DFT and experiment find that hydrogen under-potential deposition (H_upd) results in Pt_n/ITO (n = 4, 7, and 8) adsorbing ∼2H atoms/Pt atom at the HER threshold potential, equal to ca. double the H_upd observed for Pt bulk or nanoparticles. The cluster catalysts under electrocatalytic conditions are hence best described as a Pt hydride compound, significantly departing from a metallic Pt cluster. The exception is Pt₁/ITO, where H adsorption at the HER threshold potential is energetically unfavorable. The theory combines global optimization with grand canonical approaches for the influence of potential, uncovering the fact that several metastable structures contribute to the HER, changing with the applied potential. It is hence critical to include reactions of the ensemble of energetically accessible Pt_nH_x/ITO structures to correctly predict the activity vs Pt_n size and applied potential. For the small clusters, spillover of H_ads from the clusters to the ITO support is significant, resulting in a competing channel for loss of H_ads, particularly at slow potential scan rates.