Structure-Property Relationship of Defect-Trapped Pt Single-Site Electrocatalysts for the Hydrogen Evolution Reaction

Peng Tang; Po-Yuan Huang; Jack E N Swallow; Chenbo Wang; Diego Gianolio; Hua Guo; Jamie H Warner; Robert S Weatherup; Mauro Pasta

doi:10.1021/acscatal.3c01513

Structure-Property Relationship of Defect-Trapped Pt Single-Site Electrocatalysts for the Hydrogen Evolution Reaction

ACS Catal. 2023 Jul 5;13(14):9558-9566. doi: 10.1021/acscatal.3c01513. eCollection 2023 Jul 21.

Authors

Peng Tang¹, Po-Yuan Huang¹, Jack E N Swallow¹, Chenbo Wang², Diego Gianolio³, Hua Guo¹, Jamie H Warner^{4

5}, Robert S Weatherup¹, Mauro Pasta^{1

2}

Affiliations

¹ Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom.
² Oxford Suzhou Centre for Advanced Research, 388 Ruoshui Road, Suzhou 215123, Jiangsu Province, P. R. China.
³ Diamond Light Source Ltd., Harwell Science and Innovation Campus, Chilton, Didcot, OX11 0DE, U.K.
⁴ Materials Graduate Program, Texas Materials Institute, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas, 78712, United States.
⁵ Walker Department of Mechanical Engineering, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas, 78712, United States.

Abstract

Single-site catalysts (SSCs) have attracted significant research interest due to their high metal atom utilization. Platinum single sites trapped in the defects of carbon substrates (trapped Pt-SSCs) have been proposed as efficient and stable electrocatalysts for the hydrogen evolution reaction (HER). However, the correlation between Pt bonding environment, its evolution during operation, and catalytic activity is still unclear. Here, a trapped Pt-SSC is synthesized by pyrolysis of H₂PtCl₆ chemisorbed on a polyaniline substrate. In situ heated scanning transmission electron microscopy and temperature-dependent X-ray photoelectron spectroscopy clarify the thermally induced structural evolution of Pt during pyrolysis. The results show that the nitrogen in polyaniline coordinates with Pt ions and atomically disperses them before pyrolysis and traps Pt sites at pyridinic N defects generated during the substrate graphitization. Operando X-ray absorption spectroscopy confirms that the trapped Pt-SSC is stable at the HER working potentials but with inferior electrocatalytic activity compared with metallic Pt nanoparticles. First principle calculations suggest that the inferior activity of trapped Pt-SSCs is due to their unfavorable hydrogen chemisorption energy relative to metallic Pt(111) surfaces. These results further the understanding of the structure-property relationship in trapped Pt-SSCs and motivate a detailed techno-economic analysis to evaluate their commercial applicability.