Carboxyl intermediate formation via an in situ-generated metastable active site during water-gas shift catalysis

Nicholas C. Nelson, Manh Thuong Nguyen, Vassiliki Alexandra Glezakou, Roger Rousseau, János Szanyi

Research output: Contribution to journalArticle


Definitive experimental proof for catalytic pathways and active sites during the low-temperature water-gas shift reaction remains elusive. Herein, we combine spectroscopic, kinetic and computational analyses to address the decades-long mechanistic controversy by studying the reverse water-gas shift over Pd/Al2O3. Isotopic transient kinetic analysis established the minor role of the formate intermediate, whereas hydrogen titration experiments confirmed the intermediacy of carboxyl. The ability to decouple the parallel formate and carboxyl pathways led to the identification of a distinct active site that exhibits regio- and chemoselective hydrogen addition to CO2 to yield the carboxyl intermediate. The metastable active site is formed in situ, resulting in hydroxylation of the metal–support interface and electronic restructuring. Atomistic simulations of the active site electronic structure and mechanistic landscape provided a framework that is consistent with experimental observations. Our study highlights the dynamic creation of a coordinatively unsaturated metal site caused by substrate adsorption on an adjacent support site.

Original languageEnglish
Pages (from-to)916-924
Number of pages9
JournalNature Catalysis
Issue number10
Publication statusPublished - Oct 1 2019


ASJC Scopus subject areas

  • Catalysis
  • Bioengineering
  • Biochemistry
  • Process Chemistry and Technology

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