Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

• DOI: 10.1021/jacs.2c09974
• Publication Date: 2023-01-12T04:37:56Z
• Authors: Qian Guo; Qi Zhao; Rachel Crespo-Otero; Devis Di Tommaso; Junwang Tang; Stoichko D. Dimitrov; Maria-Magdalena T...; Xuanhua Li; Ana Belén Jorge S...
• Keywords: Photocurrent

Single-atom catalysts (SACs) on hematite photoanodes are efficient cocatalysts to boost photoelectrochemical performance. They feature high atom utilization, remarkable activity, and distinct active sites. However, the specific role of SACs is not fully understood yet: Do behave as a catalytic site or spectator? By combining spectroscopic experiments computer simulations, we demonstrate that single-atom iridium (sIr) (α-Fe2O3/sIr) act true catalyst by trapping holes from providing sites for water oxidation reaction. In situ transient absorption spectroscopy showed reduced number shortened hole lifetime in presence sIr. This was particularly evident second timescale, indicative fast transfer depletion toward oxidation. Intensity-modulated photocurrent evidenced faster at α-Fe2O3/sIr/electrolyte interface compared bare α-Fe2O3. Density functional theory calculations revealed mechanism using sIr center be preferred pathway it displayed lower onset potential than Fe X-ray photoelectron demonstrated introduced mid-gap 4d state, key depletion. These combined results provide new insights into processes controlling solar enhancing performance semiconductors photo-assisted reactions.