Nonadiabatic dynamics of positive charge during photocatalytic water splitting on GaN(10-10) surface: Charge localization governs splitting efficiency

Alexey V. Akimov, James T. Muckerman, Oleg V. Prezhdo

Research output: Contribution to journalArticle

76 Citations (Scopus)

Abstract

Photochemical water splitting is a promising avenue to sustainable, clean energy and fuel production. Gallium nitride (GaN) and its solid solutions are excellent photocatalytic materials; however, the efficiency of the process is low on pure GaN, and cocatalysts are required to increase the yields. We present the first time-domain theoretical study of the initial steps of photocatalytic water splitting on a GaN surface. Our state-of-the-art simulation technique, combining nonadiabatic molecular dynamics and time-dependent density functional theory, allows us to characterize the mechanisms and time scales of the evolution of the photogenerated positive charge (hole) and the subsequent proton transfer at the GaN/water interface. The calculations show that the hole loses its excess energy within 100 fs and localizes primarily on the nitrogen atoms of the GaN surface, initiating a sequence of proton-transfer events from the surface N-H group to the nearby OH groups and bulk water molecules. Water splitting requires hole localization on oxygen rather than nitrogen, necessitating nonadiabatic transitions uphill in energy on pure GaN. Such transitions happen rarely, resulting in low yields of the photocatalytic water splitting observed experimentally. We conclude that efficient cocatalysts should favor localization of the photogenerated hole on oxygen-containing species at the semiconductor/water interface.

Original languageEnglish
Pages (from-to)8682-8691
Number of pages10
JournalJournal of the American Chemical Society
Volume135
Issue number23
DOIs
Publication statusPublished - Jun 12 2013

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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