Direct Vibrational Stark Shift Probe of Quasi-Fermi Level Alignment in Metal Nanoparticle Catalyst-Based Metal–Insulator–Semiconductor Junction Photoelectrodes

• Type of Material: Article
• Authors: Sa Suo, Emory University; Colton Sheehan, University of Pennsylvania; Fengyi Zhao, Emory University; Langqiu Xiao, University of Pennsylvania; Zihao Xu, Emory University; Jinhui Meng, Emory University; Thomas E Mallouk, University of Pennsylvania; Tianquan Lian, Emory University
• Language: English
• Date: 2023-07-05
• Publisher: American Chemical Society
• Publication Version: Final Published Version
• Copyright Statement: © 2023 The Authors.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1021/jacs.3c02333
• Title of Journal or Parent Work: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
• Volume: 145
• Issue: 26
• Start Page: 14260
• End Page: 14266
• Keywords: physical chemistry; Metal Nanoparticle Catalyst-Based Metal–Insulator–Semiconductor; Photoelectrodes
• Research Categories: Chemistry, Physical; Engineering, Materials Science

Abstract

Photoelectrodes consisting of metal–insulator–semiconductor (MIS) junctions are a promising candidate architecture for water splitting and for the CO2 reduction reaction (CO2RR). The photovoltage is an essential indicator of the driving force that a photoelectrode can provide for surface catalytic reactions. However, for MIS photoelectrodes that contain metal nanoparticles, direct photovoltage measurements at the metal sites under operational conditions remain challenging. Herein, we report a new in situ spectroscopic approach to probe the quasi-Fermi level of metal catalyst sites in heterogeneous MIS photoelectrodes via surface-enhanced Raman spectroscopy. Using a CO2RR photocathode, nanoporous p-type Si modified with Ag nanoparticles, as a prototype, we demonstrate a selective probe of the photovoltage of ∼0.59 V generated at the Si/SiOx/Ag junctions. Because it can directly probe the photovoltage of MIS heterogeneous junctions, this vibrational Stark probing approach paves the way for the thermodynamic evaluation of MIS photoelectrodes with varied architectural designs.