Direct observation of the energetics at a semiconductor/liquid junction by operando X-ray photoelectron spectroscopy

Abstract

These authors contributed equally to the work. MFL, SH and MHR contributed to the design, execution, and analysis of the experiment; EJC was critical in the design, building and testing of the end station that allows atmospheric pressure XPS data collection on a solution under potentiostatic control. ‡ Corresponding authors:

An Electrochemical, Microtopographical and Ambient Pressure X-Ray Photoelectron Spectroscopic Investigation of Si/TiO2/Ni/Electrolyte Interfaces

“…12,13 We describe herein the use of a three-electrode photoelectrochemical cell that contains a meniscus-based ∼13 nm thick electrolyte on the working electrodes formed from p + -Si/TiO 2 /Ni interfaces, which allows XPS measurements under electrochemical control through the solution. 6,7 Combined electrochemistry-photoelectron spectroscopic data that extend the previous characterization of this system 7 have been collected in this work.…”

“…This approach allows "operando" XPS studies in conjunction with a classical three-electrode potentiostatic arrangement and also facilitates investigation of the influence of the applied potential on the band-edge energies of metal, semiconductor and hybrid electrodes at such interfaces. 6,7 Band bending and band-edge shifts can thus be determined directly by this spectroscopic technique. 7 We describe herein surface-sensitive analysis techniques for the characterization of TiO 2 /Ni/electrolyte interfaces.…”

“…7 We describe herein surface-sensitive analysis techniques for the characterization of TiO 2 /Ni/electrolyte interfaces. The protection and stabilization of photoanodes for water oxidation to O 2 (g) is of interest because high performance and stability can be achieved simulta-= These authors contributed equally to this work.…”

“…[8][9][10][11] Specifically, TiO 2 has been used as a protection layer for photoelectrodes in either alkaline or acidic media. 7,[12][13][14][15][16][17] Some work indicates that annealing the TiO 2 allows for charge conduction with minimal band bending, with unannealed TiO 2 preferred for photocathodes. However, the role of the metallization layer in determining the charge-conduction properties of the films has not been well elucidated.…”

Ambient-Pressure XPS Study of a Ni–Fe Electrocatalyst for the Oxygen Evolution Reaction

“…The limitation of XPS to vacuum conditions 7 has been overcome with the recent development of ambient pressure X-ray photoelectron spectroscopy (APXPS) and third generation synchrotron radiation sources that have enabled XPS analysis under electrochemical reaction conditions of solid-gas interfaces in solid-state electrochemical cells, 8,9 at the triple-phase boundary between gas phase, electrolyte and electrocatalyst in proton exchange membrane fuel cells and electrolyzers, [9][10][11] and at the solidliquid interface in three-electrode electrochemical cells. [12][13][14] The latter approach is used here to study a Ni-Fe electrocatalyst for water splitting. Measurements of the binding energy shifts in the O 1s spectrum of H 2 O both in the gas and liquid phases were observed as well as shifts in the Ni and Fe core-levels with changes in applied potential.…”