Phase transitions in NiO during the Oxygen Evolution Reaction assessed via electrochromic phenomena through operando UV-Vis spectroscopy

DOI: 10.1016/j.electacta.2024.144626

Authors: Harol Moreno Fernández (Technical University of Darmstadt) , Julia Gallenberger (Technical University of Darmstadt) , Crizaldo Mempin (Technical University of Darmstadt) , Isobel Khalek (University of Bristol) , Marie Neumann (Technical University of Darmstadt) , Soroush Lotfi (Technical University of Darmstadt) , Sun Myung Kim (Technical University of Darmstadt) , Mohan Li (GSI Helmholtzzentrum für Schwerionenforschung; Technical University of Darmstadt) , Chuanmu Tian (Technical University of Darmstadt) , Jan P. Hofmann (Technical University of Darmstadt)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Electrochimica Acta , VOL 682

State: Published (Approved)
Published: June 2024
Diamond Proposal Number(s): 31938

Abstract: Due to its high activity and stability, nickel oxide (NiO) has shown significant promise as an electrocatalyst for the alkaline oxygen evolution reaction (OER). In parallel, NiO exhibits a well-known electrochromic phenomenon, changing its optical properties in response to an applied electric potential. This study investigates the relationship between NiO phase changes that occur during the OER and the connected optical modulation using operando UV-visible reflectance spectroscopy. The correlation between the OER activity and the electrochromic behavior of NiO is explored, providing insights into the underlying physicochemical mechanisms governing both phenomena. Strong reduction of the reflected light at higher applied potentials cannot be attributed solely to the change in optical bandgap due to the phase change or the change in the material's refractive index when different phases form. Therefore, in-gap states responsible for increasing the absorption at higher applied potentials were experimentally characterized by ultraviolet photoelectron spectroscopy (UPS) and X-ray absorption spectroscopy (XAS). The results show that phase changes in NiO during OER influence its optical absorption characteristics, which in turn give access to following active phase changes of the electrocatalyst material through a non-invasive, optical, operando probe in real time allowing for kinetic studies of the involved solid-state conversion reactions.

Journal Keywords: NiO; alkaline water electrolysis; O2 evolution reaction; phase transition; electrochromism; defect formation

Subject Areas: Chemistry, Materials


Instruments: B18-Core EXAFS

Other Facilities: PM3 at HZB BESSY II

Added On: 01/07/2024 08:59

Documents:
Phase transitions in NiO during the oxygen evolution reaction assessed via electrochromic phenomena through operando UV Vis spectroscopy.pdf

Discipline Tags:

Physical Chemistry Catalysis Chemistry Materials Science

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) Extended X-ray Absorption Fine Structure (EXAFS)