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Tuning electrochemically driven surface transformation in atomically flat LaNiO3 thin films for enhanced water
Christoph Baeumer1,2,3,4, Jiang Li5, Qiyang Lu6,7,8,9
1Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA. c.baeumer@utwente.nl.
Nature Materials
|January 12, 2021
Summary
The surface termination of lanthanum nickelate (LaNiO3) thin films significantly impacts oxygen evolution reaction electrocatalysis. Nickel-terminated surfaces are more active due to a stable NiO2 layer, unlike La-terminated surfaces.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Science
Background:
- Rational electrocatalyst design relies on structure-activity relationships using bulk and surface descriptors.
- Electrocatalytic surface transformations complicate the identification of effective descriptors.
Purpose of the Study:
- To investigate how the as-prepared surface composition of (001)-terminated LaNiO3 epitaxial thin films influences surface transformation and oxygen evolution reaction (OER) electrocatalytic activity.
- To understand the origin of activity differences between Ni- and La-terminated surfaces.
Main Methods:
- Synthesis of (001)-terminated LaNiO3 epitaxial thin films.
- Electrochemical measurements to assess OER activity.
- Spectroscopic analysis to probe surface composition and structure.
- Density-functional theory (DFT) calculations to model surface transformations and energetics.
Main Results:
- The Ni-terminated LaNiO3 surface exhibits significantly higher OER activity compared to the La-terminated surface, with overpotential differences up to 150 mV.
- A thermodynamically stable, disordered NiO2 surface layer forms on Ni-terminated surfaces during OER operation.
- This active NiO2 phase is kinetically inaccessible for La-terminated surfaces.
Conclusions:
- The as-prepared surface termination of LaNiO3 critically dictates its surface transformation pathway and resulting electrocatalytic performance.
- Modifying a single atomic layer at the surface allows tuning of surface transformation pathways.
- Active electrocatalytic surface phases are dependent on the initial surface termination.
