2 research outputs found
Band-Engineered LaFeO-LaNiO Thin Film Interfaces for Electrocatalysis of Water
Transition metal oxides have generated significant interest for their
potential as catalysts for the oxygen evolution reaction (OER) in alkaline
environments. Iron and nickel-based perovskite oxides have proven particularly
promising, with catalytic over-potentials rivaling precious metal catalysts
when the alignment of the valence band relative to the OER reaction potential
is tuned through substitutional doping or alloying. Here we report that
engineering of band alignment in LaFeO/LaNiO (LFO/LNO)
heterostructures via interfacial doping yields greatly enhanced catalytic
performance. Using density functional theory modeling, we predict a 0.2 eV
valence band offset (VBO) between metallic LNO and semiconducting LFO that
significantly lowers the barrier for hole transport through LFO compared to the
intrinsic material and make LFO a p-type semiconductor. Experimental band
alignment measurements using in situ X-ray photoelectron spectroscopy of
epitaxial LFO/LNO heterostructures agree quite well with these predictions,
producing a measured VBO of 0.3(1) eV. OER catalytic measurements on the same
samples in alkaline solution show an increase in catalytic current density by a
factor of ~275 compared to LFO grown on n-type Nb-doped SrTiO. These
results demonstrate the power of tuning band alignments through interfacial
band engineering for improved catalyticComment: 13 pages, 5 figures; Supplemental info: 5 pages, 5 figure
Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO Thin Films
Transition metal oxides have long been an area of interest for water
electrocatalysis through the oxygen evolution and oxygen reduction reactions.
Iron oxides, such as LaFeO, are particularly promising due to the
favorable energy alignment of the valence and conduction bands comprised of
Fe cations and the visible light band gap of such materials. In this
work, we examine the role of band alignment on the electrocatalytic oxygen
evolution reaction (OER) in the intrinsic semiconductor LaFeO by growing
epitaxial films of varying thicknesses on Nb-doped SrTiO. Using cyclic
voltammetry and electrochemical impedance spectroscopy, we find that there is a
strong thickness dependence on the efficiency of electrocatalysis for OER.
These measurements are understood based on interfacial band alignment in the
system as confirmed by layer-resolved electron energy loss spectroscopy and
electrochemical Mott-Schottky measurements. Our results demonstrate the
importance of band engineering for the rational design of thin film
electrocatalysts for renewable energy sources.Comment: 19 pages, 6 figures; authors Burton and Paudel contributed equally;
supplement: 11 pages, 7 figure