How
materials’ crystalline structure influences the underlying
electronic configuration, along with redox properties, and plays a
pivotal role in electrocatalysis is an intriguing question. Here,
solution combustion-synthesized La2–x
Sr
x
NiO4+δ (x = 0–0.8) Ruddlesden–Popper (RP) oxides were
explored for an electrocatalytic methanol oxidation reaction. Optimal
doping of bivalent Sr2+ in the A site enabled the tetragonal
distortion and oxidation of Ni2+ to Ni3+ that
resulted ultimately in enhanced covalent hybridization of Ni 3d–O
2p with a closer proximity of the O 2p band to the Fermi level. The
RP oxide La1.4Sr0.6NiO4+δ exhibited
the highest methanol oxidation reactivity vis-à-vis the formation
of HCO2H. The proposed mechanism over La1.4Sr0.6NiO4+δ considers a lattice oxygen-mediated
methanol oxidation reaction, owing to Fermi-level “pinning”
at the top of the O 2p band, which facilitated lattice oxygen atoms
prone to oxidation. A high surface concentration of the key active
species of Ni–OOH was observed to form during the methanol
oxidation reaction with the help of lattice oxygen atoms and oxygen
vacancies in La1.4Sr0.6NiO4+δ. The present study offers a uniquely comprehensive exploration of
structural and surface properties of RP oxides toward methanol oxidation
reactions.
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