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Abstract
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High-entropy perovskite oxides are promising multifunctional electrocatalysts due to their complex
defect structures derived from multi-elemental compositions. In this work, a Nd-based high-entropy perovskite,
Nd(CoNiFeMn)O3−δ (NCNFM), was synthesized using a sol–gel route to investigate the effect of
B-site configurational disorder on oxygen non-stoichiometry and electrocatalytic behaviour. Structural
characterization reveals the formation of a single-phase perovskite with randomly distributed transitionmetal
cations at the B-site. The NCNFM catalyst was deposited on nickel foam and evaluated for the
oxygen and hydrogen evolution reactions (OER and HER), overall water splitting (OWS), and the methanol
oxidation reaction (MOR). NCNFM demonstrated outstanding bifunctional activity, achieving overpotentials
of 350 mV for the OER and 144 mV for the HER at 10 mA cm−2, with Tafel slopes of 91.2 and 105 mV
dec−1, respectively, outperforming the other perovskite oxides. It obtained a cell voltage of 1.67 V at
10 mA cm−2 and maintained stability for 72 hours in a self-supported two-electrode OWS system.
NCNFM also showed superior MOR activity with a low onset potential of 1.467 V vs. RHE@100 mA cm−2,
a low Tafel slope of 49 mV dec−1, and superior stability for at least 72 hours. The excellent catalytic behaviour
of NCNFM is attributed to the synergistic effects among multiple B-site cations and the influence of
configurational entropy, which enhance oxygen vacancy concentration and overall electrocatalytic
activity.
Introduction
With the increasing need for clean energy and decreasing
fossil fuel reserves, significant discoveries have been made in
renewable energy sources in recent years.1–4 Hydrogen is considered
a clean and renewable energy source because of its
high calorific value, energy density, and absence of carbon
emissions.5,6 Technologies such as water splitting and fuel
cells are utilized for energy storage and conversion, representing
sustainable and eco-friend
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