Neodymium-based B-site high-entropy perovskite oxide nanoparticles as an efficient electrocatalyst for water splitting and methanol oxidation

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)O_3−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 transition-metal 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.