Synthesis of La₂NiMnO₆ Double Perovskite as a Highly Selective Electrocatalyst for Oxygen Reduction to Hydrogen Peroxide in Electrochemical Energy Conversion

Oxygen reduction reaction (ORR), a key process in sustainable energy conversion, utilizing a perovskite catalyst to achieve higher currents at lower overpotentials along with the production of value-added product hydrogen peroxide (H 2 O 2 ), serves the dual functionality of both energy production and a green route for H 2 O 2 generation. Here, we report the synthesis of a highly efficient double perovskite La 2 NiMnO 6 (LNMO), achieved through the incorporation of two transition metals, Ni and Mn, in the perovskite structure, and explore its activity for ORR. During ORR at a rotation rate of 1600 rpm in 1.0 M NaOH, LNMO exhibits an onset potential of 0.75 V (corresponding to a current density of 0.1 mA cm –2 ) and a Tafel slope of 95 mV dec –1, achieving over 88% H 2 O 2 selectivity and 73% faradaic efficiency across a wide potential range of 0.2–0.6 V vs RHE. Characterization techniques including OCP, EIS, ICP-OES, XRD, XPS, FE-SEM, and FTIR confirmed the successful preparation of LNMO and its catalytic activity. The kinetic investigation unveiled by the transfer coefficient (α) demonstrated that ORR on the LNMO surface followed a stepwise mechanism, involving an overall two irreversible electron transfer steps, where the first electron transfer was the rate-determining step. The analyses further revealed a diffusion-limited process for ORR accompanied by first-order kinetics with a standard rate constant ( k 0 ) of 3.97 × 10 –3 cm s –1 and a formal potential ( E 0 ) value of 0.96 V vs RHE. Finally, a stability test via chronoamperometry showed that LNMO outperformed the Pt/C catalyst.