Hollow spherical LaNiO₃ perovskite with superior multifunctional performances and durability for urea-assisted Zn-air batteries

Developing low-cost and effective catalysts for oxygen reduction reaction (ORR) and urea oxidation reaction (UOR) are highly desired in the urea-assisted Zn-air battery (UZAB) and urea splitting. Herein, a hollow spherical LaNiO₃ perovskite (LNO-H) was prepared by a hydrothermal method for ORR/UOR, UZAB and urea splitting. The LNO-H exhibited excellent performances for UOR in 1 M KOH with 0.33 M urea (E_j10 = 1.41 V vs RHE) and ORR in 1 M KOH (E_1/2 = 0.80 V vs RHE). Moreover, the LNO-H-based UZAB showed a remarkable cycling stability over 2100 h (6300 cycles) at 2 mA cm⁻². In particular, the failure mechanisms of LNO-H-based UZAB were systematically investigated by analyzing the air cathode, Zn anode and the electrolyte. The failure of LNO-H-based UZAB at 2 mA cm⁻² was mainly attributed to the formation of ZnO on the air electrode. Furthermore, K₂CO₃ on the surfaces of air electrode via the reaction of OH⁻ with CO₂ was the crucial factor for the battery failure at 10 mA cm⁻². Besides, LNO-H-based urea splitting required 1.42 V to achieve 10 mA cm⁻². This work may help to rationally design other multifunctional electrocatalysts, and achieve urea-based energy conversion in future.