Abstract

High-entropy perovskite oxides (HEPOs), incorporating five or more principal cations at the A- and/or B-sites of the ABO₃ structure, synergistically combine the configurational entropy and compositional tunability of high-entropy oxides with the structural versatility of perovskites, enabling enhanced atomic-level control over cation distribution, defect chemistry, and multifunctional properties. However, the controlled synthesis of structurally stable HEPOs remains challenging. Herein, we introduce a rapid and unprecedented method using continuous-wave CO₂ laser irradiation to stabilize high-entropy La(FeCoMnNi)O₃ via B-site cation engineering with LaFeO₃. The CO₂ laser, emitting 10.6-μm infrared radiation, is strongly absorbed by a metal–citrate 3D polymeric gel precursor, enabling localized heating and complete HEPO phase formation within 10 min while minimizing thermal diffusion and energy consumption. La(FeCoMnNi)O₃ demonstrates outstanding electrochemical nitrate reduction (eNO₃RR) performance for high-value ammonia (NH₃) production, attaining an NH₃ yield rate of 20.29  mg h⁻¹ cm⁻² at −0.7 V vs. RHE, with excellent cycling stability. Experimental and theoretical analyses reveal that B-site engineering induces B–O–B bond angle distortion, octahedral tilting, and d-band modulation within the perovskite lattice, enhancing electrical conductivity and NO₃⁻ activation. Practical NH₃ production via eNO₃RR was validated via Ar stripping‒acid trapping methods, and La(FeCoMnNi)O₃ was further employed as a cathode in a Zn–NO₃⁻ battery, demonstrating its multifunctionality. This study establishes CO₂ laser processing as a promising strategy for the rational design of high-entropy perovskite catalysts through precise cation tuning, which is expected to advance environmental and energy applications.